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

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 property 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.

TGraphicControl.WSRegisterClass 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

	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