Fix OpenXR module failing to build on Linux when Wayland is disabled

[juanjp600]

This should fix compile errors found by sudo.juan in the Godot Contributors Chat

#97771 suggests that the OpenXR module is only meant to use EGL when Wayland is enabled. However, only some references to EGL are excluded from compilation when Wayland is disabled, with the few that are not excluded leading to compile errors. This PR fixes the incomplete preprocessor checks that cause these errors.

[dsnopek]

Thanks!

I think these changes would be fine (because you're right that we are only using this for Wayland), however, I don't think these changes should be necessary. This code doesn't use anything Wayland-specific, it only uses EGL, so if compiling for EGL support works (and we're already wrapping this in #ifdef EGL_ENABLED), then this should work too.

That makes me wonder if there's something else going wrong and we aren't including something necessary for EGL on some systems in the OpenXR module?

[juanjp600]

If I'm understanding this correctly, the module's SCsub file only defines XR_USE_PLATFORM_EGL when Wayland is enabled:

godot/modules/openxr/SCsub

Lines 28 to 29 in a308047

	if env["wayland"]:
	env_openxr.AppendUnique(CPPDEFINES=["XR_USE_PLATFORM_EGL"])

So another approach could be to just enable this definition in all circumstances where EGL is available and not just when Wayland is enabled?

[dsnopek]

If I'm understanding this correctly, the module's SCsub file only defines XR_USE_PLATFORM_EGL when Wayland is enabled

Ah, ok, that makes sense!

Let's go with your PR then :-)

[BastiaanOlij]

Indeed, the Monado EGL extension structs and functions are only included in OpenXR when the XR_USE_PLATFORM_EGL define is set. If this code mirrors the conditions in /modules/openxr/scsub that set this, this PR is good enough. EGL is badly supported in OpenXR so its really only with the Monado runtime that its usable from what I understand.

[Repiteo]

Thanks!