This seems similar to --show-screenspace-rects which from the code seems like it should draw a box around every render surface. Not every render surface creates a render pass, but we could annotate which ones do and draw them differently.

Of course I don't know how to actually see the result, +danakj is this supposed to work for visualizing render surfaces on web content?

I think you're thinking of --show-compositor-layer-borders, which is enablable in devtools as well. There's no legend to tell whats going on, but blue border = renderpass.

> Not every render surface creates a render pass

FWIW they are 1:1

> There's no legend to tell whats going on,

cc/debug/debug_colors.h is the legend in the code

Oh, I took should_draw_into_render_pass as meaning that they weren't 1:1 :
https://cs.chromium.org/chromium/src/cc/trees/layer_tree_host_impl.cc?type=cs&q=file:layer_tree_host_impl.cc+should_draw_into_render_pass&sq=package:chromium&g=0&l=997

Anyways, thanks for the pointer.

Alex do you want to start by looking for blue layer borders and see if this is sufficient?

> Oh, I took should_draw_into_render_pass as meaning that they weren't 1:1 :

That's checking if the pass should be drawn into a parent renderpass, or just rendered and then dropped (for copying to a texture when its not part of the user-visible output).