Created attachment 610 [details]
Screenshot showing the strange boxing

SDL_CreateWindow() can pick other resolutions than the ones requested, most likely caused by this particular code and possible equivalents in other backends:
https://github.com/bobbens/naev/blob/master/src/opengl.c#L407

Tested with an actual application with 800x600 requested and the closest/smallest resolution available only being 1024x768 on a Linux machine, the result is what can be seen in the screenshot attached.

This state is undesirable and there are two possible paths I see to go from here:

 a) Keep the boxing and continue to pick other resolutions than requested, but fix the boxing to center properly (if it is not centered properly due to something I missed to specify, then sorry for that! I'm quite new to SDL 1.3)
 b) Return NULL for SDL_CreateWindow() and allow the application to do boxing itself or pick another resolution

I'd suggest/prefer going for b) since with NULL returned from SDL_CreateWindow, the unavailability becomes transparent to the application which might then want to try other desirable resolutions (which require no boxing) on its own (or do boxing as it wants to).

To make it easier as an automagical solution, a) with proper centered boxing could still be available optionally through a creation flag passed to SDL_CreateWindow, but it shouldn't be the default I guess (or there should be an easy way like a flag to turn this automagical behaviour off).