Thoughts about decoration information in the xdg_shell

Neil Roberts neil at
Mon Nov 18 07:22:23 PST 2013

Thiago Macieira <thiago.macieira at> writes:

> Make it simpler: all clients MUST be able to draw decorations. That's what 
> Wayland up until now requires anyway.

I think it's a shame to throw out the idea of making the policy be that
clients are allowed to expect SSD if they don't want to draw decorations
themselves. Requiring CSD support only makes it simpler for compositor
developers, but it adds a lot of burden on things like SDL, glut and
applications that really just want a space to render GL content into.

I guess you could make a toolkit-agnostic decorations library using
subsurfaces that these types of applications can use. However I don't
think that will solve the consistency issue because most game-type
applications will want to bundle all of their dependencies so they will
end up wanting to bundle this library. The consistency will then break
when the distro updates its version of the library.

I think the most important decision to make for xdg-shell is whether to
require CSD support or SSD support. How it is actually negotatied is not
as important. I think you have to have a policy of requiring support for
one or the other because it'd be a mess to have a situation where some
apps can't work on certain compositors.

If Gnome Shell doesn't add support for SSD then I suppose that
effectively mandates CSD support in clients that want to be portable
regardless of what is specified in xdg-shell.

It looks like the main incentive to not require SSD support is that it
creates work for the Gnome Shell developers. However you have to bear in
mind that requiring CSD also creates work for all other toolkit
developers which may turn out to be more work overall.

- Neil
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