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

# TDragDockObject.HasOnDrawImage

Checks for an assigned OnDrawDockImage event handler.

## Declaration

Source position: controls.pp line 608

`protected function TDragDockObject.HasOnDrawImage: Boolean; virtual;`

## Function result

True when an event handler has been assigned to OnDrawDockImage.

## Description

HasOnDrawImage is a Boolean function used to determine if an event handler has been assigned to the OnDrawDockImage property. The return value is True if a routine has been assigned to the property. If an event handler has not been supplied, the HintDockImage routine is assigned to the event handler, and the return value is set to True.

For platforms where the Alpha blending is not enabled for Forms, the return value is always False (determined by calling GetSystemMetrics for the SM_LCLHasFormAlphaBlend metric in the widgetset class).

HasOnDrawImage is used in methods like ShowDockImage, HideDockImage, and MoveDockImage.

## See also

TDragDockObject.ShowDockImage |  | Shows the DockRect, and remembers the coordinates in EraseDockRect.
TDragDockObject.HideDockImage |  | Hides the DockRect, and invalidates EraseDockRect to prevent further erases.
TDragDockObject.MoveDockImage |  | Moves an already visible DockRect.