Since 321 people have read my post, I thought I ought to answer the question myself, as no one else has.
Fedora looks for a keyboard in /usr/share/X11/xkb/symbols/. It will take the file that has been selected — e.g. "gb" for a UK keyboard — and look up anything that it doesn't find there in the "latin" file. Obviously, you can modify the default or add a new entry using it as a model. Keys are referred to by codes like <AC01> for the first key on the third row up of the alphanumeric area. Three have special names: <TLDE> grave (sic); <BKSL> backslash in US, hash in UK; <LSGT> backslash in UK. Characters are referred to by unicode number (e.g. U00E6) or by special names like "dead_acute" — see /usr/include/X11/keysymdef.h
A new keyboard must be listed in /usr/share/X11/xkb/rules/base.lst and defined in /usr/share/X11/xkb/rules/base.xml thus
<name> file_name </name>
<shortDescription> brief_name </shortDescription>
<description> descriptive_name </description>
If you have two keyboards installed, you can switch with a group-switch key, defined with the Gnome menu: system-preferences-keyboard.
The AltGr key is enabled by default, but a Multi or Compose key has to be selected with Gnome (try a Windows key).
Permitted combinations with diacritics are built into the kernel. Thus both
<Compose> <a> <'>
will give a-acute. You can get s-acute similarly, but not k-acute: someone thought of entering Polish, but not of transliterating Macedonian. Published lists of combinations are all wrong: to find what's available use
Last edited by DavidMcCann; 10-10-2007 at 10:55 AM.
Reason: I forgot the last sentence