Chapter 1

case 2: return EAmountOfControls;
}
return 0;
}
A dialog is also a compound control with typically only a single window. A dialog has an
unpredictable number of component controls, so instead of hardcoding the answers to
CountComponentControls()and ComponentControl() as I did above, CEikDialog
uses a variable-sized array to store dialog lines and calculates the answers for these
functions.
11.5.4 More on Drawing
Drawing to a window is easy for programs but involves complex processing by Symbian OS
as you can see in Figure 11.12.
Figure 11.12
On the client side, an application uses a CWindowGc to draw to a window. CWindowGc's
functions are implemented by encoding and storing commands in the window server's clientside
buffer. When the buffer is full, or when the client requests it, the instructions in the buffer
are all sent to the window server, which decodes and executes them by drawing directly onto
the screen, using a CFbsBitGc – a CGraphicsContext-derived class for drawing onto
bitmapped devices. Prior to drawing, the window server sets up a clipping region to ensure
that only the correct region of the correct window can be changed, whatever the current
state of overlapping windows on the screen. The window server uses the BITGDI to
'rasterize' the drawing commands.