Bug 279324 – When moving past a left-hand scrollbar, don't jump way outside the content box

• Component: Scrolling
• Status: RESOLVED FIXED

[Ahmad Saleem]

Hi Team,

While going through Blink's test cases for scrolling to see, if we have still failing cases, I came across another failing test.

Test Case: https://jsfiddle.net/fv1ymo2c/

^ Safari Technology Preview 202 still fail two RTL cases, while both Chrome Canrary 130 and Firefox Nightly 132 pases both.

Blink Commit: https://source.chromium.org/chromium/chromium/src/+/d457f863f78941ed376b463ee39476b1a1852797

I haven't checked whether we can merge it or not but just wanted to raise so we can track it.

Thanks!

[Simon Fraser (smfr)]

https://jsfiddle.net/fv1ymo2c/ passes for me locally.

[Ahmad Saleem]

Created attachment 472504 [details]
Test Case - Attached as HTML

[Ahmad Saleem]

Created attachment 472505 [details]
Safari vs Other Browsers (Firefox & Chrome)

[Radar WebKit Bug Importer]

<rdar://problem/136040116>

[Ahmad Saleem]

LayoutUnit RenderBox::verticalScrollbarWidthClampedToContentBox() const
{
    LayoutUnit width(verticalScrollbarWidth());
    ASSERT (width > LayoutUnit());
    if (width) {
        LayoutUnit minimumWidth = logicalWidth() - borderAndPaddingLogicalWidth();
        ASSERT(minimumWidth > LayoutUnit());
        width = std::min(width, minimumWidth);
    }
    return width;
}

// Return the width of the vertical scrollbar, unless it's larger than the
    // logical width of the content box, in which case we'll return that instead.
    // Scrollbar handling is quite bad in such situations, and this method here
    // is just to make sure that left-hand scrollbars don't mess up
    // scrollWidth.
    LayoutUnit verticalScrollbarWidthClampedToContentBox() const;

__

RenderBlockFlow::determineLogicalLeftPositionForChild

from

startPosition += (style().isLeftToRightDirection() ? 1 : -1) * verticalScrollbarWidth();

to

startPosition += (style().isLeftToRightDirection() ? 1 : -1) * verticalScrollbarWidthClampedToContentBox();

____

It progress first failing test `RTL scrollable with block-level child`, while I think other remaining failing is due to sub pixel inline layout.

[Ahmad Saleem]

Apply this as well - https://chromium.googlesource.com/chromium/src.git/+/49858cc9147612da1e54a673147e8020c5d7b9f9

[Ahmad Saleem]

Pull request: https://github.com/WebKit/WebKit/pull/47344

[EWS]

Committed 297945@main (be03a3a56787): <https://commits.webkit.org/297945@main>

Reviewed commits have been landed. Closing PR #47344 and removing active labels.