mutter/src/compositor/plugins

Plugins implement effects associated with WM events, such as window map,
minimizing, maximizing, unmaximizing, destruction and workspace switching. The
plugin API is documented in src/include/compositor-clutter-plugin.h; in
addition the simple plugin can be used as a reference implementation.

The API is intended to be generic, exposing no implementation details of the WM
to the plugins; this will facilitate reuse without modification with another WM
(there are plans to use the same plugin API with Matchbox 2).

Multiple plugins can implement the same effect and be loaded at the same time;
however, stacking arbitrary effects in this way might not work as expected;
this is particularly true of more complex effects, such as those for workspace
switching.

Plugins are installed in ${prefix}/lib/metacity/plugins/clutter; from there the
WM will load plugins listed in the clutter_plugins key in the Metacity gconf
general preferences group. Each entry in preferences has the format

  'name: optional parameters'

where 'name' is the name of the library without the .so suffix.

As noted above, additional parameters can be passed to the plugin via the
preference key. In such case, the plugin name is immediately followed by a
colon, separating it from the parameters. Two common parameters should be
handled by all plugins:

  'debug'   indicates that the plugin is run in a debug mode (what exactly that
            means is left to the plugin to determine).

  'disable' parameter indicates which effects within the plugin should be
            disabled; the format of the disable parameter is

              'disable: effect1[, effect2];'

            where effect1, etc., matches the effects listed in the
            compositor-clutter-plugin.h file (currently one of 'map', 'destroy',
            'maximize', 'unmaximize', 'switch-workspace'). Example 'disable:
            minimize, maximize;'.