Capturing internal state for debug investigations

[kvark]

We need to introduce some infrastructure of capturing the internal state, so that we can have a closer look at things when stuff goes out of the expected way. Most interesting things:

• metadata of all of the resources (by desriptors we pass at creation?)
• state of resource trackers on all the things: devices, command buffers, passes
• references from all around the world: other resources, trackers, active submissions

From this, we could go a step further and ask the capture about what are all the things connected to a single node (e.g. a texture), to get an idea of how it's referenced and transitioned. This could possibly be done off-line, as an extra analysis based on the captured data.

[seivan]

Does this mean of adding a Derive Debug for Adapters, Device, Pipelines etc?
Because I'd love to be able to print something and see its state/fields. Useful for learning purposes.

[kvark]

No, it means adding Serialize to structs that can be serialized, and introducing their serializable analogues for the ones that can't. We have a similar scheme implemented in WebRender, e.g. https://github.com/servo/webrender/blob/b4b0f52cba955fac9cad2e6e42c88aef65923974/webrender/src/render_backend.rs#L65-L66 , and it has shown to work exceptionally well for debugging. You can read more about it here - http://kvark.github.io/webrender/debug/ron/2018/01/23/wr-capture-infra.html

[cwfitzgerald]

Seems to have been solved by api tracing.

[kvark]

The issue is about a different debugging feature, more like what WebRender has. But I think it's fine to close this as API tracing helps with most cases.