Inside Macintosh: QuickTime Components
Use the window position request to position the user's dialog box.
You supply a pointer to a point. If you are retrieving this information, the standard dialog component places the coordinates of the upper-left corner of the dialog box into this point; if you are changing the dialog box's position, place the new coordinates into the point structure--the component uses those coordinates to position the dialog box.
Normally you should not need to use this request. By default, the standard dialog component centers the dialog box on the screen that is best-suited to display your test image. The component also saves the last window position for movable modal dialogs.