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UnlockPixels |
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| Header: | QDOffscreen.h | Carbon status: | Supported | |
Allows the Memory Manager to move the base address for the offscreen pixel map that you specify in the pm parameter.
void UnlockPixels (
PixMapHandle pm
);
A handle to an offscreen pixel map. Pass the same handle that you passed previously to the LockPixels function.
To ensure the integrity of the data in a pixel image, call LockPixels before drawing into or copying from a pixel map; then, to prevent heap fragmentation, call UnlockPixels as soon as your application finishes drawing to and copying from the offscreen pixel map.
The baseAddr field of the PixMap structure for an offscreen graphics world contains a handle instead of a pointer (which is what the baseAddr field for an onscreen pixel map contains). The LockPixels function dereferences the PixMap handle into a pointer. When you use the UnlockPixels function, the handle is recovered.
You don’t need to call UnlockPixels if LockPixels returns FALSE, because LockPixels doesn’t lock the memory for a pixel image if that memory has been purged. However, calling UnlockPixels on purged memory does no harm.
The UnlockPixels function may move or purge memory blocks in the application heap; do not call this function at interrupt time.
Supported in Carbon. Available in Carbon 1.0.2 and later when running Mac OS 8.1 or later.
© 2000 Apple Computer, Inc. (Last Updated 6/30/2000)