1555840 - Noisy updates for Scopes & Call Stack make stack navigation & stepping feel janky

Status: NEW

(DevTools :: Debugger, defect, P3)

Description

[:Harald Kirschner :digitarald]

Attachment: Chrome vs Firefox. Observe much less flickering in the sidepanels, only rarely Chrome updates the whole panel with a flickr.

Follow up from https://github.com/firefox-devtools/debugger/issues/7191 .

What were you doing?

1. When paused, step or navigate the call stack

What happened?

Scopes and Call Stack panel update in noisy fashion.

What should have happened?

Smooth updates that don't throw away UI for state that doesn't change much.

Anything else we should know?

Profile for a click on the same stack: http://bit.ly/30QXAbL

Observations

1. This shouldn't even update the Scopes panel but helps me profile the noisy update pattern
2. The state is updated first that resets the panel content to "Loading …".
3. Within 50ms, the panel has the same content again
4. A bad side effect the full panel reset is that the sidepanel scroll position is reset when the user scrolled down.

Brainstorming: Never reset the state to "loading" for any panel when it has content and just drop in the new the updated content when it is ready. Same for call stack and stepping

Comment 1

[Sorin Davidoi]

Attachment: Summary: Reduce flickering in the secondary panels