Legacy Document

Inside Macintosh: Imaging With QuickDraw /

Chapter 5 - Graphics Devices / Graphics Devices Reference

Routines for Graphics Devices

Creating, Setting, and Disposing of GDevice Records

Color QuickDraw uses GDevice records to maintain information about video devices and offscreen graphics worlds. A GDevice record must be allocated with the NewGDevice function and initialized with the InitGDevice procedure. Normally, your application does not call these routines directly. When the system starts up, it allocates and initializes one handle to a GDevice record for each video device it finds. When you use the NewGWorld function (described in the chapter "Offscreen Graphics Worlds" in this book), Color QuickDraw automatically creates a GDevice record for the new offscreen graphics world.

Whenever QuickDraw routines are used to draw into a graphics port on a video device, Color QuickDraw uses the SetGDevice procedure to make the video device for that screen the current device. Your application won't generally need to use this procedure, because when your application draws into a window on one or more screens, Color QuickDraw automatically switches GDevice records as appropriate; and when your application needs to draw into an offscreen graphics world, it can use the SetGWorld procedure to set the graphics port as well as the GDevice record for the offscreen environment. However, if your application uses the SetPort procedure (described in the chapter "Basic QuickDraw" in this book) instead of the SetGWorld procedure to set the graphics port to or from an offscreen graphics world, then your application must use SetGDevice in conjunction with SetPort.

You use the SetDeviceAttribute procedure to set attribute bits in a GDevice record.

When Color QuickDraw no longer needs a GDevice record, it uses the DisposeGDevice procedure to dispose of it. As with the other routines described in this section, your application typically does not need to use DisposeGDevice.

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Subtopics

NewGDevice

InitGDevice

SetDeviceAttribute

SetGDevice

DisposeGDevice