[Webkit-unassigned] [Bug 265963] New: Fix precedence of relative position in vertical modes

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=265963

            Bug ID: 265963
           Summary: Fix precedence of relative position in vertical modes
           Product: WebKit
           Version: Safari Technology Preview
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Keywords: BrowserCompat, WPTImpact
          Severity: Normal
          Priority: P2
         Component: CSS
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: ahmad.saleem792 at gmail.com

Hi Team,

While looking into WPT failures, I noticed that two of following tests can be progressed:

Tests: http://wpt.live/css/css-writing-modes/overconstrained-rel-pos-rtl-top-bottom-vlr-007.xht & http://wpt.live/css/css-writing-modes/overconstrained-rel-pos-rtl-left-right-vlr-009.xht

Blink Commit: https://chromium.googlesource.com/chromium/src.git/+/0f97b71bdc98d3c785b329c21134f3925f51ff3a

Merge this or take Rob's patch from bug 209080.

__

Rob's patch modified:

// https://drafts.csswg.org/css-grid/#grid-item-sizing
    bool isLtr = containingBlock()->style().isLeftToRightDirection();
    auto writingMode = containingBlock()->style().writingMode();
    if (!style().left().isAuto() || !style().right().isAuto()) {
        LayoutUnit availableWidth = hasOverridingContainingBlockContentWidth()
            ? valueOrDefault(overridingContainingBlockContentWidth()) : containingBlock()->availableWidth();
        switch (writingMode) {
            case WritingMode::HorizontalTb:
            if (!style().left().isAuto()) {
                if (!style().right().isAuto() && !containingBlock()->style().isLeftToRightDirection())
                    offset.setWidth(-valueForLength(style().right(), !style().right().isFixed() ? availableWidth : 0_lu));
                else offset.expand(valueForLength(style().left(), !style().left().isFixed() ? availableWidth : 0_lu), 0_lu); 
            } else if (!style().right().isAuto())
                offset.expand(-valueForLength(style().right(), !style().right().isFixed() ? availableWidth : 0_lu), 0_lu);
            break;
            case WritingMode::VerticalRl:
            if (!style().left().isAuto()) {
                if (!style().right().isAuto())
                    offset.setWidth(-valueForLength(style().right(), !style().right().isFixed() ? availableWidth : 0_lu));
                else
                    offset.setWidth(valueForLength(style().left(), !style().left().isFixed() ? availableWidth : 0_lu));
            } else if (!style().right().isAuto())
                offset.setWidth(-valueForLength(style().right(), !style().right().isFixed() ? availableWidth : 0_lu));
            break;
            case WritingMode::VerticalLr:
                if (!style().left().isAuto())
                    offset.expand(valueForLength(style().left(), !style().left().isFixed() ? availableWidth : 0_lu), 0_lu);
                else if (!style().right().isAuto())
                    offset.expand(-valueForLength(style().right(), !style().right().isFixed() ? availableWidth : 0_lu), 0_lu);
                    break;
            default:
                break;
        }
    }
    // If the containing block of a relatively positioned element does not
    // See <https://bugs.webkit.org/show_bug.cgi?id=26396>.
    // Another exception is a grid item, as the containing block is the grid area:
    // https://drafts.csswg.org/css-grid/#grid-item-sizing
    std::optional<LayoutUnit> top;
    std::optional<LayoutUnit> bottom;
    if (!style().top().isAuto()
        && (!style().top().isPercentOrCalculated()
            || !containingBlock()->hasAutoHeightOrContainingBlockWithAutoHeight()
        // FIXME: The computation of the available height is repeated later for "bottom".
        // We could refactor this and move it to some common code for both ifs, however moving it outside of the ifs
        // is not possible as it'd cause performance regressions.
        top = valueForLength(style().top(), !style().top().isFixed()
            ? (hasOverridingContainingBlockContentHeight() ? overridingContainingBlockContentHeight().value_or(0_lu) : containingBlock()->availableHeight())
            : LayoutUnit());
    }
    if (!style().bottom().isAuto()
        && (!style().bottom().isPercentOrCalculated()
            || !containingBlock()->hasAutoHeightOrContainingBlockWithAutoHeight()
            || containingBlock()->stretchesToViewport()
            || hasOverridingContainingBlockContentHeight())) {
        // FIXME: Check comment above for "top", it applies here too.
        bottom = valueForLength(style().bottom(), !style().bottom().isFixed()
            ? (hasOverridingContainingBlockContentHeight() ? overridingContainingBlockContentHeight().value_or(0_lu) : containingBlock()->availableHeight())
            : LayoutUnit());
    }
    if (!top && !bottom) {
        top = LayoutUnit();
        bottom = LayoutUnit();
    }
    if (!top)
        top = -bottom.value();
    if (!bottom)
        bottom = -top.value();
    switch (writingMode) {
        case WritingMode::HorizontalTb:
            offset.expand(0_lu, top.value());
            break;
        case WritingMode::VerticalRl:
        case WritingMode::VerticalLr:
            if (isLtr)
                offset.expand(0_lu, top.value());
            else
                offset.setHeight(-bottom.value());
            break;
        default:
            break;
    }

___

This compiles and progress above two test cases.

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