Bug 181269 – Swipe Back gesture to previous page causes lag in rendering

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[Cagdas Tulek]

Created attachment 330426 [details]
iOS 10.3 video capture

This bug probably happens for single page web apps. I have attached 2 video shots for iOS 10.3 and iOS 11.1 to show the difference in behavior.

I can reproduce the issue at outschool.com:
- Go to https://outschool.com/online-classes
- Click one of the class images to see the class detail page
- Use swipe back gesture to go to previous page
- Previous page renders empty for a couple of seconds and then appears fully rendered

Other remarks:
- This issue does not happen on iOS 10.3. There is still a short freeze of full UI but more acceptable than the current situation on iOS 11.1
- This issue does not happen for websites which are not single page apps. Try news.ycombinator.com as an example.
- This issue does not happen when regular back button is used instead of swiping

[Cagdas Tulek]

Created attachment 330427 [details]
iOS 11.1 video capture

[Tim Horton]

<rdar://problem/35110344>

[Tim Horton]

My fix for twitter seems to fix this site too, so I’ll use this bug (I’ve also confirmed that this site uses scrollRestoration and pushState, so it makes sense).

[Tim Horton]

Created attachment 330877 [details]
Patch

[Tim Horton]

Created attachment 330924 [details]
Patch

[Tim Horton]

Created attachment 330929 [details]
Patch

[Tim Horton]

Created attachment 330930 [details]
Patch

[Simon Fraser (smfr)]

Comment on attachment 330930 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=330930&action=review

> Source/WebKit/UIProcess/API/Cocoa/WKWebView.mm:321
> +    std::optional<uint64_t> _firstTransactionIDAfterPageRestore;

We really need a typedef for transactionIDs, or maybe use Identified or something.

> LayoutTests/swipe/pushstate-with-manual-scrollrestoration.html:9
> +history.scrollRestoration = "manual";

Maybe you should have a basic swipe test without scrollRestoration as well.

> LayoutTests/swipe/pushstate-with-manual-scrollrestoration.html:29
> +    measuredDurationShouldBeLessThan("snapshotRemoval", 1000, "Because we're using the page cache, it shouldn't be long between the gesture completing and the snapshot being removed.")

I wonder how flakey this will be on bots.

[Tim Horton]

(In reply to Simon Fraser (smfr) from comment #8)
> Comment on attachment 330930 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=330930&action=review
> 
> > Source/WebKit/UIProcess/API/Cocoa/WKWebView.mm:321
> > +    std::optional<uint64_t> _firstTransactionIDAfterPageRestore;
> 
> We really need a typedef for transactionIDs, or maybe use Identified or
> something.

Yes.

> > LayoutTests/swipe/pushstate-with-manual-scrollrestoration.html:9
> > +history.scrollRestoration = "manual";
> 
> Maybe you should have a basic swipe test without scrollRestoration as well.

Probably!

> > LayoutTests/swipe/pushstate-with-manual-scrollrestoration.html:29
> > +    measuredDurationShouldBeLessThan("snapshotRemoval", 1000, "Because we're using the page cache, it shouldn't be long between the gesture completing and the snapshot being removed.")
> 
> I wonder how flakey this will be on bots.

If it comes up, we can replace this with a bit that disables the watchdog, and just let the test time out altogether.

[EWS Watchlist]

Comment on attachment 330930 [details]
Patch

Attachment 330930 [details] did not pass mac-wk2-ews (mac-wk2):
Output: http://webkit-queues.webkit.org/results/6023578

New failing tests:
swipe/pushstate-with-manual-scrollrestoration.html

[EWS Watchlist]

Created attachment 330946 [details]
Archive of layout-test-results from ews107 for mac-sierra-wk2

The attached test failures were seen while running run-webkit-tests on the mac-wk2-ews.
Bot: ews107  Port: mac-sierra-wk2  Platform: Mac OS X 10.12.6

[Tim Horton]

Bug tracking the test failing on Mac (it’s pretty specific to the test): https://bugs.webkit.org/show_bug.cgi?id=181502. Going to skip the test on Mac for now.

[Tim Horton]

Created attachment 330975 [details]
Patch

[Tim Horton]

https://trac.webkit.org/changeset/226750/webkit

[Radar WebKit Bug Importer]

<rdar://problem/36424175>