Bug 194687 – Web Inspector: Canvas: recordings with a single frame sometimes missing TreeElement

• Status: RESOLVED
• Resolution: FIXED
• Component: Web Inspector

[Devin Rousso]

# STEPS TO REPRODUCE:
1. inspect <https://devinrousso.com/demo/WebKit/canvas.html>
2. open the Canvas tab
3. start a single-frame recording of the 2D canvas
4. click the button with "8"
5. once the recording loads, select the "Frame 1" tree element
6. start a single-frame recording of the 2D canvas
7. click the button with "9"
 => there is no "Frame 1" tree element, even though the visual action scrubber says there are at least 2 visual actions

[Devin Rousso]

AFAICT, it looks like the issue has to do with `Object.prototype.soon`.  Here's the stream of calls:

1. `appendChild` for "Initial State"
2. `soon` `updateVirtualizedElements` for the recording actions `TreeOutline`
3. the timeout from (2) fires, which actually adds the `TreeElement` from (1) to the DOM
4. `appendChild` for "Frame 1"
5. `soon` `updateVirtualizedElements` for the recording actions `TreeOutline`
 => the timeout from (5) never seems to fire

[Devin Rousso]

(In reply to Devin Rousso from comment #0)
> 5. once the recording loads, select the "Frame 1" tree element
Interestingly, the issue only reproduces when any `TreeElement` other than the first one is selected.  Additionally, the first recording (3) can be multi-frame, but the second recording (6) has to be single-frame.

[Devin Rousso]

Created attachment 362092 [details]
Patch

[Joseph Pecoraro]

Comment on attachment 362092 [details]
Patch

r=me

[WebKit Commit Bot]

Comment on attachment 362092 [details]
Patch

Clearing flags on attachment: 362092

Committed r241875: <https://trac.webkit.org/changeset/241875>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Radar WebKit Bug Importer]

<rdar://problem/48289926>