EGL_MESA_screen_surface proposal

Jon Smirl jonsmirl at gmail.com
Wed Mar 16 10:15:23 PST 2005


On Wed, 16 Mar 2005 10:18:26 -0700, Brian Paul
<brian.paul at tungstengraphics.com> wrote:
> Well, I think that's a pretty esoteric example.  We're starting to get
> into things that most people will never come across.  Still, I'm
> willing to be flexible.
> 
> Would a function like this suffice:
> 
> const char *eglQueryModeStringMESA(EGLDisplay dpy, EGLModeMESA mode);

This solves the problem. You can eliminate the interlace attibute if
this call is added.

The root of the problem is that there are more attributes on the mode
than are exposed in EGL. You could do a elgChooseMode(1024,768) and
get back 10 identical modes at the EGL level, but they would all be
different at the hardware level. EGL will pick the what it thinks is
the best mode and you won't be able to get to the others since you
can't tell them appart.

If you think it is better to leave this call out we can. The
alternative is the keypad +/- scheme that X uses to cycle through all
of the modes. The cycling scheme doesn't need a name..

> 
> The danger, of course, is that this mechanism might be abused by
> someone.  A similar example is OpenGL applications that query the
> GL_RENDERER string to check for specific information that might
> disappear in future drivers.
> 
> As a side note (not directed to Jon): I really want to keep the EGL
> API extension small and concise.  I want to capture 95% of what's
> needed now and not get too side-tracked with the other 5%.
> 
> The other 5% can be accomodated in the future with additional EGL
> extensions.  The key thing is to design the API with extensibility in
> mind.  That's why (for example) all the EGL datatypes are totally
> opaque, rather than C structs which would be a PITA to extend.
> 
> I've been involved in designing OpenGL extensions with the OpenGL ARB
> for 5 or 6 years now and I have seen first-hand how things can get
> derailed if one gets too side-tracked.  I don't want that to happen
> here.  I don't want to dictate this project, but I think my experience
> is worth something.
> 
> -Brian
> 


-- 
Jon Smirl
jonsmirl at gmail.com


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