On the Mac the OpenGL support is really good. They don't have any DirectX whatsoever so a lot of extra effort has been put into GL especially since on newer machines the entire desktop is rendered with OpenGL hardware accelerated. It has to work right or they wouldn't be able to have a stable desktop. I don't know of much use of software rendering on the Mac. The only time I see it use software is if it's a pre Quartz Extreme (GL desktop) Mac or there isn't enough videoram. My old iBook does software GL only, and works correctly and reliably even for a 10 year old machine (although the o/s has been updated since).
So you almost don't even need to worry about having SDL on the Mac because it isn't likely to be needed. The software GL works fine, and if anyone else can say otherwise I'd be surprised. I have no idea what it's like on Linux, but the same situation is true - there is no DX so OpenGL has been focussed on and made to be more reliable. I'd be surprised to hear that the software GL on Linux is unreliable. I don't at this point see any need for a fix to this problem except under Windows and I don't think porting SDL to Mac or Linux will be of any benefit. In fact it's probably pointless.
It's mainly windows that has the problems. Since windows platforms are in such great numbers, with SO many different graphics cards, drivers, implementations, o/s revisions, hardware configurations, etc, and not exactly very well standardized and highly proprietary, I'm not really surprised that things are much more unpredictable and unreliable on that platform, if only because of the number of units. If you really want to target as many people at all costs, then obviously you have to use DX first and GL second. Either that or clearly display a notice on your advertising that it is an OpenGL application and requires a working installation of OpenGL. Maybe you could find out where GL drivers can be downloaded from and include the links in your software or documentation.
If you are wanting to make your software truly cross-platform you shouldn't need to have separate code that runs only on a given platform and not others, so they should all use OpenGL. That said I'm sure some people are going to think of falling back to DX under windows, just because it seems to be a problem for some people. Either that or you can stop trying to please everyone and just put your backing behind OpenGL.
So you almost don't even need to worry about having SDL on the Mac because it isn't likely to be needed. The software GL works fine, and if anyone else can say otherwise I'd be surprised. I have no idea what it's like on Linux, but the same situation is true - there is no DX so OpenGL has been focussed on and made to be more reliable. I'd be surprised to hear that the software GL on Linux is unreliable. I don't at this point see any need for a fix to this problem except under Windows and I don't think porting SDL to Mac or Linux will be of any benefit. In fact it's probably pointless.
It's mainly windows that has the problems. Since windows platforms are in such great numbers, with SO many different graphics cards, drivers, implementations, o/s revisions, hardware configurations, etc, and not exactly very well standardized and highly proprietary, I'm not really surprised that things are much more unpredictable and unreliable on that platform, if only because of the number of units. If you really want to target as many people at all costs, then obviously you have to use DX first and GL second. Either that or clearly display a notice on your advertising that it is an OpenGL application and requires a working installation of OpenGL. Maybe you could find out where GL drivers can be downloaded from and include the links in your software or documentation.
If you are wanting to make your software truly cross-platform you shouldn't need to have separate code that runs only on a given platform and not others, so they should all use OpenGL. That said I'm sure some people are going to think of falling back to DX under windows, just because it seems to be a problem for some people. Either that or you can stop trying to please everyone and just put your backing behind OpenGL.