This fixes the artefacts appearing when only part of the screen is updated.
This version also brings ton of optimizations which might well increase performance
2 or 3 times on slower cards:
- Windows are not drawn twice anymore. Now they're drawn only to render target and
later changed parts of the render target are copied back onto screen.
- Shaders have been optimized. Some calculations moved from pixel shader to vertex shader.
- For ARGB windows, if window's opacity is 0 then it will stay transparent instead of being
replaced by blurred background.
- Blur effect should now play nicer with other effects, e.g. shadows.
svn path=/trunk/KDE/kdebase/workspace/; revision=748502
213833fc7f
