Hi,

I am currently puzzled by some code inside OSG to detect extensions. Example 
code:

_isSomethingSupported = OSG_GLES2_FEATURES || OSG_GL3_FEATURES ||
          isGLExtensionOrVersionSupported(contextID, "GL_EXT_something", 2.1);

Question 1:
Why we are sometimes testing for version? e.g. 2.1?
As the extension is in extension string anyway, is it correct to consider the 
version number as redundant while not harmful and mostly informative for 
programmer?

Problem 1:
If there is a reference to the OpenGL number (e.g. 2.1), it is not possible to 
disable the functionality by osg::setGLExtensionDisableString(). Is it true?

Question 2:
Why we are using OSG_GL3_FEATURES ? The extension should be included in the 
extension string in my opinion. Or, am I mistaken?

Problem 2: The same as problem 1 - functionality can not be disabled if using 
OSG_GL3_FEATURES.

Question 3:
Is the extension string of OpenGL ES the same as on standard OpenGL? Will it, 
for instance, contain GL_ARB_multitexture of OpenGL 1.3?

Thx,
John
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