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Inside Macintosh: Imaging With QuickDraw /

Chapter 6 - Offscreen Graphics Worlds / Offscreen Graphics Worlds Reference

Routines / Saving and Restoring Graphics Ports and Offscreen Graphics Worlds

GetGWorld

To save the current graphics port (basic, color, or offscreen) and the current GDevice record, use the GetGWorld procedure.

PROCEDURE GetGWorld (VAR port: CGrafPtr; VAR gdh: GDHandle);

port

A pointer to an offscreen graphics world, color graphics port, or basic graphics port, depending on which is the current port.

gdh

A handle to the GDevice record for the current device.

DESCRIPTION

The GetGWorld procedure returns a pointer to the current graphics port in the port parameter. This parameter can return values of type GrafPtr, CGrafPtr, or GWorldPtr, depending on whether the current graphics port is a basic graphics port, color graphics port, or offscreen graphics world. The GetGWorld procedure returns a handle to the GDevice record for the current device in the gdh parameter.

After using GetGWorld to save a graphics port and a GDevice record, your application can later use the SetGWorld procedure, described next, to restore them.

SPECIAL CONSIDERATIONS

The GetGWorld procedure may move or purge memory blocks in the application heap. Your application should not call this procedure at interrupt time.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the GetGWorld procedure are

Trap macro	Selector
_QDExtensions	$00080005

SEE ALSO

Listing 6-1 on page 6-5 and Listing 6-2 on page 6-10 illustrate how to use the GetGWorld procedure to save the current graphics port for an active window, the SetGWorld procedure to change the current graphics port to an offscreen graphics world, and then SetGWorld again to restore the active window as the current graphics port.