Bug 231989 – Content offset in this codepen when switching tabs

• Component: Scrolling
• Status: RESOLVED FIXED

[Simon Fraser (smfr)]

Load https://codepen.io/isladjan/pen/abdyPBw and scroll in the lower pane. Now switch to another tab in Safari, and switch back. The bottom content is now entirely or partially missing.

[Simon Fraser (smfr)]

The compositing layers for the RenderSVGRoot and its siblings has different positions after switching tabs

[Simon Fraser (smfr)]

I think this is scrolling tree related. When we rebuild the scrolling tree after the view is reattached on tab switch, the iframe's scrolling tree node has a 0,0 scroll position rather than the correct one, causing the position:fixed to get mis-positioned.

[Simon Fraser (smfr)]

Created attachment 441985 [details]
Patch

[Simon Fraser (smfr)]

Created attachment 442049 [details]
Patch

[Simon Fraser (smfr)]

Created attachment 442063 [details]
Patch

[Tim Horton]

Comment on attachment 442063 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=442063&action=review

> Tools/TestWebKitAPI/Tests/mac/ScrollingCoordinatorTests.mm:39
> +static void synthesizeWheelEvents(NSView *view, CGPoint locationInView, CGSize delta)

Surely not unique to this test, should it be on TestWKWebView?

> Tools/TestWebKitAPI/Tests/mac/ScrollingCoordinatorTests.mm:82
> +        return [obj hasPrefix:@"        (last committed scroll position"];

Somewhat eww

> Tools/TestWebKitAPI/Tests/mac/ScrollingCoordinatorTests.mm:115
> +    NSWindow *hostWindow = [webView window];

Doesn't TestWKWebView have helpers for moving in and out of window too? I guess your test is platform specific so it doesn't really matter.

> Tools/TestWebKitAPI/Tests/mac/ScrollingCoordinatorTests.mm:125
> +    scrollY = waitForScrollEventAndReturnScrollY(webView.get(), [](WKWebView* webView) {

Star's on the wrong side etc.

[Simon Fraser (smfr)]

Created attachment 442070 [details]
Patch

[Radar WebKit Bug Importer]

<rdar://problem/84525145>

[EWS]

Committed r284654 (243374@main): <https://commits.webkit.org/243374@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 442070 [details].

Reverted r284654 for reason:

Reverting because this commit caused scrolling tests to fail

Committed r284685 (243405@main): <https://commits.webkit.org/243405@main>

[Simon Fraser (smfr)]

Created attachment 442190 [details]
Patch

[EWS]

Committed r284738 (243447@main): <https://commits.webkit.org/243447@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 442190 [details].