typedef SInt16 DragRegionMessage;
enum {
    kDragRegionBegin = 1,
    kDragRegionDraw = 2,
    kDragRegionHide = 3,
    kDragRegionIdle = 4,
    kDragRegionEnd = 5
};

Constant descriptions

kDragRegionBegin

Your drag drawing callback function receives this message when a drag is being started and it is time to initialize your drawing function. You should not draw anything to the screen when you receive this message.The showRegion parameter to your drag drawing callback function contains the drag region that was passed to the TrackDrag function and the showOrigin parameter contains the mouseDown location that was specified to the TrackDrag function. This location is the origin of the drag region.The hideRegion parameter is NULL when your drag drawing callback function receives this message.

kDragRegionDraw

Your drag drawing callback function receives this message when you should move your drag region from the area of the screen defined by the hideRegion parameter to the area of the screen defined by the showRegion parameter.The showRegion parameter contains the drag region that was passed to the TrackDrag function, offset to the current pinned mouse location. This region represents the area of the screen that must be drawn into.The hideRegion parameter contains the drag region as it is currently visible on the screen from the last call with a dragRegionDraw message. This region represents the area of the screen that must be restored. Any part of the drag region that was previously obscured by a call with the dragRegionHide message is not included in this hideRegion parameter.

kDragRegionHide

Your drag drawing callback function receives this message when you should remove part of the drag region from the screen. You receives this message when the drag has ended or when part of the region must be obscured for drawing operations to occur underneath the drag region.The showRegion parameter is NULL when your drag drawing callback function receives this message.The hideRegion parameter contains the part of the currently visible drag region that must be removed from the screen.

kDragRegionIdle

Your drag drawing callback function receives this message when the drag region has not moved on the screen and no drawing is necessary. You can use this message if animation of the drag region is necessary.The showRegion parameter contains the drag region as it is currently visible on the screen.The hideRegion parameter is NULL when your drag drawing callback function receives this message.

kDragRegionEnd

Your drag drawing callback function receives this message when the drag has completed and it is time to deallocate any allocations made from within your drag drawing callback function. Your drag drawing callback function will have already received a dragRegionHide message to hide the entire drag region before receiving this message. After you receive this message, your drag drawing callback function will not be called again for the duration of the drag.Both the showRegion and hideRegion parameters are NULL when your drag drawing callback function receives this message.

© 2001 Apple Computer, Inc. (Last Updated July 17, 2001)