root/Source/core/css/resolver/StyleAdjuster.cpp

DEFINITIONS

1. isAtShadowBoundary
2. addIntrinsicMargins
3. equivalentBlockDisplay
4. doesNotInheritTextDecoration
5. isInTopLayer
6. isDisplayFlexibleBox
7. isDisplayGridBox
8. parentStyleForcesZIndexToCreateStackingContext
9. hasWillChangeThatCreatesStackingContext
10. adjustRenderStyle
11. adjustStyleForTagName
12. adjustOverflow
13. adjustStyleForDisplay

/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
 * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
 * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
 * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
 * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
 * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
 * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
 * Copyright (C) Research In Motion Limited 2011. All rights reserved.
 * Copyright (C) 2013 Google Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#include "config.h"
#include "core/css/resolver/StyleAdjuster.h"

#include "HTMLNames.h"
#include "SVGNames.h"
#include "core/dom/ContainerNode.h"
#include "core/dom/Document.h"
#include "core/dom/Element.h"
#include "core/dom/NodeRenderStyle.h"
#include "core/html/HTMLIFrameElement.h"
#include "core/html/HTMLInputElement.h"
#include "core/html/HTMLTableCellElement.h"
#include "core/html/HTMLTextAreaElement.h"
#include "core/frame/FrameView.h"
#include "core/frame/Settings.h"
#include "core/rendering/RenderTheme.h"
#include "core/rendering/style/GridPosition.h"
#include "core/rendering/style/RenderStyle.h"
#include "core/rendering/style/RenderStyleConstants.h"
#include "core/svg/SVGSVGElement.h"
#include "platform/Length.h"
#include "platform/transforms/TransformOperations.h"
#include "wtf/Assertions.h"

namespace WebCore {

using namespace HTMLNames;

// FIXME: This is duplicated with StyleResolver.cpp
// Perhaps this should move onto ElementResolveContext or even Element?
static inline bool isAtShadowBoundary(const Element* element)
{
    if (!element)
        return false;
    ContainerNode* parentNode = element->parentNode();
    return parentNode && parentNode->isShadowRoot();
}


static void addIntrinsicMargins(RenderStyle* style)
{
    // Intrinsic margin value.
    const int intrinsicMargin = 2 * style->effectiveZoom();

    // FIXME: Using width/height alone and not also dealing with min-width/max-width is flawed.
    // FIXME: Using "quirk" to decide the margin wasn't set is kind of lame.
    if (style->width().isIntrinsicOrAuto()) {
        if (style->marginLeft().quirk())
            style->setMarginLeft(Length(intrinsicMargin, Fixed));
        if (style->marginRight().quirk())
            style->setMarginRight(Length(intrinsicMargin, Fixed));
    }

    if (style->height().isAuto()) {
        if (style->marginTop().quirk())
            style->setMarginTop(Length(intrinsicMargin, Fixed));
        if (style->marginBottom().quirk())
            style->setMarginBottom(Length(intrinsicMargin, Fixed));
    }
}

static EDisplay equivalentBlockDisplay(EDisplay display, bool isFloating, bool strictParsing)
{
    switch (display) {
    case BLOCK:
    case TABLE:
    case BOX:
    case FLEX:
    case GRID:
        return display;

    case LIST_ITEM:
        // It is a WinIE bug that floated list items lose their bullets, so we'll emulate the quirk, but only in quirks mode.
        if (!strictParsing && isFloating)
            return BLOCK;
        return display;
    case INLINE_TABLE:
        return TABLE;
    case INLINE_BOX:
        return BOX;
    case INLINE_FLEX:
        return FLEX;
    case INLINE_GRID:
        return GRID;

    case INLINE:
    case INLINE_BLOCK:
    case TABLE_ROW_GROUP:
    case TABLE_HEADER_GROUP:
    case TABLE_FOOTER_GROUP:
    case TABLE_ROW:
    case TABLE_COLUMN_GROUP:
    case TABLE_COLUMN:
    case TABLE_CELL:
    case TABLE_CAPTION:
        return BLOCK;
    case NONE:
        ASSERT_NOT_REACHED();
        return NONE;
    }
    ASSERT_NOT_REACHED();
    return BLOCK;
}

// CSS requires text-decoration to be reset at each DOM element for tables,
// inline blocks, inline tables, shadow DOM crossings, floating elements,
// and absolute or relatively positioned elements.
static bool doesNotInheritTextDecoration(const RenderStyle* style, const Element* e)
{
    return style->display() == TABLE || style->display() == INLINE_TABLE
        || style->display() == INLINE_BLOCK || style->display() == INLINE_BOX || isAtShadowBoundary(e)
        || style->isFloating() || style->hasOutOfFlowPosition();
}

// FIXME: This helper is only needed because pseudoStyleForElement passes a null
// element to adjustRenderStyle, so we can't just use element->isInTopLayer().
static bool isInTopLayer(const Element* element, const RenderStyle* style)
{
    return (element && element->isInTopLayer()) || (style && style->styleType() == BACKDROP);
}

static bool isDisplayFlexibleBox(EDisplay display)
{
    return display == FLEX || display == INLINE_FLEX;
}

static bool isDisplayGridBox(EDisplay display)
{
    return display == GRID || display == INLINE_GRID;
}

static bool parentStyleForcesZIndexToCreateStackingContext(const RenderStyle* parentStyle)
{
    return isDisplayFlexibleBox(parentStyle->display()) || isDisplayGridBox(parentStyle->display());
}

static bool hasWillChangeThatCreatesStackingContext(const RenderStyle* style, Element* e)
{
    for (size_t i = 0; i < style->willChangeProperties().size(); ++i) {
        switch (style->willChangeProperties()[i]) {
        case CSSPropertyOpacity:
        case CSSPropertyTransform:
        case CSSPropertyWebkitTransform:
        case CSSPropertyTransformStyle:
        case CSSPropertyWebkitTransformStyle:
        case CSSPropertyPerspective:
        case CSSPropertyWebkitPerspective:
        case CSSPropertyWebkitMask:
        case CSSPropertyWebkitMaskBoxImage:
        case CSSPropertyWebkitClipPath:
        case CSSPropertyWebkitBoxReflect:
        case CSSPropertyWebkitFilter:
        case CSSPropertyZIndex:
        case CSSPropertyPosition:
            return true;
        case CSSPropertyMixBlendMode:
        case CSSPropertyIsolation:
            if (RuntimeEnabledFeatures::cssCompositingEnabled())
                return true;
            break;
        default:
            break;
        }
    }
    return false;
}

void StyleAdjuster::adjustRenderStyle(RenderStyle* style, RenderStyle* parentStyle, Element *e)
{
    ASSERT(parentStyle);

    // Cache our original display.
    style->setOriginalDisplay(style->display());

    if (style->display() != NONE) {
        if (e)
            adjustStyleForTagName(style, parentStyle, *e);

        // Per the spec, position 'static' and 'relative' in the top layer compute to 'absolute'.
        if (isInTopLayer(e, style) && (style->position() == StaticPosition || style->position() == RelativePosition))
            style->setPosition(AbsolutePosition);

        // Absolute/fixed positioned elements, floating elements and the document element need block-like outside display.
        if (style->hasOutOfFlowPosition() || style->isFloating() || (e && e->document().documentElement() == e))
            style->setDisplay(equivalentBlockDisplay(style->display(), style->isFloating(), !m_useQuirksModeStyles));

        adjustStyleForDisplay(style, parentStyle);
    }

    // Make sure our z-index value is only applied if the object is positioned.
    if (style->position() == StaticPosition && !parentStyleForcesZIndexToCreateStackingContext(parentStyle))
        style->setHasAutoZIndex();

    // Auto z-index becomes 0 for the root element and transparent objects. This prevents
    // cases where objects that should be blended as a single unit end up with a non-transparent
    // object wedged in between them. Auto z-index also becomes 0 for objects that specify transforms/masks/reflections.
    if (style->hasAutoZIndex() && ((e && e->document().documentElement() == e)
        || style->opacity() < 1.0f
        || style->hasTransformRelatedProperty()
        || style->hasMask()
        || style->clipPath()
        || style->boxReflect()
        || style->hasFilter()
        || style->hasBlendMode()
        || style->hasIsolation()
        || style->position() == StickyPosition
        || style->position() == FixedPosition
        || isInTopLayer(e, style)
        || hasWillChangeThatCreatesStackingContext(style, e)))
        style->setZIndex(0);

    // will-change:transform should result in the same rendering behavior as having a transform,
    // including the creation of a containing block for fixed position descendants.
    if (!style->hasTransform() && (style->willChangeProperties().contains(CSSPropertyWebkitTransform) || style->willChangeProperties().contains(CSSPropertyTransform))) {
        bool makeIdentity = true;
        style->setTransform(TransformOperations(makeIdentity));
    }

    if (doesNotInheritTextDecoration(style, e))
        style->setTextDecorationsInEffect(style->textDecoration());
    else
        style->addToTextDecorationsInEffect(style->textDecoration());

    if (style->overflowX() != OVISIBLE || style->overflowY() != OVISIBLE)
        adjustOverflow(style, e);

    // Cull out any useless layers and also repeat patterns into additional layers.
    style->adjustBackgroundLayers();
    style->adjustMaskLayers();

    // Let the theme also have a crack at adjusting the style.
    if (style->hasAppearance())
        RenderTheme::theme().adjustStyle(style, e, m_cachedUAStyle);

    // If we have first-letter pseudo style, transitions, or animations, do not share this style.
    if (style->hasPseudoStyle(FIRST_LETTER) || style->transitions() || style->animations())
        style->setUnique();

    // FIXME: when dropping the -webkit prefix on transform-style, we should also have opacity < 1 cause flattening.
    if (style->preserves3D() && (style->overflowX() != OVISIBLE
        || style->overflowY() != OVISIBLE
        || style->hasFilter()))
        style->setTransformStyle3D(TransformStyle3DFlat);

    if (e && e->isSVGElement()) {
        // Only the root <svg> element in an SVG document fragment tree honors css position
        if (!(isSVGSVGElement(*e) && e->parentNode() && !e->parentNode()->isSVGElement()))
            style->setPosition(RenderStyle::initialPosition());

        // RenderSVGRoot handles zooming for the whole SVG subtree, so foreignObject content should
        // not be scaled again.
        if (isSVGForeignObjectElement(*e))
            style->setEffectiveZoom(RenderStyle::initialZoom());

        // SVG text layout code expects us to be a block-level style element.
        if ((isSVGForeignObjectElement(*e) || isSVGTextElement(*e)) && style->isDisplayInlineType())
            style->setDisplay(BLOCK);
    }

    if (e && e->renderStyle() && e->renderStyle()->textAutosizingMultiplier() != 1) {
        // Preserve the text autosizing multiplier on style recalc.
        // (The autosizer will update it during layout if it needs to be changed.)
        style->setTextAutosizingMultiplier(e->renderStyle()->textAutosizingMultiplier());
        style->setUnique();
    }
}

void StyleAdjuster::adjustStyleForTagName(RenderStyle* style, RenderStyle* parentStyle, Element& element)
{
    // <div> and <span> are the most common elements on the web, we skip all the work for them.
    if (isHTMLDivElement(element) || isHTMLSpanElement(element))
        return;

    if (isHTMLTableCellElement(element)) {
        // If we have a <td> that specifies a float property, in quirks mode we just drop the float property.
        // FIXME: Why is this only <td> and not <th>?
        if (element.hasTagName(tdTag) && m_useQuirksModeStyles) {
            style->setDisplay(TABLE_CELL);
            style->setFloating(NoFloat);
        }
        // FIXME: We shouldn't be overriding start/-webkit-auto like this. Do it in html.css instead.
        // Table headers with a text-align of -webkit-auto will change the text-align to center.
        if (element.hasTagName(thTag) && style->textAlign() == TASTART)
            style->setTextAlign(CENTER);
        if (style->whiteSpace() == KHTML_NOWRAP) {
            // Figure out if we are really nowrapping or if we should just
            // use normal instead. If the width of the cell is fixed, then
            // we don't actually use NOWRAP.
            if (style->width().isFixed())
                style->setWhiteSpace(NORMAL);
            else
                style->setWhiteSpace(NOWRAP);
        }
        return;
    }

    if (isHTMLTableElement(element)) {
        // Sites commonly use display:inline/block on <td>s and <table>s. In quirks mode we force
        // these tags to retain their display types.
        if (m_useQuirksModeStyles)
            style->setDisplay(style->isDisplayInlineType() ? INLINE_TABLE : TABLE);
        // Tables never support the -webkit-* values for text-align and will reset back to the default.
        if (style->textAlign() == WEBKIT_LEFT || style->textAlign() == WEBKIT_CENTER || style->textAlign() == WEBKIT_RIGHT)
            style->setTextAlign(TASTART);
        return;
    }

    if (isHTMLFrameElement(element) || isHTMLFrameSetElement(element)) {
        // Frames and framesets never honor position:relative or position:absolute. This is necessary to
        // fix a crash where a site tries to position these objects. They also never honor display.
        style->setPosition(StaticPosition);
        style->setDisplay(BLOCK);
        return;
    }

    if (isHTMLRTElement(element)) {
        // Ruby text does not support float or position. This might change with evolution of the specification.
        style->setPosition(StaticPosition);
        style->setFloating(NoFloat);
        return;
    }

    if (isHTMLLegendElement(element)) {
        style->setDisplay(BLOCK);
        return;
    }

    if (isHTMLMarqueeElement(element)) {
        // For now, <marquee> requires an overflow clip to work properly.
        style->setOverflowX(OHIDDEN);
        style->setOverflowY(OHIDDEN);
        return;
    }

    if (element.isFormControlElement()) {
        if (isHTMLTextAreaElement(element)) {
            // Textarea considers overflow visible as auto.
            style->setOverflowX(style->overflowX() == OVISIBLE ? OAUTO : style->overflowX());
            style->setOverflowY(style->overflowY() == OVISIBLE ? OAUTO : style->overflowY());
        }

        // Important: Intrinsic margins get added to controls before the theme has adjusted the style,
        // since the theme will alter fonts and heights/widths.
        //
        // Don't apply intrinsic margins to image buttons. The designer knows how big the images are,
        // so we have to treat all image buttons as though they were explicitly sized.
        if (style->fontSize() >= 11 && (!isHTMLInputElement(element) || !toHTMLInputElement(element).isImageButton()))
            addIntrinsicMargins(style);
        return;
    }
}

void StyleAdjuster::adjustOverflow(RenderStyle* style, Element* element)
{
    ASSERT(style->overflowX() != OVISIBLE || style->overflowY() != OVISIBLE);

    // If either overflow value is not visible, change to auto.
    if (style->overflowX() == OVISIBLE && style->overflowY() != OVISIBLE) {
        // FIXME: Once we implement pagination controls, overflow-x should default to hidden
        // if overflow-y is set to -webkit-paged-x or -webkit-page-y. For now, we'll let it
        // default to auto so we can at least scroll through the pages.
        style->setOverflowX(OAUTO);
    } else if (style->overflowY() == OVISIBLE && style->overflowX() != OVISIBLE) {
        style->setOverflowY(OAUTO);
    }

    // Table rows, sections and the table itself will support overflow:hidden and will ignore scroll/auto.
    // FIXME: Eventually table sections will support auto and scroll.
    if (style->display() == TABLE || style->display() == INLINE_TABLE
        || style->display() == TABLE_ROW_GROUP || style->display() == TABLE_ROW) {
        if (style->overflowX() != OVISIBLE && style->overflowX() != OHIDDEN)
            style->setOverflowX(OVISIBLE);
        if (style->overflowY() != OVISIBLE && style->overflowY() != OHIDDEN)
            style->setOverflowY(OVISIBLE);
    }

    // Menulists should have visible overflow
    if (style->appearance() == MenulistPart) {
        style->setOverflowX(OVISIBLE);
        style->setOverflowY(OVISIBLE);
    }

    // Spec: http://www.w3.org/TR/SVG/masking.html#OverflowProperty
    if (element && element->isSVGElement()) {
        if (style->overflowY() == OSCROLL)
            style->setOverflowY(OHIDDEN);
        else if (style->overflowY() == OAUTO)
            style->setOverflowY(OVISIBLE);

        if (style->overflowX() == OSCROLL)
            style->setOverflowX(OHIDDEN);
        else if (style->overflowX() == OAUTO)
            style->setOverflowX(OVISIBLE);
    }
}

void StyleAdjuster::adjustStyleForDisplay(RenderStyle* style, RenderStyle* parentStyle)
{
    if (style->display() == BLOCK && !style->isFloating())
        return;

    // FIXME: Don't support this mutation for pseudo styles like first-letter or first-line, since it's not completely
    // clear how that should work.
    if (style->display() == INLINE && style->styleType() == NOPSEUDO && style->writingMode() != parentStyle->writingMode())
        style->setDisplay(INLINE_BLOCK);

    // After performing the display mutation, check table rows. We do not honor position: relative table rows or cells.
    // This has been established for position: relative in CSS2.1 (and caused a crash in containingBlock()
    // on some sites).
    if ((style->display() == TABLE_HEADER_GROUP || style->display() == TABLE_ROW_GROUP
        || style->display() == TABLE_FOOTER_GROUP || style->display() == TABLE_ROW)
        && style->position() == RelativePosition)
        style->setPosition(StaticPosition);

    // Cannot support position: sticky for table columns and column groups because current code is only doing
    // background painting through columns / column groups
    if ((style->display() == TABLE_COLUMN_GROUP || style->display() == TABLE_COLUMN)
        && style->position() == StickyPosition)
        style->setPosition(StaticPosition);

    // writing-mode does not apply to table row groups, table column groups, table rows, and table columns.
    // FIXME: Table cells should be allowed to be perpendicular or flipped with respect to the table, though.
    if (style->display() == TABLE_COLUMN || style->display() == TABLE_COLUMN_GROUP || style->display() == TABLE_FOOTER_GROUP
        || style->display() == TABLE_HEADER_GROUP || style->display() == TABLE_ROW || style->display() == TABLE_ROW_GROUP
        || style->display() == TABLE_CELL)
        style->setWritingMode(parentStyle->writingMode());

    // FIXME: Since we don't support block-flow on flexible boxes yet, disallow setting
    // of block-flow to anything other than TopToBottomWritingMode.
    // https://bugs.webkit.org/show_bug.cgi?id=46418 - Flexible box support.
    if (style->writingMode() != TopToBottomWritingMode && (style->display() == BOX || style->display() == INLINE_BOX))
        style->setWritingMode(TopToBottomWritingMode);

    if (isDisplayFlexibleBox(parentStyle->display()) || isDisplayGridBox(parentStyle->display())) {
        style->setFloating(NoFloat);
        style->setDisplay(equivalentBlockDisplay(style->display(), style->isFloating(), !m_useQuirksModeStyles));
    }
}

}