1573562 - Prevent previews from flashing effect when stepping

Status: NEW

(DevTools :: Debugger, enhancement, P3)

Description

[David Walsh :davidwalsh]

Attachment: Inline-Preview-Flashing.gif

When paused and then stepping, the inline preview blocks "flash" quickly (hide and show), despite the values not having changed.

We should persist these elements during stepping and not show/hide them as we're paused.

Comment 1

[:Harald Kirschner :digitarald]

Beyond the flashing, it is also visible that lines slightly shift. Not sure if this should be tackled here or an extra bug.

Comment 2

[:Harald Kirschner :digitarald]

Related to bug 1555840, so fixes this might consider both bugs.

Comment 3

[Sorin Davidoi]

Attachment: perf(inline-previews): Don't add and remove when stepping

Keep track of the previous inline previews and use them as fallback. This prevents the previews from being removed and re-added when stepping, but it introduced another problem: we can't really tell when the previous previews should be used or not. This is because we don't know when resuming if the debugger is going to pause again. In light of this, I don't think we can avoid some timeout logic (e.g. display the previous previews for 600ms after the current previews are missing).

To sum it up:

• This reduces the flickering which is also a performance improvement
• Has a bug where the previews are displayed after the debugger is resumed
• The browser_dbg-inline-preview mochitest is failing

I'm looking forward to feedback for how to address point number two. Will fix the failing test after an agreement is reached and implemented.

This also partially addresses https://bugzilla.mozilla.org/show_bug.cgi?id=1578219.

Comment 4

[Andrei Petcu]

Also a dupe here https://github.com/firefox-devtools/debugger/issues/8291