The Developer’s Cry

Yet another blog by a hobbyist programmer

Fullscreen GL …

Programming games is fun. Games typically run in fullscreen mode, so in today’s world, it’s important to have a portable way of setting a full screen mode. It looks like this is more of a hassle than you’d think it is.

I’m fond of SDL because it’s quite a powerful library. There is a SDL_WM_ToggleFullScreen() function that lets you switch between full screen and windowed mode. I noticed however, that on the Mac, the full screen mode of SDL would actually resize the application window to maximum size rather than take up the whole screen. The problem is that the Apple menu bar remains visible on the top of the screen, and also the dock would still pop up when you move the mouse to the bottom of the screen.
In Windows, I found that it helps to resize the window to the maximum resolution before trying to toggle to full screen.
The man page of SDL_WM_ToggleFullscreen() does say that toggling to full screen is not supported on all platforms.
To my astonishment, there is a rather simple fix for this, but first I’d like to tell you about the little adventure I had with GLUT.

Because of the full screen problem I had with SDL, I decided to switch to GLUT and try that out. GLUT is real easy to use, because it feels much more high-level than SDL and you quickly get results with little effort. GLUT features a so called ‘GameMode’ in which it switches to a full screen mode. While this seems to work across platforms, I’m having an incredibly pesky issue in that the screen is no longer being updated—all animations and movement appear frozen although the display function is being called. It’s like glutSwapBuffers is not swapping buffers anymore or so?
Switch back to windowed mode, and everything works perfectly again. It’s not the obvious beginners mistake of not re-initializing GL … I don’t know what it is, and I spent way too much time on trying to get this to work. Searching the web also doesn’t turn up much information, other than people saying that GLUT is bugged and you should use SDL.
What’s also really odd, is that GLUT allowed me to set a 10000x3000 video mode on my 1440x900 monitor. SDL doesn’t let you do weird things like that.

Exit GLUT, it’s nice for trying out a quick scene, but for anything larger, I’m through with it.
Getting back to SDL, it turns out to be amazingly simple to enter full screen mode. Forget about SDL_WM_ToggleFullScreen(), as it’s useless. Use SetVideoMode() instead:

SetVideoMode(max_xres, max_yres, bpp, SDL_OPENGL|SDL_FULLSCREEN);

The maximum resolution can be obtained by using SDL_ListModes(). You should always use this, as a good program knows what video modes are supported and what modes are not.
You can switch back to windowed mode by omitting the SDL_FULLSCREEN flag, and mind to set the window size back to it’s original size.
The beauty of all of this is that it appears to be portable, too. As to why anyone ever thought up a broken SDL_WM_ToggleFullScreen() function, we’ll probably never know.