[cairo] Cairo and WinCe image drawing

[Stefan Klug]

Hi everybody,

first big thanks and keep up the great work to all cairo developers...

I'm currently developing a WinCe application with heavy graphic usage in 
fullscreen mode.
I'd like to get away from my old graphic engine and port everything to 
cairo to stay as platform independent as possible.

Compiling Cairo for WinCe works after some modifications mainly to the 
win32 surface. Font rendering is still on my ToDo list.

The problem is, that it's rather slow.
(Dragging a fullscreen image should be possible at 24fps but I get 
around 5fps (no exact measurement))
I'm only drawing untransformed images at integer positions.
The main bottleneck seems to be the transfer of imagedata to the target 
surface.
As cairo internally only works with 4 bytes per pixel (even in RGB24 
mode as far as I can see) the amount of memory to transfer is rather big 
for a ARM powered CE Device.
Wouldn't it be possible to introduce a CAIRO_FORMAT_RGB16_565 format? 
This could greatly improve speed for image drawing on most of the WinCe 
devices out there as the frame buffer uses 2bytes per pixel.
I think the image drawing functions wouldn't be a big problem as pixman 
already supports these formats. But I don't have any knowledge about the 
internals of the path rasterization functions.

Or did I completely miss some something.

Regards
    Stefan