1547115 - Logpoints on Gmail in large prettified file completely freezes main thread

Status: RESOLVED FIXED

(DevTools :: Debugger, defect)

Description

[:Harald Kirschner :digitarald]

What were you doing?

1. Open Gmail and log in
2. In DevTools Inspector, pick the body elements events bubble and find the click event (points to https://mail.google.com/_/scs/mail-static/_/js/k=gmail.main.en.…/m=b in my case)
3. Click through to the file to open it in Debugger
4. Should land on b.addEventListener(c.toString(), e, f);
5. Add a logpoint on that line, logging c, e, f
6. Refresh page

What happened?

Logs are coming in until Firefox's main UI freezes. Closing Debugger works and "thaws" Firefox.

What should have happened?

No freezing, just happy logging.

Anything else we should know?

https://profiler.firefox.com/public/e8ddd2b865dbcc465f3a616312780c2cce2049bf/flame-graph/?globalTrackOrder=0&localTrackOrderByPid=66792-0~&thread=0&v=3

addSources and insertSourceActors change redux state and cause codemirror to do expensive renderings on the large prettified file by calling disableEmptyLines in resource://devtools/client/debugger/src/components/Editor/EmptyLines.js. This seems to happen continuesly, even though nothing in the debugger changes.

Comment 1

[Logan Smyth [:loganfsmyth]]

I think I introduced this in https://phabricator.services.mozilla.com/D24443 by making the empty line selector non-memoized. I'll verify.

Comment 2

[Logan Smyth [:loganfsmyth]]

Attachment: Bug 1547115 - Memoize breakableLines to avoid resetting in editor often. r=davidwalsh

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5293fd5ae92f
Memoize breakableLines to avoid resetting in editor often. r=jlast

Comment 4

[Stefan Hindli [:stefan_hindli]]

https://hg.mozilla.org/mozilla-central/rev/5293fd5ae92f