Bug 179072 – Web Inspector: Canvas Tab: selecting Frame tree element should update preview/slider, does nothing

• Component: Web Inspector
• Status: RESOLVED FIXED

[Blaze Burg]

Steps to reproduce:

- Capture a bunch of frames that change slightly, like webkit.org or acko.net animated backgrounds
- Select a frame, go between frames with arrow keys
=> Preview doesn't update, unless going to "initial state"

This is really annoying because I want to quickly find a frame with a particular visual feature or glitch. If I use the slider to try and scrub, then the preview flickers a lot as it needs to show all intermediate clear() calls.

When I select a frame tree element, I would expect it to show the a preview after the final output-affecting command in the frame window. That way I can expand an interesting frame and see how it's built up from an initial clear() call.

[Radar WebKit Bug Importer]

<rdar://problem/35278711>

[Devin Rousso]

The original Recording tab had this functionality.  The new Canvas tab removed it (<https://webkit.org/b/177606>).  I don't take multi-frame recordings very often, so I'm don't have a strong opinion about how it should work.

[Devin Rousso]

Created attachment 325869 [details]
Patch

[Matt Baker]

Comment on attachment 325869 [details]
Patch

r=me, with some thoughts:

I left this behavior out during the redesign, because of the effect it has on the slider when selecting actions in the sidebar with up/down keys. Doing nothing when selecting a frame tree element probably wasn't the right choice, but was done to prevent this:

With multiple frames expanded, select the first frame:

Frame 1*
  Action 1
  Action 2
Frame 2
  Action 3

=> Slider shows 2 of 3

Press down arrow once:

Frame 1
  Action 1*
  Action 2
Frame 2
  Action 3

=> Slider shows 1 of 3

For the change in the slider to be monotonic, selecting a frame tree element would need to select the first child action instead of the last. But this prevents skipping to the end of the recording by selecting the last frame tree element.

[WebKit Commit Bot]

Comment on attachment 325869 [details]
Patch

Clearing flags on attachment: 325869

Committed r224475: <https://trac.webkit.org/changeset/224475>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.