[QUOTE=BingoBingo;1291569]The only last thing I am wondering if anyone can enlighten me on is:
It says WGL_EXT_create_context_es2_profile has 47% coverage, but the GLX_EXT_create_context_es2_profile equivalent only has 17% (from gpuinfo.org).
Is this because the GLX version only shows on GLX/Linux and the WGL version only shows on WGL/Windows?[/QUOTE]
Yes, that’s part of it. The coverage percentage is apparently computed based on “all” reports ever collected over all time, even those
[li]collected before these extensions were even defined 6 years ago, and/or [/li][li]collected on platforms for which the extension doesn’t even make sense (e.g. GLX on Windows), and [/li][li]counting multiple reports submitted from the same PC/OS install as separate reports. [/li][/ul]
So the coverage doesn’t really tell you as much as you might hope about how pervasive an extension is now, particularly for platform-specific WSI extensions.
You can look at how many Windows and Linux reports there have been (over all time) and compute a coverage for those extensions based upon that (incidentally, it’s 86.32% for the GLX extension on Linux and 61.56% for the WGL extension on Windows). But even that’s not ideal because as I said this statistic still includes reports submitted before those extensions were even defined and counts multiple reports per machine/OS install separately.
Instead, what I do when I’m considering whether to support (or require) an extension is to look back and see when it was first offered in GL drivers for the vendor(s) whose drivers I’m targeting, and base my decision on that (that same site, http://www.gpuinfo.org/, is very useful for that). If it’s been out for years, there’s no good reason in most cases that users can’t just update their GL drivers and get the support they need.
What I think would be really useful to get as a coverage statistic on gpuinfo.org is the percentage of reports submitted in the last 1 or 2 years which supported (or didn’t support) the extension. With that you could get a better feel for how pervasive an extension is nowadays on GL drivers that developers at least have been running lately.
I am surprised the GLX is such low coverage compared to WGL?
I think there are probably multiple reasons for that. Based on personal experience, I can tell you when I was doing full-time GL development on Linux for work, I never Downloaded the gpuinfo.org app and submitted reports. Just never got into it, and don’t even think I knew about the download package. However, when I flipped to doing GL dev on Windows a few years ago, I started submitting reports pretty much whenever I updated my GL driver. Part of the reason is the Windows binary “just works”. No need to go download other packages. Whereas the Linux binary requires shared libraries not delivered with the glcapsviewer executable. If you don’t have them, you need to go get and install them or build them. Yes, you can do that, but not everyone will take the time. Hopefully this illustrates how it might inhibit submission of reports on Linux versus Windows, slanting the report counts toward Windows.