Source/WebCore/layout/inlineformatting/InlineLineBreaker.cpp

/*
 * Copyright (C) 2018 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. AND ITS CONTRIBUTORS ``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 ITS 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 OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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 */

#include "config.h"
#include "InlineLineBreaker.h"

#if ENABLE(LAYOUT_FORMATTING_CONTEXT)

#include "Hyphenation.h"
#include "InlineItem.h"
#include "InlineTextItem.h"

namespace WebCore {
namespace Layout {

LineBreaker::BreakingContext LineBreaker::breakingContext(const InlineItem& inlineItem, LayoutUnit logicalWidth, const LineContext& lineContext)
{
    // First content always stays on line.
    if (lineContext.isEmpty || logicalWidth <= lineContext.availableWidth)
        return { BreakingBehavior::Keep, isAtBreakingOpportunity(inlineItem) };

    if (inlineItem.isHardLineBreak())
        return { BreakingBehavior::Keep, isAtBreakingOpportunity(inlineItem) };

    if (is<InlineTextItem>(inlineItem))
        return { wordBreakingBehavior(downcast<InlineTextItem>(inlineItem), lineContext.isEmpty), isAtBreakingOpportunity(inlineItem) };

    // Wrap non-text boxes to the next line unless we can trim trailing whitespace.
    auto availableWidth = lineContext.availableWidth + lineContext.trimmableWidth;
    if (logicalWidth <= availableWidth)
        return { BreakingBehavior::Keep, isAtBreakingOpportunity(inlineItem) };
    return { BreakingBehavior::Wrap, isAtBreakingOpportunity(inlineItem) };
}

LineBreaker::BreakingBehavior LineBreaker::wordBreakingBehavior(const InlineTextItem& inlineItem, bool lineIsEmpty) const
{
    // Word breaking behaviour:
    // 1. Whitesapce collapse on -> push whitespace to next line.
    // 2. Whitespace collapse off -> whitespace is split where possible.
    // 3. Non-whitespace -> first run on the line -> either split or kept on the line. (depends on overflow-wrap)
    // 4. Non-whitespace -> already content on the line -> either gets split (word-break: break-all) or gets pushed to the next line.
    // (Hyphenate when possible)
    // 5. Non-text type -> next line
    auto& style = inlineItem.style();

    if (inlineItem.isWhitespace())
        return style.collapseWhiteSpace() ? BreakingBehavior::Wrap : BreakingBehavior::Split;

    auto shouldHypenate = !m_hyphenationIsDisabled && style.hyphens() == Hyphens::Auto && canHyphenate(style.locale());
    if (shouldHypenate)
        return BreakingBehavior::Split;

    if (style.autoWrap()) {
        // Break any word
        if (style.wordBreak() == WordBreak::BreakAll)
            return BreakingBehavior::Split;

        // Break first run on line.
        if (lineIsEmpty && style.breakWords() && style.preserveNewline())
            return BreakingBehavior::Split;
    }

    // Non-breakable non-whitespace run.
    return lineIsEmpty ? BreakingBehavior::Keep : BreakingBehavior::Wrap;
}

bool LineBreaker::isAtBreakingOpportunity(const InlineItem& inlineItem)
{
    if (inlineItem.isHardLineBreak())
        return true;

    if (is<InlineTextItem>(inlineItem))
        return downcast<InlineTextItem>(inlineItem).isWhitespace();
    return !inlineItem.isFloat() && !inlineItem.isContainerStart() && !inlineItem.isContainerEnd();
}

}
}
#endif