Your application and the Window Manager work together to display windows on the screen. Once you have created a window and made it visible, the Window Manager automatically draws the window's structure region (that is, its "frame") in the appropriate location. The Window Manager does not typically draw any content in a window; it only draws the color or pattern of the content region. Your application is responsible for drawing content such as text or graphics in the window's content region.
When the user exposes a window that has previously been obscured, the Window Manager redraws the exposed, invalid portions of the window. If some part of the window's content region is exposed, the Window Manager redraws it to the current content color and adds it to the window's update region. You can use the Mac OS 8.5 Window Manager to set a window's content region to a specific color or pattern, which the Window Manager then uses to redraw the content region of the window. Figure 1-7 shows an example of a window for which the content region has been set to a pattern.
Figure 1-7 A window with a patterned content area
The Mac OS 8.5 Window Manager provides the following functions for redrawing a window's content region. See Drawing in a Window's Content Region for further discussion and an example of how your application might call these functions.