Legacy Document

Inside Macintosh: Imaging With QuickDraw /

Chapter 3 - QuickDraw Drawing / QuickDraw Drawing Reference

Routines / Determining Whether QuickDraw Has Finished Drawing

QDDone

Although you will probably never need to determine whether QuickDraw has completed drawing, you can do so by using the QDDone function.

FUNCTION QDDone (port: GrafPtr): Boolean;

port

The GrafPort record for a graphics port in which your application has begun drawing; if you pass NIL, QDDone tests all open graphics ports.

DESCRIPTION

The QDDone function returns TRUE if all drawing operations have finished in the graphics port specified in the port parameter, FALSE if any remain to be executed. If you pass NIL in the port parameter, then QDDone returns TRUE only if drawing operations have completed in all ports.

The QDDone function may be useful if a graphics accelerator is present and operating asynchronously. You could use it to ensure that all drawing is done before issuing new drawing commands, and to avoid the possibility that the new drawing operations might be overlaid by previously issued but unexecuted operations.

SPECIAL CONSIDERATIONS

The QDDone function has little or no usefulness.

If a graphics port draws a clock or some other continuously operating drawing process, QDDone may never return TRUE.

To determine whether all drawing in a color graphics port has completed, you must coerce its CGrafPort record to a GrafPort record, which you pass in the port parameter.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the QDDone function are

Trap macro	Selector
_QDExtensions	$00040013