GlfwApplication: Workaround for DPI scaling

[costashatz]

This PR offers a workaround for DPI scaling when monitor size is equal to zero in GlfwApplication..

[mosra]

Merged as 411e349, thank you!

[mosra]

@costashatz looking at release notes of glfw 3.3.1, I see "zero monitor size" being fixed: https://www.glfw.org/changelog.html .. should we remove this workaround again? (I assume distros that already have 3.3 would get 3.3.1 soon, and those that are on 3.2 and older won't upgrade to 3.3.0 because that would make no sense.)

[codecov-io]

Codecov Report

Merging #388 into master will increase coverage by 1.67%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #388      +/-   ##
==========================================
+ Coverage    72.4%   74.07%   +1.67%     
==========================================
  Files         354      364      +10     
  Lines       18753    21099    +2346     
==========================================
+ Hits        13578    15630    +2052     
- Misses       5175     5469     +294

Impacted Files	Coverage Δ
src/Magnum/GL/BufferTexture.h	20% <0%> (-5%)	⬇️
src/Magnum/SceneGraph/AbstractFeature.h	45.94% <0%> (-4.06%)	⬇️
src/Magnum/Shaders/Phong.cpp	75.4% <0%> (-3.67%)	⬇️
src/Magnum/Shaders/Flat.cpp	73.49% <0%> (-2.19%)	⬇️
src/Magnum/GL/RectangleTexture.h	5.88% <0%> (-1.81%)	⬇️
src/Magnum/GL/Context.h	90.69% <0%> (-0.97%)	⬇️
src/Magnum/GL/CubeMapTextureArray.h	1.13% <0%> (-0.4%)	⬇️
src/Magnum/Trade/LightData.cpp	100% <0%> (ø)	⬆️
src/Magnum/Animation/Interpolation.cpp	100% <0%> (ø)	⬆️
src/Magnum/Math/Quaternion.h	100% <0%> (ø)	⬆️
... and 94 more

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[costashatz]

@costashatz looking at release notes of glfw 3.3.1, I see "zero monitor size" being fixed: https://www.glfw.org/changelog.html .. should we remove this workaround again? (I assume distros that already have 3.3 would get 3.3.1 soon, and those that are on 3.2 and older won't upgrade to 3.3.0 because that would make no sense.)

@mosra sorry for the late reply! I was on vacation..

I will check whether on my system this was fixed. Because this was a singularity container and maybe the version freezes to 3.3..

Does it hurt to keep it there? I mean performance-wise.

[mosra]

No worries :)

Performance-wise it doesn't hurt, but it's a no-longer-needed cruft that enlarges the surface for potential bugs. If you can confirm this is no longer needed, I'll remove it, otherwise I'll at least add a note that this workaround is obsolete since 3.3.1.