Bug 106946 – Sticky-position elements can jump around/hide on rubber-banding

• Status: RESOLVED
• Resolution: FIXED
• Component: Layout and Rendering

[Simon Fraser (smfr)]

Sticky-postion elements behave oddly on rubber-banding. For example, the bug review bar on https://bugs.webkit.org/attachment.cgi?id=179870&action=review jumps around and disappear when you rubber-band at the top of the document.

[Radar WebKit Bug Importer]

<rdar://problem/13019346>

[Beth Dakin]

I think I know how to fix this.

[Beth Dakin]

Created attachment 183585 [details]
Patch

[Simon Fraser (smfr)]

Comment on attachment 183585 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=183585&action=review

> Source/WebCore/rendering/RenderBoxModelObject.cpp:513
>      LayoutRect viewportRect = view()->frameView()->visibleContentRect();
> +    viewportRect.setLocation(toPoint(view()->frameView()->scrollOffsetForFixedPosition()));

We do this in so many places that I think it's time to add something to FrameView for this. Maybe viewportConstrainedObjectRect() ?

[Beth Dakin]

Created attachment 183588 [details]
Patch

[Simon Fraser (smfr)]

Comment on attachment 183588 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=183588&action=review

> Source/WebCore/page/FrameView.h:194
> +    LayoutRect viewportConstrainedVisibleContentRect() const;

I think this deserves a comment saying how it's different from visibleContentRect() (rubber-banding and zooming).

[Beth Dakin]

Thank you! I added a comment http://trac.webkit.org/changeset/140229

[Benjamin Poulain]

It looks like this caused a regression on fast/css/sticky/sticky-top-zoomed.html:
    http://build.webkit.org/results/Apple%20MountainLion%20Release%20WK2%20(Tests)/r140230%20(4996)/results.html

[Simon Fraser (smfr)]

I think that change is expected, since this commit made sticky take zooming into account. We'll have to fix the ref test.

[Jer Noble]

Filed https://bugs.webkit.org/show_bug.cgi?id=107356, tracking the test failure.  Test was added to TestExpectations in <http://trac.webkit.org/changeset/140234>.