Asset data from code is not sent to the GPU appropriately (on webgl2) about bevy

[CptPotato]

I'm wondering how this even works. I'm 99% sure that graphics APIs don't let you bind the same image as render attachment and another input image in the same pass, unless working with storage images in compute.

Does bevy implicitly copy the texture in the background? Otherwise you could try rendering to a separate texture (essentially double buffering) to see if that resolves the issue. Though I'm not positive that this is the source of the problem.

[mxple]

I did a bunch of testing and I'm still not completely sure what the issue is. Here's what I found though:
On WASM/WebGL:

• Draw image STRAIGHT to the screen
  • On frame 0+, the initial image is drawn clearly to the screen
• Draw image via custom material to the SCREEN
  • On frame 0-4, the image is not drawn (?) but there IS clear color from the camera
  • On frame 4+, the image is drawn to the screen
• Pass image through custom shader/material and render to ITSELF, then draw the image to the screen
  • On frame 0+, a solid rectangle of red (#2A0000) is drawn to the screen

On native:

• Draw image STRAIGHT to the screen
  • On frame 0, nothing is drawn. The screen is black.
  • On frame 1+, the image is drawn to the screen
• Draw image via custom material to the SCREEN
  • On frame 0, nothing is drawn. The screen is black.
  • On frame 1+, the image is drawn to the screen
• Pass image through custom shader/material and render to ITSELF, then draw the image to the screen
  • On frame 0, nothing is drawn. The screen is black.
  • On frame 1+, the image is drawn to the screen normally (correct behavior)

I conducted the tests by putting a stop point after RenderApp::Cleanup.

Is it byte alignment? Code execution speed? The backend/drivers? The difference in behavior between wasm and native is very confusing.

Attached is the red rectangle of despair.