[Mesa-dev] [PATCH] GLX: Add an env var to enable the support of GLX extensions needing both client and server support, in case of client support and direct rendering.

[Kenneth Graunke]

On Wednesday, June 18, 2014 11:32:45 PM Axel Davy wrote:
> In the case of XWayland, there's no accelerated indirect rendering.
> For example GLX_ARB_create_context is not advertised by the server,
> and according to the spec, we are not allowed to advertise it
> to the application because of that.
> 
> This env var makes Mesa ignore this restriction, and
> a GLX extension is advertised whenever the client supports it.
> 
> Signed-off-by: Axel Davy <axel.davy at ens.fr>
> ---
>  src/glx/glxextensions.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)

In this specific case, I think it might make sense to just advertise the 
extension and return a GLX error if asked for indirect rendering.  Or, just 
lie and return a direct rendering context.

That would make the common case that most people want (GLX_ARB_create_context 
for direct rendered 3.2+ core profile stuff) work out of the box, without the 
need for environment variables.  It's technically out of spec, but for X on 
Wayland, I think it's not unreasonable.

On the other hand, supporting AIGLX of sorts might be possible...

With XWayland, there are really a couple layers to "indirect" rendering...
1. Doing it X client side (direct rendering)
2. Doing it in the XWayland X11 server/Wayland client (semi-indirect).
3. Doing it wherever Weston/etc are running (total indirect).

It seems like XWayland could support AIGLX with model #2 - X clients would 
speak GLX protocol to XWayland, which could then do the GL.  Model #3 seems 
like something we should avoid at all costs.

Of course, I don't know that there's any *benefit* to supporting AIGLX in 
XWayland, so...my real suggestion is to just raise a GLX error or lie if asked 
to create an indirect context.

--Ken
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