[Impeller] Performance overlay is broken.

[chinmaygarde]

The overlay uses direct Skia calls instead of going through the display list interface. This makes the graphs not show up (though the text is visible).

The overlay must be retooled to use display list APIs instead of Skia ones.

[chinmaygarde]

xref b/279222257

[chinmaygarde]

I realize the team doesn't use the overlay for analyzing performance since there are better tools out there. But from the user perspective, the overlay is easy to setup to get a high level overview of the relative performance of Impeller and the legacy backend. The graphs not showing up is a rough and a poor first experience. Elevating priority for this reason.

[cbracken]

Hit this today on macOS :) Agreed with @chinmaygarde that while this isn't the end of the world, it's a really nice quick-and-dirty check to see whether you're dropping frames, so would be great to support.

[lukepighetti]

Having this not work feels weird since we've been able to rely on it for years. Would be nice to have an indication that this is known to not work.

[matanlurey]

This sounds interesting, I'd like to work on this issue!

[matanlurey]

Some notes for myself:

• Flutter performance profiling is the user-facing documentation.
• It can be enabled in devtools, and I think with P in debug or profile mode (though profile mode is recommended).
• The code appears to be in performance_overlay_layer.cc and friends. For me to figure out: it's already using DlCanvas*, what else needs to change to make it backend agnostic?

Here is an example with the Skia backend:

And with Impeller enabled: