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Inside Macintosh: QuickDraw GX Environment and Utilities /

Chapter 2 - QuickDraw GX Memory Management / About QuickDraw GX Memory Management

Memory Heaps

QuickDraw GX applications use an application heap and one or more graphics client heaps. The application heap memory holds your code and data structures. This is the part of memory where you allocate variables and your application executes. You can access any data structure in the application heap. Your application manages its own structures in the application heap and makes function calls to obtain or modify the contents of the graphics client heap.

The QuickDraw GX graphics client heap memory holds the QuickDraw GX objects you create. The graphics client heap consists of one or more blocks of discontiguous memory that QuickDraw GX uses to allocate its objects, structures, and variables. QuickDraw GX memory is private so, in general, you cannot directly access the contents of a graphics client heap.

The graphics client heap and the application heap work independently. For example, QuickDraw GX can execute from the memory on an accelerator card. As a result, QuickDraw GX never moves application memory. In addition, Macintosh Memory Manager functions cannot modify QuickDraw GX objects. QuickDraw GX has its own internal memory manager and memory management functions for interacting with its objects.