Legacy Document

Inside Macintosh: Imaging With QuickDraw /

Chapter 6 - Offscreen Graphics Worlds / Offscreen Graphics Worlds Reference

Routines / Managing an Offscreen Graphics World's Pixel Image

GetGWorldPixMap

Use the GetGWorldPixMap function to obtain the pixel map created for an offscreen graphics world.

FUNCTION GetGWorldPixMap (offscreenGWorld: GWorldPtr): 
                          PixMapHandle;

offscreenGWorld

A pointer to an offscreen graphics world.

DESCRIPTION

The GetGWorldPixMap function returns a handle to the pixel map created for an offscreen graphics world. In the offscreenGWorld parameter, pass the pointer returned to your application by the NewGWorld function when you created the offscreen graphics world. Your application can, in turn, pass the handle returned by GetGWorldPixMap as a parameter to other QuickDraw routines that accept a handle to a pixel map.

On a system running only basic QuickDraw, the GetGWorldPixMap function returns the handle to a 1-bit pixel map that your application can supply as a parameter to the other routines related to offscreen graphics worlds. However, your application should not supply this handle to Color QuickDraw routines.

SPECIAL CONSIDERATIONS

To ensure compatibility on systems running basic QuickDraw instead of Color QuickDraw, use GetGWorldPixMap whenever you need to gain access to the bitmap created for a graphics world--that is, do not dereference the GWorldPtr record for that graphics world.

The GetGWorldPixMap function is not available in systems preceding System 7. You can make sure that the GetGWorldPixMap function is available by using the Gestalt function with the gestaltSystemVersion selector. Test the low-order word in the response parameter; if the value is $0700 or greater, then GetGWorldPixMap is available.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the GetGWorldPixMap function are

Trap macro	Selector
_QDExtensions	$00040017

SEE ALSO

The Gestalt function is described in the chapter "Gestalt Manager" of Inside Macintosh: Operating System Utilities.