GLUT: support more glutGet() attributes

[Beuc]

Adding support for more glutGet() queries for webgl attributes i.e. antialias/alpha/depth/stencil.

[kripken]

Thanks @Beuc, looks good with a test.

[kripken]

indentation looks wrong here

[Beuc]

Sorry, a tab got included instead of spaces. Fixed :)

[kripken]

Thanks, looks good, just need a test before merging.

[Beuc]

I added a test case. It's run twice because there's currently no support for destroying/recreating webgl contexts. I also needed a gratuitous glClear() call to prevent library_gl.js from being stripped (GL.xxx referenced in library_glut.glutCreateWindow).

[Beuc]

For the record I don't understand why the test fails at circleci.
It works fine here with both Firefox and Chromium. Any way to get more info/output?

[kripken]

I think some or all of those errors are due to previous issues we had on incoming. Please merge in latest incoming to here, that may fix things.

[Beuc]

I rebased the patch on incoming.
It still works OK locally.
Crossing fingers X

[kripken]

Looks like it fixed everything but the new test added here. I think the issue there is that the bot doesn't have graphics hardware, so you need to annotate the test with @requires_graphics_hardware (see the annotation on test_webgl_context_attributes for example).

[Beuc]

Hmm, still no luck.
The test that requests nothing (no alpha/aa/depth/stencil) passes.
The one that requests all of them doesn't pass.
What kind of graphic context does this CI environment get?
Also, any way to get the printf output for that test?

[kripken]

It's kind of an odd graphics context, see .circleci/config.yml (search for openbox). But it should run things ok.

Getting printf is possible with emrun, for example, if you replace the btest with

    run_process([PYTHON, EMCC, path_from_root('tests', 'browser_test_hello_world.c'), '-o', 'hello_world.html', '--emrun'])
    run_process([PYTHON, path_from_root('emrun'), 'hello_world.html'])

That will build the file for emrun, then run it in emrun, which will log out stderr to the console. (Note that you need to remove stuff like REPORT_RESULT, unless you also handle that.)

[kripken]

Might be worth comparing to the other tests that use antialiasing/stencil/etc. - they do pass, so finding what the difference is might help.

[Beuc]

(OMG what have I gotten myself into -_-' I don't even need that patch.. ;))
It looks like the other test cases also suffer from the lack of antialias in the CI environment.
This can be reproduced with locally with export LIBGL_ALWAYS_SOFTWARE=1.
I duplicated and skipped the test case accordingly.

[kripken]

Cool, makes sense. Will merge after CI finishes.

[Beuc]

Yay!