3 This page describes how to add a custom layout or option so that it will be
4 parsed by libxkbcommon.
6 **The below requires libxkbcommon as keymap compiler and does not work in X**.
10 libxkbcommon searches the following paths for XKB configuration files:
11 - `$XDG_CONFIG_HOME/xkb/`, or `$HOME/.config/xkb/` if the `$XDG_CONFIG_HOME`
12 environment variable is not defined
14 - `$XKB_CONFIG_ROOT` if set, otherwise `<datadir>/X11/xkb/` (path defined by the
15 `xkeyboard-config` package, on most distributions this is
18 A keymap created with `xkb_keymap_new_from_names()` will look up those paths in
19 order until the required data is found.
21 **Note: Where libxkbcommon runs in a privileged context, only the system
22 (datadir) path is available.**
24 Each directory should have one or more of the following subdirectories:
26 - `geometry` (libxkbcommon ignores this directory)
34 Due to how XKB is configured, there is no such thing as a "layout" in XKB
35 itself, or, indeed, any of the rules, models, variant, options (RMLVO) decribed
36 in `struct xkb_rule_names`. RMLVO names are merely lookup keys in the
37 rules file provided by xkeyboard-config to map to the correct keycode, compat,
38 geometry (ignored by libxkbcommon), symbols and types (KcCGST). The KcCGST data
39 is the one used by XKB and libxbkcommon to map keys to actual symbols.
41 For example, a common RMLVO configuration is layout "us", variant "dvorak" and
42 option "terminate:ctrl_alt_bksp". Using the default rules file and model
43 this maps into the following KcCGST components:
47 xkb_keycodes { include "evdev+aliases(qwerty)" };
48 xkb_types { include "complete" };
49 xkb_compat { include "complete" };
50 xkb_symbols { include "pc+us(dvorak)+inet(evdev)+terminate(ctrl_alt_bksp)" };
51 xkb_geometry { include "pc(pc105)" };
55 A detailed explanation of how rules files convert RMLVO to KcCGST is out of
56 scope for this document. See [the rules file](md_doc_rules-format.html) page
62 Adding a layout requires that the user adds **symbols** in the correct location.
64 The default rules files (usually `evdev`) have a catch-all to map a layout, say
65 "foo", and a variant, say "bar", into the "bar" section in the file
66 `$xkb_base_dir/symbols/foo`.
67 This is sufficient to define a new keyboard layout. The example below defines
68 the keyboard layout "banana" with an optional variant "orange"
71 $ cat $XDG_CONFIG_HOME/xkb/symbols/banana
72 // Like a US layout but swap the top row so numbers are on Shift
73 default partial alphanumeric_keys
76 name[Group1]= "Banana (US)";
78 key <AE01> { [ exclam, 1] };
79 key <AE02> { [ at, 2] };
80 key <AE03> { [ numbersign, 3] };
81 key <AE04> { [ dollar, 4] };
82 key <AE05> { [ percent, 5] };
83 key <AE06> { [ asciicircum, 6] };
84 key <AE07> { [ ampersand, 7] };
85 key <AE08> { [ asterisk, 8] };
86 key <AE09> { [ parenleft, 9] };
87 key <AE10> { [ parenright, 0] };
88 key <AE11> { [ underscore, minus] };
89 key <AE12> { [ plus, equal] };
92 // Same as banana but map the euro sign to the 5 key
93 partial alphanumeric_keys
94 xkb_symbols "orange" {
95 include "banana(basic)"
96 name[Group1] = "Banana (Eurosign on 5)";
101 The `default` section is loaded when no variant is given. The first example
102 sections uses ``include`` to populate with a symbols list defined elsewhere
103 (here: section `basic` from the file `symbols/us`, aka. the default US keyboard
104 layout) and overrides parts of these
105 symbols. The effect of this section is to swap the numbers and symbols in the
106 top-most row (compared to the US layout) but otherwise use the US layout.
108 The "orange" variant uses the "banana" symbols and includes a different section
109 to define the eurosign. It does not specificially override any symbols.
111 The exact details of how `xkb_symbols` work is out of scope for this document.
115 For technical reasons, options do **not** have a catch-all to map option names
116 to files and sections and must be specifically mapped by the user. This requires
117 a custom rules file. As the `evdev` ruleset is hardcoded in many clients, the
118 custom rules file must usually be named `evdev`.
121 $ cat $XDG_CONFIG_HOME/xkb/rules/evdev
123 custom:foo = +custom(bar)
124 custom:baz = +other(baz)
129 This rules file maps the RMLVO option "custom:foo" to the "bar" section in the
130 `symbols/custom` file and the "custom:baz" option to the "baz" section in the
131 `symbols/other` file. Note how the RMLVO option name may be different to the
132 file or section name.
134 The `include` statement includes the system-provided `evdev` ruleset. This
135 allows users to only override those options they need.
137 The files themselves are similar to the layout examples in the previous section:
140 $ cat $XDG_CONFIG_HOME/xkb/symbols/custom
141 // map the Tilde key to nothing on the first shift level
142 partial alphanumeric_keys
144 key <TLDE> { [ VoidSymbol ] };
147 $ cat $XDG_CONFIG_HOME/xkb/symbols/other
148 // map first key in bottom row (Z in the US layout) to k/K
149 partial alphanumeric_keys
151 key <AB01> { [ k, K ] };
155 With these in place, a user may select any layout/variant together with
156 the "custom:foo" and/or "custom:baz" options.