How to further enhance XKB configuration
: The Basics
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2. The Basics
At the startup (or at later at user's command) X server starts its xkb
keyboard module extension and reads data from a compiled configuration
file.
This compiled configuration file is prepared by the program xkbcomp
which behaves altogether as an ordinary compiler (see man xkbcomp).
Its input are human readable xkb configuration files which are verified and
then composed into a useful xkb configuration. Users don't need to mess with
xkbcomp themselves, for them it is invisible. Usually, it is started
upon X server startup.
As you probably already know, the xkb configuration consists of five
main modules:
- Keycodes
Tables that defines translation from keyboard scan codes into reasonable
symbolic names, maximum, minimum legal keycodes, symbolic aliases and
description of physically present LED-indicators. The primary sence of
this component is to allow definitions of maps of symbols (see below)
to be independent of physical keyboard scancodes. There are two main
naming conventions for symbolic names (always four bytes long):
- names which express some traditional meaning like
<SPCE> (stands for space bar) or
- names which express some relative positioning on a keyboard, for
example
<AE01> (an exclamation mark on US keyboards), on
the right there are keys <AE02>, <AE03>
etc.
- Types
Types describe how the produced key is changed by active modifiers (like
Shift, Control, Alt, ...). There are several predefined types which
cover most of used combinations.
- Compat
Compatibility component defines internal behaviour of modifiers. Using
compat component you can assign various actions (elaborately described
in xkb specification) to key events. This is also the place where
LED-indicators behaviour is defined.
- Symbols
For i18n purposes, this is the most important table. It defines what
values (=symbols) are assigned to what keycodes (represented by their
symbolic name, see above). There may be defined more than one value
for each key and then it depends on a key type and on modifiers state
(respective compat component) which value will be the resulting one.
- Geometry
Geometry files aren't used by xkb itself but they may be used by some
external programs to depict a keyboard image.
All these components have the files located in xkb configuration tree
in subdirectories with the same names (usually in /usr/lib/X11/xkb).
How to further enhance XKB configuration
: The Basics
Previous: Overview
Next: Enhancing XKB Configuration
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