2013-02-14  Anton Vayvod  <avayvod@chromium.org>

        [Text Autosizing] Combine narrow descendants of a cluster into groups that should be autosized with the same multiplier.

        https://bugs.webkit.org/show_bug.cgi?id=109825

        Enhancement of the approach introduced in https://bugs.webkit.org/show_bug.cgi?id=109573.

        Instead of using the same text size multiplier for all narrow descendants of any autosizing

        cluster, group the descendants by how much narrower they are than the cluster's

        |blockContainingAllText| and process each group separately with a different multiplier for

        each one.

        For example, we want nested comments on the page to be autosized as a group but separately

        from a sidebar on the same page.

        Reviewed by NOBODY (OOPS!).

        Updated the existing test to verify the patch.

        * rendering/TextAutosizer.cpp:

        (WebCore::TextAutosizer::processClusterInternal):

            Splits the narrow descendants of the autosizing cluster into groups before processing

            each group individually.

        (WebCore::TextAutosizer::getNarrowDescendantsGroupedByWidth):

            Sorts the narrow descendants of the given cluster into groups, combining them by the

            difference between their content widths. If sorted by width, two consecutive nodes

            belong to the same group if their width difference is no greater than 100 CSS units.

        * rendering/TextAutosizer.h:

            New method definitions.

namespace {

// Compares the width of the specified cluster's roots in descending order.

bool clusterWiderThanComparisonFn(const TextAutosizingClusterInfo& first, const TextAutosizingClusterInfo& second)

{

    return first.root->contentLogicalWidth() > second.root->contentLogicalWidth();

}

} // namespace

void TextAutosizer::getNarrowDescendantsGroupedByWidth(const TextAutosizingClusterInfo& parentClusterInfo, Vector<Vector<TextAutosizingClusterInfo> >& groups)

{

    ASSERT(parentClusterInfo.blockContainingAllText);

    ASSERT(groups.isEmpty());

    Vector<TextAutosizingClusterInfo> clusterInfos(parentClusterInfo.narrowDescendants);

    if (clusterInfos.isEmpty())

        return;

    std::sort(clusterInfos.begin(), clusterInfos.end(), &clusterWiderThanComparisonFn);

    groups.grow(1);

    // If the width difference between two consecutive elements of |clusterInfos| is greater than

    // this empirically determined value, the next element should start a new group.

    const float maxWidthDifferenceWithinGroup = 100;

    for (size_t i = 0; i < clusterInfos.size(); ++i) {

        groups.last().append(clusterInfos[i]);

        if (i + 1 < clusterInfos.size()) {

            float currentWidth = clusterInfos[i].root->contentLogicalWidth();

            float nextWidth = clusterInfos[i + 1].root->contentLogicalWidth();

            if (currentWidth - nextWidth > maxWidthDifferenceWithinGroup)

                groups.grow(groups.size() + 1);

        }

    }

}

    // Returns groups of narrow descendants of a given autosizing cluster. The groups are combined

    // by the difference between the width of the descendant and the width of the parent cluster's

    // |blockContainingAllText|.

    static void getNarrowDescendantsGroupedByWidth(const TextAutosizingClusterInfo& parentClusterInfo, Vector<Vector<TextAutosizingClusterInfo> >&);

2013-02-14  Anton Vayvod  <avayvod@chromium.org>

        [Text Autosizing] Combine narrow descendants of a cluster into groups that should be autosized with the same multiplier.

        https://bugs.webkit.org/show_bug.cgi?id=109825

        Verify that narrow descendants are grouped and autosized separately according to the

        difference between the descendant's width and the width of its enclosing cluster's

        |blockContainingAllText|.

        Reviewed by NOBODY (OOPS!).

        * fast/text-autosizing/narrow-descendants-combined-expected.html:

        * fast/text-autosizing/narrow-descendants-combined.html:

    <div style="width: 240px">

        This text should be autosized to 20px computed font-size as it is combined with the next and the last narrow siblings and the maximum width is 400px.

    </div>

    <div style="width: 240px">

        This text should be autosized to 20px computed font-size as it is combined with the next and the last narrow siblings and the maximum width is 400px.

    </div>