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Reference for unit 'Controls' (#lcl)

TControl.DoDragMsg

Handler for a drag message, sent by the DragManager to the current target control.

Declaration

Source position: controls.pp line 1476

protected function TControl.DoDragMsg(

ADragMessage: TDragMessage;

APosition: TPoint;

ADragObject: TDragObject;

ATarget: TControl;

ADocking: Boolean

):LRESULT; virtual;

Arguments

`ADragMessage`		The task to perform.
`APosition`		The mouse position in screen coordinates.
`ADragObject`		The drag object.
`ATarget`		The drop target, Nil if none.
`ADocking`		Distinguishes between a drag-drop and drag-dock operation.

Function result

The Result member is polymorphic:

For dmFindTarget, the result is a reference to the the target control. For dmDragDropm the result is zero (0). For other drag messages, the result indicates acceptance of the drop message.

Description

These messages can be sent while dragging:

dmFindTarget: Request to determine the possible target control for an drop. A TControl returns itself, a TWinControl finds the child control closest to the mouse position.
dmDragEnter, dmDragLeave, dmDragMove: Notification of mouse moves. Invokes DragOver, or DockOver if docking. Result indicates acceptance of a drop.
dmDragDrop: The dragged object has been dropped onto this control. Invokes DragDrop, or DockDrop if docking.

The Source argument of the invoked methods is the DragDockObject when docking. If the DragObject has been AutoCreated, the dragged control is passed as the Source. Otherwise, the DragObject itself is passed as Source.

Version 3.2

Generated 2024-02-25

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