Contains extra controls commonly used in Lazarus forms.

extctrls.pp contains extra controls commonly used in Lazarus Component Library (LCL) applications. It adds components to the following tabs in the Lazarus IDE Component Palette:

Standard Tab

- TRadioGroup
- TCheckGroup
- TPanel

Additional Tab

- TImage
- TShape
- TBevel
- TPaintBox
- TNotebook
- TLabeledEdit
- TSplitter
- TTrayIcon
- TControlBar
- TFlowPanel

System Tab

- TTimer
- TIdleTimer

Register but not displayed

- TPage

Specifies an event handler triggered before a page in displayed.

TBeforeShowPageEvent is an object procedure which specifies an event handler triggered before a page in displayed. TBeforeShowPageEvent can be used to perform actions needed to configure the page or its parent control before the new page is displayed.

TBeforeShowPageEvent is the type used to implement the OnBeforeShow event handler in TPage.

Object for the event notification.
The page instance for the notification.
The ordinal position for the page in the parent control.
Specifies an event handler signalled to draw the background for an image.

TImagePaintBackgroundEvent is an object procedure which specifies an event handler signalled to draw the background for a TImage class instance. TImagePaintBackgroundEvent is the type used to implement the OnPaintBackground event handler in TCustomImage.

Object for the event notification.
Canvas for the image is drawn.
Rectangle with the dimensions for the image.
TPage
: One of the pages in a tabbed Notebook.

TPage is a TCustomControl descendant that implements a page displayed in a tabbed Notebook.

Multi-Page Controls How to use StdCtrls, ComCtrls or ExtCtrls.
Gets the ordinal position for the page in the TNotebook.

GetPageIndex is an Integer function used to get the ordinal position for the page in the TNotebook.

GetPageIndex checks the value in Parent to ensure that a TNotebook instance has been assigned as the parent control. The IndexOf method in TNotebook is used to get the position for the current page. When Parent is unassigned, or not derived from TNotebook, the value -1 is used as the return value.

Ordinal position for the page, or -1 when the Parent control is unassigned or not a TNotebook instance.
Sets the value for the Parent property.
TControl.Parent
New value for the property.
Constructor for the class instance.

Create is the overridden constructor for the class instance. Create calls the inherited constructor, and sets the default values for properties in the class instance. The following properties are updated in the method:

ControlStyle
  Includes the values csAcceptsControls, csDesignFixedBounds, csNoDesignVisible, and csNoFocus in the set.
Align
  Set to alClient. The height and width for the page depend on the dimensions for the parent control.
Caption
  Set to an empty string ('').
Visible
  Set to False.

Owner of the class instance.
Destructor for the class instance.

Destroy is the overridden destructor for the class instance. Destroy ensures that the page is also removed from the page list maintained in the Parent control (TNotebook). The action is not performed when the Parent control has csDestroying in its ComponentState, or when Parent has not been assigned.

Destroy calls the inherited destructor prior to exiting from the method.

Ordinal position for the page in its Notebook.

PageIndex is a read-only Integer property which contains the ordinal position for the page in its TNotebook container. The return value is -1 when the Parent control is unassigned, or not derived from TNotebook.

TCustomPage.PageIndex TControl.Parent
Event handler signalled before a page is displayed.

OnBeforeShow is a TBeforeShowPageEvent property that contains the event handler signalled before a page is displayed. Applications must assign an object procedure to the event handler to respond to the event notification.

Event handler signalled before the page is displayed.

OnBeforeShow is a TBeforeShowPageEvent property with the event handler signalled before a page is displayed. It allows an application to make any preparations needed for the page or its contents. It is signalled (when assigned) when the value for the PageIndex property is changed in a TNotebook instance.

Represents page names and class instances for a notebook.

TUNBPages is a TStrings descendant used to represent the names, TPage instances, and the owner class in TNotebook. TUNBPages extends the ancestor class by providing overridden methods needed to add, insert, delete and locate pages with a specified name or TPage class instance.

TUNBPages is used in the implementation of the TNotebook class.

Gets the owner for the TNotebook instance for the pages.
Owner of the TNotebook instance for the pages.
Gets the name for the page stored at the specified position in the list of pages.

Get is an overridden String function used to get the name for the page stored at the specified position in the list of pages.

Index contains the ordinal position in the page list for the requested page. Index must be a valid position in the page list or an Exception is raised. The return value contains the name assigned to the TPage instance stored at the specified position.

Calls RaiseGDBException to raise an exception when Index is not valid for the page list in the class instance. Raised with the exception message: 'TUNBPages.Get Index out of bounds'.
Name for the page at the specified position.
Ordinal position for the page requested in the method.
Gets the number of pages defined in the page list.
Value for the Count property.
Gets the TPage class instance stored at the specified ordinal position in the page list.
TPage class instance at the specified position.
Ordinal position in the list of pages for the requested page object.
Ensures that the index value is valid before accessing the TPage object.

Put is overridden in TUNBPages to set the name for the page object at the specified position. Put ensures that the value in Index is valid. Index must contain a value in the range 0 to the number of defined pages - 1. An exception is raised when Index contains an invalid value.

Put sets the name in the TPage object at the specified position to the value in S.

Calls RaiseGDBException with the exception message 'TUNBPages.Put Index out of bounds' when Index contains an invalid value.
TStrings
Ordinal position for the page object updated in the method.
Name stored in the requested page object.
Constructor for the class instance.
Notebook that is the owner of the class instance.
Destructor for the class instance.
Creates a new page instance with the specified name.

Add is an overridden Integer function used to create a new TPage instance with the name specified in S. The page object is created using the return value from GetNotebookOwner as the owner of the class instance. Add calls the AddObject method to store the page object in the list of pages for the notebook.

The return value contains the ordinal position in the page list where the page object was stored.

Ordinal position where the page object was stored.
Name for the page added in the method.
Adds the specified page object to the list of pages.
Ordinal position in the page list where the page object was stored.
Identifier used as the name and/or caption for the page object.
Page object stored in the method.
Removes all page objects stored in the list of pages.

Clear is an overridden method which implements the abstract virtual method declared in the TStrings ancestor. Clear is used to remove all TPage instances stored in the the internal page list. It calls the Delete method to remove the last TPage instance in the list until all items in the list have been deleted.

Deletes the page at the specified position in the list of pages.
Ordinal position in the list of pages for page removed in the method.
Gets the ordinal position for the specified page object in the list of pages.
TStrings.IndexOfObject
Ordinal position for the page object.
The page object to locate in the list of pages.
Inserts a page with the specified name at the given position in the list of pages.
TStrings.Insert
Ordinal position where the page is stored.
Name for new page.
Moves the active page to a position in the page list.

Move is an overridden procedure in TUNBPages. It re-implements the method defined in the TStrings ancestor class. Move is used to relocate the active page in a NoteBook control to a new position in the page list.

Move uses the internal TNotebook member that is the owner of the class instance to retrieve the current page and its ordinal position.

CurIndex is set to the PageIndex for the active page in the Notebook component. NewIndex specifies the new ordinal position in the page list for the TPage instance.

The Move method in the internal page list (TObjectList) is called to move the TPage instance from using the required positions. The PageIndex for the TNotebook control is reset to re-activate the page moved in the operation.

Move does NOT call the inherited method.
TNotebook.Pages TNotebook.PageIndex TNotebook.IndexOf TPage TStrings.Move
Current position for the active page.
New position in the page list for the page.
TNotebook
is a container for a series of pages placed together.

TNotebook is a control which can hold a series of pages placed together. Only one page is shown at a time and this control is completely custom drawn, which means that it is available and looks the same in any widgetset which supports TCustomControl. The pages are containers which can hold controls. This control never has tabs. If you are looking for a control with tabs and pages, please see TPageControl instead.

To use a Notebook, select its icon from the 'Additional' tab of the Component Palette and place it on the Form. Adjust its size, position, alignment and anchoring as required, by moving the object on the Form or by using the Object Inspector.

Pages are added to the NoteBook by selecting the control and right-clicking with the mouse to get a pop-up menu whose first item is 'Add Page'. Pages already in the NoteBook can be edited by selecting the appropriate ActivePage in the Object Inspector and modifying its properties or adding additional components to that Page.

TPage Multi-Page Controls How to use StdCtrls, ComCtrls or ExtCtrls.
Gets the value for the ActivePage property.
Value for the property.
Gets the value for the ActivePageComponent property.
Value for the property.
Gets the value for the indexed Page property.
Page object at the specified position in the list of pages.
Ordinal position for the requested page object in the list of pages.
Gets the value for the PageCount property.
Value for the property.
Gets the value for the PageIndex property.
Value for the property.
Sets the value for the PageIndex property.
New value for the property.
Sets the value for the Pages property.
New value for the property.
Constructor for the class instance.

Create is the overridden constructor for the class instance.

Create calls the inherited constructor using TheOwner as the owner of the class instance. Create allocates resources needed for members in the class instance, and sets the default values for the following properties:

ControlStyle
  Set to an empty set ([]).
PageIndex
  Set to -1 to indicate that no page is selected or visible in the notebook.
Bounds
  Set to the default size for the class (GetControlClassDefaultSize).

Owner of the class instance.
Destructor for the class instance.

Destroy is the overridden destructor for the class instance. Destroy ensures that resources allocated to the internal page list member are freed. Destroy calls the inherited destructor prior to exiting from the method.

Displays the specified control (page object).

ShowControl is an overridden procedure used to display the control specified in AControl. ShowControl checks the internal list of pages for the value specified in AControl. The ordinal position for the page object, when found, is assigned to the PageIndex property and causes the page object to become visible.

ShowControl calls the inherited method prior to exit.

No actions are performed in the method when AControl is the same as the control stored in the ActivePageComponent property.
Page object to display in the notebook control.
Gets the ordinal position in the list of pages for the specified page object.
Ordinal position for the requested page object.
Page object to locate in the list of pages.
Gets the name for the active page object in the notebook control.

ActivePage is a read-only String property which provides the name for the active page object in the notebook control. The value in PageIndex is used to access the page object instance in the Page property. Its Name property is used as the property value.

Use ActivePageComponent to get the TPage instance representing the active page object.

Should not be published because reading the property value can raise an exception.
Gets the TPage instance representing the active page in the notebook control.

ActivePageComponent is a read-only TPage property which represents the active page in the notebook control.

Should not be published because reading the property value can raise an exception.
Provides access to a page object in the notebook control by its ordinal position in the list of pages.

Page is an indexed read-only TPage property used to access a page object for the notebook control by its ordinal position in the list of pages.

Ordinal position for the requested page object.
Indicates the number of page objects defined for the notebook control.

PageCount is a read-only Integer property that indicates the number of page objects defined for the notebook control. The value in PageCount is determined by the total number of entries stored in the list of Pages.

Use methods and properties in Pages to maintain the page names used in the notebook control.

Ordinal position for the active page in the notebook control.

PageIndex is an Integer property that indicates the ordinal position for the active page in the notebook control.

A value assigned to the property must must be in the range -1 to the number of defined Pages - 1. No actions are performed in the method when the new value for PageIndex is not in the required range.

Setting the value in the property causes the active page object to be hidden; it is hidden at run-time and design-time using the Visible and ControlStyle properties. The OnBeforeShow event handler in the newly selected page object is signalled (when assigned). The page object is displayed by updating its Visible, ControlStyle, and Align properties.

The default value for the property is -1, and indicates that a page is not currently selected or available.

Contains the page names defined for the notebook control.

Pages is a TStrings property which contains the page names defined for the notebook control.

Setting a new value in Pages causes the new page names to be compared to the internal page objects in the notebook. New or altered pages are added or replaced in the notebook. An existing page object not present in the new page names is deleted; the Application singleton is notified that the page object is being released and allowed to process the message.

The value in Pages is not assigned at design-time.

TTimer
is an elapsed timer useful in many applications.

TTimer is a TCustomTimer descendant which implements an elapsed timer useful in many applications. It inherits most of its properties from TCustomTimer.

TIdleTimerAutoEvent
is an enumerated type containing the events relevant to a timer.

TIdleTimerAutoEvent is an enumerated type containing the events relevant to a timer. TIdleTimerAutoEvent is the type used for the AutoStartEvent and AutoEndEvent properties in TCustomIdleTimer. Values in the enumeration are used when a timer executes its DoOnIdle, DoOnIdleEnd, and DoOnUserInput methods.

Timer responds to idle start events.
Time responds to idle end events.
Time responds to user input events.
TIdleTimerAutoEvents
is set type used to store TIdleTimerAutoEvent values.
Not used in the current LCL version.
Implements the base class for TIdleTimer.

TCustomIdleTimer is a TCustomTimer descendant which implements the base class for TIdleTimer. TCustomIdleTimer extends the ancestor class to use events which toggle the timer state. In addition, support is provided for adding and removing its event handlers in the global TApplication instance.

Updates the event handlers used in the Application singleton.

UpdateHandlers is a procedure used to update the event handler assignments in the Application singleton based on the value in the AutoEnabled property. When AutoEnabled is True, the following methods are assigned as event handler:

DoOnIdle
  Assigned using Application.AddOnIdleHandler
DoOnIdleEnd
  Assigned using Application.AddOnIdleEndHandler
DoOnUserInput
  Assigned using Application.AddOnUserInputHandler

No assignments are made to the Application singleton at design-time, or when the component is being loaded or destroyed.

When AutoEnabled is False, the event handler routines are disconnected from the Application singleton.

No actions are performed when handlers have not been previously assigned to Application, or Application has not been assigned (contains Nil).
Sets the value for the AutoEnabled property.

Calls UpdateHandlers to add or remove event handlers assigned in the Application singleton.

Application
New value for the property.
Performs actions which execute the idle timer.

DoOnIdle is a procedure which performs the actions needed to execute the idle timer. The value in FireOnIdle is used to determine whether the timer can be executed for the idle state. When FireOnIdle is True, the DoOnTimer method is called to signal the OnTimer event handler (when assigned) and the value in the Done argument is set to False.

The AutoEnabled property is checked to determine if the value in the Enabled property can be updated to reflect the state needed for the AutoEndEvent and AutoStartEvent properties. If AutoEndEvent contains itaOnIdle, the value in Enabled is set to False. If AutoStartEvent contains itaOnIdle, the value in Enabled is set to True.

The Enabled property is not modified when AutoEnabled contains False.

DoOnIdle is assigned as a handler for the Application singleton in the UpdateHandlers method.

Object for the event notification.
True if the idle timer has already executed its OnTimer event handler.
DoOnIdleEnd
performs actions when the idle state ends for the timer.
Object for the event notification.
DoOnUserInput
performs the code for responding to user input.
Object for the event notification.
Message examined in the method.
Performs actions needed when the component has finished loading during LCL component streaming.

Loaded is an overridden procedure used to perform actions needed when the component has finished loading in the LCL component streaming mechanism. Loaded calls the inherited method, and calls UpdateHandlers to connect/disconnect event handlers in the Application singleton.

TComponent
Constructor for the class instance.

Create is the overridden constructor for the class instance. Create calls the inherited constructor using TheOwner as the owner of the class instance. Create sets the default values for the following properties:

AutoEnabled
  Set to False
AutoStartEvent
  Set to itaOnIdle
AutoEndEvent
  Set to itaOnUserInput

TCustomTimer.Create
Owner of the class instance.
Destructor for the class instance.

Destroy sets the value in AutoEnabled to False, and calls the inherited destructor.

Controls whether the idle timer can be automatically enabled or disabled.

AutoEnabled is a Boolean property which controls whether the idle timer can be automatically Enabled (or disabled) in event handler routines. The default value for the property is False, and indicates that event handlers in the timer are not assigned to the Application singleton in the UpdateHandlers method.

The value in AutoEnabled is used in the DoOnIdle, DoOnIdleEnd, and DoOnUserInput methods. When AutoEnabled contains False, these routines do not perform actions which toggle the value in the Enabled property.

AutoStartEvent
- the event that triggers autostart (either idle time-out or user input).

AutoStartEvent defines, when Enabled is automatically set to True. This is one of the following events:

- on application becomes idle
- on application stops being idle (e.g. user input or some timer fired)
- user input, e.g. key press, mouse move

The default value for the property is itaOnIdle.

AutoEndEvent
- the event that stops the timer by setting Enabled to False.

AutoEndEvent defines, when Enabled is automatically set to False. This is one of the following events:

- on application becomes idle
- on application stops being idle (e.g. user input or some timer fired)
- user input, e.g. key press, mouse move

The default value for the property is itaOnUserInput.

FireOnIdle
- Boolean property determining whether the timer should fire when idle.

The default value for the property is False.

TIdleTimer
: A timer to measure idle time between processes.

TIdleTimer: A timer to measure idle time between processes.

TShapeType
is an enumerated type with values representing standard geometric shapes.

TShapeType is an enumerated type with values that represent standard geometric shapes. TShapeType is the type used to implement the Shape property in TShape.

Draws a rectangle shape in the client area for a TShape control.
Draws a square shape in the client area for a TShape control.
Draws a rectangle shape with radiused corners in the client area for a TShape control.
Draws a square shape with radiused corners in the client area for a TShape control.
Draws a ellipse shape that fits in the client area for a TShape control.
Draws a circle shape that fits in the client area for a TShape control.
Draws a four point polygon in the client area for a TShape control. Same as stDiamond.
Draws a four point polygon in the client area for a TShape control. Same as stSquaredDiamond.
Draws an upward pointing triangle in the client area for a TShape control.
Draws a triangle pointing to the left in the client area for a TShape control.
Draws a triangle pointing to the right in the client area for a TShape control.
Draws a downward-pointing triangle in the client area for a TShape control.
Draws a five-point star shape in the client area for a TShape control.
Draws a five-point star shape (center angle points down) in the client area for a TShape control.
TShape
draws an arbitrary geometric shape.

TShape is a TGraphicControl descendant used to draw an arbitrary geometric shape. It may be one of a series of standard shapes defined in the TShapeType enumeration.

It can be displayed using the Paint method, or the Brush and Pen tools.

Sets the value for the Brush property.
New value for the property.
Sets the value for the Pen property.
New value for the property.
Sets the value for the Shape property.
New value for the property.
Gets the default size for instances of the control.

GetControlClassDefaultSize is an overridden TSize class function which provides the default size for instances of the control. The return value is updated in the method to use dimensions of 65 x 65 pixels.

GetControlClassDefaultSize is called from the Create method, and used to set the initial value in the Bounds for the control.

TControl.GetControlClassDefaultSize
TSize instance with the dimensions for instances of the control class.
Create
- constructor for TShape: calls inherited Create, sets default styles and bounds, creates pen and brush.
TGraphicControl.Create
Owner of the class instance.
Destroy
- destructor for TShape: frees pen and brush, then calls inherited Destroy.
TGraphicControl.Destroy
Draws the shape for the control on its Canvas.

Paint is an overridden procedure used to draw the shape for the control on its Canvas. Paint uses the Pen, Brush, and Shape defined in the control. Drawing methods in Canvas are called to render the desired Shape to a rectangle using the Width and Height defined in the component.

Paint calls the inherited Paint method to signal an OnPaint event handler assigned in the class instance.

TGraphicControl.Paint
StyleChanged
- method for handling change of style by Sender.
Object for the event notification.
The Brush to be used for coloring this shape.
The Pen to be used for drawing this shape.
Indicates the geometric shape drawn in the control.

Shape is a TShapeType property that specifies the geometric shape drawn in the control. See for the values that can be assigned to the property.

Enumerated type with the drawing styles available when resizing using a splitter.

TResizeStyle is an enumerated type with the drawing styles and actions available when resizing using a splitter. TResizeStyle is the type used to implement the ResizeStyle property in TCustomSplitter.

Draw a line, but don't update splitter position during movement.
Draw nothing and don't update splitter position during movement.
draw a dot pattern, but don't update splitter position during movement.
Draw nothing, but update splitter position during movement
Specifies an event handler signalled to determine if the given offset is valid for a splitter control.

TCanOffsetEvent is the type used to implement the OnCanOffset property in TCustomSplitter. It is signalled from the CheckOffset method when the splitter is moved.

Object for the event notification.
Offset value examined in the routine.
True if the offset value is valid.
TCanResizeEvent
- generic event handling method for resizing using splitter.

TCanResizeEvent specifies an event handler signalled when a control is resized. Use to the arguments to the event handler to access the new size for the control and to set a flag that indicates if the new value is acceptable.

TCanResizeEvent is the type used to implement the OnCanResize event handler in TCustomSplitter and TCustomControlBar.

Object generating the event notification.
New size for the resize operation.
Indicates if the new value is accepted.
TCustomSplitter
is the base type for TSplitter.

TCustomSplitter is a TCustomControl descendant which implements a control used to resize, position and align a control to which it is anchored. TCustomSplitter displays a vertical or a horizontal bar anchored to the side of another control. Use the Align property to specify the orientation for the splitter control, and the adjacent control to which it is attached. When the splitter is moved with the mouse, the adjacent control with the same Align value will be resized.

This class defines many of the basic properties for the children classes, such as positioning, sizing and alignment.

Another usage scenario allows setting the Align property to alNone, and using AnchorSides and ResizeAnchor.

TCustomSplitter is the base type for TSplitter.

Gets the value for the ResizeControl property.
Value for the property.
Sets the value for the Beveled property.
New value for the property.
Sets the value for the MinSize property.
New value for the property.
Handles the CM_ENABLEDCHANGED message.

Calls the inherited method, and performs the UpdateCursor method to apply the cursor shape needed for the value in ResizeAnchor.

TWinControl.CMEnabledChanged
Message with parameters handled in the method.
Adjust anchor settings to reflect the value in the Align property.

AdaptAnchors is a TAnchors function used to adjust the anchor settings for the control to reflect the value in the Align property. a contains the initial anchors used in the method, and is assigned as the default return value.

The Align property is used to determine the correct TAnchorKind values used in the return value for the method. The following TAnchorKind values are included/excluded from the result based on the value in Align:

alLeft
  Includes akLeft. Excludes akRight.
alTop
  Includes akTop. Excludes akBottom.
alRight
  Includes akRight. Excludes akLeft.
alBottom
  Includes akBottom. Excludes akTop.

AdaptAnchors is called when a new value is assigned to the Align or Anchors properties.

TAnchors settings derived in the method.
Initial TAnchors values used in the method.
CheckNewSize
ensures the new size is appropriate; returns True if successful.

CheckNewSize signals the OnCanResize event handler (when assigned) to examine and validate the value in NewSize. The values in NewSize and Result can be updated in the event handler as needed. True indicates that the value in NewSize is acceptable.

CheckNewSize is used in the implementation of the MoveSplitter method.

True when NewSize is an acceptable size for the splitter.
New sized for the splitter.
Signals the OnCanOffset event handler to determine the offset used when aligning the control, and the success or failure of the calculation.
Used in the implementation of the MoveSplitter method.
FindAlignControl
returns the main alignment control.
FindAlignOtherControl
returns another alignment control (the splitter may have to align two controls)
Initiates the splitter movement operation.

Overridden in TCustomSplitter. Calls the inherited method, and ensures that the absolute mouse position is used when the left mouse button is depressed; The X and Y arguments are not valid during a resize operation.

Calls GetCursorPos to capture the mouse position, and calls StartSplitterMove to initiate the splitter movement operation.

TControl.MouseDown
Button examined in the method.
Modifier for the mouse button.
Horizontal coordinate for the mouse event.
Vertical coordinate for the mouse event.
Starts mouse capture and tracking for the control.

Calls the inherited method. No additional actions are performed in the method at design-time, or when mouse capture has already been enabled for the control. Ensures that the internal flag used to track mouse entry into the control is set, and the control is refreshed by calling Invalidate.

TControl.MouseEnter
Perform actions when the mouse pointer exits the control.

MouseLeave is an overridden method used to perform actions when the mouse pointer exits the control. MouseLeave calls the inherited method on entry.

No additional actions are performed in the method at design-time.

At run-time, the internal flag that indicates if the control is hovered is reset. The Invalidate method is called to force the control to be redrawn.

TControl.MouseLeave
Draws the splitter control.

Paint is an overridden procedure used to draw the splitter control. Paint calls the inherited Paint method, and adds additional logic to handle drawing the splitter control.

The OnPaint event handler is signalled (when assigned) to draw the splitter control.

When OnPaint is unassigned (contains Nil), an internal routine is used to paint the gripper bar using the TThemedRebar settings in ThemeServices. The control is drawn using the theme settings needed for the state in the Enabled and Beveled properties, and the internal MouseInControl member.

TCustomControl.Paint TCustomControl.OnPaint TControl.Enabled
Sets the value for the Align property.

Updates the value in ResizeAnchor to match the new value for the property. When set to a value other than alClient, the bounds for the control are adjusted to keep the width or height as needed for the new property value.

TControl.SetAlign
New value for the Align property.
Sets the value for the Anchors property.

SetAnchors is an overridden procedure used to implement the write access specifier for the Anchors property. SetAnchors calls AdaptAnchors to ensure that the new value for the property reflects the setting in the Align property. SetAnchors calls the inherited method prior to exit.

TControl.Anchors
New value for the property.
Sets the value for the ResizeAnchor property.
New value for the property.
Sets the value for the ResizeControl property.
New value for the property.
StartSplitterMove
- method for starting movement of the splitter, given the mouse position MouseXY.
Performs actions when splitter movement is stopped at the specified mouse position.

StopSplitterMove calculates the offset for the mouse position relative to the position where the drag operation was started, and calls MoveSplitter to apply the changed position. The OnMoved event handler is signalled (when assigned).

No actions are performed in method if a drag operation has not been started using StartSplitterMove.

TPoint instance with the coordinates for the mouse pointer.
Updates the cursor to reflect the ResizeAnchor for the splitter.

When the splitter is Enabled, the value in Cursor is changed. crHSplit is used when ResizeAnchor contains akLeft or akRight. For other values, crVSpit is used.

If the splitter is not Enabled, Cursor is set to the crDefault cursor shape.

TControl.Enabled TCursor
Constructor for the class instance.

Create is the overridden constructor for the class instance, and calls the inherited method on entry.

Create sets the default values for properties, including:

- Align
- AutoSnap
- Beveled
- MinSize
- ResizeAnchor
- ResizeStyle
- Width
- AccessibleRole
- AccessibleDescription

TCustomControl.Create
Owner for the class instance.
AnchorSplitter
anchors the splitter to AControl using the specified Kind of anchor.

Updates values in ResizeAnchor, Anchors and AnchorSide to reflect the value in Kind. Calls UpdateCursor to set the cursor shape for the anchor kind. Resizes the splitter to reflect the new value in ResizeAnchor.

Contains the anchored control that is re-sized when the splitter is moved.
Gets the adjacent anchored control that is re-sized when the splitter is moved.
TControl instance opposite of the anchor side.
MoveSplitter
moves the splitter by an amount specified in Offset.
SetSplitterPosition
- to specified NewPosition.
GetSplitterPosition
returns the current position of the splitter.
Current position for the splitter.
Specifies the placement of the control inside its Parent.

Align is a TAlign property which specifies how the control is aligned to its parent control. The default value for the property is alLeft in TCustomSplitter.

TControl.Align
AutoSnap automatically moves the splitter to the zero position when split size becomes smaller than the value in MinSize.

AutoSnap is a Boolean property. AutoSnap automatically moves the splitter to the zero position when split size becomes smaller than the value in MinSize. Contains True when snapping to grid positions.

Indicates whether the edges of the splitter bar are beveled.
The shape for the mouse pointer when the control is dragged.

Cursor is a TCursor property with the cursor resource constant displayed when the splitter control is dragged. The default value for the property is crHSplit in TCustomSplitter. The value is updated in the UpdateCursor method to reflect the ResizeAnchor for the control.

crHSplit
  Used when ResizeAnchor contains akLeft or akRight.
crVSplit
  Used when ResizeAnchor contains akRight or akBottom.
crDefault
  Used when the splitter control is not Enabled.

TControl.Enabled TControl.Cursor TAnchorKind
Minimum size for either of the anchored controls on opposing sides of the splitter.

MinSize indicates the smallest size allowed for either of the anchored controls on opposing sides of the splitter. MinSize is used in the MoveSplitter method to prevent adjacent controls from becoming too small when the splitter is dragged. The default value for the property is 30 (pixels). When set to 0 (zero), an adjacent control can be resized until is no longer visible. MinSize does not accept negative Integer values in the property.

Event handler signalled to calculate the offset when the splitter is dragged, and to accept or reject the offset value.

Signalled from the CheckOffset method when the splitter control is dragged. The Accept argument can be set to False to reject the offset value for the splitter, and prevent the resize operation.

Event handler signalled to determine if the splitter control can be resized / dragged / moved.

OnCanResize is a TCanResizeEvent proprety with the event handler signalled to determine if the splitter control can be resized. OnCanResise is signalled (when assigned) from the CheckNewSize method using the splitter control and the new size for the anchored control as arguments. The Accept argument can be updated in the event handler to indicate whether the new size is acceptable (True) or rejected (False).

Event handler signalled when the splitter has been dragged / moved.

OnMoved is a TNotifyEvent property with the event handler signalled when the splitter control has been dragged / moved. It is signalled (when assigned) from the StopSplitterMove method when the mouse button is released to end the drag operation. It occurs after the splitter has been moved using the MoveSplitter method.

Indicates the orientation and alignment for the splitter control.

ResizeAnchor is a TAnchorKind property which indicates the AnchorSide (and the associated Control) used to align the splitter. The default value for the property is akLeft, and causes the splitter to align to the control for the corresponding position in AnchorSide. akLeft and akRight allow the splitter to be moved along the horizontal axis. akTop and akBottom allow the splitter to be moved along the vertical axis.

Changing the value for the property causes the UpdateCursor method to be called to set the cursor shape displayed when the splitter control is dragged.

ResizeAnchor is linked to the Align property in TCustomSplitter. Changing the value in Align causes ResizeAnchor (and Cursor) to be updated with corresponding values as needed.

ResizeAnchor is used in the MoveSplitter method to determine the size for the splitter control and the limits for the resize operation. It is used in MouseMove to determine the starting position and offset used when the control is dragged.

TControl.AnchorSide
Display style used when the splitter control is moved.

ResizeStyle is a TResizeStyle property with the display style used when the splitter control is moved. The default value for the property is rsUpdate, and causes anchored control(s) and the splitter position to be updated when the position is changed. rsLine and rsPattern indicate the splitter position in the corresponding style, but do not update the sizes for the anchored controls until the resize operation is completed. rsNone does not update the splitter position (or anchored controls) when moved; the update occurs when the resize operation is completed.

The value in ResizeStyle is used in the MoveSplitter, StartSplitterMove, and StopSplitterMove methods.

TSplitter
: A vertical or horizontal bar placed on a panel or form, to separate sub-panels functionally.

TSplitter is a vertical or horizontal bar that can be placed on a panel or form, to separate sub-panels functionally and allow re-sizing of the sub-panels.

The splitter extends for the full height (if vertical) or full width (if horizontal) of the parent control (form or panel) and is anchored to the edges; its position along the length or height of the parent is determined by the programmer or user by moving the whole control with the mouse, and its size can be adjusted using the sizing bars and with the ResizeAnchor property.

How to use StdCtrls, ComCtrls or ExtCtrls.
Implements a control with a rectangular drawing area using a given Font and Color.

TPaintBox is a TGraphicControl descendant which implements a control with a rectangular drawing area using a given Font and Color. Like its ancestor, TPaintBox provides a Canvas which is used to draw on the control surface. It provides an overridden Paint method to configure the Pen, Brush, and Font for the Canvas prior to calling the inherited Paint method. Use the OnPaint event handler to perform drawing operations needed for the control.

TGraphicControl How to use StdCtrls, ComCtrls or ExtCtrls.
Draws the content for the control.

Paint is an overridden procedure used to draw the control.

At design-time, a dashed black line is drawn around the area for the control and across its opposing corners. No other actions are performed in the method at design-time.

At run-time, the OnPaint event handler is used to render the content for the control using the Font and Color properties. The inherited Paint method is called to signal the event handler.

TGraphicControl.Paint
Gets the default size used for new instances of the class.

The default dimensions used in TPaintBox are 105 pixels wide x 105 pixels high.

TControl.GetControlClassDefaultSize
TSize instance with the default dimensions for a new TPaintBox control.
Constructor for the class instance.

Create is the constructor for TPaintBox. It calls the inherited Create method, and sets the initial bounds and style for the control.

TGraphicControl.Create
Owner of the class instance.
Implements the base class for TImage.

TCustomImage is a TGraphicControl descendent, and the base class for TImage. It is a lightweight and fast class used to display a graphic image using one of the image formats supported in the LCL. This includes:

- Bitmap
- Pixmap
- PNG
- JPEG
- GIF
- TIFF
- Icon

Use the Picture property to assign, load or save an image using one of the supported formats.

The Canvas property is used to render the graphic image in Picture, or to perform custom drawing operations on the image.

Use properties in the class instance to control how the image is rendered, including: AntialiasingMode, Center, Stretch, Transparent, and Proportional.

Do not create instances of TCustomImage; use the TImage descendant instead.

Use TImageList when a list of images with scaling capabilities is needed.

TGraphicControl TPicture TGraphic TCanvas TImageList
Gets the value for the Canvas property.
Value for the property.
Sets the value for the AntialiasingMode property.
New value for the property.
Sets the value for the Picture property.
New value for the property.
Sets the value for the Center property.
New value for the property.
Sets the value for the KeepOriginXWhenClipped property.
New value for the property.
Sets the value for the KeepOriginYWhenClipped property.
New value for the property.
Sets the value for the Proportional property.
New value for the property.
Sets the value for the Stretch property.
New value for the property.
Sets the value for the StretchInEnabled property.
New value for the property.
Sets the value for the StretchOutEnabled property.
New value for the property.
Sets the value for the Transparent property.
New value for the property.
Registers the class with the widgetset.

Calls the RegisterCustomImage method in the widgetset class.

Performs actions needed when the Picture property has been changed.

PictureChanged is a procedure used to perform actions needed when the Picture property has been changed. PictureChanged adjusts the size for an assigned bitmap in Picture, and sets its bitmap transparency to the value in the Transparent property. PictureChanged calls Invalidate to cause the image to be repainted. The OnPictureChanged event handler is signalled (when assigned) prior to exiting from the method.

PictureChanged is assigned as the OnChange event handler for the Picture property in the constructor for the class instance.

Object instance for the change notification.
Gets the preferred width and height used as the default size for the control.

CalculatePreferredSize is an overridden method in TCustomImage. It calculates the preferred width and height for the control, which is used by the LCL auto-sizing algorithms as the default size. In TCustomImage, the values in the PreferredWidth and PreferredHeight arguments are set to the Width and Height used in the Picture property. The WithThemeSpace argument is not used in the method.

CalculatePreferredSize does not call the inherited method.

TPicture TControl.CalculatePreferredSize
Preferred width for the control instance.
Preferred height for the control instance.
Indicates if additional space is reserved for theme element details. Not used in TCustomImage.
Gets the default size for a new instance of the class type.

GetControlClassDefaultSize is an overridden method in TCustomImage. It sets the Width and Height in the TSize return value to 90 x 90 pixels. It does not call the inherited method.

TControl.GetControlClassDefaultSize
Dimensions used for a new instance of the class type.
Draws the image to the control canvas.

Paint is an overridden procedure used to draw the image to the control Canvas. At design-time, a dashed black line is drawn around the image as a frame to mark the dimensions for its content.

No additional actions are performed in the method when a TGraphic instance has not been assigned to the Graphic property in Picture.

Paint uses the Canvas from the ancestor class as the target for the drawing operation. The value in AntialiasingMode is assigned to the corresponding property in the Canvas. The rectangle returned from DestRect is used as the drawing area.

Paint signals the OnPaintBackground event handler (when assigned) using the canvas and drawing rectangle to render the background for the image. The StretchDraw method in the Canvas is used to render the image content.

Paint calls the inherited method to ensure that the OnPaint event handler is signalled (when assigned).

TCanvas TCanvas.StretchDraw TGraphicControl.Paint TGraphicControl.OnPaint
Constructor for the class instance.

Create is the constructor for TCustomImage, and calls the inherited Create method. It then sets the default values for the style, bounds and other local variables. Creates allocates resources for the Picture property.

TGraphicControl.Create
Owner of the class instance.
Destructor for the class instance.

Destroy is the destructor for TCustomImage. It free resources allocated to the Picture property, and then calls the inherited Destroy method.

TGraphicControl.Destroy
Canvas used to draw the image.

TCustomImage re-implements the read access specifier for the property to ensure that a drawing surface is available in Picture. When not assigned, a temporary TBitmap instance is created and used as the image class in the Picture property. The Canvas for the bitmap is used as the property value. If the TCanvas has already been assigned, the inherited Canvas property (from TGraphicControl) is used.

TPicture TGraphicControl.Canvas
Gets the rectangle where the image is painted.

DestRect is a TRect function used to get the rectangle where the image is drawn.

Rectangle where the image is drawn in the Paint method.
Causes the control to be repainted.

Invalidate is an overridden procedure which causes the control to be repainted. Invalidate is called when the content or dimensions for the image have been changed.

Invalidate extends the ancestor method to include logic that reduces the number of calls to the Paint method, and avoids flicker caused by the redundant calls. It uses an internal flag in the class to determine if the Paint method has already been called, but has not yet been completed. If the flag has not been set, the inherited Invalidate method is called to refresh the control using its visibility and control style settings.

No actions are performed in the method when Paint is already active.
TControl.IsVisible TControl.ControlStyle TControl.Invalidate
Indicates if anti-aliasing is used when rendering the image.

AntialiasingMode is a TAntialiasingMode property which indicates if anti-aliasing is used when rendering the image. The value in AntialiasingMode is assigned to the TCanvas instance used in the Paint method. Changing the value in the property causes the PictureChanged method to be called to invalidate and repaint the image to its canvas.

The default value for the property is amDontCare, and indicates that the default anti-aliasing mode for the platform, OS, or widget set is used.

Indicates if the image should be centered.

Center is a Boolean property which indicates if the image is drawn aligned to the center of the client area for the control. Center is used in the DestRect method to find the horizontal and vertical coordinates for the Picture aligned to the ClientWidth and ClientHeight for the control.

Changing the value for the property causes the PictureChanged method to be called to invalidate and repaint the image.

The default value for the property is False.

Preserves the Left coordinate when a clipped image is centered.

The default value for the property is False.

Preserves the Top coordinate when a clipped image is centered.

The default value for the property is False.

Contains the image displayed in the control.

Picture is a TPicture property which contains the dimensions, format, and data for the image displayed in the control. Resources are allocated for Picture in the constructor; this includes use of the PictureChanged method as the OnChange event handler for the property.

Picture is used when the control needs to access its canvas for drawing operations. Drawing operations use the bitmap for the Picture when possible instead of the canvas for the form. It is also examined/updated when PictureChanged is called after values for properties like Proportional, Stretch, Centered, Transparent. and AntialiasingMode are changed.

TPicture TPicture.OnChange
Indicates if the image is resized to the client area for the control.

Stretch is a Boolean property which indicates if the image content is resized to the client area for the control. It is used in the DestRect method (along with Proportional) to calculate the rectangle needed to render the image content.

Changing the value in Stretch causes the PictureChanged method to be called.

The default value for the property is False.

Allows the image to be resized proportionally when the image drawing area is expanded.

The default value for the property is True.

Allows the image to be resized proportionally when the image drawing area is shrunk.

The default value for the property is True.

Indicates if the image has a clear, non-opaque background.

Transparent is a Boolean property which indicates if the image uses a clear, non-opaque background. The value for the property is used in the PictureChanged method to set the transparency for the bitmap in Picture. Changing the value for the property causes PictureChanged to be called to update the image data assigned to Picture and to repaint the control.

The default value for the property is False.

Use AntialiasingMode to enable or disable use of the rendering technique. Use the OnPaintBackground event handler to render a custom background for the image.

True if image is proportional.

Proportional is a Boolean property which indicates if the proportions (the ratio of width to height) for an image are maintained when it is resized. When set to True, a change to the image size maintains the ratio of width to height for the original image. Proportional is used (along with Stretch) in the DestRect method to determine the rectangle needed to render the image in the control.

Changing the value for the property causes the PictureChanged method to be called.

The default value for the property is False.

Event handler signalled when Picture is changed.

OnPictureChanged is a TNotifyEvent property which contains the event handler signalled then the Picture property is changed. OnPictureChanged is signalled from the PictureChanged method, and allows actions to be performed after updates to image properties and the Invalidate method has been called.

Event handler signalled to draw the background for the image.

OnPaintBackground is a TImagePaintBackgroundEvent property which implements an event handler signalled to paint the background for an image. OnPaintBackground is signalled from the Paint method using the Canvas and DestRect for the image as arguments. The event occurs immediately prior to the image being drawn using its canvas handle.

Implements a graphic image placed on a form, and usually loaded from a picture file.

TImage is a TCustomImage descendent which implements a lightweight and fast class used to display a graphic image using one of the image formats supported in the LCL. This includes:

- Bitmap
- Pixmap
- PNG
- JPEG
- GIF
- TIFF
- Icon

Use the Picture property to assign, load or save an image using one of the supported formats.

Use the Canvas property to render the graphic image in Picture, or to perform custom drawing operations.

Use properties in the class instance to control how the image is rendered, including: AntialiasingMode, Center, Stretch, Transparent, and Proportional.

TImage inherits most of its properties from its ancestors, TCustomImage, TGraphicControl and TControl

Use TImageList when a list of images with scaling capabilities is needed.

TGraphicControl TPicture TGraphic TCanvas TImageList
TBevelStyle
is an enumerated type with bevel style values: lowered or raised.
Draws the bevel so it appears lower than the surface for the control.
Draws the bevel so it appears highter than the surface for the control.
TBevelShape
is an enumerated type for shapes used in a bevel.

TBevelShape is an enumerated type representing the shapes available for a bevel.

- bsBox
- bsFrame
- bsTopLine
- bsBottomLine
- bsLeftLine
- bsRightLine

Uses a raised or lowered box for the bevel.
Uses a raised or lowered outline around a control.
Draws a solid line at the top of a control.
Draws a solid line at the bottom of a control.
Draws a solid line on the left edge of a control.
Draws a solid line on the right edge of a control.
Draws an empty space as the bevel around a control.
A bevel placed around the edge of buttons and other components.

The appearance of the Bevel is governed by and .

Sets the value for the Style property.
New value for the property.
Sets the value for the Shape property.
New value for the property.
Gets the default size for new instances of the class.

GetControlClassDefaultSize is an overridden TSize class function used to get the default size for new instances of the class. GetControlClassDefaultSize sets the dimensions in the return value to 50 pixels x 50 pixels.

TControl.GetControlClassDefaultSize
Default size for a new instance of the class.
Handles paint requests received from the parent control.

Paint is an overridden procedure used to perform paint requests received by the parent control.

Paint checks the value in Style to determine the Pen colors used to draw the bevel. The Shape property determines the drawing primitives used to render the bevel to its Canvas.

No actions are performed in the method when Shape contains the value bsSpacer.

Paint calls the inherited method to trigger the OnPaint event handler (when assigned).

TGraphicControl.Canvas TGraphicControl.Paint TGraphicControl.OnPaint
Constructor for the class instance.

Create is the overridden constructor for TBevel. Create calls the inherited Create method, and sets the initial values used in the ControlStyle, Style, Shape, and Bounds properties.

ControlStyle
  Removes csSetCaption and csOpaque from existing values in ControlStyle.
Style
  Set to the value bsLowered.
Shape
  Set to the value bsBox.
Bounds
  Calls SetInitialBounds to store the values from GetControlClassDefaultSize in Bounds.

TGraphicControl.Create
Owner of the class instance.
Destructor for the class instance.
Calls the inherited destructor.
TGraphicControl.Destroy
Copies property values from Source to the current class instance.

Assign copies the contents of Source to Self, if the classes of the destination and source classes are compatible.

The TPersistent implementation of Assign does nothing but call the AssignTo method for the source. This means that if the destination class does not know how to assign the contents of the source class, the source class instance is asked to assign itself to the destination class. This means that it is necessary to implement only one of the two methods so that two classes can be assigned to one another.

In general, a statement of the form:

Destination:=Source;

(where Destination and Source are classes) does not achieve the same as a statement of the form.

Destination.Assign(Source);

After the former statement, both Source and Destination will point to the same object. The latter statement will copy the contents of the Source class to the Destination class.

TPersistent
Shape
- whether a box, a frame or a line along one of the edges.

Shape is a TBevelShape property which indicates the shape drawn as the bevel on the control. The default value for the property is bsBox, and causes a simple box to be drawn to represent the bevel. Changing the value for the property causes the control to be redrawn.

Use Style to indicate whether the shape is drawn as a raised or lowered area on the control surface.

Shape and Style are used in the Paint method to draw the control on its Canvas.

Indicates whether the bevel is drawn using a raised or a lowered style.

Style is a TBevelStyle property which indicates whether the bevel is drawn as a raised or a lowered area on the control surface. The default value for the property is bsLowered. Changing the value for the property causes the control to be redrawn.

Shape and Style are used in the Paint method to draw the control on its Canvas.

The relief in Style is achieved by drawing the opposite edges of the bevel Shape using contrasting colors. bsLowered uses cl3DHighlight and cl3DShadow for the color combination. bsRaised uses the same colors - but on the opposite edges.

TBevelStyle
Makes the control visible or hidden.

The Visible property represents the ability to see a visual control. If Visible is True the control is shown, otherwise it is hidden. Calling Show sets Visible to True. Setting Visible to False is equivalent to calling Hide method.

The Visible property does not depend on control's parent visibility. Use the IsVisible method to consider this and get the real visibility for the control.
TControl.IsVisible TControl.Hide TControl.Show
TColumnLayout
is an enumerated type which determines the layout direction used to arranged data in columns.

TColumnLayout is an enumerated type which determines the layout direction used to arranged data in columns. TColumnLayout is the type used to implement the ColumnLayout property in TCustomRadioGroup and TCustomCheckGroup.

Items are arranged horizontally, and advances vertically.
Items are arranged vertically, and advances horizontally.
TCustomRadioGroup
is the base type for TRadioGroup.

A group of related but mutually exclusive radio buttons, selectable by the user.

This class defines Items, where the captions of the individual radio boxes are stored, Rows and Columns for arranging the radio boxes. The ColumnLayout property is used to determine whether the data are arranged down the columns first, or across the rows first.

Performs actions needed when a radio button in the group is clicked.

Clicked is a procedure used to perform actions needed when a radio button in the group is clicked. Clicked calls the CheckItemIndexChanged method to update the state for the radio buttons in the group, and to signal the OnClicked and OnSelection event handlers (when assigned).

Clicked is assigned to the OnClick event handler for each TRadioButton in the group. Use the Items property to specify the radio buttons required for the grouped control.

TRadioButton TRadioButton.OnClick
Object instance for the event notification.
Implements the OnEnter event handler assigned to radio buttons in the group.
Implements the OnExit event handler assigned to radio buttons in the group.
Performs actions needed to handle key down messages for radio buttons in the group.

ItemKeyDown handles the following unshifted virtual key codes:

VK_LEFT
  Moves the selection to the prior radio button, with wrapping.
VK_RIGHT
  Moves the selection to the next radio button, with wrapping.
VK_UP
  Moves the selection to the radio button in the prior row, with wrapping.
VK_DOWN
  Moves the selection to the radio button in the next row, with wrapping.

If Shift contains a key modifier, or Key has not been handled, the KeyDown method from the ancestor class is called to handle the values in Key and Shift.

TWinControl.KeyDown
Handles key up messages for radio buttons in the group.

Calls the KeyUp method in the ancestor class to handle the values in Key and Shift.

Handles key press characters for radio buttons in the group.

Calls the KeyPress method from the ancestor class to handle the character value in Key.

Handles UTF-8 key press characters for radio buttons in the group.

Calls the OnUTF8KeyPress method in the ancestor class to handle the UTF-8-encoded character in UTF8Key.

Implements the OnResize event handler assigned to radio buttons in the group.
ItemResize
is an empty implementation in the current LCL version.
Sets the value for the AutoFill property.
New value for the property.
Sets the value for the ColumnLayout property.
New value for the property.
Updates the number of radio buttons displayed on each line based on the layout policy for child controls.
Adds or removes radio buttons to match the names defined in Items.
Ensures that checked radio buttons have their TabStop property set to True.
Calls the UpdateItems method to add or remove radio buttons for the grouped control.
Updates the radio buttons and the number of radio buttons per line for the control.
UpdateRadioButtonStates
including implementing any pending changes.

Updates the value in ItemIndex, and the tabs stop settings for all checked radio buttons in the control. ItemIndex is set to -1 when none of the radio buttons in the control have their Checked property set to True.

Reads the values for the control and checks whether ItemIndex is valid.

ReadState is used when the component is read using the LCL component streaming mechanism. ReadState ensures that ItemIndex contains a value that is valid for the defined Items in the grouped control.

TComponent
TFiler instance used to read the values for the control.
Sets the value for the Items property.
New value for the property.
Sets the value for the Columns property.
New value for the property.
Sets the value for the ItemIndex property.
New value for the property.
Gets the value for the ItemIndex property.
Value for the property.
CheckItemIndexChanged
- find out if the index for an item has changes.
Constructor for the class instance.

Create is the constructor for TCustomRadioGroup.It calls the inherited Create method, then sets the list of radio buttons, and initializes layout and sizing properties.

TCustomGroupBox.Create
Owner of the class instance.
Destructor for the class instance.

Destroy is the destructor for TCustomRadioGroup. It frees the Items and radio buttons allocated in the class, and calls the inherited Destroy method.

TWinControl.Destroy
Indicates if modification of the RadioGroup is permitted.

CanModify is a Boolean function which indicates if modification of the RadioGroup is permitted. CanModify always returns True in TCustomRadioGroup.

True when the control can be modified.
Flips the horizontal display order for child controls.
FlipChildren is an empty implementation in TCustomRadioGroup.
True if all descendent child controls are affected in the method.
Indicates the number of rows in which Items (radio buttons) are held.

Rows is an Integer function which returns the number of rows needed to represents the radio buttons defined in the grouped control. The return value is the result of dividing the total number of Items by the number of Columns. The return value is zero (0) when no Items have been defined in the control.

Number of rows.
Indicates if radio buttons are resized to fill the available space in the control.

AutoFill is a Boolean property which indicates whether child controls (radio buttons) are resized to fill the available space in the control. When AutoFill is set to True, child controls are resized by setting the EnlargeHorizontal and EnlargeVertical properties in ChildSizing to the value crsHomogenousChildResize. When AutoFill is set to False, the properties in ChildSizing are set to the value crsAnchorAligning.

DisableAlign
is called on entry to the method, and EnableAlign is called prior to exiting from the method.

AutoFill is set to True in the Create constructor.

The ordinal position in Items for the selected radio button in the group.

ItemIndex is an Integer property with the ordinal position for the selected radio button in the group. It refers to the position in Items with the caption for the radio button. The default value for the property is -1, and indicates that a radio button is not selected for the group.

ItemIndex must be in the range -1..Items.Count-1. An Exception is raised with the message in rsIndexOutOfBounds if an invalid value is used.

When the value for the property is changed, the OnClick event handler is signalled (when assigned). In addition, the OnSelectionChanged is signalled (when assigned). Both events occur even if the Handle has not been allocated in the widgetset class. This is Delphi compatible.

Use the OnItemEnter and OnItemExit event handlers to perform actions when the focus or selection for a radio button is changed, as opposed to a change in the properties for the group control.

Some widgetsets do not allow a radio button group to be unselected, or have no selected radio button. For this reason, a hidden radio button exists in TCustomRadioGroup and is selected when ItemIndex is set to -1.
Contains the captions for the radio button displayed in the control.

Items is a TStrings property which contains the captions for the radio buttons displayed in the grouped control. Changing the value in Items causes the UpdateItems and UpdateControlsPerLine methods to be called to add or remove radio buttons (when needed) and to adjust Rows for the number of Columns in the control.

Number of columns used to display radio buttons in the control.

Columns is an Integer property that indicates the number of columns used to display the radio buttons in the control. Columns must contain a positive non-zero value; use of an invalid value causes an Exception to be raised.

Changing the value in Columns causes the UpdateControlsPerLine to be called.

The default value for the property is 1.

Raises an exception when the property value is less than 1. Raised with the message 'TCustomRadioGroup: Columns must be >= 1'.
Fill direction for columns on the grouped control.

ColumnLayout is a TColumnLayout property which indicates the direction used to fill columns in the group control. The default value for the property is clHorizontalThenVertical, and causes columns to filled horizontally before advancing to the next row.

Use Columns to specify the number of columns displayed for the Items on the grouped control.

Event called when the selected item is changed.

OnClick is different from the usual event TControl.OnClick. Instead of occurring on a mouse click on the control, this event is occurs when the currently selected item changes. It will not occur if a click does not make the selection change, will not occur upon clicking a already selected item and will occur if one changes the selection via the keyboard. It also occurs when the item is changed programmatically. This is done for Delphi compatibility.

Note that Lazarus also offers another event for the same task with a better name: see OnSelectionChanged for more details.

TControl.OnClick
Event handler signalled when a radio button in the group receives focus.

OnItemEnter is a TNotifyEvent property that implements the event handler signalled when a radio button in the group receives focus. It occurs when the value in ItemIndex has been changed. An application must implement and assign an object procedure to the property to respond to the event notification. The Sender argument contains the radio button which is selected in the control.

OnItemEnter is signalled (when assigned) from the ItemEnter method.

OnItemEnter was added in LCL version 2.2, and should be used in place of the OnEnter event handler. This change is Delphi compatible.
Added in LCL version 2.2.0.
TRadioButton.OnEnter
Event handler signalled when a radio button in the group loses focus.

OnItemExit is a TNotifyEvent property which implements an event handler signalled when a radio button in the group loses focus. It occurs when the value in ItemIndex is changed. The Sender argument contains the radio button which has been de-selected in the control. An application must implement and assign an object procedure to the property to respond to the event notification.

OnItemExit is signalled from the ItemExit method (when assigned).

OnItemExit was added in LCL version 2.2, and should be used in place of the OnExit event handler. This change is Delphi compatible.
Added in LCL version 2.2.0.
TRadioButton.OnExit
Event called when the selected item changes.

This event was introduced in Lazarus 0.9.31, and is called when the selected item is changed. It is triggered when changed using the mouse or the keyboard, and is triggered when the selected item is changed programmatically.

Introduced in Lazarus 0.9.31
TRadioGroup
is a group of related but mutually exclusive radio buttons, requiring the user to select one of a set of alternatives.

TRadioGroup: A group of related but mutually exclusive radio buttons, requiring the user to select one of a set of alternatives. As one button becomes selected, the remaining buttons in the group become automatically deselected.

To Use this control, place it in the required position on the form, then in the Object Inspector select Items and click on the ellipsis (...) to open the string editor. Type in the captions to accompany each check box, then close the string editor and you will see a series of Radio Boxes with their captions displayed beside them. (Note - unlike TCheckGroup, there is no special RadioGroup editor).

Inherits properties from TCustomRadioGroup and TCustomGroupBox.

TRadioGroup behaves differently from a group of TRadioButton controls placed arbitrarily around a form.

In the case of TRadioButton, the mutual exclusivity is a feature that applies to any RadioButton anywhere in the Form, and the RadioButtons can be rearranged in any order or placed anywhere within the containing Form, while in TRadioGroup the exclusivity applies only to buttons within the Group, which are ordered strictly according to their ItemIndex within the Items stringlist.

TRadioButton is an entity in itself, with a number of additional properties, whereas the buttons within TRadioGroup are not separate entities, but rather are simply entries in a list of strings, each of which is associated with the on-screen image of a RadioButton.

The example shows the difference between the use of TRadioButton and TRadioGroup.

TRadioButton How To Use Standard Controls
Items
- a string list containing the captions of the radio boxes.

Items - a string list containing the captions of the radio boxes.

Use the String List editor, opened by selecting Items and the ellipsis (...) in the Object Inspector, to insert the captions for the radio boxes, and determine their order and layout using the Rows, Columns and ColumnLayout properties.

TCheckGroupClicked
specifies a generic event handler method for a click in a check group.
Object generating the event notification.
Ordinal position for the checkbox Item clicked in the control.
TCustomCheckGroup
is the base type for TCheckGroup.

TCustomCheckGroup is the base type for TCheckGroup. This class defines Items, where the captions for individual check boxes are stored, Rows and Columns for arranging the check boxes, and ColumnLayout to determine whether the data are arranged down the columns first, or across the rows first.

TCustomGroupBox
Gets the value for the indexed Checked property.
Value for the property.
Ordinal position for the check box examined in the method.
Gets the value for the indexed CheckEnabled property.
Value for the property.
Ordinal position for the check box examined in the method.
Performs actions needed when a check box in the grouped control is clicked.

Clicked is a procedure which performs actions needed when a check box in the grouped control is clicked. Sender contains the TCheckBox instance generating the click notification. Clicked checks the internal list of check boxes to find the ordinal position for the control in Sender, and calls DoClick to trigger the OnItemClick event handler.

No actions are performed in the method if Sender is not found in the list of check boxes for the grouped control.

Clicked is used as the OnClick event handler in the TCheckBox instances created in UpdateItems.

TCheckBox.OnClick
Check box generating the click notification.
Signals the OnItemClick event handler when a check box in the control is clicked.
Ordinal position for the check box clicked in the grouped control.
Implements the OnKeyDown event handler assigned to checkboxes in the control.
Object generating the event notification.
Key examined in the method.
Key modifier examined in the method.
Implements the OnKeyUp event handler assigned to checkboxes in the control.
Object generating the event notification.
Key examined in the method.
Key modifier examined in the method.
Implements the OnKeyPress event handler assigned to checkboxes in the control.
Object generating the event notification.
Key examined in the method.
Implements the OnUTF8KeyPress event handler assigned to checkboxes in the control.
Object generating the event notification.
UTF code point examined in the method.
Raises an exception when the specified Index is not valid for the number of Items in the control.
Ordinal position examined in the method.
Sets the value for the AutoFill property.
New value for the property.
Sets the value for the indexed Checked property.
Ordinal position for the checkbox updated in the method.
New value for the checkbox.
Sets the value for the indexed CheckEnabled property.
Ordinal position for the checkbox updated in the method.
New value for the enable state in the checkbox.
Sets the value for the ColumnLayout property.
New value for the property.
Adds or removes checkboxes for the Items defined for the control.
Updates the ChildSizing property to use the number of Columns defined in the control.
Updates the control when the Items property is changed.

Calls UpdateItems to refresh the checkboxes displayed for the grouped edit control.

Updates both the Items and the number of controls per line.

Calls OwnerFormDesignerModified to notify the owner form when the control has been modified at design-time.

OwnerFormDesignerModified
Sets the value for the Items property.

Calls the Assign method in Items to store the specified Value. Updates the group by re-creating the check-box controls needed for the values in Items. Re-displays the control using the required number of Columns.

New value for the property.
Sets the value for the Columns property.

Raises an Exception if the new property value is less than 1. At minimum, a single column is required.

Re-displays the control using the required number of Columns.

New value for the property.
DefineProperties
- overrides the method inherited from TComponent, defines the top, left properties.
TComponent
TFiler instance used to read and write the content for the control.
Reads LCL component streaming data from a stream.
TStream instance with values read in the method.
Writes LCL component streaming data to a stream.
TStream instance where values are written in the method.
Performs actions needed when the component has finished loading from the LCL component streaming mechanism.

Overridden in TCustomCheckGroup to call the UpdateItems method when the component has finished loading from the LCL streaming mechanism.

TComponent
Constructor for the class instance.

Create is the overridden constructor for TCustomCheckGroup. It calls the inherited Create method. It also sets styles, creates lists, and initializes sizing and layout properties in the control.

TCustomGroupBox.Create
Owner of the class instance.
Destructor for the class instance.

Destroy is the overridden destructor for TCustomCheckGroup. It frees items and check boxes in the control, and calls the inherited Destroy method.

TWinControl.Destroy
Flips child controls horizontally.

Child controls arranged in left-to-right order appear in right-to-left order after flipping. Any anchors are adjusted accordingly.

FlipChildren is an empty implementation in TCustomCheckGroup; no flipping is performed for the control.

TWinControl.FlipChildren
True all child controls and their descendants are flipped.
Number of rows need to display Items (check boxes ) defined in the control.

Rows is an Integer function which returns the number of rows needed to represents the check boxes defined in Items. The return value is the result of dividing the total number of Items by the number of Columns. The return value is zero (0) when no Items have been defined in the control.

The number of rows used for the Items.
Indicates if check boxes are resized to fill the available space in the control.

AutoFill is a Boolean property which indicates whether child controls (check boxes) are resized to fill the available space in the control. When AutoFill is set to True, child controls are resized by setting the EnlargeHorizontal and EnlargeVertical properties in ChildSizing to the value crsHomogenousChildResize. When AutoFill is set to False, the properties in ChildSizing are set to the value crsAnchorAligning.

DisableAlign
is called on entry to the method, and EnableAlign is called prior to exiting from the method.

AutoFill is set to True in the Create constructor.

String list with the captions for the check boxes in the grouped edit control.

Items is a TStrings property which stores the captions for the check boxes on the grouped edit control. Items also determines the number of TCheckBox controls created and displayed for the control. Setting a new value for the property causes the list of check boxes and the columns in the control to be updated.

When the class instance is created, a TCheckGroupStringList instance is assigned to the member variable for the Items property. The implementation type contains a reference to the class instance, and provides access to values in Checked and CheckEnabled when adding or removing entries in Items.

Whether an individual entry in the list is Checked.

Checked is an indexed Boolean property used to read or write the state for a check box at the ordinal position specified in Index.

Ordinal position in Items for the requested check box.
CheckEnabled
- whether a given (indexed) entry in the list is allowed to be checked.

CheckEnabled is an indexed Boolean property used to maintain the Enabled property for the check box at the position specified in Index. Index contains the ordinal position in the list of check boxes for the control, and must be in the range 0..Items.Count-1. An exception is raised when Index is not within the required range.

Use the Checked property to determine if a check box has its Checked property set to True.

Use Items to maintain the Captions for the check boxes displayed in the grouped edit control.

Ordinal position for the check box examined in the method.
Columns
is the number of columns in which the Items (check boxes) are arranged.

Columns is an Integer property which specifies the number of columns used to display the check boxes for the grouped edit control. Changing the value in the property causes the UpdateControlsPerLine method to be called. The new value for the property must be a positive non-zero value or an exception is raised.

The value in Columns is used as the number of controls displayed per line in the ChildSizing property.

The default value for the property is 1.

TWinControl.ChildSizing
ColumnLayout
HorizontalThenVertical
or vice versa.

ColumnLayout is a TColumnLayout property which specifies the layout strategy used when rendering the Items in the grouped edit control. The default value for the property is clHorizontalThenVertical, and causes check boxes to be drawn horizontally for the required number of Columns before advancing.

Assigning a new value for the property causes ChildSizing to be updated to use the corresponding value in its Layout property.

TWinControl.ChildSizing
OnItemClick
- event handler signalled when the mouse is clicked on one of the Items in the control.

OnItemClick is a TCheckGroupClicked property used as the event handler signalled when a check box is clicked for the grouped edit control. Applications must implement and assign an object procedure using the signature in TCheckGroupClicked to respond to the input event.

TCheckGroup
is a group of Check Boxes physically and logically grouped together on a form.

TCheckGroup is a group of Check Boxes physically and logically grouped together on a form.

To use this control, place it in the required position on the form, then either right-click on the control to see the pop-up CheckGroup editor, or in the Object Inspector select Items and click on the ellipsis (...) to open the string editor. In either case, type in the captions to accompany each check box, then close the string or CheckGroup editor and you will see a series of boxes with their captions displayed beside them.

Inherits properties from TCustomCheckGroup and TCustomGroupBox.

TRadioGroup How To Use Standard Controls
String which appears at the top of the grouped edit control.

Caption is the string which appears as a caption at the top of the grouped edit control to describe the function of the Check Group as a whole.

Items
- a string list containing the captions of the check boxes.

Items is a string list containing the captions for the check boxes displayed in the grouped edit control.

Use the String List editor or the CheckGroup editor (opened by right-clicking on the control in the Form) to insert the captions for the check boxes, and determine their order and layout.

Implements a label bound to another control.

TBoundLabel is a TCustomLabel descendant which implements a label bound to another control. TBoundLabel is the type used to implement the EditLabel property in TCustomLabeledEdit and TLabeledEdit.

Use Caption to assign the text displayed in the label. Use Layout to specify the text alignment used for the Caption value.

The FocusControl property specifies the control given focus when a Dialog accelerator key or other input event in the class is handled. Use one of the AnchorSide* properties to specify the edge anchored to the FocusControl.

Other than a constructor, the class does not have any new methods or event handlers.

Constructor for the class instance.
Create
is the constructor for TBoundLabel. It calls the inherited Create method, and makes itself a SubComponent of the Owner. The Caption in the control is changed to the Name in the Owner.
TCustomLabel.Create
Owner for the class instance.
FocusControl
is the control to receive focus when the label is activated.

FocusControl also receives key messages in the DialogChar method.

TLabelPosition
is an enumerated type with values that represent the position of a label relative to an associated control: i. e. above, below, left, or right.
Label is displayed above the control.
Label is displayed below the control.
Label is displayed to the left of the control.
Label is displayed to the right of the control.
Defines a edit control with a label bound to the control.

TCustomLabeledEdit : The base type for LabeledEdit.

Note particularly the EditLabel property (see TBoundLabel), which contains the label attached to the Edit control.

TCustomEdit TCustomLabel
Sets the value for the LabelPosition property.
New value for the property.
Sets the value for the LabelSpacing property.
New value for the property.
Sets the value for the Parent property.

SetParent is overridden in TCustomLabeledEdit to ensure that the EditLabel for the control is properly aligned after the value in Parent is changed. Calls DoPositionLabel to set the label visibility and position the label using the value in LabelPosition and LabelSpacing.

TControl.Parent TControl.SetParent
New parent for the control.
Sets the value for the Name property and the Caption in the label.

SetName is overridden in TCustomLabeledEdit to assign the new value for the property to the Caption in EditLabel at design-time. SetName calls the inherited method prior to exit.

TControl.SetName
New value for the property.
Performs actions needed when the component has finished loading in the LCL streaming mechanism.

Loaded is overridden in TCustomLabeledEdit to position the EditLabel by calling the DoPositionLabel method. Loaded calls the inherited method.

TComponent
DoPositionLabel
- perform the code for positioning the label.

DoPositionLabel is a procedure used to place the EditLabel relative to the companion control. No actions are performed in the method when EditLabel is unassigned (contains Nil).

DoPositionLabel ensures that DisableAlign is called in the Parent control (when assigned). EnableAlign is called for the Parent control prior to exiting from the method.

DoPositionLabel updates EditLabel to use the values assigned to the Parent and Visibility properties. The values in LabelPosition and LabelSpacing are used to determine the anchoring to the companion control applied to EditLabel.

TControl.Visible TWinControl.DisableAlign TWinControl.EnableAlign TControl.Parent
Handles a notification when a component is added to or removed from the control.

Notification is overridden in TCustomLabeledEdit to ensure that a reference to the EditLabel property is released when Operation contains the value opRemove. Notification calls the inherited method.

TControl.Notification
Component for the event notification.
Operation for the event notification.
Handles the CM_BIDIMODECHANGED control message for the control.

Ensures that an assigned EditLabel uses the value stored in the BiDiMode property. Calls DoPositionLabel to update the control layout and position, and calls Invalidate to force the control to be redrawn.

Calls the inherited CMBiDiModeChanged method.

TWinControl.Invalidate TWinControl.CMBiDiModeChanged TControl.BiDiMode
Message handled in the method.
CreateInternalLabel
- method for internally creating label.

CreateInternalLabel is a method used to allocate resources for the EditLabel property in the class instance. TCustomLabeledEdit creates the TBoundLabel class instance used in EditLabel, and updates its ControlStyle property to prevent selection at design-time (csNoDesignSelectable). The current class instance is used as the FocusControl in EditLabel.

No actions are performed in the method if EditLabel has already been assigned in the class instance.

CreateInternalLabel is used in the implementation of the Create constructor.

Create
- constructor for TCustomLabeledEdit: calls inherited Create then sets initial position and label spacing.
TCustomEdit.Create TBoundLabel.Create
Owner of the class instance.
EditLabel
- the label attached to the edit box.
LabelPosition
- whether above, below, to the left or to the right of the Edit box.
LabelSpacing
- the distance between the Label and the Edit box.
Labelled Edit is an Edit Box with a permanently attached Label.

TLabeledEditis an Edit Box with a permanently attached Label.

Saves time and effort over placing separate Label and Edit Box on Form. The properties are described in the parent component, TCustomLabeledEdit from which most of the properties are inherited.

TCustomEdit TBoundLabel
Alias for the TBevelCut type.

TPanelBevel is an alias to the TBevelCut type. TPanelBevel is the type used to implement the BevelInner and BevelOuter properties in TCustomPanel.

TBevelCut
Defines the range of values allowed in a bevel width.

TBevelWidth is an Integer range type which defines the range of values allowed in properties using the type. TBevelWidth is the type used to implement the BevelWidth property in TCustomPanel.

The base class for a general container which can hold other objects. It has a customizable border and a central text.

TCustomPanelis the base type for TPanel.

A Panel is a defined rectangular area on a form into which other components can be placed to group them functionally and geographically. TCustomPanel defines the positioning and beveling properties of any descendent classes, and provides methods for painting and writing text to the panel.

Draws a bevel using the color and width defined for the panel.

PaintBevel is a procedure used to draw the bevel for the panel using the values in the BevelColor and BevelWidth properties. ARect is the rectangle with the coordinates where the bevel is drawn. ABevel contains the style used to draw the bevel.

No actions are performed in the method when ABevel contains the value bvNone.

PaintBevel uses the Canvas for the control as the target for the drawing operation. The Frame3D method in the Canvas is used to draw the bevel with the required color, width, and style for the panel.

PaintBevel is used in the implementation of the Paint method to draw using both the BevelInner and BevelOuter styles.

TCustomControl.Canvas
Sets the value for the Alignment property.
New value for the property.
Sets the value for the BevelColor property.
New value for the property.
Sets the value for the BevelInner property.
New value for the property.
Sets the value for the BevelOuter property.
New value for the property.
Sets the value for the BevelWidth property.
New value for the property.
Sets the value for the WordWrap property.
New value for the property.
Adjusts the specified rectangle to account for border and bevels used in the control.

AdjustClientRect is an overridden procedure used to adjust the drawing rectangle in ARect to account for borders and bevels used on the panel. AdjustClientRect calls the inherited method, and calculates the number of pixels required for the settings in BorderWidth, BeveInner, and BevelOuter. AdjustClientRect calls InflateRect to adjust ARect by the calcluated border and bevel widths.

AdjustClientRect is called when the control is autosize or aligned.

TWinControl.BorderWidth TWinControl.AdjustClientRect
Drawing rectangle adjusted in the method.
Gets the size used for new instance of the class type.

GetControlClassDefaultSize is overridden to provide the default size for new instances of the class type. The return value is a TSize type which contains the dimensions for the new control. The CX member contains the Width for the panel, and defaults to 170 pixels. The CY member contains the Height for the panel, and defaults to 50 pixels.

TControl.GetControlClassDefaultSize
TSize value with the default dimensions for new class instances.
Performs actions needed when the component has finished loading in the LCL streaming mechanism.

Loaded is an overridden procedure used to perform actions needed when the component has finished loading in the LCL component streaming mechanism. Loaded calls the inherited method, and calls UpdateParentColorChange to adjust the ControlStyle when ParentColor is in use.

TControl.ControlStyle TComponent
Stores the specified value as the Caption for the control.

RealSetText is an overridden procedure used to store the specified value as the Caption for the control. RealSetText calls the inherited method to store the text, and then calls the Invalidate method to repaint the control.

TControl.RealSetText
New text value used as the caption for the control.
Paints the panel including the bevels and caption defined for the control.

Paint is an overridden procedure which paints the panel including the bevels and caption defined for the control. Paint calls GetClientRect to get the rectangle used to draw the control. PaintBevel is called to draw both the inner and outer bevels for the control (when used).

When Caption contains a String value (other than an empty string), the Canvas for the control is used to render the text. Values in the BiDiMode, WordWrap, and Layout properties are applied to the text as needed.

Paint calls the inherited Paint method prior to exit.

TCustomControl.Paint
Sets the background used for the parent control.

SetParentBackground is an overridden procedure used to the set the background used for the parent control. SetParentBackground ensures that the ControlStyle property is updated to include or omit the value csOpaque. When AParentBackground contains True, the value is excluded from ControlStyle. When AParentBackground contains False, the value is included in ControlStyle.

SetParentBackground calls the inherited method prior to exit.

TWinControl.SetParentBackground
When True, the panel is drawn with transparency.
Updates the control to reflect changes to the ParentColor property.

UpdateParentColorChange updates the control to reflect changes to the ParentColor property.

When ParentColor is True, the parent color is used, so the value csOpaque is excluded from the ControlStyle property. Otherwise, Parent color is not used, and the value csOpaque is included in the ControlStyle property.

UpdateParentColorChange is called from the Loaded method when the component has finished loading using the LCL component streaming mechanism. It is also called from the CMParentColorChanged method when the change message is handled for the control.

Indicates if the Caption can be word wrapped when painted.

WordWrap is a Boolean property which indicates if the text in the Caption property can be word wrapped into multiple lines when painting the control. The default value for the property is False, and indicates that word wrapping is not used for the caption. Changing the value in WordWrap causes the Invalidate method to be called to repaint the control.

WordWrap is used in the Paint method to initialize properties in the TTextStyle argument used to render the text rectangle for the caption to its Canvas.

TTextStyle TControl.Invalidate
Constructor for the class instance.

Create is the constructor for TCustomPanel. It calls the inherited Create method, and sets the initial style, bevel, color, alignment and bounds for the control.

TCustomControl.Create
Owner of the class instance.
Specifies the placement of the control inside its Parent.

Align is a TAlign property which specifies how the control is aligned to its parent control. The default value for the property is alNone.

alNone
  The control is not aligned. It uses it Top, Left, Height, and Width to place the control in the parent.
alTop
  Aligns the control to the top of the parent control, and adjusts it Width to fill the parent control.
alBottom
  Aligns the control to the bottom of the parent control, and adjusts its Width to fill the parent control.
alLeft
  Aligns the control to the left edge of the parent control, and adjusts its Height to fill the parent control.
alRight
  Aligns the control to the right edge of the parent control, and adjusts its Height to fill the parent control.
alClient
  Aligns the control fill the unused Height and Width for the parent control.
alCustom
  Aligns the control by calling the OnAlignInsertBefore or OnAlignPosition event handlers in the parent control.

Alignment
- whether text is left or right justified, or centered.

Alignment is a TAlignment property that indicates how the text (or Caption) is aligned on the panel. The default value for the property is taCenter, and causes text to be aligned to the center of the panel. Changing the value in Alignment causes the Invalidate method to be called to repaint the control.

TControl.Invalidate TCustomEdit.Alignment TAlignment
Color used to draw bevels for the panel.

BevelColor is a TColor property that specifies the color used to draw bevels for the panel. BevelColor is used in the PaintBevel method; it is passed as an argument to Canvas drawing routines when BevelColor contains a value other than clDefault.

The default value for the property is clDefault. Changing the value in BevelColor causes the Invalidate to be called to repaint the control.

TWinControl.Invalidate
BevelInner
- determines the nature of the Inner Bevel of the panel (whether raised, lowered etc)
BevelOuter
- determines the nature of the Outer Bevel of the panel (whether raised, lowered etc)
BevelWidth
- the Width of the panel's bevel in pixels.
Contains the background color for the panel.

Color is a TColor property with the background color for the panel. It sets the default value for the property.

The default value in Color is the same as the value in the parent window Color property. If the color is clDefault , the result will need to be resolved using the GetDefaultColor method. Convenience routines which obtain the color by resolving clDefault and ParentColor are also provided in TControl.GetColorResolvingParent and TControl.GetRGBColorResolvingParent.

TControl.Color
FullRepaint
- if True, the panel needs to be fully repainted after each change.

Exists only for Delphi compatibility; it has no effect in LCL.

Indicates if the background from the parent control is used to draw the background for the control.

When ParentBackground is True, the control uses the background from the parent color (including any theme drawing features from ThemeServices).

ParentBackground is used in conjunction with the ControlStyle property. Changing the value in ParentBackground causes the ControlStyle property to be updated to reflect the property setting. When the property is set to True, the value csOpaque is excluded from ControlStyle to allow the default background to be drawn. When the property is set to False, the value csOpaque is included in the ControlStyle property.

The default value for the property is True.

TControl.ControlStyle TWinControl.ParentBackground
Indicates if the control is drawn using the color in the parent control.

When ParentColor is True, the control is drawn using the Color from the parent control. When ParentColor is False, the Color property is used to draw the control.

The default value for the property is True.

Changing the value for the property causes the UpdateParentColorChange method to be executed.

TControl.ParentColor
Enables or disables navigation using the Tab key.

The default value for the property is False in TCustomPanel.

TWinControl.TabStop
Implements a general purpose container which can hold other components.

TPanel is a TCustomPanel descendant which defines a rectangular area on a form into which components can be placed to group them functionally and geographically. TPanel is a general container for other components, and has a customizable border and caption.

Determines whether a DockManager is used for this DockSite.

The default value for the property is True in TPanel.

When UseDockManager is set to True, and DockSite is also set to True, a DockManager is created automatically. When set to False, an existing DockManager is ignored. If you want to use a special DockManager, install it before setting UseDockManager to True.

TWinControl.UseDockManager
Represents the flow styles used in TCustomFlowPanel.

TFlowStyle is an enumerated type which contains values that represent the flow styles available in TCustomFlowPanel. It is the type used to implement the FlowStyle property in TCustomFlowPanel.

Controls flow from left to right, then top to bottom.
Controls flow from right to left, then top to bottom.
Controls flow from left to right, then bottom to top.
Controls flow from right to left, then bottom to top.
Controls flow from top to bottom, then left to right.
Controls flow from bottom to top, then left to right.
Controls flow from top to bottom, then right to left.
Controls flow from bottom to top, then right to left.
Represents the wrapping strategies used in TCustomFlowPanel.

TWrapAfter is an enumerated type with values that specify the wrapping strategy for controls in TCustomFlowPanel.

Automatically wrap when the control exceeds the bounds.
Always wrap after this control.
Try not to wrap after this control, if the control is already at the beginning.
Never wrap after this control.
Implements a collection item for the TFlowPanelControlList collection.

TFlowPanelControl is a TCollectionItem descendant which implements a collection item maintained in TFlowPanelControlList. TFlowPanelControl provides properties and methods need to represent a flowed control in the collection, and provides support for the IObjInspInterface used in the Lazarus Object Inspector.

Sets the value for the Control property.
New value for the property.
Sets the value for the WrapAfter property.
New value for the property.
Gets the value for the DisplayName property.
TCollectionItem.DisplayName
Value for the property.
Sets the value for the Index property.
TCollectionItem.Index
New value for the Index property.
implement persistence in the control.

AssignTo is an overridden method used to implement persistence in the control. AssignTo provides support for storing property values from the current class instance into the Dest argument when it is derived from TFlowPanelControl. Otherwise, the inherited AssignTo method is called.

TPersistent
Persistent object where property values are stored.
Gets the TFlowPanelControlList instance that owns the collection item.
TFlowPanelControlList instance that owns the collection item.
Gets the TCustomFlowPanel instance that owns the collection and its items.
TCustomFlowPanel instance that owns the collection and its items.
Implements the AllowAdd method from the IObjInspInterface interface.
Used by the Lazarus object inspector.
Implements the AllowDelete method from the IObjInspInterface interface.
Used by the Lazarus object inspector.
The associated control to the flow panel control item.
Don't set the Control property manually. It is used internally by the designer.
Determines the wrap policy after this control.
Ordinal position for the flowed control in the TFlowPanelControlList collection.

Index is a published property in TFlowPanelControl. Changing the value in Index causes the owner panel to call its ReAlign method when it is not being loaded, updated, or destroyed.

TWinControl.Realign TCollectionItem.Index TComponent.ComponentState
Implements a collection for TCustomFlowPanel collection items.

TFlowPanelControlList is a TOwnedCollection descendant. TFlowPanelControlList implements the IObjInspInterface interface which allows the collection to be used in the Lazarus Object Inspector.

Gets the value for the indexed Items property.
Value for the property.
Ordinal position in the collection for the requested item.
Sets the value for the indexed Items property.
Ordinal position in the collection for the specified item.
New value for the property.
Gets the owner of the collection as a TCustomFlowPanel instance.
The flow panel which owns the collection and its items.
Adds a TFlowPanelControl instance to the owned collection.
TFlowPanelControl instance created in the method.
Adds the specified control to the Items for the collection.
Control to locate and optionally add in the method.
Position in Items where the control is stored, or -1 to add the item.
Removes the collection item with the specified control.
Control used to locate the collection item deleted in the method.
Constructor for the class instance.
Owner of the class instance.
Gets the ordinal position of the specified control in the list of controls.
Ordinal position in the list for the control.
Control to locate in the list.
Provides indexed access to controls stored in the container.

Items is an indexed TFlowPanelControl property which provides access to the flow panel controls in the container. Items is the default property for the collection.

Use the Add or the AddControl method to add a flow panel control to the collection.

Use RemoveControl to remove a flow panel control from the collection.

Ordinal position for the requested control.
Implements the AllowAdd method in the IObjInspInterface interface.

Used in the Lazarus object inspector.

Implements the AllowDelete method in the IObjInspInterface interface.

Used in the Lazarus object inspector.

The base class for TFlowPanel.
Sets the value for the AutoWrap property.
New value for the property.
Sets the value for the ControlList property.
New value for the property.
Sets the value for the FlowStyle property.
New value for the property.
Sets the value for the FlowLayout property.
New value for the property.
Handles the CM_CONTROLCHANGE message.

Calls DisableAlign prior to adding (inserting) the control in ControlList. Calls ReAlign when the control is added, and calls EnableAlign prior to exit.

The CM_CONTROLCHANGE message is ignored when the component is being loaded using LCL steaming. No actions are performed in the method when csLoading is in the ComponentState property.
Message with parameters examined in the method.
Performs layout and alignment for flowed controls on the panel.

AlignControls is an overridden procedure used to perform layout and alignment for flowed controls on the panel.

AlignControls does NOT call the inherited method.
CalculatePreferredSize is an overridden procedure used to calculate the preferred height and width for the flow panel. CalculatePreferredSize calls the inherited method.
Constructor for the class instance.

Create is the overridden constructor for the class instance, and calls the inherited constructor. Create ensures that resources are allocated for the ControlList property, and sets the default value for AutoWrap to True.

Owner of the class instance.
Destructor for the class instance.

Destroy is the overridden destructor for the class instance. Destroy calls the inherited destructor, and frees resources allocated to the ControlList property.

Gets the ordinal position in ControlList for the specified control.

GetControlIndex is a convenience method used to get the ordinal position in ControlList for the specified TFlowPanelControl. Calls TFlowPanelControlList.IndexOf to get the return value, which can be -1 if AControl is not found in ControlList.

Use SetControlIndex to set the ordinal position in ControlList for the specified flowed control.

TCollectionItem.Index
Position in the control list for the specified control, or -1 when not found.
Flowed control to locate in ControlList.
Sets the Index position in ControlList for the specified control.
Control to locate and update in the list of controls.
Value assigned to the Index property for the specified control.
Determines if controls in TCustomFlowPanel are wrapped.

The default value for the property is True in TFlowPanel.

Collection used to stored TFlowPanelControl instances on the panel.
Contains the flow direction used to position controls on the panel.
Use FlowLayout to set the layout (alignment) for the non-flow coordinate. The default value is tlTop.

In case of horizontal/vertical flow style: tlTop: top/left alignment in row/column tlCenter: center tlBottom: bottom/right.

Implements a container with flowed layout for its controls.

Use TFloatPanel if you need a container with a float layout. The Anchors and Align properties of child controls are ignored. The floating direction is determined with FlowStyle property.

Determines if child controls are automatically wrapped when needed.

The default value for the property is True in TFlowPanel.

Determines whether a DockManager is used for this DockSite.

The default value for the property is True in TFlowPanel.

When UseDockManager is set to True, and DockSite is also set to True, a DockManager is created automatically. When set to False, an existing DockManager is ignored. If you want to use a special DockManager, install it before setting UseDockManager to True.

TWinControl.UseDockManager
TBalloonFlags
enumerated type for flags used in Tray Icon balloons.

TBalloonFlags is an enumerated type with values representing flags used in Tray Icon balloon hints. It is the type used to implement the BalloonFlags property in TCustomTrayIcon.

No icon is displayed on a balloon hint.
Displays an Information icon on a balloon hint.
Displays a Warning icon on a balloon hint.
Displays an Error icon on a balloon hint.
Defines the base class for a multi-platform system tray icon component.

TCustomTrayIcon is the base class for TTrayIcon, a multi-platform system tray icon component. It allows an icon to be displayed in the system tray when the Application or Form is active. TCustomTrayIcon provides properties, methods, and events used to configure, display, and control the tray icon. The component is supported on multiple platforms, but its implementation is platform-specific.

On the Windows platform, the system tray is usually located on the bottom-right corner of the screen, but it can be located on other edges for the physical screen. For other platforms, the position and other features varies according to the window or display manager in use.

Use Icon to set the icon image type displayed for the control. Use Icons to assign a list of images displayed as the animated icon for the control when the Show method is called.

Use BalloonFlags, BalloonHint, BalloonTimeout and BalloonTitle to format and display balloon hints for the tray icon. If balloon hints are not supported for the platform, an internal TPopupNotifier is used to display the Hint for the control.

Use PopUpMenu to set the menu displayed when the icon is right clicked with the mouse.

Assign routines to the event handlers to perform actions needed when the icon is clicked - or when mouse move, up, or down messages are received.

TCustomTrayIcon / TTrayIcon are partially compatible with the Delphi VCL component. It adds an OnPaint event handler which does not exist in Delphi. It omits properties like IconIndex and OnBalloonClick.
Gets the value for the AnimateInterval property.
Value for the AnimateInterval property.
Gets the value for the Canvas property.
Value for the Canvas property.
Prevents the tray icon from being displayed during component streaming.

InternalShow is called when the Show method is executed during LCL component streaming. InternalShow sets a flag to enable delayed display when csLoading is in the ComponentState property. No additional actions are performed in the method during LCL component streaming.

The return value contains the result from the Show method in WidgetSetClass. Visible is updated to reflect the state indicated in the widget set class. The value in Animate is used to enable or disable the animation timer for the class instance.

TLCLComponent.WidgetSetClass TWSCustomTrayIcon
True when the tray icon is enabled and visible.
Sets the value for the Animate property.
New value for the Animate property.
Sets the value for the AnimateInterval property.
New value for the AnimateInterval property.
Sets the value for the Hint property.
New value for the Hint property.
Sets the value for the Icon property.
New value for the Icon property.
Sets the value for the Icons property.
New value for the Icons property.
Sets the value for the PopupMenu property.
New value for the PopUpMenu property.
Sets the value for the Visible property.
New value for the Visible property.
Performs actions needed when the pop-up notifier is closed.

HandleNotifierClose ensures that the internal balloon hint timer for the tray icon is disabled when the pop-up notifier is closed or destroyed. HandleNotifierClose is assigned to the OnClose event handler in the internal TPopupNotifier class instance used in the tray icon.

TPopupNotifier.OnClose
Object instance for the event notification.
Action to perform; not used in the method.
Implements the event handler signalled when the timer in the tray icon has expired.

HandleNotifierTimeout is a procedure which implements an event handler used to disabled the timer and to close the pop-up notifier for the tray icon. HandleNotifierTimeout is used as the OnTimer event handler in the TTimer class instance used in the component.

Object instance for the event notification.
Implements the event handler signalled when the interval for the animation timer has elapsed.

HandleOnAnimateTimer is a procedure used to implement an event handler signalled when the interval for the animation timer has elapsed. HandleOnAnimateTimer retrieves and displays a bitmap stored in the Icons property when the interval for the timer has elapsed. An internal counter is incremented in the handler to indicate the next image used in the animation sequence. The counter is reset to zero (0) when the last bitmap in Icons is used. HandleOnAnimateTimer calls the InternalUpdate method to refresh the widget set class for the tray icon.

HandleOnAnimateTimer is assigned to the OnTImer event handler for the internal TTimer instance used as the animation timer.

Use Animate to control whether animations are displayed for the tray icon.

Use AnimateInterval to specify the number of elapsed milliseconds allowed before the event handler in the animation timer is signalled.

Object instance for the event notification.
Implements an event handler signalled when the Icon is changed for the component.

IconChanged is a procedure which implements an event handler signalled when the Icon is changed for the component. IconChanged ensures that the WidgetSetClass is notified of the change to the tray icon.

No actions are performed in the event handler if a Handle has already been assigned (contains a non-zero value) for the component.

IconChanged is assigned as the OnChange event handler for the Icon property in the constructor for the class instance.

TIcon.OnChange
Object instance for the event notification.
Performs action when a component is added to or removed from the class instance at run-time.

Notification is an overridden procedure used to perform actions when a component is added or removed at run-time. Notification calls the inherited method, and ensures that the PopUpMenu for the tray icon is set to Nil when the component is removed.

TComponent
Component for the notification.
Operation for the notification.
Performs actions needed when the component has finished loading from the LCL streaming mechanism.

Loaded is an overridden procedure used to perform actions needed when the component has finished loading from the LCL streaming mechanism. Loaded calls the inherited method, and calls the InternalShow method to display the tray icon.

TComponent
Operating system Handle for the Tray Icon.

Handle is a public HWND member that represents the operating system handle for the control. Handle has a non-zero value when the widgetset class instance for the control has been allocated. The value in Handle is used (when assigned) in the private IconChanged event handler.

Constructor for the class instance.

Create is the overridden constructor for the class instance, and calls the inherited constructor on entry. If AOwner is not Nil, the new component attempts to insert itself in the list of owned components in the owner class instance.

Creates sets the default values for properties in the class instance, like:

- BalloonTimeout (3000ms or 3 seconds)
- ShowIcon (True)
- BalloonFlags (bfNone)
- Visible (False)

Create allocates resources for members which implement the Icon and Icons properties, and internal TTimer instances used for animated icons and balloon hints. A TPopupNotifier instance is also created for platforms without native support for balloon hint display.

TComponent.Create
Destructor for the class instance.

Destroy is the overridden destructor for the class instance. Destroy calls the Hide method at run-time to ensure that the widgetset class instance is not visible and its animation timer is disabled. It frees resources allocated in the constructor for members in the class instance. Destroy calls the inherited method prior to exit. This allows Free notifications to be performed for ancestor components, and to free child components for the control.

TComponent.Destroy
Removes the icon from the System Tray.

Hide is a Boolean function used to hide the tray icon and to remove it from the tray area in the task bar.

No actions are performed in the method when Visible is set to False, or at design-time, or when the component is loaded from the LCL streaming mechanism.

Hide sets the value in the Visible property to False, and calls the namesake method in the WidgetSetClass. The internal animation timer for the tray icon is also disabled in the method.

The return value is True when the tray icon is successfully hidden. For other conditions, the return value is False.

TComponent.ComponentState
Displays the icon in the System Tray.

Show is a Boolean function used to display the tray icon in the system tray. The return value is True if the control is successfully displayed in the method, or the control is already visible. No additional actions are performed in the method when Visible is already set to True.

The return value is always False at design-time. At run-time, the InternalShow method is called to display the control (with delayed loading) and to set the state for the internal animation timer to the value in Animate.

Show is called when the value for the Visible property is changed to True.

Updates the control for any pending changes.

The behavior of this method depends on the widgetset.It was added to provide a way to update items which either cannot be updated automatically when changed, or would be too inefficient to be updated on each change.

One example of this is the tray icon menu under LCL-Carbon. It is not automatically updated when changes are made to it's associated LCL TPopUpMenu, but changes are updated when InternalUpdate is called. This happens because the tray icon menus are Cocoa menus which don't match the Carbon menus from LCL-Carbon.

Similar things happen in other widgetsets, so InternalUpdate can be expected to update the menu and/or icon of the tray icon, if this is necessary. If such an update is not required, for example because it is automatically updated on each change, then InternalUpdate will simply do nothing, so it is always a safe function to call, regardless of the widgetset.

Displays a balloon hint window near the tray icon.

ShowBalloonHint displays a small balloon-like window near the tray icon. It can be used to send notifications about the status of an action, or notify of a received message or any other event which doesn't require an immediate response.

The ShowBalloonHint method in the widgetset class is called to display the hint window. For platforms which do not provide native balloon hint support, an internal TPopupNotifier is used to display the values in BalloonTitle and BalloonHint. GetPosition is called to determine the coordinates for the balloon hint, and the ShowAtPos method in the pop-up notifier is called to display the values.

The balloon hint window disappears after the BalloonHintTimeout interval has elapsed, or when the user clicks on the close button for the balloon hint.

TPopupNotifier

TODO: Which platforms have native balloon hint support?

Gets the position for the tray icon on the display.

GetPosition is a TPoint function used to get the position of the tray icon on the display. GetPosition calls the namesake method in the WidgetSetClass to get the location for the tray icon. The coordinates in the return value are used to determine the location for a BalloonHint window for the tray icon.

For the Windows platform, an approximate location in the tray area in the Windows taskbar is used. For other platforms, the position is dependent on the window manager or desktop environment. It may also contain an empty rectangle as the position value.

Indicates if animations are displayed on the tray icon.

Animate is a Boolean property that indicates if the tray icon is displayed as an animation.

The default value for the property is False. Set Animate to True to enable the internal animation timer using the interval in AnimateInterval, and to start the animation sequence using the images stored in the Icons property. Setting Animate to True does not enable the animation timer if the control is not Visible.

Use the Icon property to set the TIcon instance displayed when Animate is set to False.

Defines the time interval between updates to the image for the tray icon.

AnimateInterval is a Cardinal property that defines the elapsed time interval between updates to the image displayed on the tray icon. The default value for the property is 1000 (milliseconds), and causes the animation timer to refresh the image on the tray icon every second.

Update the Icons property to contain the bitmap images displayed in the animation sequence.

Set Animate to True to enable the animation timer using the value in AnimateInterval when the control is Visible.

Defines the balloon flag displayed for the tray icon balloon hint.

BalloonFlags is a TBalloonFlags property which identifies an icon displayed for the content in the balloon hint window. BalloonFlags are used when the widget set class displays the balloon hint window for the tray icon. The default value for the property is bfNone. See for more information about the values in the enumeration and their meanings.

The text displayed in the balloon hint window.

BalloonHint is a String property which contains the text displayed in a balloon hint window. It is used along with BalloonTimeout, BalloonTitle, and BalloonFlags in the ShowBalloonHint method. It is different than the value in the Hint property; Hint is used for mouse hover events.

The interval after which the balloon hint disappears.

BalloonTimeout is an Integer property which contains the duration that a balloon hint window is visible before it is closed. The default value for the property is 3000 (milliseconds) or 3 seconds.

The value in BalloonTimeout is assigned as the internal for the internal timer activated when the ShowBalloonHint method is called. Set values in BalloonHint, BalloonTitle, BalloonFlags, and BalloonTimeout prior to calling the ShowBalloonHint method.

Title used for the balloon hint window.

BalloonTitle is a String property which contains the title used for a balloon hint window displayed for the control. BalloonTitle is used - along with BalloonHint, BalloonTimeout, and BalloonFlags - when the ShowBalloonHint method is called.

Canvas for the class instance.

Canvas is a read-only TCanvas property which gets the drawing surface for the tray icon control. The property value contains the TCanvas instance provided by the widgetset class. For some platforms, this is the canvas for the Icon. For others, it is the handle for the system tray class instance.

TCustomTrayIcon does not use Canvas directly in its implementation.

Pop-up menu displayed when right mouse button is clicked over the icon for the control.

PopUpMenu is a TPopupMenu property which contains the menu displayed when the Right mouse button is clicked on the Icon for the class instance. Setting a new value for the property causes the existing pop-up menu instance to be removed from the free notification list for the control. The new pop-up menu instance is added to the free notification list. It is used when the widgetset class instance detects a Right mouse button event over the control.

Use the OnMouseDown, OnMouseMove, or OnMouseUp to implement callbacks for mouse events in the widgetset class.

TPopUpMenu
The Icon or picture that displayed on the tray icon.

Icon is a Icon property with the static icon displayed in the system tray for the control.

Use Icons to assign the bitmap images displayed as an animation sequence when Animate is set to True.

Use ShowIcon to indicate whether the Icon is displayed for the control. This feature is platform-specific. Use the OnPaint event handler and Canvas to perform drawing operations for the tray icon when ShowIcon is set to False.

TIcon
Image list with the bitmaps used for an animated icon.

Icons is a TCustomImageList property with the bitmap images displayed for an animated icon. Icons is used when the Animate property is set to True.

Setting a new value for the property causes the widgetset class to be updated when the control is Visible. The current animation step (or frame) is reset to 0 to prevent an index out-of-bounds exception.

Use Icon to set the single image displayed on the tray icon when Animate is set to False.

TCustomImageList
Hint text displayed when the mouse is hovered over the tray icon.

Hint is a String property with the text displayed when the mouse is hovered over the tray icon in the system tray. Changing the value for the property causes the InternalUpdate method to be called when the control is Visible.

Hint is separate and distinct from the value in BalloonHint, which is displayed (on supported platforms) when the ShowBalloonHint method is called.

Indicates whether the Icon is drawn by the control (in its widgetset class).

ShowIcon is a Boolean property which indicates if the image in Icon is displayed when the control is redrawn. The default value for the property is True, and causes the widgetset class for the control to draw the image in Icon when the control is Visible. When set to False, it is assumed that the OnPaint event handler and Canvas are used to draw the Icon in application code.

The OnPaint event handler is not signalled on the Windows platform.
Indicates if the tray icon is displayed in the system tray.

Visible is a Boolean property which indicates if the control is displayed in the system tray. The default value for the property is False.

The value for the property is updated in methods where the control is displayed or hidden. It is set to True in the private InternalShow method, and to False in the Hide method. Setting a new value for the property causes the Show or Hide method to be called depending on the new property value.

The value in Visible may continue to be False after calling the Show method; it must be successfully displayed by the widgetset class before the property is set to True.
Event handler signalled when a mouse button is single-clicked on the tray icon.

OnClick is a TNotifyEvent property with the event handler signalled when the Left mouse button is single-clicked on the tray icon. An application can implement and assign an object procedure to the event handler to perform any actions needed when the tray icon is clicked.

Use OnDblClick to perform actions needed when the Left mouse button is double-clicked on the tray icon.

When both OnClick and OnDblClick are assigned, OnClick is signalled twice for a mouse double-click event. Once before OnDblClick, and once after OnDblClick.

Use OnMouseUp and OnMouseDown if another mouse button (other than mbLeft), the keyboard modifier like Shift/Ctrl/Alt, or the mouse coordinates must be examined.

Event handler signalled when a mouse button is double-clicked on the tray icon.

OnDblClick is a TNotifyEvent property with the Event handler signalled when the Left mouse button is double-clicked on the tray icon. An application can implement and assign an object procedure to the event handler to perform any actions needed when the tray icon is double-clicked.

Use OnClick to perform actions needed when the Left mouse button is single-clicked on the tray icon.

When both OnClick and OnDblClick are assigned, OnClick is signalled twice for a mouse double-click event. Once before OnDblClick, and once after OnDblClick.

Use OnMouseUp and OnMouseDown if another mouse button (other than mbLeft), the keyboard modifier like Shift/Ctrl/Alt, or the mouse coordinates must be examined.

Event handler signalled when a mouse button down event is detected for the tray icon.

OnMouseDown is a TMouseEvent property with the event handler signalled when a mouse button down event is detected for the tray icon. Arguments passed to the event handler identify:

Sender
  The object for the event notification.
Button
  The mouse button for the event.
Shift
  The state for the Shift / Ctrl / Alt keys.
X and Y
  The current coordinates for the mouse pointer.

An application must implement and assign an object procedure using the signature for the event handler to respond to the notification.

Use OnMouseUp to respond to the mouse up event for a mouse button.

TMouseEvent TMouseButton TShiftState
Event handler signalled when a mouse button up event is detected for the tray icon.

OnMouseUp is a TMouseEvent property with the event handler signalled when a mouse button up event is detected for the tray icon. Arguments passed to the event handler identify:

Sender
  The object for the event notification.
Button
  The mouse button for the event.
Shift
  The state for the Shift / Ctrl / Alt keys.
X and Y
  The current coordinates for the mouse pointer.

An application must implement and assign an object procedure using the signature for the event handler to respond to the notification.

Use OnMouseDown to respond to the mouse down event for a mouse button.

TMouseEvent TMouseButton TShiftState
Event handler signalled when a WM_MOUSEMOVE message is handled for the tray icon.

OnMouseMove is a TMouseMoveEvent property with the event handler signalled when a mouse move message is handled in the message processing loop for the task bar / system tray. It is signalled (when assigned) when the WM_MOUSEMOVE message is detected in the WndProc routine for the system tray. Arguments for the event handler include the Application for the event notification, the Ctrl/Alt/Shift state for the mouse event, and the current coordinates for the mouse pointer.

OnMouseMove is a callback routine provided for the widgetset class instance.

Event handler signalled to implement custom drawing for the tray icon.

OnPaint is a TNotifyEvent property with the event handler used to implement custom drawing for the tray icon. It is signalled when the widgetset class executes its internal paint routine. The handle in Canvas is valid when OnPaint is executed, and can be used to perform drawing operations for the control Icon.

OnPaint is not implemented for the Win32 platform.
TNotifyEvent

This needs help. Behavior is widgetset-specific. QT has already drawn the clipping rectangle and the icon. What about GTK and Mac?

Implements a multi-platform system tray component.

TTrayIcon is a TCustomTrayIcon descendant which implements a multi-platform System Tray component. It allows an icon to be displayed in the system tray when the Application or Form is active. TTrayIcon provides properties, methods, and events used to configure, display, and control the tray icon. It sets the visibility for properties from ancestor classes. The component is supported on multiple platforms, but its implementation is platform-specific.

On the Windows platform, the system tray is usually located on the bottom-right corner of the screen, but it can be located on other edges for the physical screen. For other platforms, the position and other features varies according to the window or display manager in use.

Use Icon to set the icon image type displayed for the control. Use Icons to assign a list of images displayed as the animated icon for the control when the Show method is called.

Use BalloonFlags, BalloonHint, BalloonTimeout and BalloonTitle to format and display balloon hints for the tray icon. If balloon hints are not supported for the platform, an internal TPopupNotifier is used to display the Hint for the control.

Use PopUpMenu to set the menu displayed when the icon is right clicked with the mouse.

Assign routines to the event handlers to perform actions needed when the icon is clicked - or when mouse move, up, or down messages are received.

TCustomTrayIcon / TTrayIcon are partially compatible with the Delphi VCL component. It adds an OnPaint event handler which does not exist in Delphi. It omits properties like IconIndex and OnBalloonClick.
Represents the drawing styles available for tool bar bands.

TBandDrawingStyle is an enumeration type with values representing the drawing styles available for tool bar bands. TBandDrawingStyle is the type used for the DrawingStyle property in TCustomControlBar.

Bands are drawn noramlly using the color for the control bar.
Bands are drawn using a gradient for the background colors.
Represents the paint options enabled when drawing a TControlBar.

TBandPaintOption is an enumerated type with values that represent the paint options enabled when drawing a TControlBar instance. Values from TBandPaintOption are stored in the TBandPaintOptions type, and passed as an argument to a TBandPaintEvent event handler.

Band is drawn with a grabber or gripper.
Band is drawn with a frame around the outer edges.
Band is drawn using a gradient in the background color.
Not used internally, but available to OnBandPaint.
Stores values from the TBandPaintOption enumeration.
Specifies an event handler signalled when a control band is dragged.
Specifies an event handler used to get layout and positioning information for control bands.

TBandInfo is the type used to implement the OnBandInfo event handler in TCustomControlBar.

Object for the notification event.
Specifies an event handler signalled when a control band is moved.
Object instance for the event notification.
Control for the event notification.
Display rectangle for the event notification.
Specifies an event handler used to perform actions needed when a band in TCustomControlBar is painted.

TBandPaintEvent specifies an object procedure used to perform actions needed when a band in TCustomControlBar control is painted. TBandPaintEvent is the type used to implement the OnBandPaint event handler in TCustomControlBar.

Arguments passed to the procedure identify the TCustomControlBar drawn in the band, and the Canvas and drawing rectangle used in the drawing operation. Options define the drawing features enabled for the band.

Object for the notification.
Control which owns the control band for the notification.
Canvas for the control bar where the handler draws the control band.
Dimensions for the control bar band.
Paint options for the control bar.
Defines the range of values available for the RowSize property in TCustomControlBar.

TRowSize a range type which defines the range of values available for the RowSize property in TCustomControlBar. Essentially, any positive non-zero Integer value. TRowSize is the type used to implement the RowSize property in TCustomControlBar.

Represents band move states in TCtrlBand.

Used in the implementation of MouseUp, MouseMove, and MouseDown methods in TCustomControlBar.

A control band cannot be dragged.
A control band is ready for a drag operation.
A control band is being dragged after a mouse down event.
Represents cursor shapes displayed when the mouse hovers over different areas in a control band.
Uses the default cursor shape.
Uses the grabber cursor shape.
Uses the "not available" cursor shape.
Represents a band and control displayed by TControlBar.

TCtrlBand is a class used to represent a band displayed on TCustomControlBar / TControlBar. It provides properties needed for the Control drawn on the band, its visibility, and position and size information.

TCtrlBand is the type created and stored in the TCtrlBands container.

Gets the value for the BandRect property.
Value for the property.
Gets the value for the Bottom property.
Value for the property.
Gets the value for the Right property.
Value for the property.
Sets the value for the BandRect property.
New value for the property.
Sets the value for the Right property.
New value for the property.
Contains the bounds for the band control.

BandRect is a TRect property which contains the bounds for the band control. BandRect is used in methods which set the layout and placement for the the band control, like InitializeBand and MoveBand.

Values in BandRect are read from the Left, Right, Width, and Height properties in the control. When setting the value for the property, the Left, Right, Width, and Height properties are updated using the values provided in the rectangle.

Position of the bottom of the band control.
Bottom
is a read-only Integer property which contains the vertical position that is the bottom of the band control. The value in Bottom is derived using the Top and Height properties, which are updated when a value is assigned to the BandRect property.
Contains the control displayed on the band.

Control is a TControl property which contains the TToolBar or TToolButton displayed in the band control. The value in Control is assigned in either the Loaded or the InsertControl methods in TCustomControlBar.

Stored Height for the Control used during resizing.

ControlHeight is an Integer property which represents the height for the TWinControl in the Control property. The value in ControlHeight is assigned when a TCustomControlBar is aligned to the band control.

Stored Left position for the Control used in comparisons during resizing.
The value is updated in the AlignControlToBand method in TCustomControlBar, and provides convenient access to the property value in Control.
Stored Top position for the Control used in comparisons during resizing.

The value is updated in the AlignControlToBand method in TCustomControlBar, and provides convenient access to the property value in Control.

Stored Width for the Control used in comparisons during resizing.

The value is updated in the AlignControlToBand method in TCustomControlBar, and provides convenient access to the property value in Control.

Stores the visibility for the Control.

Updated and used in the CheckBandsSizeAndVisibility method in TCustomControlBar.

Stored Height for the band used in comparisons during resizing.

The value is updated in the AlignControlToBand method in TCustomControlBar, and provides convenient access to the property value in Control.

Stores the initial Left position for the band during a move operation.

Updated in the InitializeMove method in TCustomControlBar.

Stores the initial Top position for the band during a move operation.

Updated in the InitializeMove method in TCustomControlBar.

Contains the Left position for the band.

Updated when a value is assigned to the BandRect property, and in the AlignControlToBand method in TCustomControlBar.

Contains the Right position for the band.

Updated when a value is assigned to the BandRect property, and in the AlignControlToBand method in TCustomControlBar.

Contains the Top position for the band.

Updated when a value is assigned to the BandRect property, and in the AlignControlToBand method in TCustomControlBar.

Indicates if the band and its Control are visible.
Contains the dimensions for the band.

Updated when a value is assigned to the BandRect property, and in the AlignControlToBand method in TCustomControlBar.

Container used to store TCtrlBand instances.

TCtrlBands is a container for TCtrlBand instances. TCtrlBands provides a GetIndex method used to access TCtrlBand items stored in the container by their ordinal positions.

Gets the ordinal position for the specified control in the container.
Ordinal position for the requested control, or -1 when not found in the container.
The control to locate in the TCtrlBand items in the container.
Implements a panel used to maintain and manage tool bars and tool buttons on a form.

TCustomControlBar is a TCustomPanel descendant used to maintain and manage tool bars and tool buttons added to the container.

Internally, it uses a TCtrlBands member to represent the TToolBar, TToolButton, or TCoolBar classes added to the container. Use InsertControl and RemoveControl to maintain items in the container at run-time, or use the design-time support provided in the Lazarus Form Designer.

TToolBar TCoolBar TToolButton
Sets the value for the DrawingStyle property.
New value for the property.
Sets the value for the GradientDirection property.
New value for the property.
Sets the value for the GradientEndColor property.
New value for the property.
Sets the value for the GradientStartColor property.
New value for the property.
Sets the value for the Picture property.
New value for the property.
Sets the value for the RowSize property.
New value for the property.
Space reserved for the horizontal border in a control bar.
Space reserved for the vertical border in a control bar
Space reserved as the width of the grabber in a control bar.
Space needed for the width of the grabber including the control bar and its border.
Member with the list of TCtrlBand instances for the control bar.
Member with the band move status flag for the control bar.
Member with the cursor lock flag set when ChangeCursor is called.
Member with the default cursor shape for the control bar.
Member with the band under the mouse cursor during a drag operation.
Member with the initial coordinates for the band being dragged on the control bar.
Member with the width for inner bevels following a CM_BORDERCHANGED control message.
Member with a flag set to prevent resizing while the row size is updated for the control bar.
Member with the Width for the control bar after its Handle is created.
Member with the visible bands for the control bar.
Member with the visible bands on the control bar excluding a band being dragged.
Aligns the control bar to the specified control band.
Aligns visible control bands in the container.
Temporarily disables AutoSizing during the alignment process. Restores AutoSizing prior to exiting from the method.
Calculates the vertical space needed for the control bar.
Number of pixels need for the height of the control bar.
Toolbar or Toolbutton control examined in the method.
Calculates the vertical space needed for the control bar when RowSnap is enabled.
Calculates the cumulative width for all borders and bevels used on the control bar.
Gets the largest value in the Bottom property for visible bands on the control bar.
Changes the cursor to the specified shape.

ACursor contains the cursor shape requested in the method. The value in ACursor is translated into one the following cursor constants, and assigned to the Cursor property:

cdDefault
  Uses the default Cursor for the control.
cdGrabber
  Uses the crDrag cursor constant as the cursor shape.
cdRestricted
  Uses the crNo cursor constant as the cursor shape.

Cursor shape requested in the method.
Updates the size and visibility for TCtrlBand instances defined in the control bar.

Calls InitializeBand (when needed) for a TCtrlBand with a visibility different than the value in the control bar. Calls SortVisibleBands when a TCtrlBand is hidden. Calls NormalizeRows to display TCtrlBand instances in the order defined by their Bottom property. Recalculates the positions and dimensions for visible TCtrlBand instances, including the space reserved for the Grabber bar and borders.

Handles the CM_BIDIMODECHANGED message.
Handles the CM_BORDERCHANGED message.
Ensures the default cursor and width values are assigned when the window handle is created.
Signals the OnBandMove event handler for the specified control and drawing rectangle.
Signals the OnBandPaint event handler using the arguments to the method.
Signals an assigned OnBandDrag event handler and starts a drag operation.
Signals the OnBandInfo event handler to store control information in the arguments to the method.
Class constructor used to initial class constants.
Configures a band and calculates its row position, order, and geometry including client decorations.
Prepares visible bands on the control bar for a drag and drop operation.
Performs actions needed when component loading has been completed.
Determines if the display rectangles for two bands overlap.
True when the rectangles overlap horizontally or vertically.
Handles a mouse down message in the control.

Overridden to provide support for dragging the control band under the mouse cursor.

TControl.MouseDown
Handles a mouse move message while dragging a control band.
TControl.MouseMove
Handles a mouse up message that ends a drag operation for a control band.
TControl.MouseUp
Determines the new position for a band moved using the mouse or by settings its coordinates, and rearranges adjacent bands (and rows) as needed.
Orders visible bands in the control, and removes empty rows.
Draws the control with its image, decorations, and visible bands.
TCustomPanel.Paint
Redraws the control bar when the internal update counter reaches 0.

Assigned as the OnChange event handler for the Picture property.

Signals the OnResize event handler (when assigned) and re-aligns bands and their controls when needed.
TControl.Resize
Sets the Cursor to the specified TCursor shape.

SetCursor is an overridden method in TCustomControlBar used to set the cursor to the specified cursor shape. It calls the inherited method on entry to perform the CM_CURSORCHANGED control message for the control. This triggers the ChangeCursor method which applies the cursor shape in Value. Value is also stored in the FDefCursor member as the default cursor shape.

TControl.SetCursor
TCursor shape
Shifts the position for the specified range of bands by the specified amount and limit.
Calculates the number of visible bands (and controls) and optionally sorts bands to reflect their coordinates.
Handles the LM_SIZE message.

Overridden to resize and arrange visible bands on the control when the size for the control bar is changed.

TWinControl.WMSize
Window message handled in the method.
Member with the update counter for the control bar.
Constructor for the class instance.

Create is the overridden constructor for the class instance. Create allocates resources needed to store the bands for the control bar, and calls the inherited constructor. Creates sets the default values for properties, including:

- ControlStyle
- AutoDrag
- AutoDock
- BevelOuter
- BevelInner
- DockSite
- GradientDirection
- GradientStartColor
- GradientEndColor
- RowSize
- RowSnap

Resources are allocated for the Picture property, and its OnChange event handler is set to the PictureChanged method.

Creates set the initial bounds for the class instance using a width of 100 pixels, and a height of 50 pixels.

Owner of the class instance.
Destructor for the class instance.

Destroy is the overridden destructor for the class instance. Destroy frees resources allocated to the Picture property, as well as the internal TCtrlBands container. Destroy calls the inherited destructor prior to exit.

Increments the internal counter used to track the number of active update requests.

Used in conjunction with EndUpdate to consolidate redraw requests for the control. Various methods check the value in the internal update counter before calling Invalidate to ensure that an unfinished update is not in progress. Invalidate is called in these methods when the internal counter reaches 0 (zero).

Decrements the internal counter used to track update requests, and calls Invalidate when the counter is zero (0)

Used in conjunction with BeginUpdate to consolidate redraw requests for the control. Various methods check the value in the internal update counter before calling Invalidate to ensure that an unfinished update is not in progress. Invalidate is called in these methods when the internal counter reaches 0 (zero).

Flips the horizontal display order for child controls.
FlipChildren is an empty implementation in TCustomControlBar.
When True all descendent controls are flipped as well.
Gets the visible control for a band under the specified coordinates.
The tool bar or tool button in the band at the specified position, or Nil when a visible control is not found.
Horizontal position for the test.
Vertical position for the test.
Creates and stores a new band for the specified control.

InsertControl is an overridden procedure used to create, initialize, and store a TCtrlBand for the specified control. InsertControl calls the method inherited from TWinControl, and creates and stores a new TCtrlBand instance for the control in AControl.

TWinControl.InsertControl
Tool bar or tool button added to the new band in the control bar.
Ordinal position in the bands where the control is inserted.
Gets the control band at the specified mouse coordinates.
TCtrlBand instance at the specified coordinates, or Nil when not on a visible band.
Horizontal coordinate for the mouse pointer.
Vertical coordinate for the mouse pointer.
True if the mouse coordinates are over the grabber for the band.
Removes the specified band from the control bar.
Band removed from the control bar.
Aligns controls for the bands to the control bar.

Calls the AlignControlsToBands method to align / resize controls on the visible bands for the control bar.

Not used in the current LCL implementation.

The default value for the property is True.

Not used in the current LCL implementation.
Indicates if the control allows a band to be dragged even when DragManager is not used.

Indicates if the control can call DragControl to move a band on the control using the mouse. The default value for the property is True.

Called from the MouseMove method when DragManager does not handle the request.

Indicates if bands are automatically sized and positioned for the control bar.

When AutoSize is False, the CheckBandsSizeAndVisibility method is called to Resize the bands in the control bar. When set to False, the inherited method is used. In addition, AutoSize determines if InvalidatePreferredSize is used when setting the value for the RowSize property.

Allows drag-docking of controls onto this control.

A DockSite reacts on controls dragged over this control, signals acceptance and where a dragged control would be dropped. The default value for the property is True in TCustomControlBar.

TWinControl.DockSite
Fill style used for bands on the control bar.

DrawingStyle is a TBandDrawingStyle property which indicates the fill style applied to the control bar. The default value for the property is dsNormal. Set DrawingStyle to dsGradient to draw the control bar using a gradient defined by the values in GradientDirection, GradientStartColor, and GradientEndColor.

Controls the direction for a gradient drawn on the control bar.

GradientDirection is a TGradientDirection property which controls the direction for a gradient drawn on the control bar. The default value for the property is gdVertical. Changing the value for the property causes the Invalidate method to be performed when BeginUpdate has not yet been called.

GradientDirection is used when the DrawingStyle property contains the value dsGradient. Set the values in GradientStartColor and GradientEndColor to define the colors used to draw the gradient.

Specifies the initial color used in a gradient drawn on the control bar.
Specifies the ending color used in a gradient drawn on the control bar.
Optional image drawn before the visible bands for the control bar.

Picture is a TPicture property which contains an optional image drawn on the client rectangle for the control bar. The image is tiled to fill the client area (if needed) immediately prior to drawing the visible bands for the control bar.

Picture is used in the Paint method.

PictureChanged is assigned as the OnChange event handler for the Picture property in the constructor for the class.

Height used for a band or a row of bands displayed on the control bar.

RowSize is a TRowSize property which specifies the height for a row or band displayed on the control bar. The default value for the property is 26.

Changing the value in the property causes the bands for the control bar to be resized and realigned. The Invalidate method will be called to repaint the control if BeginUpdate is not already active.

Indicates if a band or row of bands snaps to the height for the control bar.

RowSnap is a Boolean property which indicates if a band or row of bands snaps to the height for the control bar. The default value for the property is True. When set to False, each band on the control bar calcuates its own height and allocates additional space for bevels.

Used in the CalcBandHeight method, and when a new value is assigned to the RowSize property.

Event handler signalled when a drag operation is about to begin for a band on the control bar.

OnBandDrag can be used to determine if the TCtrlBand instance can be used in a drag and drop operation. The Drag argument can be set to False in the event handler to prevent the drag and drop operation.

Called from the DragControl method before the Drag manager starts the drag and drop operation for the band.

DragManager TDragManager
Event handler signalled to get the insets rectangles, preferred size, and row count for the control bar.

OnBandInfo is a TBandInfoEvent property with the event handler signalled to get the insets rectangles, preferred size, and row count for the control bar. Called from the GetControlInfo method (if assigned) when a new control is added to the control bar.

Event handler signalled when a control band is moved on the control bar.

Signalled from the DoBandMove method (when assigned) using the TCustomControlBar and TCtrlBand instances as arguments. It occurs when the visibility and size for bands on the control are updated.

Event handler signalled to render a visible band on the specified control with the specified paint options.

OnBandPaint is a TBandPaintEvent property with the event handler signalled to render a band with the specified paint options. OnBandPaint is signalled from the DoBandPaint method, and occurs when the Paint method draws each of the visible bands for the control bar.

Not used in the current implementation of TCustomControlBar / TControlBar.
Not used in the current implementation of TCustomControlBar / TControlBar.
Event handler signalled to perform default drawing in the inherited Paint method.

OnPaint is a TNotifyEvent property with the event handler signalled to draw the control bar on its Canvas. An object procedure which draws all aspects of the control must be implemented and assigned to the property.

The Sender argument provides access to properties and methods for the control instance. It must be cast to TCustomControlBar to access members for the class type.

Use the Canvas property to render the background for the control in the event handler. The values from Font and Color are already applied to the corresponding properties in Canvas.

OnPaint is signalled from the inherited Paint method, and occurs before the OnBandPaint event handler in the control is signalled.

TCustomControl.Paint TCustomControl.OnPaint
Implements a panel used to maintain and manage tool bars and tool buttons.

TControlBar implements a panel used to maintain and manage tool bars and toolbuttons on a form. TControlBar is a TCustomControlBar descendant, and sets the visibility for properties from the ancestor class.

Drawing style for the inner bevel on the control.

The default value for the property is bvRaised in TControlBar.

TCustomPanel.BevelInner
Drawing style for the outer bevel on the control.

The default value for the property is bvLowered in TControlBar.

TCustomPanel.BevelOuter
Provides a wrapper for the Frame3D method in TCanvas.

Frame3D is a procedure which provides a wrapper for the Frame3D method in TCanvas. ACanvas is the TCanvas instance used to perform the Frame3D method with the settings in the specified arguments.

TCanvas.Frame3D
Canvas used to perform the 3D drawing routine.
Coordinates for the drawing operation.
Pen color used to draw left and top lines in the frame.
Pen color used to draw right and bottom lines in the frame.
Width required for the 3D frame.
Registers components for use in the Lazarus IDE.

Registers components for use in the Lazarus IDE.

Adds the following components to the Standard tab:

- TRadioGroup
- TCheckGroup
- TPanel

Adds the following components to the Additional tab:

- TImage
- TShape
- TBevel
- TPaintBox
- TNotebook
- TLabeledEdit
- TSplitter
- TTrayIcon
- TControlBar
- TFlowPanel

Adds the following components to the System tab:

- TTimer
- TIdleTimer

Registers the TPage component as a component with no icon in the component palette.

MultiPageControls
- controls that offer a selection of alternative pages for display.

MultiPageControls - controls that offer a selection of alternative pages for display.

A number of controls, found in Units ExtCtrls and ComCtrls, offer the ability to create multi-page forms with a series of Tabs along one edge that allow the user to select one of the Pages for display and interaction.

These include: TPageControl, TNoteBook, TTabControl and THeaderControl (the Header Control components have a very different structure and function). Icons for all of these exist on the Additional or Common Controls tabs of the Component Palette in the Lazarus IDE.

While the various components may look superficially similar, they differ in properties, inheritance, method of adding additional pages, behavior at run-time, methods for referencing pages and so on.

We have to be very clear when using the various properties, to distinguish between the word 'Tab' as referring to a Tab indicating an identifier for a page, and 'Tab' as referring to the TAB key on the standard keyboard. In common with most Lazarus components, it is possible to enable each control to be included in the TabOrder of TabStops for a Form, so that the component can be reached by repeated pressing of the TAB key, and we must not confuse this use of 'Tab' with the use to denote a Page.

The properties CanTab, TabStop and TabOrder refer to the use of the TAB key to navigate to the relevant control.

Properties such as Tabs, TabIndex, IndexOfTabAt(), TabIndexAtClientPos(), TabPosition, TabHeight, TabWidth, TabVisible, OnCloseTabClicked refer to the use for Page selection.

TTabControl and TPageControl are both descended from TCustomNoteBook (which is in turn descended from TWinControl) and have many inherited properties in common. TPageControl has, in general, more advanced features and is probably intended to replace TNoteBook.

The following table summarizes the main differences between the two components.

| Property or method | TNoteBook | TPageControl
Pages, ActivePage | String, TPage | TTabSheet, a more advanced version of TPage
Drag/Drop/Dock | Drag properties, but minimal Dock or Drop | Full Drag, Drop, Dock properties and methods
Indexing | PageIndex | ActivePageIndex, TabIndex
Showing/Hiding Tabs | ShowTabs | TabVisible in TTabSheet
Hints | No Hinting methods | ShowHint, ParentShowHint
Font | No Font properties | Font, ParentFont
Sensing position of Tab | None | TabPosition, OnGetSiteInfo
Options | Published property Options, include nboShowCloseButtons, nboMultiLine | No published Options property, but inherits Options (public property) from TCustomNoteBook, so they could be set explicitly in code

The individual Pages in both of the above controls (descended from TCustomNoteBook) are separate and can have their own specific collections of widgets which appear only when the relevant Page is selected by its Tab.

In contrast, the TTabControl component (descended from TCustomTabControl) has only one display area (Protected property DisplayRect), but the image displayed in it is determined by which tab has been selected. Each Tab has an index value which is used to select the appropriate image from an indexed ImageList and display it in the Display Rectangle.

The properties of the Tabs in TTabControl are very configurable compared with those in the controls derived from TCustomNoteBook, allowing for instance the creation of multi-line captions, the placement of images on Tabs, the possibility of the Owner routine determining the drawing of the tab, the configuration of Tab size, the selection of multiple tabs. The trade-off is that the display area is restricted in what it can display, and is essentially confined to display of images.

To use any of the above controls, select them from the relevant tab on the IDE Component Palette and drop them on the form in the required position. Fill in as many relevant properties as you can in the Object Inspector.

To add Tabs or Pages to the controls, select the control with a left mouse click or by selecting from the Component menu in the Object Inspector, then right-click on the component to get a pop-up menu, whose first item will be 'Add Page' or 'Add Tab'.

The Tabs in TTabControl can be edited by selecting 'Tabs' in the Object Inspector, clicking on the ellipsis (...) and using the string editor that pops up.

The pages inTNoteBook or TPageControl can be edited by selecting the ActivePage in the Object Inspector and then editing the properties of the individual page.

THeaderControl offers a widget that could be placed along the edge of a Panel or Form, allowing a highly customized mechanism for selection. However, there are no intrinsically associated display areas, and it is the developer's responsibility to supply an index associated with the selection from the THeaderControl and determining what action is to occur or what is to be displayed in any attached Panel or Form.

When the control is first selected from the Component Palette and placed on a Form, it consists of an unadorned rectangle. However, selecting the control and right-clicking (or selecting the 'Sections' property in the Object Inspector) gives access to a Sections editor (a StringList editor) and Sections can be added to the control. The sections are separated by vertical lines, and each section can have a string inserted as a label, associated with an Index value. The Sections can be rearranged, re-ordered, or be individually painted.

In a typical application a THeaderControl and a TPanel or TForm would be docked together, and code would be written to find which Section of the Header had been selected, then use its index to control the display in the other docked control.