Why is glewIsSupported() wrong?

OpenGL OpenGL: Advanced Coding
1

I have the following code:


    GLenum err = glewInit();
    cerr << glGetString(GL_EXTENSIONS) << "
";
    if (err != GLEW_OK ||
        !glewIsSupported("GL_ARB_color_buffer_float GL_EXT_framebuffer_object GL_EXT_packed_depth_stencil"))
        capable = false;

The printout of the extensions clearly indicates that all three of those extensions are present, yet the glewIsSupported() call is returning false. If I break it down to three separate checks, the first two work but GL_EXT_packed_depth_stencil does not register as present (despite being in the GL_EXTENSIONS printout).

What could possibly be causing this?

2

GL_EXT_packed_depth_stencil is part of core OpenGL3.0. Are you sure that u have setup an opengl 3 context? how are u initializing the context? Are u using freeglut? let us know the details about it.

3

No need for GL 3 context since the date of this extension (2005), cf http://www.opengl.org/registry/specs/EXT/packed_depth_stencil.txt

This extension has no functions, so try to use its tokens, and see if it works.

For about glew, I never used it so I can’t know. But try to check glewexperimental (http://glew.sourceforge.net/basic.html), or put less extension in glewIsSupported.

4

Simply removing the check “solved” the problem, since the extension works without incident. I still find it extremely strange that this was happening though and I’m curious what could have caused it.

I always figured that glewIsSupported was just parsing the string returned by glGetString, but maybe not?

5

Look at the code if you want to know :slight_smile: