Re: [Chromium-dev] OpenGL-ES

[Brian P. <bri...@tu...>]

James Amendolagine wrote:
> On Thu, 2004-09-16 at 18:46, Brian Paul wrote:
> 
>>James Amendolagine wrote:
>>
>>>On Thu, 2004-09-16 at 13:41, Mike Houston wrote:
>>>
>>>
>>>>I don't think anyone is currently working on this, but the extensions 
>>>>should be easy to add if you were so inclined.  You can pretty much just 
>>>>replicate the floating point versions and use the new types.
>>>>
>>>>The EGS stuff looks to be more tricky...
>>>
>>>Actually I believe it's EGL..
>>>
>>>
>>>By the way, I've just started working with Chromium (a couple of weeks
>>>ago), and I'm very impressed. 
>>>
>>>
>>>So if no-one has done this before, I'll just jump in and do it myself. 
>>>
>>>
>>>I don't understand the internals well enough yet to have a very useful
>>>opinion, but one of my concerns with adding the calls as extensions is
>>>will the SPU's still work? ie will the state tracking still be valid?
>>>
>>>
>>>When any of the OpenGL version of these ES calls are made: 
>>>glClearColorx
>>>glClearDepthf
>>>glClearDepthx
>>>glColor4x
>>>glDepthRangef
>>>glDepthRangex
>>>
>>>I imagine that chromium records the state. I guess that I could just
>>>replicate the state management that is being done within the associated
>>>OpenGL Chromium call. 
>>>
>>>so I add a call glClearColorx, and look at the origional glClearColor,
>>>and just replicate most of the function...
>>>
>>>It looks like this would be done in state_tracker/state_buffer.c
>>
>>Would it be feasible to simply translate the glFoox functions into the 
>>corresponding conventional OpenGL functions at the dispatch layer? 
>>That is:
>>
>>void glClearDepthx(GLclampx value)
>>{
>>    glClearDepth(FixedToDouble(value));
>>}
>>
>>That could be implemented in the opengl_stub/* files fairly easily, I 
>>think, without having to touch the rest of the system.
>>
>>I haven't looked at the ES functions closely enough to know if there's 
>>any potential pitfalls.
> 
> 
> I'm going to spend the rest of the day stepping through the debugger to
> get a better feel for what's going on inside chromium -- to avoid
> getting too deep into a discussion and only guessing a the details. 
> 
> 
> 
> 
> My first thoughts on the above are this though: 
> void glClearDepthx(GLclampx value)
> 
>>{
>>    glClearDepth(FixedToDouble(value));
>>}
>>
>>
> 
> 
> This would give chromium the ability to look like gl-es to gl-es
> applications, and render on OpenGL targets. It would also allow the
> entire chromium system, spu's etc to function -- but would it give the
> ability to render to gl-es targets?

No.  That would be a lot more work.  Going through all of Chromium and 
disabling the non-ES functions would be too much work to even 
consider.  Despite all the Python auto-code generation (derived from 
the API description file), there's lots of hand coding that would be 
effected.

One potential short-cut would be to modify the render SPU so that 
calls to non-ES functions would get no-op'd and others (such as 
glClearDepth) would get translated into the ES counterparts (such as 
glClearDepthx).

-Brian