EGL_MESA_screen_surface version 3

[Ian Romanick]

Michel Danzer wrote:
> On Fri, 2005-03-18 at 07:46 -0700, Brian Paul wrote:
> 
>>    5. Should the EGL_PHYSICAL_WIDTH/HEIGHT_EGL tokens be kept?  They're
>>       not always reliable (i.e. projectors) but can still be used to
>>       determine the pixel aspect ratio.
> 
> 
> If they're only useful for the pixel aspect ratio, they could be
> replaced by a single token for that.

This is the only issue that I have any strong feeling about.  If the 
only reliable use is to determine the aspect ratio, then we should just 
provide that value.  However, is this the aspect ratio of the display or 
of a pixel?  I assume it's the aspect ratio of the display, but should 
the pixel aspect be provided?  Either way, a single integer won't 
suffice.  How would 16:9 or 4:3 be represented?

>>    7. How should the notion of a screen's "native" mode be expressed?
>>       For example LDC panels have a native resolution and refresh rate
>>       but may support other sub-optimal resolutions.
>>
>>       At this time, the EGL_OPTIMAL_MESA values may be specified in
>>       eglChooseModeMESA() for EGL_WIDTH, EGL_HEIGHT, etc.
>>
>>       However, that violates the principle that eglChooseModeMESA()
>>       should be fully implementable in terms of the eglGetModesMESA and
>>       eglGetModeAttribMESA functions (as for eglChooseConfig).
> 
> Another option would be a special attribute like EGL_OPTIMAL. Modes that
> have this set would be preferred. The native resolution should be
> covered by the preference for larger modes, or are there displays that
> handle larger than native resolution?

So, would a multi-state value like GLX_VISUAL_CAVEAT_EXT work here?  We 
could also do something like GLX_SGIX_visual_select_group.  In that 
extension each fbconfig has a value, which is completely hidden from the 
application, that is used to break ordering ties.  I don't know if 
either of those is the right answer, but there is at least some 
implementation / usage experience with both.

http://oss.sgi.com/projects/ogl-sample/registry/EXT/visual_rating.txt
http://oss.sgi.com/projects/ogl-sample/registry/SGIX/visual_select_group.txt