Ok... so an update:
The most recent Debian 2.5 packages seem to default to 1024x768 in the bottom left of a 1920x1080 screen.
2.6-dev correctly detects 1920x1080 but sets both monitors to shared output. It also gives the correct full screen resolutions (3840x1080 and 1920x1080) in the options. Using SDL_VIDEO_FULLSCREEN_HEAD=0 does limit it to only display on a single monitor.
My concern however was with the almost stable 2.5, especially if it will finally get an official release in Debian (and derivatives) and other distros. It might put people off if they get this odd sized and misaligned screen, especially as there is no way to fix it in the options, you need to edit the config file and specify the height & width manually.
So after adding my own definition (24) for 1080p to cl_video.cpp and compiling the code, it still defaults to 1024x768 in a bigger window (so there is no detection happening there), but the option does appear in the list of available modes in the Options, and when selecting it and restarting the game, it does restart at the correct res.
I think this little change would make life easier for newbies to get into the game if we can't fix the detection issue for 2.5
diff --git a/src/client/cl_video.cpp b/src/client/cl_video.cpp
index ed74f43..dab46fb 100644
--- a/src/client/cl_video.cpp
+++ b/src/client/cl_video.cpp
@@ -70,7 +70,8 @@ static const vidmode_t vid_modes[] =
{ 1400, 1050, 20 }, /* samsung x20 */
{ 1440, 900, 21 },
{ 1024, 600, 22 }, /* EEE PC */
- { 800, 480, 23 } /* OpenPandora */
+ { 800, 480, 23 }, /* OpenPandora */
+ { 1920, 1080, 24 } /* 1080p */
};
/**