Xorg hell

XKCD weighs in, 2011-10-12

Ahhh, XFree86/Xorg. What a steaming pile of FUBAR it's been. Things are rapidly getting better, though (unfortunately, the framebuffer kernel layer now seems to be rotting slightly -- there's no intention, from what I can tell, to support Intel 965 for instance). I use Intel 965 video extensively, and have for some time -- info within might only be applicable to that card, and of course all of this may vary based on your Debian setup.

Good links

• "Sharpening the Intel Driver Focus" at Keith Packard's blog
• "A New Job, but Old Performance Fixes" at Carl Worth's blog
• "The X Window Innovation; Welcome to the New Xorg" on the Free Software Magazine's Xorg tags, and also "Xorg's Innovation: It's Not ALL About the Graphics (but there is quite a lot of it)" from those same tags

Keyboards

• Disable NumLock/CapsLock entirely via xmodmap -e "keycode # = """.
  • Replace # with the scancode (use xev and look for keycode)

Terminology

• Display: An X server, made up of one or more screens
• Screen: A display area for an X server, made up of one or more outputs, having the name hostname:displaynumber.screennumber
  • hostname should be left blank for local displays
• Monitor: An output/port to a physical display device, having a resolution and a position within a screen
  • LVDS: Integrated LCD (digital, differential signaling)
  • TMDS: DVI, HDMI (digital, differential signaling)
  • VGA: HD-15 (3-row DE-15) (analog)
  • S-Video: Mini-DIN 4 (analog)
• crtc? pipe?

Diagnostics/Control

• xdpyinfo(1) - X server information
  • Use the -ext extensionName option for extension-specific info (-ext all for all)
• xvinfo(1) - X-Video extension information
• glxinfo(1) - OpenGL implementation information (via GLX)
• glewinfo(1) - OpenGL extension information
• visualinfo(1) - OpenGL visual info
• xrandr(1) RandR (X Resize, Rotate and Reflect) extension information and control (operates on Monitors)
• xprop(1) Window and font property information (select window with mouseclick, -id or -name)
• fbset(1) Framebuffer information and control (use -i to get more (basic) info)
• xdriinfo(1) DRI (Direct Rendering Infrastructure) driver information for all screens
  • xdriinfo nscreens for screen count, xdriinfo driver screenno for drivers
  • xdriinfo option drivername/screenno for detailed configuration (as set using driconf(1))
• xbacklight(1) device backlight information and control
• xprop(1), xwininfo(1) display information about X objects specified via command line or mouse click

Sample Output

All output is from an i965 on a 64-bit Core 2 Duo machine.

• xdpyinfo output
• XVInfo output
• GLXInfo output
• glewinfo output
• visualinfo output
• xrandr output
• xdriinfo output

Multiple Monitors

• Xinerama, though venerable, is no longer the preferred methodology; XRandR has your back.
  • Ulrich Drepper has a good article
• Four modes: clone, span mode, extended desktop, multiseat
  • Clone: same image on each monitor (good for presentations etc)
  • Span mode: Stretch desktop of resolution 2M+N across two monitors of resolutions M and N
  • Extended desktop: Disjoint desktops of resolution M and N on monitors of resolutions M and N
  • Multiseat: Two distinct displays/inputs/users
• http://wiki.debian.org/XStrikeForce/HowToRandR12 seems up-to-date and useful

Configuration

• These days, the less in your xorg.conf, the (likely, almost certain) better
• Most necessary modules are these days automatically loaded or builtin
• xrandr obsoletes most monitor setup requirements, so long as DDC/EDID work

See Also

• GNOME page
• Intel 965 page
• CUDA page
• Video Acceleration on Linux