Re: Why run xserver on the OpenGL API?

Jon Smirl wrote:
> --- Keith Packard <[email protected]> wrote:
> 
>>>2) With OpenGL under xserver all windows will always have the OpenGL API
>>>available. xlib can slowly phased out. OpenGL is a well designed API
>>
>>suitable of
>>
>>>the next 10 years. 
>>
>>I'm not sure this is desirable; with the 2D Render API sitting atop GL 
>>where GL is available, having apps use that API will still let us run 
>>reasonably fast software implementations, Mesa still has a lot of 
>>overhead, especially on machines with limited CPU performance (or a lack 
>>of an FPU, like arm machines).

There's only a limited window of time where these incomplete machines will 
continue to exist.  I'm told we'll be seeing full GL implementations right 
down to cellphone devices within a year or so.  I don't think it's wise to 
design to a disappearing anomoly - ie non-GL capable hardware.

> Limited machines could just continue to use the existing xlib API and existing
> xservers.
> 
> What you don't want to do is make OpenGL an option in the new desktop servers.
> If it is a known fact that OpenGL will be in every freedesktop xserver no matter
> what the hardware, then apps will get written to use it. But if OpenGL is an
> option, few people will write to it - that's the state we're in right now.
> Instead they will stick with the 'standard' xlib API because it will be more
> 'compatible'. Every window created on the xserver needs to support OpenGL from
> day one.

I hadn't thought this through, but it makes a lot of sense.

> Apps that are targeted to tiny machines will use xlib. freedesktop xserver will
> of course support xlib as a compatility mode. Besides, whose to say that we
> won't see OpenGL on tiny machines, that's what EmbeddedGL is all about. keithw
> can give us some size numbers for EmbeddedGL.

Even embedded GL is a bit of a mistake for broad deployments for the reason 
listed above - all new hardware will support full GL very soon.

> Even if we shipped a fully OpenGL enabled xserver today it will still take years
> for a significant number of apps to get converted. Converting toolkits to OpenGL
> will be a big help. But we need to get the full 3D conversion in motion since we
> don't want to end up five years from now with all MS apps converted and nothing
> happening on Linux. The decision to convert the industry to 3D hardware has
> already been made (because of MS); we just have to decide if Linux to going to
> take advantage of it.

I really like this long view you're taking, Jon.

Keith