Fix glLogicOp by using QOpenGLFunctions_3_0 instead of GLES2 + WGL
Summary:
I did some tests and it seems Linux is not affected by this bug.
For Nvidia it seems to break with driver 375.63+. (tested 368.81 - 378.49)
For AMD I couldn't find a driver it would run correctly. (tested 13.251, 15.200)
For Intel, this is my main computer running linux and I would rather not mess with its configurations too much..
Unfortunately I don't have a mac so I couldn't do any testing for it.
I suspect the bug to be driver related and tried to debug wglgetProcAddress or rather the ICD implementation DrvGetProcAddress (nvoglv64.dll) once I ruled out invalid context, the possibility of wglMakeCurrent grabbing the wrong context, init failure, ... It is rather strange that only glLogicOp and none of the sync functions seem to be affected.
First I came to a different conclusion so some material I gathered as proof become worthless but for some trivia, here some disassembly (https://gist.github.com/Joefish/c300ebac0cb579334838927d8cad26ba)
The patch uses QOpenGLFunctions_3_0 to obtain an object pointer to supported GL functions instead of GLES2 compatible QOpenGLFunction + extension loading.
According to Steam, Krita needs "Modern (since 2009) graphics / Intel HD" so GL3.2 sounds like a reasonable target, even for macs (in my opinion). It would also give a clear support target (instead of GLES2 + extensions), make many checks obsolete and in this case also circumvent a bug by just getting an offset table to the desired function subset. I think to remember than QPainter depends on deprecated GL functions and that's why 3.2core can't be set by default but Nimmy's opengl branch he already uses GL3.2Core (Core probably for compatiblity with OSX) like commit dd32d5e421a4a357e268bd2dbb8b679b6ddd2699
So, according to KisOpenGL::setDefaultFormat 3.0 is fine and once the way is free for 3.2 we can bump it up.
Test Plan:
- Krita built with patch applied on Linux/Windows
- Open an image and see if the brush outline is XOR'd accordingly
Reviewers: Nim, dkazakov
Reviewed By: Nim, dkazakov
Subscribers: dkazakov
Differential Revision: https://phabricator.kde.org/D4506