Screen handling

Neither the window server nor the UI control framework are dependent on screen size. At system start time, the window server interrogates the HAL to find out the size of the screen.

Since Symbian OS is implemented on many different phones with varying screen sizes, applications should be written to be independent of the screen size where possible.

Some phones running Symbian OS support multiple screen modes — for instance, 2- and 4-bit-per-pixel modes, allowing 4 or 16 shades of grey. On a phone, there is a strong incentive to use 2bpp if possible, and 4bpp only when necessary, to avoid the drain on batteries caused by the data transfer which supports screen refresh.

The window server keeps track of the windows visible on the screen, and automatically switches the screen to the mode which uses the least power but supports all the modes of these windows. On a machine like that described above, the 2bpp mode would be used unless part of at least one 4bpp window was visible on the screen.