Merge lp:~widelands-dev/widelands/fix_context_selection into lp:widelands

[SirVer]

On newer libmesa versions, context creation fails if we use SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_COMPATIBILITY). Disabling this *should* still give us a reasonable context (either core, which we need or compatible which will still contain all of what we need + some).

Verified on the server (linux, mesa + xvfb) and on Mac OS and it still does the right thing.

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 5138. State: errored. Details: https://travis-ci.org/widelands/widelands/builds/540496020.
Appveyor build 4920. State: failed. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_fix_context_selection-4920.

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 5140. State: passed. Details: https://travis-ci.org/widelands/widelands/builds/540645510.
Appveyor build 4922. State: success. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_fix_context_selection-4922.

[kaputtnik (franku)]

Should this be tested some how or are the Travis/Appveyor builds enough testing?

[GunChleoc (gunchleoc)]

Tested on 2 Linux and 1 Windows machines. I'll merge this now, because it seems to be OK.

@kaputtnik: Can you test with your old laptop some time too, just in case?

@bunnybot merge

review: Approve

[kaputtnik (franku)]

Will do next weekend :-)

=== modified file 'src/graphic/gl/initialize.cc'
--- src/graphic/gl/initialize.cc	2019-05-18 10:47:45 +0000
+++ src/graphic/gl/initialize.cc	2019-06-03 08:29:33 +0000
@@ -46,7 +46,6 @@
 	SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);
 	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
 	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
-	SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_COMPATIBILITY);
 	SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 16);
 	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);