Dominus let me know via the Aiera IRC channel that there have been reports that Apple’s latest version of OS X, code-named “Lion”, breaks fullscreen capability for SDL-based games. Utilities like DOSBox, and Ultima engine remakes like Exult, Pentagram, Nuvie, and xu4, are all affected, and will not work in fullscreen mode under the latest OS X (version 10.7).

The issue is rather technical, but here is what appears to be a basic summary:

CGDisplayBaseAddress() has been deprecated in 10.6 and while it still exists on 10.7, it now returns NULL instead of the display’s base address. SDL_SetVideoMode() ends up calling a number of deprecated CG functions via the Quartz implementation including CGDisplayBaseAddress(). It is SDL_SetVideoMode()’s call to SDL_ClearSurface() that actually causes the crash when it tries to clear the frame buffer memory at address zero. 

A new set of APIs has been added as of 10.6 and while they let you capture a display, they do not allow direct frame buffer access. Quartz or OpenGL are the only methods that can update a captured display. 

The work to switch to the new APIs in the context of SDL is not trivial.

Apple is rather notorious, in my experience, for being something of an ass when it comes to deprecating functions between OS revisions; I recall the days when Nuvie had different build versions published for OS X Leopard and Tiger; the build for one absolutely would not run on the other. To be fair, if memory serves, that had more to do with a change in the bit-length of a particular variable type…but even so, it’s still illustrative of Apple’s rather heavy-handed method of discontinuing programmatic support for deprecated items.

And now it appears that SDL has been affected by that same attitude.

I’m sure a workaround will appear shortly, one which will be incorporated into these various projects in due time. For the moment, though, be thou advised that running your favourite Ultima games in fullscreen under OS X will probably result in crashes.