[compiz] Plugin Dependencies

[David Reveman]

On Thu, 2007-02-22 at 15:46 +0000, Ben Reeves wrote:
> I'm continuing to work on compiz-settings now. The most common
> complaintat the moment is the way it activates plugins, a lot will
> fail to activate due to being loaded in the wrong order. At the moment
> It has a small db of known plugins and has load_before and load_after
> for each one, however if a plugin is unknown it will be loaded last
> and will fail to activate. 

You shouldn't keep a small db of known plugins. The dbus plugin should
be able to give you the dependencies of any plugin so you can sort them
properly and generate proper error messages if some plugin can't
possibly be loaded due to some conflicts.

> 
> I think it would be much better if every plugin carries it's own
> load_before, load_after and depends_on options and the core then
> decides in what order to activate the plugins. This would make writing
> a settings manager much easier, make it easier to start compiz and
> save duplicated effort so that each settings manager doesn't have to
> do it's own form of dependency generation. To activate a plugin the
> settings manager could simply send a dbus signal activate "cube" and
> the core would return whether it has activate any dependencies e.g.
> activated "rotate" and if plugin activation was successful or not. 
> 
> What do you think?

I don't see any good reason to why we would want the dependency order
resolved by the core. We can add an utility function and put it in core
or better in some shared library which can be used to solve dependencies
at the plugin or application level. What do you think?

That plugins can be stacked differently, is a feature. It might not be
incredibly useful right now but I think it will be later on so I'd like
to keep it.

- David