Chapter 1

In the last chapter, we concentrated on the drawing-related interactions between
CCoeControl and RWindow (and, occasionally, RBackedUp-Window). In this chapter,
we've introduced key processing, which brings in RWindowGroup and CCoeAppUi. The
window server classes involved here are part of a small window class hierarchy, defined in
w32std.h, and illustrated in Figure 12.7:
Figure 12.7
For much of the time, you can call these classes' functions through the control environment.
Nevertheless, it is useful to understand them because the control environment is not
designed to encapsulate the window server. Rather, the control environment provides a
convenience layer for lodger controls and compound controls, and for the window server's
major functions such as drawing, pointer, and key event handling.
I won't be providing detailed information on these facilities but I'll give enough of an overview
that you can understand what's available and find the information you need in the SDK.
Class Name Description
RWindowTreeNode Base class for all windows: a node in the tree that defines z-order
RWindowGroup Unit of keyboard focus, and top-level owner of displayable
windows
RWindowBase Base class for all displayable windows
RBlankWindow Entirely blank window
RDrawableWindow Base class that defines windows which support drawing
RBackedUpWindow Backed-up window: window server redraws invalid areas
RWindow Standard window: application redraws invalid areas
For most application programming, the most important concrete classes are RWindow and
RWindowGroup. These are described in more detail in the following two sections.
Because all displayable windows are ultimately owned by a window group, a window group
is the top-level node in the tree that defines z-order. This means that all windows belonging
to an application move back and forth in the z-order as a group. We can therefore use the
terms 'foreground application' and 'application whose window group has focus'
interchangeably.
Note
The window server allows applications to have more than one window group,
but the control environment supports only a single window group per