Feature/egl context priority

[cmeissl]

This PR adds support for egl context priority using the EGL_IMG_context_priority egl extension.

It also changes the multigpu code to request a high priority context by default.

[Drakulix]

Can we make the second commit add the priority as constructor arguments for the GbmGlesBackend and EglGlesBackend instead?

[cmeissl]

Can we make the second commit add the priority as constructor arguments for the GbmGlesBackend and EglGlesBackend instead?

Yes, though we only have a default impl and with_factory. I can add a new function taking the priority, but what should the default do? An alternative would be to not request any priority by default and use the factory for this. I considered that first, but that forces downstream to use the factory which can be easily forgotten.

[Drakulix]

Can we make the second commit add the priority as constructor arguments for the GbmGlesBackend and EglGlesBackend instead?

Yes, though we only have a default impl and with_factory. I can add a new function taking the priority, but what should the default do? An alternative would be to not request any priority by default and use the factory for this. I considered that first, but that forces downstream to use the factory which can be easily forgotten.

I guess we have two options:

• Make Default do what it currently does. A context with "medium" or "default" priority. Additionally add a with_priority-constructor. The factory-constructor would remain unchanged.
• Drop Default and force downstream to always specify a priority or at least explicitly pass None for "default priority" (if not using a factory).

I am happy with both options.

[i509VCB]

I believe vulkan has an extension similar to this, so we can elect to specify a priority from the multigpu code, although it's an optional extension: https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_KHR_global_priority.html

[cmeissl]

Can we make the second commit add the priority as constructor arguments for the GbmGlesBackend and EglGlesBackend instead?

Yes, though we only have a default impl and with_factory. I can add a new function taking the priority, but what should the default do? An alternative would be to not request any priority by default and use the factory for this. I considered that first, but that forces downstream to use the factory which can be easily forgotten.

I guess we have two options:

* Make `Default` do what it currently does. A context with "medium" or "default" priority. Additionally add a `with_priority`-constructor. The factory-constructor would remain unchanged.

* Drop `Default` and force downstream to always specify a priority or at least explicitly pass `None` for "default priority" (if not using a factory).

I am happy with both options.

I opted for the first option, which really seems more sensible as Medium is defined as the default by the spec (and it does not break the API)

[codecov-commenter]

Codecov Report

Patch coverage: 1.16% and project coverage change: -0.07% ⚠️

Comparison is base (5affbde) 22.94% compared to head (e5e1d0c) 22.88%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1133      +/-   ##
==========================================
- Coverage   22.94%   22.88%   -0.07%     
==========================================
  Files         143      143              
  Lines       22972    23050      +78     
==========================================
+ Hits         5272     5275       +3     
- Misses      17700    17775      +75     

Flag	Coverage Δ
wlcs-buffer	20.00% <1.16%> (-0.07%)	⬇️
wlcs-core	19.65% <1.16%> (-0.07%)	⬇️
wlcs-output	8.10% <1.16%> (-0.03%)	⬇️
wlcs-pointer-input	21.67% <1.16%> (-0.07%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
src/backend/egl/context.rs	0.00% <0.00%> (ø)
build.rs	80.72% <100.00%> (+0.23%)	⬆️

... and 2 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.