It uses a new config group Blacklist in kwinrc with two subgroups for Lanczos and Blur.
The key of each entry in the group referrences the vendor either using GL_VENDOR or GL_RENDERER, e.g. "Intel" in renderer for Intel based chips.
The value of the entries is a stringlist containing exactly the renderer information. This way it is possible to blacklist several mesa driver versions which are buggy.
The blacklist is currently empty and will be filled with a kconf update script (which could also be done by distributions). So all users who experience problems and are subscribed to the bugs receiving this message, please upload your glxinfo.
An example for a blacklist:
[Blacklist][Lanczos]
NVIDIA=GeForce 9400M/PCI/SSE2
CCBUG: 243181
CCBUG: 242985
svn path=/trunk/KDE/kdebase/workspace/; revision=1146195
4111a9f051