[Cogl] Building minimal linux with cogl/ clutter

[Robert Bragg]

Cogl can now be used to render directly to the framebuffer using the
Linux Kernel Mode Setting api in libdrm. Currently this is only really
working in the experimental wip/fosdem-2012 branch where we have been
using that branch to successfully adapt the Mutter compositor into a
hybrid X and Wayland compositor.

If you fetch this branch you can pass --enable-kms-egl-platform to
./configure and if you have enabled multiple backends in cogl you can
force the kms backing either via cogl api or by setting
COGL_RENDERER=egl_kms in your environment.
After FOSDEM next week we hope to clean up the work in this branch and
land it in master.
The branch currently depends on some experimental patches for Mesa
that were sent to the wayland devel mailing list. You can get these
for now by cloning my user branch on fd.o:
http://cgit.freedesktop.org/~rib/mesa/ There have actually been some
more recent patches sent to the mailing list but we haven't yet
updated Cogl to work with those patches; we'll probably do that
shortly after FOSDEM.

In conjunction with the Cogl branch you can also use the experiment
wip/fosdem-2012 branch of Clutter, you just need to use
CLUTTER_BACKEND=eglnative and CLUTTER_INPUT_BACKEND=evdev.

You should note that these branches are quite experimental so you may
have some teething issues playing with them but I hope you are assured
that we are definitely interested in supporting direct rendering to
the framebuffer via KMS.

So you know; although some of this work is driven by wayland work we
have been doing, it's not a requirement to use wayland to use these
branches.

One notable thing you would have to deal with yourself if rendering
directly to the framebuffer is VT switching. We don't have code in
Cogl to deal with that since for our use case we've put that code into
Mutter. If you track the wip/wayland branch for mutter on
git.gnome.org though you can probably borrow some of the tty code we
have there.

I hope that helps.

kind regards,
- Robert
On Fri, Oct 14, 2011 at 10:34 AM, Martin Voigt <voigt.m at gmail.com> wrote:
> Hey *,
>
> what would be the best way to build clutter for a minimal, single user
> (runlevel 1) linux system (possibly) without x? Video supports drm. I
> guess the options are:
>
> * cogl with wayland
> * cogl with xlib-egl (would require x, but running clutter as X root
> window could be an option)
>
> Is it possible to build
>
> * cogl with rendering directly to drm/ framebuffer, without wayland or xlib?
>
> By "framebuffer" I mean the video framebuffer, not an offscreen buffer
> as the cogl documentation uses the term.
>
> Thanks in advance,
> Martin
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