[Fwd: Re: CVS Update: xc (branch: trunk)]

[Adam Jackson]

On Tuesday 04 January 2005 17:27, Roland Mainz wrote:
> Keith Whitwell wrote:
> > Please don't do this - this is not "better" or reccomended GL usage.
>
> Uhm... why ? Multiple GL experts claimed that X11R6.8.0 glxgears is
> "broken" (based in the internal feedback from
> https://bugs.freedesktop.org/show_bug.cgi?id=1793)

I'm sorry, but #1793 is about glxgears showing time-domain aliasing on 
Solaris.  This is completely expected behaviour for GL apps not using vsync 
or a synchronization extension.

> and suggested either 
> an event-driven application model or to call at least |glFinish()|. The
> first option wasn't possible (which would be preferable here as both
> client and Xserver can run "decoupled" but still avoiding that the
> client can send rendering instructions faster then the server can handle
> them) as it seems to require GLX 1.3 so I used |glFinish()|.

The bug, then, is that we don't support GLX 1.3.

> > The problem as such is with the driver not the application, and GL
> > applications in general do not do this.   By hiding the behaviour in
> > glxgears you are removing the incentive to fix the real problem.
>
> The original behaviour (in Xorg X11R6.7.x) was to call |XSync()| which
> was considered a ugly hack. Then I removed that for X11R6.8.x, resulting
> in the current problem. But if you look at my patch you'll see that you
> can get all the old behaviour:
> % glxgears -no_glfinish_after_frame # will restore the original
> X11R6.8.0 spam-to-death behaviour,
> % glxgears -no_glfinish_after_frame -xsync_after_frame # will restore
> the original X11R6.7.0 behaviour. Additionally you can ask for two other
> methods of sync'ing (see -sched_yield_after_frame and
> -xflush_after_frame) so everyone should be happy (well, I would prefer
> the event-driven model but it seems someone will have to update the GLX
> wire protocol level first... ;-().

You do four methods of syncing in a row.  All by default.  Including XSync.  
How is that better than the 6.7 behaviour, if that was considered a hack?

- ajax
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