todo

按照官方的说法：Cairo is a vector graphics library with cross-device output support. 翻译过来

Need to finish up libpixman to the point where there X server can use
it in place of its original copy of all this code (eg. in fb).  This
means merging features that have happened in either tree since the
birth of libpixman. Off-hand I can think of the following things that
have happened:

	* libpixman has fix for transform + repeat
	* X server has some (MMX? SSE?) optimized compositing code

But see the logs for more details.