Add OpenGL timer queries to OpenGL3 backend

[clayjohn]

Fixes: #66464

This is useful for the visual debugger, printing FPS, and the in-editor FPS display

As implemented GPU profiling only works on Desktop devices. There is a GPU timing API that also works on mobile (glBeginQuery/glEndQuery), But it can only measure the time elapsed between two points, it cannot capture timestamps. I initially implemented this with glBeginQuery/glEndQuery but I could not get accurate frame timings.

[BastiaanOlij]

Looks cool, my only remark is that if I read it right, this is always on? Do we want that? And do we want this in the runtime version? Or should we add some ifdefs to only include it in debug or tool builds?

[Calinou]

Looks cool, my only remark is that if I read it right, this is always on? Do we want that? And do we want this in the runtime version? Or should we add some ifdefs to only include it in debug or tool builds?

In Godot, Vulkan timer queries work in release builds too. This is useful for two reasons:

• You can use GPU timer queries for dynamic resolution (to avoid taking CPU bottlenecks into account). This is often how AAA games do dynamic resolution.
• https://github.com/godotengine/godot-benchmarks needs it 🙂

[clayjohn]

Looks cool, my only remark is that if I read it right, this is always on? Do we want that? And do we want this in the runtime version? Or should we add some ifdefs to only include it in debug or tool builds?

For the reasons that Calinou lists above, I think we want this to always be available, the same as it is for the RenderingDevice backend.

[akien-mga]

Thanks!