WebGL glGetBufferSubData warning

[clayjohn]

Godot version

3.5 rc 2

System information

Intel Graphics 400, Linux, Firefox, GLES3

Issue description

The below warning is printed to the console when running certain scenes in the WebGL2 renderer.

I beleive that particles are responsible for this.

In any case, It appears the issue comes from our OpenGL Buffer usage. We typically use *_draw hints and *_copy hints when creating Buffer objects. On desktop this is perfectly allowed as the hints are just hints. On the web, ANGLE is very strict about hints and appears to be telling us that we are causing a pipeline stall by reading from a buffer that was not created with a *_read hint.

To resolve this issue, we likely need to create a staging buffer each time that we use glGetBufferSubData, copy the data to the staging buffer and then copy the data to the CPU.

Steps to reproduce

Run the Web editor and inspect the console output

Minimal reproduction project

No response