pub fn begin_frame(window: &Window)Expand description
Promote the tree the last frame recorded and start a fresh one, claiming
this frame for window. Called from the inspector’s render, which runs
before any of this frame’s prepaints, so elements in every other window
this thread draws are skipped for the rest of the frame.
There is one tree per thread, so two inspectors in two windows take the claim from each other every frame and both come up empty. Showing each of them a tree of both windows would be worse.