Source/WebCore/style/StyleChange.cpp

/*
 * Copyright (C) 2013, 2016 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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#include "config.h"
#include "StyleChange.h"

#include "RenderStyleConstants.h"
#include "RenderStyle+GettersInlines.h"
#include <wtf/text/AtomString.h>

namespace WebCore {
namespace Style {

OptionSet<Change> determineChanges(const RenderStyle& s1, const RenderStyle& s2)
{
    OptionSet<Change> result;

    if (!s1.nonInheritedEqual(s2))
        result.add(Change::NonInherited);
    if (!s1.nonFastPathInheritedEqual(s2))
        result.add(Change::Inherited);
    if (!s1.fastPathInheritedEqual(s2))
        result.add(Change::FastPathInherited);

    if (!s1.descendantAffectingNonInheritedPropertiesEqual(s2))
        result.add(Change::Inherited);

    // We just detach if a renderer acquires or loses a column-span, since spanning elements
    // typically won't contain much content.
    auto columnSpanNeedsNewRenderer = [&] {
        if (!s1.columnSpanEqual(s2))
            return true;
        if (s1.columnSpan() != ColumnSpan::All)
            return false;
        // Spanning in ignored for floating and out-of-flow boxes.
        return s1.isFloating() != s2.isFloating() || s1.hasOutOfFlowPosition() != s2.hasOutOfFlowPosition();
    };

    auto needsRendererUpdate = [&] {
        if (s1.display() != s2.display())
            return true;
        if (s1.hasPseudoStyle(PseudoElementType::FirstLetter) != s2.hasPseudoStyle(PseudoElementType::FirstLetter))
            return true;
        if (columnSpanNeedsNewRenderer())
            return true;
        // When text-combine is on, we use RenderCombineText, otherwise RenderText.
        // https://bugs.webkit.org/show_bug.cgi?id=55069
        if (s1.hasTextCombine() != s2.hasTextCombine())
            return true;
        if (s1.content() != s2.content())
            return true;
        return false;
    };

    if (needsRendererUpdate())
        result.add(Change::Renderer);

    // Query container changes affect descendant style.
    if (!s1.containerTypeAndNamesEqual(s2))
        result.add(Change::Container);

    return result;
}

TextStream& operator<<(TextStream& ts, Change change)
{
    switch (change) {
    case Change::NonInherited: ts << "NonInherited"_s; break;
    case Change::FastPathInherited: ts << "FastPathInherited"_s; break;
    case Change::Inherited: ts << "Inherited"_s; break;
    case Change::Container: ts << "Container"_s; break;
    case Change::Renderer: ts << "Renderer"_s; break;
    }
    return ts;
}

TextStream& operator<<(TextStream& ts, OptionSet<Change> changes)
{
    auto separator = ""_s;
    for (auto change : changes)
        ts << std::exchange(separator, ", "_s) << change;
    return ts;
}

} // namespace Style

} // namespace WebCore