[Overview][Constants][Types][Classes][Procedures and functions][Variables][Index] | Reference for unit 'Controls' (#lcl)

# TControlChildSizing.OnChange

Event handler signalled when the size or layout for child controls has been changed.

## Declaration

Source position: controls.pp line 1986

`public property TControlChildSizing.OnChange : TNotifyEvent read FOnChange write FOnChange;`

## Description

OnChange is a TNotifyEvent property with the event handler signalled (when assigned) from the Change method. It occurs after child controls have been resized and/or realigned.

The Sender argument is the TControlChildSizing instance for the event notification.

In a TWinControl instance, its DoChildSizingChange method is assigned as the default handler routine used in OnChange. It invalidates the preferred sizes for the child controls, and calls their Realign method.

## See also

TControlChildSizing.Change |  | Notifies the Control of the child sizing changes and signals the OnChange event handler.
TWinControl.DoChildSizingChange |  | Called after a change in ChildSizing information to trigger further processing.
TWinControl.Realign |  | Adjusts the size and placement for the control and all of its children.
TControl.InvalidatePreferredSize |  | Marks the preferred size as invalid for this control and all parents (implies that we will look for another).