GPU Markers

[kvark]

When debugging a complex graphical application, having named marker groups/events is essential. On GL, these are glPushGroupMarker and friends. Other APIs supposedly provide similar functionality, and if not - we can always just have a blanket implementation.

Rough design:

let marker = encoder.push_marker("Alpha entities");
... 
encoder.pop_marker(marker);

Here, marker is set to #[must_use] and potentially asserting/erroring in the destructor to make it pseudo-linear.

We also need to ensure the things are pushed/popped in the right order. Perhaps, something like a one-use phantom type would be sufficient? E.g.

enum MarkerAll {};
enum MarkerAlpha {};
let marker_all = encoder.push_marker::<MarkerAll>(()); // type `Marker1<MarkerAll>`;
let marker_alpha = encoder.push_marker::<MarkerAlpha>(marker_all); // type `Marker2<MarkerAlpha, MarkerAll>`;
// draw stuff here
let marker_all = encoder.pop_marker(marker_alpha);
encoder.pop_marker(marker_all);

[msiglreith]

Other interesting concepts added by the vulkan debug extension and also supported by some OpenGL implementation, which could be taken into consideration:

• Non-region markers / Event markers (mark a single place in the trace)
• Object/Resource Naming and Tagging

For more details checkout this great blogpost (https://www.saschawillems.de/?page_id=2017), also showing the renderdoc support.
Related OpenGL specifications (https://www.khronos.org/registry/OpenGL/extensions/KHR/KHR_debug.txt) and (https://www.khronos.org/registry/OpenGL/extensions/EXT/EXT_debug_marker.txt) (older)

[kvark]

Let's consider this fixed by #3169