http://bugs.winehq.org/show_bug.cgi?id=27959
--- Comment #9 from Steven redalert.commander@gmail.com 2011-08-13 10:13:47 CDT --- Thanks for looking into this Stefan.
I did another test with wine 1.3.26 (with the offending commit) using twinview as you suggested. C&C Generals Zero Hour doesn't even start, it gives me the message that directX 8.1 isn't installed (same message as I used to have when an x-org update overwrites some link from the NVidia driver, not a problem anymore since I switched to Debian provided drivers). Starcraft 2 does start in twinview mode, with a good framerate, yet only shows on the first monitor with large black areas to the left and right giving a 'vertically compressed' image (still on the first monitor, second monitor doesn't show anything different than with xinerama). I'm able to move the mouse, but unable to click any button, or the area where they should be, the game still reacts to the keyboard as it should.
When in xinerama mode I ran the following command: $ glxinfo | grep "direct rendering" direct rendering: Yes
This drastic drop in framerate only appears to be affecting wine, native games like chromium BSU and open arena run fine. However not every game in wine is affected, GTA Vice City runs fine.