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Inside Macintosh: Imaging With QuickDraw /

Chapter 5 - Graphics Devices / Graphics Devices Reference

Routines for Graphics Devices

Determining the Characteristics of a Video Device

For drawing images that are optimized for every screen they cross, your application can use the DeviceLoop procedure. The DeviceLoop procedure searches for graphics devices that intersect your window's drawing region, and it calls your drawing procedure for each different video device it finds. The DeviceLoop procedure provides your drawing procedure with information about the current device's pixel depth and other attributes.

To determine whether the flag bit for an attribute has been set in the gdFlags field of a GDevice record, your application can use the TestDeviceAttribute function.

To determine whether a video device supports a specific pixel depth, your application can also use the HasDepth function, described on page 5-32. To change the pixel depth of a video device, your application can use the SetDepth function, described on page 5-33.

If you need to determine the resolution of the main device, you can use the ScreenRes procedure.

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Subtopics

DeviceLoop

TestDeviceAttribute

ScreenRes