Writing Compatible Graphics Applications

Over the years, some developers have written applications that modify the

QuickDraw data structures directly, rather than using the routines

provided for that purpose. Then, when engineers at Apple improve

QuickDraw, the applications break. As QuickDraw, graphics applications,

and cards such as graphics accelerators grow more complex, the problem

becomes acute. This section points to new routines you can use to signal

QuickDraw when your application modifies certain data structures directly

so that QuickDraw can take note and act accordingly.

Applications should not directly change fields in graphics data structures, but

should use the following routines instead:

Using these routines rather than directly modifying the data structures

ensures that your application will fully benefit from any future improvements

to QuickDraw. In particular, the off-screen graphics world routines

described in the Graphics Devices Manager remove much of the need for

directly modifying graphics data structures.

Apple strongly recommends that new applications follow these guidelines;

asynchronously operating graphics cards especially need close co operation

It is possible to make existing applications more compatible by calling one of

the following procedures after directly changing a QuickDraw data structure

and before calling any other QuickDraw routine:

These procedures inform QuickDraw that a direct modification has occurred

so it can update its tracking of the graphics environment.