Martin Vermeer wrote:
...and more importantly, you just confirmed my diagnosis of the problem. There is something in qt, or LyX's use of qt, that responds very badly to DRI both being turned on and practically unusable.
Clearly, qt4 think it is clever to use DRI for some things when it is available. It is probably faster than "standard X" when hardware is used for DRI, but much slower when the software fallback is used.
A user with trouble can run "glxinfo". If one of the first lines says "direct rendering: no", then software DRI is in use, and commenting out DRI from the "Module" section in xorg.conf will fix the performance problem. The long-term fix is to report the bug to qt developers. The information "glxinfo" displays is available to qt too, through standard DRI operations. They should not blindly use DRI if available - only if "direct rendering" is hw accelerated. Otherwise it is not a win. I have reported this qt4 bug through the debian bug report system - lets hope they fix it as the fix is a simple one. Helge Hafting
