Xorg-7.7 Testing and Configuration

Testing Xorg

To test the Xorg installation, issue startx. This command brings up a rudimentary window manager called twm with three xterm windows and one xclock window. The xterm window in the upper left is a login terminal and running exit from this terminal will exit the X Window session. The third xterm window may be obscured on your system by the other two xterms.

Generally, there is no specific configuration required for Xorg, but customization is possible. For details see the section called “Setting up Xorg Devices” below.

Checking the Direct Rendering Infrastructure (DRI) Installation

DRI is a framework for allowing software to access graphics hardware in a safe and efficient manner. It is installed in X by default (using MesaLib) if you have a supported video card.

To check if DRI drivers are installed properly, check the log file /var/log/Xorg.0.log for statements such as:

(II) intel(0): direct rendering: DRI2 Enabled


(II) NOUVEAU(0): Loaded DRI module


DRI configuration may differ if you are using alternate drivers, such as those from NVIDIA or ATI.

Although all users can use software acceleration, any hardware acceleration (DRI2) is only available to root and members of the video group.

If your driver is supported, add any users that might use X to that group:

usermod -a -G video <username>

Another way to determine if DRI is working properly is to use one of the two optionally installed OpenGL demo programs in MesaLib-10.2.7. From an X terminal, run glxinfo and look for the phrase:

name of display: :0
display: :0  screen: 0
direct rendering: Yes

If direct rendering is enabled, you can add verbosity by running LIBGL_DEBUG=verbose glxinfo. This will show the drivers, device nodes and files used by the DRI system.

To confirm that DRI2 hardware acceleration is working, you can (still in the X terminal) run the command glxinfo | egrep "(OpenGL vendor|OpenGL renderer|OpenGL version)". If that reports something other than Software Rasterizer then you have working acceleration for the user who ran the command.

If your hardware does not have any DRI2 driver available, it will use a Software Rasterizer for Direct Rendering. In such cases, you can use a new, LLVM-accelerated, Software Rasterizer called LLVMPipe. In order to build LLVMPipe just make sure that LLVM-3.5.0 is present at MesaLib build time. Note that all decoding is done on the CPU instead of the GPU, so the display will run slower than with hardware acceleration. To check if you are using LLVMpipe, review the output ot the glxinfo command above. An example of the output using the Software Rasterizer is shown below:

OpenGL vendor string: VMware, Inc.
OpenGL renderer string: Gallium 0.4 on llvmpipe (LLVM 3.2, 256 bits)
OpenGL version string: 2.1 Mesa 9.1-devel (git-cb3b172)

You can also force LLVMPipe by exporting the LIBGL_ALWAYS_SOFTWARE=1 environment variable when starting Xorg.

Again, if you have built the Mesa OpenGL demos, you can also run the test program glxgears. This program brings up a window with three gears turning. The X terminal will display how many frames were drawn every five seconds, so this will give a rough benchmark. The window is scalable, and the frames drawn per second is highly dependent on the size of the window. On some hardware, glxgears will run synchronized with the vertical refresh signal and the frame rate will be approximately the same as the monitor refresh rate.

Hybrid Graphics

Hybrid Graphics is still in experimental state for Linux. Xorg Developers have developed a technology called PRIME that can be used for switching between integrated and muxless discrete GPU at will. Automatic switching is not possible at the moment.

In order to use PRIME for GPU switching, make sure that you are using Linux Kernel 3.4 or later (recommended). You will need latest DRI and DDX drivers for your hardware and Xorg Server 1.13 or later with an optional patch applied.

Xorg Server should load both GPU drivers automaticaly. In order to run a GLX application on a discrete GPU, you will need to export the DRI_PRIME=1 environment variable. For example,

DRI_PRIME=1 glxinfo | egrep "(OpenGL vendor|OpenGL renderer|OpenGL version)"

will show OpenGL vendor, renderer and version for the discrete GPU.

If the last command reports same OpenGL renderer with and without DRI_PRIME=1, you will need to check your installation.

Xft Font Protocol

Xft provides antialiased font rendering through Freetype, and fonts are controlled from the client side using Fontconfig. The default search path is /usr/share/fonts and ~/.fonts. Fontconfig searches directories in its path recursively and maintains a cache of the font characteristics in fonts.cache-1 files in each directory. If the cache appears to be out of date, it is ignored, and information is (slowly) fetched from the fonts themselves. This cache can be regenerated using the fc-cache command at any time. You can see the list of fonts known by Fontconfig by running the command fc-list.

If you've installed Xorg in any prefix other than /usr, the X fonts were not installed in a location known to Fontconfig. This prevents Fontconfig from using the poorly rendered Type 1 fonts or the non-scalable bitmapped fonts. Symlinks were created from the OTF and TTF X font directories to /usr/share/fonts/X11-{OTF,TTF}. This allows Fontconfig to use the OpenType and TrueType fonts provided by X (which are scalable and of higher quality).

Fontconfig uses names such as "Monospace 12" to define fonts. Applications generally use generic font names such as "Monospace", "Sans" and "Serif". Fontconfig resolves these names to a font that has all characters that cover the orthography of the language indicated by the locale settings. Knowledge of these font names is included in /etc/fonts/fonts.conf. Fonts that are not listed in this file are still usable by Fontconfig, but they will not be accessible by the generic family names.

Standard scalable fonts that come with X provide very poor Unicode coverage. You may notice in applications that use Xft that some characters appear as a box with four binary digits inside. In this case, a font set with the available glyphs has not been found. Other times, applications that don't use other font families by default and don't accept substitutions from Fontconfig will display blank lines when the default font doesn't cover the orthography of the user's language. This happens, e.g., with Fluxbox in the ru_RU.KOI8-R locale.

In order to provide greater Unicode coverage, it is recommended that you install these fonts:

  • DejaVu fonts - These fonts are replacements for the Bitstream Vera fonts and provide Latin-based scripts with accents and Cyrillic glyphs.

  • FreeFont - This set of fonts covers nearly every non-CJK character, but is not visually pleasing. Fontconfig will use it as a last resort to substitute generic font family names.

  • Microsoft Core fonts - These fonts provide slightly worse Unicode coverage than FreeFont, but are better hinted. Be sure to read the license before using them. These fonts are listed in the aliases in the /etc/fonts/conf.d directory by default.

  • Firefly New Sung font - This font provides Chinese coverage. This font is listed in the aliases in the the /etc/fonts/conf.d directory by default.

  • Arphic fonts - A similar set of Chinese fonts to the Firefly New Sung font. These fonts are listed in the aliases in the /etc/fonts/conf.d directory by default.

  • Kochi fonts - These provide Japanese characters, and are listed in the aliases in the /etc/fonts/conf.d directory by default.

  • Baekmuk fonts - These fonts provide Korean coverage, and are listed in the aliases in the /etc/fonts/conf.d directory by default.

  • Cantarell fonts - The Cantarell typeface family provides a contemporary Humanist sans serif. It is particularly optimised for legibility at small sizes and is the preferred font family for the GNOME-3 user interface.

The list above will not provide complete Unicode coverage. For more information, please visit the Unicode Font Guide.

Rendered examples of many of the above fonts can be found at this font analysis site.

As a font installation example, consider the installation of the DejaVu fonts. From the unpacked source directory, run the following commands as the root user:

install -v -d -m755 /usr/share/fonts/dejavu &&
install -v -m644 *.ttf /usr/share/fonts/dejavu &&
fc-cache -v /usr/share/fonts/dejavu

Setting up Xorg Devices

For most hardware configurations, modern Xorg will automatically get the server configuration correct without any user intervention. There are, however, some cases where auto-configuration will be incorrect. Following are some example manual configuration items that may be of use in these instances.

Setting up X Input Devices

For most input devices, no additional configuration will be necessary. This section is provided for informational purposes only.

A sample default XKB setup could look like the following (executed as the root user):

cat > /etc/X11/xorg.conf.d/xkb-defaults.conf << "EOF"
Section "InputClass"
    Identifier "XKB Defaults"
    MatchIsKeyboard "yes"
    Option "XkbOptions" "terminate:ctrl_alt_bksp"

Fine Tuning Display Settings

Again, with modern Xorg, little or no additional configuration is necessary. If you should need extra options passed to your video driver, for instance, you could use something like the following (again, executed as the root user):

cat > /etc/X11/xorg.conf.d/videocard-0.conf << "EOF"
Section "Device"
    Identifier  "Videocard0"
    Driver      "radeon"
    VendorName  "Videocard vendor"
    BoardName   "ATI Radeon 7500"
    Option      "NoAccel" "true"

Another common setup is having multiple server layouts for use in different environments. Though the server will automatically detect the presence of another monitor, it may get the order incorrect:

cat > /etc/X11/xorg.conf.d/server-layout.conf << "EOF"
Section "ServerLayout"
    Identifier     "DefaultLayout"
    Screen      0  "Screen0" 0 0
    Screen      1  "Screen1" LeftOf "Screen0"
    Option         "Xinerama"

Last updated on 2013-05-05 11:02:40 -0700