In my OpenGL application on Ubuntu (12.10), I've issued the following GLFW window hints when creating a window:
glfwWindowHint(GLFW_CLIENT_API, GLFW_OPENGL_API);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_VISIBLE, GL_TRUE);
glfwWindowHint(GLFW_SAMPLES, 0);
glfwWindowHint(GLFW_RED_BITS, 24);
glfwWindowHint(GLFW_GREEN_BITS, 24);
glfwWindowHint(GLFW_BLUE_BITS, 24);
glfwWindowHint(GLFW_ALPHA_BITS, 8);
// Create Opengl Window
window = glfwCreateWindow(width, height, windowTitle.c_str(), NULL, NULL);
centerWindow();
glfwMakeContextCurrent(window);
But this results in an OpenGL context being created with an associated window with pixel color bit depth of R-G-B-A = 8-8-8-8. To check this I used the following code after creating my GLFW window:
int count;
const GLFWvidmode * mode = glfwGetVideoMode(monitor);
cout << "Current video mode: " <<
mode->redBits << "-" <<
mode->greenBits << "-" <<
mode->blueBits << endl;
cout << "All possible video modes: " << endl;
mode = glfwGetVideoModes(monitor, &count);
for(int i = 0; i < count; i++) {
cout << mode->redBits << "-" <<
mode->greenBits << "-" <<
mode->blueBits << endl;
}
Surprisingly I get 8-8-8-8 for my current video mode, and for all possible video modes. I'm sure this cannot be the case, as my monitor (Samsung S23B550) can display mono-colored gradients without any mach banding issues, which means it should be at least 16-24 bit depth per color channel. I'm also using a modern graphics card (Nvidia GT650M), which should have a framebuffer that supports between 24-32bits per channel.
The only odd thing to take into account is that my graphics card uses the Nvidia Optimus technology, which means that if I want to use my dedicated graphics card on Linux, I have to use optirun (Bumblee) for graphics card switching (integrated-to-dedicated), which I do when I run my OpenGL applications.