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Elektrified X.org released (was: X configuration paradigm, and a proposal)
- From: Avi Alkalay <avibrazil gmail com>
- To: Development discussions related to Fedora Core <fedora-devel-list redhat com>, xdg-list <xdg-list freedesktop org>, Discuss issues related to the xorg tree <xorg freedesktop org>, Elektra <registry-list lists sourceforge net>, "Timothy D. Witham" <wookie osdl org>
- Subject: Elektrified X.org released (was: X configuration paradigm, and a proposal)
- Date: Tue, 30 Nov 2004 10:25:09 -0300
For people that still don't know the Elektra Project
(http://elektra.sourceforge.net), it provides an alternative back-end
for text configuration files. So instead, for example, the
human-readable-only xorg.conf file, we'll have a hierarchy of
key/value pairs easily and precisely accessible by X.org and also any
other programs through an API or command, and human beings too.
Same concept as GConf, but designed for system-wide use.
We've been working on X.org source code to do exactly what we just
described above. And it is ready for use, tested even with very
complex X.org configurations. A patched X server will convert your
xorg.conf file automatically, even the most complex ones, including
It is available at
You'll find there the patch against X.org source, the patch against
Fedora Core 3 RPM spec file (to see how to build it), and the README
file, which is pasted in this e-mail bellow.
We'll write patches for other software, and everybody is invited to
join this integration effort.
Elektra Project <http://elektra.sf.net>
ELEKTRIFIED X.ORG: PRECISE AND PROGRAMATICALY EASY X CONFIGURATION
Your X server has to work with your installed video card, monitor, find
your font server and dirs, modules, extensions, drivers, plugins.
You have to tell him how to integrate it all through its xorg.conf file.
If you need to change something, you start a text editor and use your
human brain and eyes to find the correct line, understand it, have the
skills to change it, and change it in order to work.
This is good for advanced technical guys, but very bad for people that
don't have this skills, and in fact, don't really want to. He just
wants to change the screen resolution to make that projector work with his
laptop, and go ahead with his sales presentation. This is just an example.
The point is: it is very difficult to make simple programs or scripts
that make simple changes to X configuration. Another example is a monitor
vendor that wants to support X, and for this he'd like to provide easy
installation of his product, without having to ask his user to read
documentation about horizontal Sync, and vertical refresh rates. For him
again is difficult to write some simple software that preciselly changes X
configuration to work correctly with his product.
The xorg.conf file (as most Unix configuration files) was designed for
The Elektra Project (http://elektra.sourceforge.net) introduces a new way
to handle configurations through a clean API (or command line
tool) that accesses atomic configuration data, into a standarized
hierarchycal tree of key-value pairs. It is similar to GConf, but
designed for system-wide use, which also implies it does not have
And this is what this patch is about: to make the X server look for its
configurations into a machine-ready tree of key-value pairs, instead of
the human-ready xorg.conf.
So where you had to look for "Device radeon" into a "Section Device",
with the key/value tree, X and other programs can look for it
system/sw/xorg/current/Devices/Videocard0/Driver = radeon
Where you once had to "vi" your "Section Monitor", now X and other
programs can do it accessing the keys:
system/sw/xorg/current/Monitors/Monitor0/HorizSync = 31.5 - 48.5
system/sw/xorg/current/Monitors/Monitor0/VertRefresh = 40.0 - 70.0
system/sw/xorg/current/Monitors/Monitor0/ModelName = IBM T40 LCD Panel
system/sw/xorg/current/Monitors/Monitor0/VendorName = IBM
Where once the salesman above had to "vi" the Screen Section to change
the resolution, color depth, etc, a program can help him accessing:
And so on....
We believe an elektrified X server can leverage more plug-and-play
configurations, providing configuration power to HW vendors in a
very simple way, and making users experience less painfull.
BEHAVIOR OF AN ELEKTRIFIED X SERVER
A patched X server will look for its configuration keys under the
system/sw/xorg/current first, then if not found it tries
If not found, it will default to some xorg.conf file, parse it, and store
in its internal structures, then convert and commit it to a set of
keys under system/sw/xorg/current, and reload these keys.
So you get automatic one-time conversion from xorg.conf to the
hierarchycal configuration key/value pairs
Very complex examples of xorg.conf files were tested for conversion. Even
undocumented configuration parameters (because the original source was
used as the reference).
The Elektrifyied X server also works for the Red Hat Graphical Boot,
where you still don't have mounted partitions, network, etc.
You'll need the elektra-devel package installed in order to build X with
1. Download and unpack X.org source code from
2. Download the xorg-x11-6.8.1-elektra.patch file from
3. Apply it:
~/src/xc$ cd ..
~/src$ patch -p0 < xorg-x11-6.8.1-elektra.patch
~/src$ cd xc
~/src/xc$ # ...configure your build in host.def
4. Enable the patch:
~/src/xc$ echo "#define UseElektra" >> config/cf/host.def
5. Build X.Org
You'll find the new X server as file xc/programs/Xserver/Xorg .
The patch will add the following files:
elektra.h (exported methods)
elektra.c (key fetching and X structs integration business logic)
xorg-example.conf (a very complex conf file to test conversion)
xelektrify.c (cmd to convert xorg.conf->keys and vice-versa)
README.Elektra (this file)
And it will instrument
to trigger the one-time conversion, and key fetching logic.
And instrument the Imakefiles for correct builds:
If "#define UseElektra" is not present in host.def, the patch is
completelly disabled, and you'll get a binary-identicall built as before
applying the patch. All patched code are surrounded by #ifdefs.
ELEKTRA MEETS X.ORG SOURCE CODE
or how we wrote the patch....
X.org has an xorg.conf parser that takes this steps to handle
1. Lexically parse the xorg.conf file
2. Put each Section info in an equivalent struct
3. Encapsulate all structs together and pass them to a validator
4. Use structs to define X behavior
This process is triggered by the xf86HandleConfigFile() method from
Each xorg.conf Section has an equivalent structure defined in
and the lexycall analyzer code to parse each Section is under
A fully parsed file has its equivalent structures encapsulated in a
parent XF86Config struct. We have:
struct XF86ConfModuleRec for the "Section Modules"
struct XF86ConfMonitorRec for the "Section Monitor"
struct XF86ConfDeviceRec for the "Section Device"
These structs are a pure computer representation of the text in each
Section, so the methods under "parser/" convert text to structs, and
the structs to text. This is how original X.org source handles xorg.conf.
The Elektrification add methods that act in steps 1 and 2 above. And also
include methods to convert each struct to a KeySet. Both old (xorg.conf)
and new (Elektra) ways to get configuration information can live together
and they are actually used to automatically convert xorg.conf to keys. So
at the first time you'll run your elektrified X server, it will:
1. Not find configuration keys (because it is the first time)
2. Parse xorg.conf into structs
3. Convert structs to Keys
4. Commit the keys to key database
5. Reload configurations from the key database
See the behavior in the previous section.
After assembling the XF86Config C structure, X will decode all its info
into more practicall parameters for its further operation.
As a side note, with a key/value pair configuration hierarchy paradigm,
the XF86Config assembling code (the parser) could be avoided, making X
look for its configurations in a programatically easier, yet
human-readable, configuration organization.
We worked at the parser level to keep compatibility and to not go too
deep in X.org source code.
The Elektra Project
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