Render wgpu frames as webview overlay

[Armaldio]

Hey all 👋

I'm trying to render a wgpu frame over the webview with the goal to support the steam overlay.
Here is my advancement so far:

Kooha-2024-12-09-08-13-17.mp4

The green part is wgpu rendering to the window.
You can see the webview buttons rendering on top of it
What I'm trying to do is to have the webview under the wgpu frames with transparency (to show the overlay over the webview)
Using maybe some sort of frame ordering, I don't know

My work is based on:

• https://github.com/clearlysid/tauri-wgpu-cam/blob/main/src-tauri/src/main.rs
• Render WebView on Top of Native GPU Rendered Content [feat]  #8246
• https://github.com/FabianLars/tauri-v2-wgpu
• [bug] Flickering with raw display handle + winit + wgpu + tauri v2 + transparency #9220
• WebView2 based app and Steam Overlay MicrosoftEdge/WebView2Feedback#4019

Other solutions I've explored but don't know the viability:

• Do some headless wgpu rendering to compute a texture, send the buffer to the frontend and draw it into a canvas, on top of the rest.
  • I've see 300ms rendering on a low-end PC so i'm concerned about performance
  • I don't know how to handle mouse events since only an image of the overlay is transfered
• Use a second window:
  stacking two windows on top of each other
  make the overlay window topmost, transparent, frameless
  when overlay is present disable passthrough, otherwise enable passthrough (to allow mouse clicks and other to hit the correct window)
  • I'm also concerned it doesn't work in practice
  • What about fullscreen ?

What do you think about these solutions ?