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Docs: LCL/comctrls. Adds topics for changes in 76bbc6e2. Issue #19169.

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* TLVChangingEvent
* TCustomListView.CanChange
* TCustomListView.OnChanging
* TListView.OnChanging
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dsiders 2024-01-06 20:27:50 +00:00
parent bb694c4b08
commit 471bba54b8
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docs/xml/lcl/comctrls.xml
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@ -12122,6 +12122,75 @@ TLVChangeEvent is the type used for the <var>OnChange</var> property in
<short>Indicates the property value that was changed in Item.</short>
</element>
<element name="TLVChangingEvent">
<short>
Defines an event handler signalled when a widgetset class is updating an item
on a list view control.
</short>
<descr>
<p>
<var>TLVChangingEvent</var> is an object procedure used to define the event
handler signalled when a list item on a TListView is being updated by the
widgetset class instance. It is the type used to implement the OnChanging
property in TCustomListView, and allows the pending change to be accepted or
rejected on an item-by-item basis.
</p>
<p>
The <var>Sender</var> argument contains the object for the event notification,
It must be cast to TCustomListView to access properties and methods specific to
the list view control.
</p>
<p>
<var>Item</var> contains the TListItem instance on the list view control which
is being updated, and the values for the modified list item.
</p>
<p>
<var>Change</var> indicates which value in Item is being modified: the caption
text, the image for the item, or the item drawing state. See TItemChange for
the values used in the argument, and their meanings.
</p>
<p>
<var>AllowChange</var> is a variable Boolean argument which allows the handler
to indicate whether the change is accepted or rejected. Set AllowChange to
<b>False</b> to reject the modified value in Item.
</p>
<p>
See <link id="TCustomListView.OnChanging">TCustomListView.OnChanging</link>
for more information about the event notification for the list view control.
</p>
</descr>
<version>
Added in LCL version 4.0.
</version>
<seealso>
<link id="TItemChange"/>
<link id="TListItem"/>
<link id="TCustomListView.OnChanging"/>
<link id="TCustomListView.Items"/>
</seealso>
</element>
<element name="TLVChangingEvent.Sender">
<short>
Object (TCustomListView control) for the event notification.
</short>
</element>
<element name="TLVChangingEvent.Item">
<short>
List item with the pending change,
</short>
</element>
<element name="TLVChangingEvent.Change">
<short>
Identifies the list item value changed in the notification.
</short>
</element>
<element name="TLVChangingEvent.AllowChange">
<short>
Indicates whether the change is accepted or rejected in the event handler.
<b>True</b> for an accepted change.
</short>
</element>
<element name="TLVDataFindEvent">
<short>
Specifies an event handler used to locate a list view item using the
@ -13356,6 +13425,7 @@ and List View Work Areas.
<element name="TCustomListView.FHoverTime"/>
<element name="TCustomListView.FUpdateCount"/>
<element name="TCustomListView.FOnChange"/>
<element name="TCustomListView.FOnChanging"/>
<element name="TCustomListView.FOnColumnClick"/>
<element name="TCustomListView.FOnCompare"/>
<element name="TCustomListView.FOnData"/>
@ -14110,6 +14180,13 @@ item are changed.
CNNotify updates property values and calls methods in the class instance as
needed to respond to the notification message.
</p>
<p>
Please note that LVN_ITEMCHANGING control notification is handled in the
ListViewParentMsgHandler routine in the widgetset class for the Windows
platform. Changes are accepted and applied when CanChange in the list view
control returns <b>True</b>. No additional processing is performed for the
notification message in the Windows message process loop.
</p>
</descr>
<seealso/>
</element>
@ -14531,6 +14608,63 @@ the programmer has assigned a method to this event.
<short/>
</element>
<element name="TCustomListView.CanChange">
<short>
Indicates whether a change notification can be applied for an item on the list
view control.
</short>
<descr>
<p>
<var>CanChange</var> is a <var>Boolean</var> function used to determine whether
a change notification message for an item in a list view control can be
accepted and applied. CanChange is called from the widgetset class instance,
and occurs when change notification messages are handled for the list view
control.
</p>
<p>
CanChange signals the OnChanging event handler (when assigned) to determine the
return value for the method. The return value is <b>True</b> if the changed
value in AItem is accepted and can be applied to the list item. The return
value is <b>False</b> if the modification is rejected in the OnChanging event
handler.
</p>
<remark>
Interestingly, the return value is True if AChange contains an Integer value
that is <b>not</b> represented in the TItemChange enumeration. In this case,
the OnChanging event is <b>not</b> signalled.
</remark>
<p>
In the current LCL implementation, CanChange and OnChanging apply to the
Windows widgetset only. Other platforms do not generate a change notification
for item values.
</p>
</descr>
<version>
Added in LCL version 4.0.
</version>
<seealso>
<link id="TCustomListView.OnChanging"/>
<link id="TLVChangingEvent"/>
<link id="TItemChange"/>
</seealso>
</element>
<element name="TCustomListView.CanChange.Result">
<short>
Returns <b>True</b> if the modified value in the list item is accepted.
</short>
</element>
<element name="TCustomListView.CanChange.AItem">
<short>
List item with the modified value examined in the method.
</short>
</element>
<element name="TCustomListView.CanChange.AChange">
<short>
Indicates which value in the list item has been modified. Corresponds to the
ordinal values in the TItemChange enumeration.
</short>
</element>
<element name="TCustomListView.ColClick">
<short>
Performs actions to handle a mouse click on a Report view column header.
@ -16200,6 +16334,46 @@ a list item has been changed.
<seealso/>
</element>
<element name="TCustomListView.OnChanging">
<short>
Event handler signalled when a change notification is received for a list item.
</short>
<descr>
<p>
<var>OnChanging</var> is a <var>TLVChangingEvent</var> property with the event
handler signalled when a change notification is handled for the list view
control. It allows modifications to list items to be handled on an item-by-item
basis. It is signalled from the CanChange method (when assigned), and occurs
when the widgetset class handles change notification messages for the control.
</p>
<p>
An application can implement and assign a handler to the property to determine
whether a pending change is accepted or rejected for a list item.
</p>
<p>
See <link id="TItemChange">TItemChange</link> for the changes items or states
available in the event notification.
</p>
<p>
See <link id="TLVChangingEvent">TLVChangingEvent</link> for more information
about the event type and its arguments.
</p>
<p>
Please note that CanChange and OnChanging are relevant for the Windows platform
only. Other platforms do not generate or handle change notifications for list
item values.
</p>
</descr>
<version>
Added in LCL version 4.0.
</version>
<seealso>
<link id="TCustomListView.CanChange"/>
<link id="TLVChangingEvent"/>
<link id="TItemChange"/>
</seealso>
</element>
<element name="TCustomListView.OnColumnClick">
<short>
Event handler signalled when a column header for the control is clicked.
@ -18417,6 +18591,7 @@ GetRGBColorResolvingParent method.
<element name="TListView.OnAdvancedCustomDrawItem" link="#lcl.comctrls.TCustomListView.OnAdvancedCustomDrawItem"/>
<element name="TListView.OnAdvancedCustomDrawSubItem" link="#lcl.comctrls.TCustomListView.OnAdvancedCustomDrawSubItem"/>
<element name="TListView.OnChange" link="#lcl.comctrls.TCustomListView.OnChange"/>
<element name="TListView.OnChanging" link="#lcl.comctrls.TCustomListView.OnChanging"/>
<element name="TListView.OnClick" link="#lcl.controls.TControl.OnClick"/>
<element name="TListView.OnColumnClick" link="#lcl.comctrls.TCustomListView.OnColumnClick"/>
<element name="TListView.OnCompare" link="#lcl.comctrls.TCustomListView.OnCompare"/>