[compiz] Extension languages and Compiz.

Mike Dransfield mike at blueroot.co.uk
Thu Apr 26 04:35:15 PDT 2007

Robert Carr wrote:
> My recent work on Compiz-scheme has brought to my attention several
> problems preventing a real compiz extension language.
> Note that when I refer to an extension language, I am not referring to
> the ability to add plugins in some other languages, but more of
> something in the vein of emacs lisp.
> The major problem right now is extension languages are locked in to
> one plugin and what core exposes. What I mean by this is it's easy to
> add support for something like:
> (window-rule (make-rule (set-opacity-when (window-is tooltipp) 0.5)))
> However it's impossible to add support for something like:
> (scale-window-when (window-is negativep)).

I am not sure what your ultimate goals are, but this particular
example would be easy if you added a custom match handler to
the neg plugin.

AFAIK scale includes a scale_match action which you could pass
'neg=1' and that would only scale neg'd windows.

> There are two possible solutions to this:
> 1. Add basic support for a specific interpreter in core. Core would
> expose wrapper functions around the interpreter to easily enable
> plugins to add C functions to the interpreter. On one hand, we
> probably want to avoid binding core to a specific interpreter, on the
> other hand this sounds rather pleasant compared to the alternative.
> 2. Add an interpreter interface, with wrappable functions for plugins
> embedding a specific interpreter to wrap. I think it is abundantly
> obvious why such an interface would be unreasonably complex and likely
> bug ridden, exposing no specifics of an interpreter to individual
> plugins, but still having conversion from interpreter types->native
> types (a variable number of arguments per function + return types),
> plus adding new types and other constructs is exceedingly difficult,
> and complex to the point where I don't think we would want it.
> Does anyone else have any thoughts?
> Regards,
> Robert
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