Libgliar

Libgliar is a library that can fake the OpenGL context information returned by a user's GPU while an OpenGL program runs. It works on Linux systems only and it must be preloaded before running the program to which we need to "lie" about the context info.

Libgliar gets the desired (fake) context information from a configuration file (gliar.conf or ~/.gliar.conf) and returns that information instead of the real OpenGL call result.

Usage:
gliar opengl_program_name

At the moment it can fake the following information:
GL_EXTENSIONS
GL_VENDOR
GL_RENDERER
GL_VERSION
GL_SHADING_LANGUAGE_VERSION
GL_MAJOR_VERSION
GL_MINOR_VERSION
GL_NUM_EXTENSIONS
GL_NUM_SHADING_LANGUAGE_VERSIONS
GL_MAX_TEXTURE_UNITS
GL_MAX_TEXTURE_IMAGE_UNITS
GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS
GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS
GL_MAX_TEXTURE_SIZE
GL_MAX_CUBE_MAP_TEXTURE_SIZE
GL_MAX_TEXTURE_COORDS
GL_MAX_VERTEX_ATTRIBS
GL_MAX_VERTEX_UNIFORM_VECTORS
GL_MAX_FRAGMENT_UNIFORM_VECTORS
GL_MAX_VARYING_VECTORS
GL_MAX_COLOR_ATTACHMENTS_EXT
GL_MAX_RENDERBUFFER_SIZE_EXT
GL_MAX_PROGRAM_INSTRUCTIONS_ARB
GL_MAX_PROGRAM_NATIVE_INSTRUCTIONS_ARB
GL_MAX_PROGRAM_TEMPORARIES_ARB
GL_MAX_PROGRAM_NATIVE_TEMPORARIES_ARB
GL_MAX_PROGRAM_PARAMETERS_ARB
GL_MAX_PROGRAM_NATIVE_PARAMETERS_ARB
GL_MAX_PROGRAM_ATTRIBS_ARB
GL_MAX_PROGRAM_NATIVE_ATTRIBS_ARB
GL_MAX_PROGRAM_ADDRESS_REGISTERS_ARB
GL_MAX_PROGRAM_NATIVE_ADDRESS_REGISTERS_ARB
GL_MAX_PROGRAM_LOCAL_PARAMETERS_ARB
GL_MAX_PROGRAM_ENV_PARAMETERS_ARB
GL_MAX_PROGRAM_ALU_INSTRUCTIONS_ARB
GL_MAX_PROGRAM_NATIVE_ALU_INSTRUCTIONS_ARB

I use this library when I debug programs that change their behavior according to the OpenGL extensions supported, the OpenGL version, the shading language version or any other information from the above. This way, I don't have to build these programs in different machines to test the different behaviors.

Note: The library can only restrict the capabilities of a GPU, not "emulate" non supported features. For example: if the gliar.conf contains an extension that is not supported by the user's real GPU, the library will return a warning that it will ignore the extension.

The code of the gliar library can be found here: https://launchpad.net/libgliar

(License: GPL v.3, Copyright: Canonical Ltd, Author: Eleni Maria Stea)