How to capture frames?

[John-Nagle]

What's the right way to capture the frame just rendered, for routine screenshots and such? There's start_capture and stop_capture:

pub fn start_capture(&self)

Starts frame capture.
Source
pub fn stop_capture(&self)

Stops frame capture.

That's all the documentation says. Those work with the RenderDoc graphics debugger, and don't really synchronize with rendering. The usage I've found is start_capture, wait one second, stop_capture, check if you got something.

There are a few relevant crates.

• Egui has something called Capture.
• There's crabgrab. That's abandoned.

This is a common use case. What's best practice?

[JMS55]

Start/stop capture are just for renderdoc captures (they need better docs).

If you want to do something like "take a screenshot" you'll have to copy the texture to a buffer and then map it and read it back on the CPU.

[John-Nagle]

Right, I figured that out by looking at the code.

I tried using Egui's "Capture", but so far it's not capturing. I'm probably doing something wrong. There is almost no documentation, but there is an example that's egui on top of winit, without wgpu. I'm trying to do this in a program that uses wgpu. What I think the egui Capture is doing is asking the compositor for a copy of the window. Not sure, though.