Am 24.07.2014 um 14:13 schrieb Yves Bailly <yves.bai...@verosoftware.com>:

> 
> [Whenever a "Core Profile" is explicitly requested rendering stops workin]
> 
> If I try using some other version:
>   fmt.setVersion(3, 3);
>   fmt.setProfile(QGLFormat::CoreProfile);
> ...getGetString(GL_VERSION) gives "3.3.0" (as expected),

Not directly related to the actual problem, but just to add: in my 
understanding the actual OpenGL driver is free to choose a higher API version 
(e.g. 4.4), even when you explicitly request an older one (e.g. 3.3) - as long 
as the returned context is backwards-compatible, that is!

I am not sure whether that is the case here (all 3.3 shaders and GL code would 
run without modification in 4.4), but in general that is so.

So the fact that you really received a 3.3 context when asking for one from a 
4.4 capable driver is "possible" and maybe even "likely", but not necessarily 
"to be expected".

IIRC on OS X 10.9 you always get a 4.1 context, even when asking for a 3.2 
context (on hardware that supports it).

> but no triangle displayed.

Probably again because you are getting a "Core Profile".

> With:
>   fmt.setVersion(2, 1);
> ...getGetString(GL_VERSION) gives "4.4.0" (unexpected), and no triangle 
> displayed.

As already mentioned in a previous reply: maybe a bit "unexpected", but totally 
fine, because you get a "Compatibility" profile.



> 
> With simply requesting the profile, without giving a version:

Doesn't make sense really: profiles are only introduced on OpenGL 3.2 and above 
:)
> 
> Any idea about what's going on?

I strongly assume that you're not using any "fixed pipeline" functions such as 
glVertex etc. ;) so my best bet would be your shader code: did you copy/paste 
from some older OpenGL (ES) 2 shaders?

Check the GL error state then and when and especially the shader compile/link 
logs (return values)!

Cheers,
  Oliver
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