Raster has hot code path when resizing windows.

Hi,

I was trying to figure out why resizing was so sluggish in Linux (kde, kwin) so i did a callgrind to figure it out.
What i did was putting kwin in callgrind then just resize a window in all possible ways for 10 - 20 seconds. After that you get roughly this output as attached.
gray_set_cell has a very high usage of 40% of that callgrind. The second highest one is gray_render_line with "just" 16,6 percent.

This is probably not the whole reason why resizing is sluggish in linux but this hot path certainly contributes to it for Qt applications.

Now whenever i report issues i often hear the excuse that i "might" use low end hardware. Since apparently that often the case. Well, i can assure you that's not the case here, just look at my specs:
AMD 6870 on gallium
AMD Phenom 1100T CPU
6GB memory
SSD drive

So no, it certainly is not my specs.

Kind regards,
Mark