Inside Macintosh: Macintosh Toolbox Essentials
The Window Manager maintains information about the windows on the desktop in a private structure called the window list. The window list contains pointers to all windows on the desktop, both visible and invisible, and contains other information that the Window Manager uses to maintain the desktop.
Your application should not directly access the information in a window list. The structure of the window list is private to the Window Manager.
The global variable WindowList contains a pointer to the first window in the window list. If you need this pointer, do not access it directly. Instead, use the accessors LMSetWindowList (LMSetWindowList) and LMGetWindowList (LMGetWindowList) .