Bug 185635

Summary:	Web Inspector: Canvas: it takes over a minute to process a 2 second recording
Product:	WebKit	Reporter:	Nikita Vasilyev <nvasilyev>
Component:	Web Inspector	Assignee:	Matt Baker <mattbaker>
Status:	RESOLVED WONTFIX
Severity:	Normal	CC:	hi, inspector-bugzilla-changes, mattbaker, webkit-bug-importer
Priority:	P2	Keywords:	InRadar
Version:	WebKit Nightly Build
Hardware:	All
OS:	All
See Also:	https://bugs.webkit.org/show_bug.cgi?id=175282
Bug Depends on:	185758
Bug Blocks:	173807

Description Nikita Vasilyev 2018-05-14 17:38:37 PDT

Steps:
1. Go to http://www.blobsallad.se
2. Open Canvas tab in Web Inspector
3. Press the record button for the Blob canvas
4. Wait for two seconds
5. Press the stop button

Actual:
It took over a minute to show the recording. "Processing recording" stayed on for over a minute.

Expected:
The recording shows in a few seconds. If that isn't possible, it should show the recording with limited features at first.

Comment 1 Radar WebKit Bug Importer 2018-05-14 17:38:57 PDT

<rdar://problem/40240813>

Comment 2 Devin Rousso 2018-05-15 01:23:35 PDT

This is most likely caused by <https://webkit.org/b/175282>.  There is no "easy" way to quickly determine if a particular visual action caused some pixels to change on the canvas, so we have to resort to checking every single pixel.  On larger canvases, this can take a long time, and the problem is compounded if there are a large number of visual actions in the recording.

Comment 3 Matt Baker 2018-05-18 14:08:13 PDT

This was addressed in https://bugs.webkit.org/show_bug.cgi?id=185758.