Another thought about CSS themes

There is a standard set of buttons you can use in Metacity.  Here is a rather nice diagram I drew a few months ago which tells you what they are and what they do.

The question I am pondering is whether we should allow window managers which use Cowbell CSS themes to specify new buttons outside the standard set of menu, close, minimize, maximize, shade, stick, above.

Why we should:

• I want to make Cowbell as usable as possible by other window managers.  If a window manager has a button that can't be represented in that set, they can't use the theme format.
• I would like to add new buttons to Metacity anyway, like screenshot and share.

Why we shouldn't:

• Most importantly, themes need to declare how to draw buttons.  If we're going to allow people to come up with arbitrary buttons, how is the theme going to know how to draw them?  People can't write themes which know how to draw every button type anyone could ever dream up in the future.  I discussed this in more depth here.