Add set_interface for access by GDNative

[BastiaanOlij]

Ok, I've completely redone this and added a few additional changes to this.

We can now call the set_interface through a new GDNative ARVR API call.

As I'm adding a new API level I've also added another often requested feature and that is to get access to the depth buffer.
This is important in XR for re-projection during frame drops and to enable stuff like LIV (https://www.liv.tv/) and other mixed reality solutions.

I've also added an option to provide an external depth buffer alongside the external color buffer.

The depth buffer changes are pretty experimental especially on GLES2 as there is no way to switch between render buffer and texture.

[akien-mga]

Still crashing with:

modules/gdnative/arvr/arvr_interface_gdnative.cpp:84:20: runtime error: member access within misaligned address 0x00000000000a for type 'const struct godot_arvr_interface_gdnative', which requires 8 byte alignment
0x00000000000a: note: pointer points here
<memory cannot be printed>
handle_crash: Program crashed with signal 11
Dumping the backtrace. Please include this when reporting the bug on https://github.com/godotengine/godot/issues
[1] bin/godot.x11.tools.64s() [0x171b67a] (/home/runner/work/godot/godot/platform/x11/crash_handler_x11.cpp:54)
[2] /lib/x86_64-linux-gnu/libc.so.6(+0x46210) [0x7f053eab4210] (??:0)
[3] ARVRInterfaceGDNative::set_interface(godot_arvr_interface_gdnative const*) (/home/runner/work/godot/godot/modules/gdnative/arvr/arvr_interface_gdnative.cpp:84)
[4] ARVRInterfaceGDNative::_set_interface(long) (/home/runner/work/godot/godot/modules/gdnative/arvr/arvr_interface_gdnative.cpp:90)

For the reference, here's what that CI Linux build with sanitizers and test project does:

godot/.github/workflows/linux_builds.yml

Lines 188 to 210 in 6b48fce

	# We should always be explicit with our flags usage here since it's gonna be sure to always set those flags
	- name: Compilation
	env:
	SCONS_CACHE: ${{github.workspace}}/.scons_cache/
	run: |
	scons tools=yes target=debug use_asan=yes use_ubsan=yes
	ls -l bin/
	# Download and test project to check leaks and invalid memory usage.
	# CI has no audio device, so use the Dummy audio driver to avoid spurious error messages.
	- name: Importing and running project project
	run: |
	wget2 https://github.com/qarmin/RegressionTestProject/archive/3.2.zip
	unzip 3.2.zip
	mv "RegressionTestProject-3.2" "test_project"
	echo "----- Open editor to check for memory leaks -----"
	DRI_PRIME=0 xvfb-run bin/godot.x11.tools.64s --audio-driver Dummy -e -q --path test_project 2>&1 | tee sanitizers_log.txt || true
	misc/scripts/check_ci_log.py sanitizers_log.txt
	echo "----- Run and test project -----"
	DRI_PRIME=0 xvfb-run bin/godot.x11.tools.64s 30 --video-driver GLES3 --audio-driver Dummy --path test_project 2>&1 | tee sanitizers_log.txt || true
	misc/scripts/check_ci_log.py sanitizers_log.txt

[BastiaanOlij]

Note before this gets lost and forgotten. After discussion on godot chat about this we've decided to do this more proper and add the required function to the ARVR GDNative API. Will find some time for that soonish.

[BastiaanOlij]

Ok, so I redid this whole thing and just updated the opening text. Also added access to the depth buffer.

[akien-mga]

Thanks!