BlockFormattingContextQuirks.cpp   [plain text]

/*
 * Copyright (C) 2018 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *    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
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 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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#include "config.h"
#include "BlockFormattingContext.h"

#if ENABLE(LAYOUT_FORMATTING_CONTEXT)

#include "LayoutBox.h"
#include "LayoutContainer.h"
#include "LayoutState.h"

namespace WebCore {
namespace Layout {

static const Container& initialContainingBlock(const Box& layoutBox)
{
    auto* containingBlock = layoutBox.containingBlock();
    while (containingBlock->containingBlock())
        containingBlock = containingBlock->containingBlock();
    return *containingBlock;
}

static bool isQuirkContainer(const Box& layoutBox)
{
    return layoutBox.isBodyBox() || layoutBox.isDocumentBox() || layoutBox.isTableCell();
}

static bool hasMarginBeforeQuirkValue(const Box& layoutBox)
{
    return layoutBox.style().hasMarginBeforeQuirk();
}

bool BlockFormattingContext::Quirks::needsStretching(const LayoutState& layoutState, const Box& layoutBox)
{
    ASSERT(layoutBox.isInFlow());
    // In quirks mode, body stretches to html and html to the initial containing block (height: auto only).
    if (!layoutState.inQuirksMode())
        return false;

    if (!layoutBox.isDocumentBox() && !layoutBox.isBodyBox())
        return false;

    return layoutBox.style().logicalHeight().isAuto();
}

HeightAndMargin BlockFormattingContext::Quirks::stretchedHeight(const LayoutState& layoutState, const Box& layoutBox, HeightAndMargin heightAndMargin)
{
    ASSERT(layoutBox.isDocumentBox() || layoutBox.isBodyBox());

    auto& documentBox = layoutBox.isDocumentBox() ? layoutBox : *layoutBox.parent();
    auto& documentBoxDisplayBox = layoutState.displayBoxForLayoutBox(documentBox);
    auto documentBoxVerticalBorders = documentBoxDisplayBox.borderTop() + documentBoxDisplayBox.borderBottom();
    auto documentBoxVerticalPaddings = documentBoxDisplayBox.paddingTop().valueOr(0) + documentBoxDisplayBox.paddingBottom().valueOr(0);

    auto strechedHeight = layoutState.displayBoxForLayoutBox(initialContainingBlock(layoutBox)).contentBoxHeight();
    strechedHeight -= documentBoxVerticalBorders + documentBoxVerticalPaddings;

    LayoutUnit totalVerticalMargin;
    if (layoutBox.isDocumentBox()) {
        // Document box's margins do not collapse.
        auto verticalMargin = heightAndMargin.nonCollapsedMargin;
        totalVerticalMargin = verticalMargin.before + verticalMargin.after;
    } else if (layoutBox.isBodyBox()) {
        // Here is the quirky part for body box:
        // Stretch the body using the initial containing block's height and shrink it with document box's margin/border/padding.
        // This looks extremely odd when html has non-auto height.
        auto verticalMargin = Geometry::estimatedMarginBefore(layoutState, documentBox) + Geometry::estimatedMarginAfter(layoutState, documentBox);
        strechedHeight -= verticalMargin;

        auto nonCollapsedValues = heightAndMargin.nonCollapsedMargin;
        totalVerticalMargin = nonCollapsedValues.before + nonCollapsedValues.after;
    }

    // Stretch but never overstretch with the margins.
    if (heightAndMargin.height + totalVerticalMargin < strechedHeight)
        heightAndMargin.height = strechedHeight - totalVerticalMargin;

    return heightAndMargin;
}

bool BlockFormattingContext::Quirks::shouldIgnoreMarginBefore(const LayoutState& layoutState, const Box& layoutBox)
{
    if (!layoutBox.parent())
        return false;

    return layoutState.inQuirksMode() && isQuirkContainer(*layoutBox.parent()) && hasMarginBeforeQuirkValue(layoutBox);
}

}
}

#endif