static void framebuffer_callback(GLFWwindow *window, int width, int height) {
	state.screen_width = width;
	state.screen_height = height;
	state.viewport.x = 0;
	state.viewport.y = 0;
	state.viewport.w = width;
	state.viewport.h = height;

	float current_aspect = (float)width / (float)height;
	float aspect_ratio = 4.f/3.f;

	if(current_aspect > aspect_ratio) {
		float new_width = height * aspect_ratio;
		state.viewport.x = (width - new_width) / 2;
		state.viewport.w = new_width;
	} else if(current_aspect < aspect_ratio) {
		float new_height = width / aspect_ratio;
		state.viewport.y = (height - new_height) / 2;
		state.viewport.h = new_height;
	}
}

static void toggle_fullscreen(bool enable) {
	static int windowed_x;
	static int windowed_y;
	static int windowed_width;
	static int windowed_height;

	if(enable) {	// Save current windowed size and position
		glfwGetWindowPos(window, &windowed_x, &windowed_y);
		glfwGetWindowSize(window, &windowed_width, &windowed_height);

		GLFWmonitor *monitor = glfwGetPrimaryMonitor();
		const GLFWvidmode *mode = glfwGetVideoMode(monitor);

		glfwSetWindowMonitor(window, monitor, 0, 0, mode->width, mode->height, mode->refreshRate);

	} else {			// Restore to saved windowed position/size
		glfwSetWindowMonitor(window, 0, windowed_x, windowed_y, windowed_width, windowed_height, 0); // 0 = don't change refresh rate
	}
}

static void key_callback(GLFWwindow *window, int key, int scancode, int action, int mods) {
	struct nes_state *nes_state = (struct nes_state*)glfwGetWindowUserPointer(window);

	if(action == GLFW_RELEASE) {
		switch(key) {
			case GLFW_KEY_F12: {
				state.toggle_crt_emulation = !state.toggle_crt_emulation;
			} break;

			case GLFW_KEY_F11: {
				if(!(mods & GLFW_MOD_SHIFT)) {
					if(state.fullscreen) {
						toggle_fullscreen(false);
						state.fullscreen = false;
					} else {
						toggle_fullscreen(true);
						state.fullscreen = true;
					}
				} else {
#ifdef PROFILER
					state.overlay = !state.overlay;
#endif
				}
			} break;

			default: break;
		}
	}
}