Unit 'Controls' Package
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TControl.DoDragMsg

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

Declaration

Source position: controls.pp line 1403

protected function TControl.DoDragMsg(

  ADragMessage: TDragMessage;

  APosition: TPoint;

  ADragObject: TDragObject;

  ATarget: TControl;

  ADocking: Boolean

):PtrInt; 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.



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