Rendering stops after entering WebXR with Godot 4.2-beta4

[dsnopek]

Godot version

v4.2.beta4.official [93cdacb]

System information

Chromium-based browsers (Brave with the WebXR emulator addon)

Issue description

When exporting the Godot XR Tools demo for web using Godot 4.2-beta3, everything works fine!

However, when exporting with Godot 4.2-beta4, the demo appears to stop rendering (completely black screen) after clicking the "Enter VR" button. There are no errors or messages in the console providing any hints.

I haven't had a chance yet to bisect and find which change is causing this regression.

UPDATE: Git bisect points to PR #83649 as the cause of the regression

Steps to reproduce

1. Download the Godot XR Tools demo
2. Open with Godot 4.2-beta4
3. Export for web
4. Open in your browser and click the "Enter VR" button

Minimal reproduction project

Use the Godot XR Tools demo

[dsnopek]

Git bisect points to PR #83649 as the cause of the regression

[dsnopek]

I've narrowed it down to this line in renderer_viewport.cpp:

bool can_draw_2d = !p_viewport->disable_2d && p_viewport->view_count == 1; // Stereo rendering does not support 2D, no depth data

If I change that to this:

bool can_draw_2d = !p_viewport->disable_2d;

... then WebXR rendering works again.

I'm not sure why WebXR depends on 2D rendering happening? I'll try to dig into it when I get a chance.

/cc @BastiaanOlij

[dsnopek]

Ah, a new piece of information: this appears to only break running WebXR in a desktop browser. Everything appears to work fine when using the Oculus Browser running standalone on the Meta Quest 2.

[dsnopek]

I just posted PR #84267 which seems to fix it in my testing, despite not really seeming like it should fix anything :-)