GLGPUMem

boost::uint32_t GLRenderer::availableMemory()
{
    boost::uint32_t memorySize;
    bool nvx = false, amd = false;
    // glew breaks glGetString(GL_EXTENSIONS), so use glGetStringi instead and look for all extensions
    GLint numExtensions;
    glGetIntegerv(GL_NUM_EXTENSIONS, &numExtensions);
    for(GLint i = 0; (i < numExtensions) && !nvx && !amd; i++)
    {
        const char* extensions = reinterpret_cast<const char*>(glGetStringi(GL_EXTENSIONS, i));
        if(strstr(extensions, "GL_NVX_gpu_memory_info")) nvx = true;
        if(strstr(extensions, "GL_ATI_meminfo")) amd = true;
    }
    #warning TODO: check if I was doing something wrong here and fix. And if I wasn't move extension query to context initialization
    // doesn't work for some reason, but calling glGetIntegerv with th nvx values works... strange
    //if(GLEW_NVX_gpu_memory_info || glewIsSupported("GL_NVX_gpu_memory_info") || glewGetExtension("GL_NVX_gpu_memory_info"))
    if(nvx)
    {
        // from http://developer.download.nvidia.com/opengl/specs/GL_NVX_gpu_memory_info.txt
        //GPU_MEMORY_INFO_DEDICATED_VIDMEM_NVX          0x9047
        //GPU_MEMORY_INFO_TOTAL_AVAILABLE_MEMORY_NVX    0x9048
        //GPU_MEMORY_INFO_CURRENT_AVAILABLE_VIDMEM_NVX  0x9049
        //GPU_MEMORY_INFO_EVICTION_COUNT_NVX            0x904A
        //GPU_MEMORY_INFO_EVICTED_MEMORY_NVX            0x904B
        glGetIntegerv(0x9049, reinterpret_cast<GLint*>(&memorySize));
        // to bytes
        memorySize *= 1024;
    }
    else if(amd)
    {
        memorySize = 0;
        // Don't really know if that does what I think it does and can't check without an AMD card
        GLint data[4];
        //VBO_FREE_MEMORY_ATI                     0x87FB
        //TEXTURE_FREE_MEMORY_ATI                 0x87FC
        //RENDERBUFFER_FREE_MEMORY_ATI            0x87FD
        glGetIntegerv(0x87FB, data);
        memorySize += data[0];
        glGetIntegerv(0x87FC, data);
        memorySize += data[0];
        glGetIntegerv(0x87FD, data);
        memorySize += data[0];
        // to bytes
        memorySize *= 1024;
    }
    else return 0;
    return memorySize;
}