Source/WebCore/rendering/RenderRubyRun.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2009 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * 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.
  *     * Neither the name of Google Inc. nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
  * OWNER 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 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 THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"

 #include "RenderRubyRun.h"

 #include "RenderRubyBase.h"
 #include "RenderRubyText.h"
 #include "RenderText.h"
 #include "RenderView.h"
 #include "StyleInheritedData.h"
 #include <wtf/StackStats.h>

 namespace WebCore {

 RenderRubyRun::RenderRubyRun(Document& document, PassRef<RenderStyle> style)
     : RenderBlockFlow(document, std::move(style))
 {
     setReplaced(true);
     setInline(true);
 }

 RenderRubyRun::~RenderRubyRun()
 {
 }

 bool RenderRubyRun::hasRubyText() const
 {
     // The only place where a ruby text can be is in the first position
     // Note: As anonymous blocks, ruby runs do not have ':before' or ':after' content themselves.
     return firstChild() && firstChild()->isRubyText();
 }

 bool RenderRubyRun::hasRubyBase() const
 {
     // The only place where a ruby base can be is in the last position
     // Note: As anonymous blocks, ruby runs do not have ':before' or ':after' content themselves.
     return lastChild() && lastChild()->isRubyBase();
 }

 bool RenderRubyRun::isEmpty() const
 {
     return !hasRubyText() && !hasRubyBase();
 }

 RenderRubyText* RenderRubyRun::rubyText() const
 {
     RenderObject* child = firstChild();
     // If in future it becomes necessary to support floating or positioned ruby text,
     // layout will have to be changed to handle them properly.
     ASSERT(!child || !child->isRubyText() || !child->isFloatingOrOutOfFlowPositioned());
     return child && child->isRubyText() ? static_cast<RenderRubyText*>(child) : 0;
 }

 RenderRubyBase* RenderRubyRun::rubyBase() const
 {
     RenderObject* child = lastChild();
     return child && child->isRubyBase() ? static_cast<RenderRubyBase*>(child) : 0;
 }

 RenderRubyBase* RenderRubyRun::rubyBaseSafe()
 {
     RenderRubyBase* base = rubyBase();
     if (!base) {
         base = createRubyBase();
         RenderBlockFlow::addChild(base);
     }
     return base;
 }

 RenderBlock* RenderRubyRun::firstLineBlock() const
 {
     return 0;
 }

 void RenderRubyRun::updateFirstLetter()
 {
 }

 bool RenderRubyRun::isChildAllowed(const RenderObject& child, const RenderStyle&) const
 {
     return child.isInline() || child.isRubyText();
 }

 void RenderRubyRun::addChild(RenderObject* child, RenderObject* beforeChild)
 {
     ASSERT(child);

     if (child->isRubyText()) {
         if (!beforeChild) {
             // RenderRuby has already ascertained that we can add the child here.
             ASSERT(!hasRubyText());
             // prepend ruby texts as first child
             RenderBlockFlow::addChild(child, firstChild());
         }  else if (beforeChild->isRubyText()) {
             // New text is inserted just before another.
             // In this case the new text takes the place of the old one, and
             // the old text goes into a new run that is inserted as next sibling.
             ASSERT(beforeChild->parent() == this);
             RenderElement* ruby = parent();
             ASSERT(ruby->isRuby());
             RenderBlock* newRun = staticCreateRubyRun(ruby);
             ruby->addChild(newRun, nextSibling());
             // Add the new ruby text and move the old one to the new run
             // Note: Doing it in this order and not using RenderRubyRun's methods,
             // in order to avoid automatic removal of the ruby run in case there is no
             // other child besides the old ruby text.
             RenderBlockFlow::addChild(child, beforeChild);
             RenderBlockFlow::removeChild(*beforeChild);
             newRun->addChild(beforeChild);
         } else if (hasRubyBase()) {
             // Insertion before a ruby base object.
             // In this case we need insert a new run before the current one and split the base.
             RenderElement* ruby = parent();
             RenderRubyRun* newRun = staticCreateRubyRun(ruby);
             ruby->addChild(newRun, this);
             newRun->addChild(child);
             rubyBaseSafe()->moveChildren(newRun->rubyBaseSafe(), beforeChild);
         }
     } else {
         // child is not a text -> insert it into the base
         // (append it instead if beforeChild is the ruby text)
         if (beforeChild && beforeChild->isRubyText())
             beforeChild = 0;
         rubyBaseSafe()->addChild(child, beforeChild);
     }
 }

 void RenderRubyRun::removeChild(RenderObject& child)
 {
     // If the child is a ruby text, then merge the ruby base with the base of
     // the right sibling run, if possible.
     if (!beingDestroyed() && !documentBeingDestroyed() && child.isRubyText()) {
         RenderRubyBase* base = rubyBase();
         RenderObject* rightNeighbour = nextSibling();
         if (base && rightNeighbour && rightNeighbour->isRubyRun()) {
             // Ruby run without a base can happen only at the first run.
             RenderRubyRun* rightRun = toRenderRubyRun(rightNeighbour);
             if (rightRun->hasRubyBase()) {
                 RenderRubyBase* rightBase = rightRun->rubyBaseSafe();
                 // Collect all children in a single base, then swap the bases.
                 rightBase->moveChildren(base);
                 moveChildTo(rightRun, base);
                 rightRun->moveChildTo(this, rightBase);
                 // The now empty ruby base will be removed below.
                 ASSERT(!rubyBase()->firstChild());
             }
         }
     }

     RenderBlockFlow::removeChild(child);

     if (!beingDestroyed() && !documentBeingDestroyed()) {
         // Check if our base (if any) is now empty. If so, destroy it.
         RenderBlock* base = rubyBase();
         if (base && !base->firstChild()) {
             RenderBlockFlow::removeChild(*base);
             base->deleteLines();
             base->destroy();
         }

         // If any of the above leaves the run empty, destroy it as well.
         if (isEmpty()) {
             parent()->removeChild(*this);
             deleteLines();
             destroy();
         }
     }
 }

 RenderRubyBase* RenderRubyRun::createRubyBase() const
 {
     auto newStyle = RenderStyle::createAnonymousStyleWithDisplay(&style(), BLOCK);
     newStyle.get().setTextAlign(CENTER); // FIXME: use WEBKIT_CENTER?
     auto renderer = new RenderRubyBase(document(), std::move(newStyle));
     renderer->initializeStyle();
     return renderer;
 }

 RenderRubyRun* RenderRubyRun::staticCreateRubyRun(const RenderObject* parentRuby)
 {
     ASSERT(parentRuby && parentRuby->isRuby());
     auto renderer = new RenderRubyRun(parentRuby->document(), RenderStyle::createAnonymousStyleWithDisplay(&parentRuby->style(), INLINE_BLOCK));
     renderer->initializeStyle();
     return renderer;
 }

 RenderObject* RenderRubyRun::layoutSpecialExcludedChild(bool relayoutChildren)
 {
     StackStats::LayoutCheckPoint layoutCheckPoint;
     // Don't bother positioning the RenderRubyRun yet.
     RenderRubyText* rt = rubyText();
     if (!rt)
         return 0;
     if (relayoutChildren)
         rt->setChildNeedsLayout(MarkOnlyThis);
     rt->layoutIfNeeded();
     return rt;
 }

 void RenderRubyRun::layout()
 {
     RenderBlockFlow::layout();

     RenderRubyText* rt = rubyText();
     if (!rt)
         return;

     rt->setLogicalLeft(0);

     // Place the RenderRubyText such that its bottom is flush with the lineTop of the first line of the RenderRubyBase.
     LayoutUnit lastLineRubyTextBottom = rt->logicalHeight();
     LayoutUnit firstLineRubyTextTop = 0;
     RootInlineBox* rootBox = rt->lastRootBox();
     if (rootBox) {
         // In order to align, we have to ignore negative leading.
         firstLineRubyTextTop = rt->firstRootBox()->logicalTopLayoutOverflow();
         lastLineRubyTextBottom = rootBox->logicalBottomLayoutOverflow();
     }

     if (style().isFlippedLinesWritingMode() == (style().rubyPosition() == RubyPositionAfter)) {
         LayoutUnit firstLineTop = 0;
         if (RenderRubyBase* rb = rubyBase()) {
             RootInlineBox* rootBox = rb->firstRootBox();
             if (rootBox)
                 firstLineTop = rootBox->logicalTopLayoutOverflow();
             firstLineTop += rb->logicalTop();
         }

         rt->setLogicalTop(-lastLineRubyTextBottom + firstLineTop);
     } else {
         LayoutUnit lastLineBottom = logicalHeight();
         if (RenderRubyBase* rb = rubyBase()) {
             RootInlineBox* rootBox = rb->lastRootBox();
             if (rootBox)
                 lastLineBottom = rootBox->logicalBottomLayoutOverflow();
             lastLineBottom += rb->logicalTop();
         }

         rt->setLogicalTop(-firstLineRubyTextTop + lastLineBottom);
     }

     // Update our overflow to account for the new RenderRubyText position.
     computeOverflow(clientLogicalBottom());
 }

 static bool shouldOverhang(bool firstLine, const RenderObject* renderer, const RenderRubyBase& rubyBase)
 {
     if (!renderer || !renderer->isText())
         return false;
     const RenderStyle& rubyBaseStyle = firstLine ? rubyBase.firstLineStyle() : rubyBase.style();
     const RenderStyle& style = firstLine ? renderer->firstLineStyle() : renderer->style();
     return style.fontSize() <= rubyBaseStyle.fontSize();
 }

 void RenderRubyRun::getOverhang(bool firstLine, RenderObject* startRenderer, RenderObject* endRenderer, int& startOverhang, int& endOverhang) const
 {
     ASSERT(!needsLayout());

     startOverhang = 0;
     endOverhang = 0;

     RenderRubyBase* rubyBase = this->rubyBase();
     RenderRubyText* rubyText = this->rubyText();

     if (!rubyBase || !rubyText)
         return;

     if (!rubyBase->firstRootBox())
         return;

     int logicalWidth = this->logicalWidth();
     int logicalLeftOverhang = std::numeric_limits<int>::max();
     int logicalRightOverhang = std::numeric_limits<int>::max();
     for (RootInlineBox* rootInlineBox = rubyBase->firstRootBox(); rootInlineBox; rootInlineBox = rootInlineBox->nextRootBox()) {
         logicalLeftOverhang = std::min<int>(logicalLeftOverhang, rootInlineBox->logicalLeft());
         logicalRightOverhang = std::min<int>(logicalRightOverhang, logicalWidth - rootInlineBox->logicalRight());
     }

     startOverhang = style().isLeftToRightDirection() ? logicalLeftOverhang : logicalRightOverhang;
     endOverhang = style().isLeftToRightDirection() ? logicalRightOverhang : logicalLeftOverhang;

     if (!shouldOverhang(firstLine, startRenderer, *rubyBase))
         startOverhang = 0;
     if (!shouldOverhang(firstLine, endRenderer, *rubyBase))
         endOverhang = 0;

     // We overhang a ruby only if the neighboring render object is a text.
     // We can overhang the ruby by no more than half the width of the neighboring text
     // and no more than half the font size.
     const RenderStyle& rubyTextStyle = firstLine ? rubyText->firstLineStyle() : rubyText->style();
     int halfWidthOfFontSize = rubyTextStyle.fontSize() / 2;
     if (startOverhang)
         startOverhang = std::min<int>(startOverhang, std::min<int>(toRenderText(startRenderer)->minLogicalWidth(), halfWidthOfFontSize));
     if (endOverhang)
         endOverhang = std::min<int>(endOverhang, std::min<int>(toRenderText(endRenderer)->minLogicalWidth(), halfWidthOfFontSize));
 }

 } // namespace WebCore
	/*
	* Copyright (C) 2009 Google 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:
	*
	* * Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* * 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.
	* * Neither the name of Google Inc. nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
	* OWNER 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 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 THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"

	#include "RenderRubyRun.h"

	#include "RenderRubyBase.h"
	#include "RenderRubyText.h"
	#include "RenderText.h"
	#include "RenderView.h"
	#include "StyleInheritedData.h"
	#include <wtf/StackStats.h>

	namespace WebCore {

	RenderRubyRun::RenderRubyRun(Document& document, PassRef<RenderStyle> style)
	: RenderBlockFlow(document, std::move(style))
	{
	setReplaced(true);
	setInline(true);
	}

	RenderRubyRun::~RenderRubyRun()
	{
	}

	bool RenderRubyRun::hasRubyText() const
	{
	// The only place where a ruby text can be is in the first position
	// Note: As anonymous blocks, ruby runs do not have ':before' or ':after' content themselves.
	return firstChild() && firstChild()->isRubyText();
	}

	bool RenderRubyRun::hasRubyBase() const
	{
	// The only place where a ruby base can be is in the last position
	// Note: As anonymous blocks, ruby runs do not have ':before' or ':after' content themselves.
	return lastChild() && lastChild()->isRubyBase();
	}

	bool RenderRubyRun::isEmpty() const
	{
	return !hasRubyText() && !hasRubyBase();
	}

	RenderRubyText* RenderRubyRun::rubyText() const
	{
	RenderObject* child = firstChild();
	// If in future it becomes necessary to support floating or positioned ruby text,
	// layout will have to be changed to handle them properly.
	ASSERT(!child \|\| !child->isRubyText() \|\| !child->isFloatingOrOutOfFlowPositioned());
	return child && child->isRubyText() ? static_cast<RenderRubyText*>(child) : 0;
	}

	RenderRubyBase* RenderRubyRun::rubyBase() const
	{
	RenderObject* child = lastChild();
	return child && child->isRubyBase() ? static_cast<RenderRubyBase*>(child) : 0;
	}

	RenderRubyBase* RenderRubyRun::rubyBaseSafe()
	{
	RenderRubyBase* base = rubyBase();
	if (!base) {
	base = createRubyBase();
	RenderBlockFlow::addChild(base);
	}
	return base;
	}

	RenderBlock* RenderRubyRun::firstLineBlock() const
	{
	return 0;
	}

	void RenderRubyRun::updateFirstLetter()
	{
	}

	bool RenderRubyRun::isChildAllowed(const RenderObject& child, const RenderStyle&) const
	{
	return child.isInline() \|\| child.isRubyText();
	}

	void RenderRubyRun::addChild(RenderObject* child, RenderObject* beforeChild)
	{
	ASSERT(child);

	if (child->isRubyText()) {
	if (!beforeChild) {
	// RenderRuby has already ascertained that we can add the child here.
	ASSERT(!hasRubyText());
	// prepend ruby texts as first child
	RenderBlockFlow::addChild(child, firstChild());
	} else if (beforeChild->isRubyText()) {
	// New text is inserted just before another.
	// In this case the new text takes the place of the old one, and
	// the old text goes into a new run that is inserted as next sibling.
	ASSERT(beforeChild->parent() == this);
	RenderElement* ruby = parent();
	ASSERT(ruby->isRuby());
	RenderBlock* newRun = staticCreateRubyRun(ruby);
	ruby->addChild(newRun, nextSibling());
	// Add the new ruby text and move the old one to the new run
	// Note: Doing it in this order and not using RenderRubyRun's methods,
	// in order to avoid automatic removal of the ruby run in case there is no
	// other child besides the old ruby text.
	RenderBlockFlow::addChild(child, beforeChild);
	RenderBlockFlow::removeChild(*beforeChild);
	newRun->addChild(beforeChild);
	} else if (hasRubyBase()) {
	// Insertion before a ruby base object.
	// In this case we need insert a new run before the current one and split the base.
	RenderElement* ruby = parent();
	RenderRubyRun* newRun = staticCreateRubyRun(ruby);
	ruby->addChild(newRun, this);
	newRun->addChild(child);
	rubyBaseSafe()->moveChildren(newRun->rubyBaseSafe(), beforeChild);
	}
	} else {
	// child is not a text -> insert it into the base
	// (append it instead if beforeChild is the ruby text)
	if (beforeChild && beforeChild->isRubyText())
	beforeChild = 0;
	rubyBaseSafe()->addChild(child, beforeChild);
	}
	}

	void RenderRubyRun::removeChild(RenderObject& child)
	{
	// If the child is a ruby text, then merge the ruby base with the base of
	// the right sibling run, if possible.
	if (!beingDestroyed() && !documentBeingDestroyed() && child.isRubyText()) {
	RenderRubyBase* base = rubyBase();
	RenderObject* rightNeighbour = nextSibling();
	if (base && rightNeighbour && rightNeighbour->isRubyRun()) {
	// Ruby run without a base can happen only at the first run.
	RenderRubyRun* rightRun = toRenderRubyRun(rightNeighbour);
	if (rightRun->hasRubyBase()) {
	RenderRubyBase* rightBase = rightRun->rubyBaseSafe();
	// Collect all children in a single base, then swap the bases.
	rightBase->moveChildren(base);
	moveChildTo(rightRun, base);
	rightRun->moveChildTo(this, rightBase);
	// The now empty ruby base will be removed below.
	ASSERT(!rubyBase()->firstChild());
	}
	}
	}

	RenderBlockFlow::removeChild(child);

	if (!beingDestroyed() && !documentBeingDestroyed()) {
	// Check if our base (if any) is now empty. If so, destroy it.
	RenderBlock* base = rubyBase();
	if (base && !base->firstChild()) {
	RenderBlockFlow::removeChild(*base);
	base->deleteLines();
	base->destroy();
	}

	// If any of the above leaves the run empty, destroy it as well.
	if (isEmpty()) {
	parent()->removeChild(*this);
	deleteLines();
	destroy();
	}
	}
	}

	RenderRubyBase* RenderRubyRun::createRubyBase() const
	{
	auto newStyle = RenderStyle::createAnonymousStyleWithDisplay(&style(), BLOCK);
	newStyle.get().setTextAlign(CENTER); // FIXME: use WEBKIT_CENTER?
	auto renderer = new RenderRubyBase(document(), std::move(newStyle));
	renderer->initializeStyle();
	return renderer;
	}

	RenderRubyRun* RenderRubyRun::staticCreateRubyRun(const RenderObject* parentRuby)
	{
	ASSERT(parentRuby && parentRuby->isRuby());
	auto renderer = new RenderRubyRun(parentRuby->document(), RenderStyle::createAnonymousStyleWithDisplay(&parentRuby->style(), INLINE_BLOCK));
	renderer->initializeStyle();
	return renderer;
	}

	RenderObject* RenderRubyRun::layoutSpecialExcludedChild(bool relayoutChildren)
	{
	StackStats::LayoutCheckPoint layoutCheckPoint;
	// Don't bother positioning the RenderRubyRun yet.
	RenderRubyText* rt = rubyText();
	if (!rt)
	return 0;
	if (relayoutChildren)
	rt->setChildNeedsLayout(MarkOnlyThis);
	rt->layoutIfNeeded();
	return rt;
	}

	void RenderRubyRun::layout()
	{
	RenderBlockFlow::layout();

	RenderRubyText* rt = rubyText();
	if (!rt)
	return;

	rt->setLogicalLeft(0);

	// Place the RenderRubyText such that its bottom is flush with the lineTop of the first line of the RenderRubyBase.
	LayoutUnit lastLineRubyTextBottom = rt->logicalHeight();
	LayoutUnit firstLineRubyTextTop = 0;
	RootInlineBox* rootBox = rt->lastRootBox();
	if (rootBox) {
	// In order to align, we have to ignore negative leading.
	firstLineRubyTextTop = rt->firstRootBox()->logicalTopLayoutOverflow();
	lastLineRubyTextBottom = rootBox->logicalBottomLayoutOverflow();
	}

	if (style().isFlippedLinesWritingMode() == (style().rubyPosition() == RubyPositionAfter)) {
	LayoutUnit firstLineTop = 0;
	if (RenderRubyBase* rb = rubyBase()) {
	RootInlineBox* rootBox = rb->firstRootBox();
	if (rootBox)
	firstLineTop = rootBox->logicalTopLayoutOverflow();
	firstLineTop += rb->logicalTop();
	}

	rt->setLogicalTop(-lastLineRubyTextBottom + firstLineTop);
	} else {
	LayoutUnit lastLineBottom = logicalHeight();
	if (RenderRubyBase* rb = rubyBase()) {
	RootInlineBox* rootBox = rb->lastRootBox();
	if (rootBox)
	lastLineBottom = rootBox->logicalBottomLayoutOverflow();
	lastLineBottom += rb->logicalTop();
	}

	rt->setLogicalTop(-firstLineRubyTextTop + lastLineBottom);
	}

	// Update our overflow to account for the new RenderRubyText position.
	computeOverflow(clientLogicalBottom());
	}

	static bool shouldOverhang(bool firstLine, const RenderObject* renderer, const RenderRubyBase& rubyBase)
	{
	if (!renderer \|\| !renderer->isText())
	return false;
	const RenderStyle& rubyBaseStyle = firstLine ? rubyBase.firstLineStyle() : rubyBase.style();
	const RenderStyle& style = firstLine ? renderer->firstLineStyle() : renderer->style();
	return style.fontSize() <= rubyBaseStyle.fontSize();
	}

	void RenderRubyRun::getOverhang(bool firstLine, RenderObject* startRenderer, RenderObject* endRenderer, int& startOverhang, int& endOverhang) const
	{
	ASSERT(!needsLayout());

	startOverhang = 0;
	endOverhang = 0;

	RenderRubyBase* rubyBase = this->rubyBase();
	RenderRubyText* rubyText = this->rubyText();

	if (!rubyBase \|\| !rubyText)
	return;

	if (!rubyBase->firstRootBox())
	return;

	int logicalWidth = this->logicalWidth();
	int logicalLeftOverhang = std::numeric_limits<int>::max();
	int logicalRightOverhang = std::numeric_limits<int>::max();
	for (RootInlineBox* rootInlineBox = rubyBase->firstRootBox(); rootInlineBox; rootInlineBox = rootInlineBox->nextRootBox()) {
	logicalLeftOverhang = std::min<int>(logicalLeftOverhang, rootInlineBox->logicalLeft());
	logicalRightOverhang = std::min<int>(logicalRightOverhang, logicalWidth - rootInlineBox->logicalRight());
	}

	startOverhang = style().isLeftToRightDirection() ? logicalLeftOverhang : logicalRightOverhang;
	endOverhang = style().isLeftToRightDirection() ? logicalRightOverhang : logicalLeftOverhang;

	if (!shouldOverhang(firstLine, startRenderer, *rubyBase))
	startOverhang = 0;
	if (!shouldOverhang(firstLine, endRenderer, *rubyBase))
	endOverhang = 0;

	// We overhang a ruby only if the neighboring render object is a text.
	// We can overhang the ruby by no more than half the width of the neighboring text
	// and no more than half the font size.
	const RenderStyle& rubyTextStyle = firstLine ? rubyText->firstLineStyle() : rubyText->style();
	int halfWidthOfFontSize = rubyTextStyle.fontSize() / 2;
	if (startOverhang)
	startOverhang = std::min<int>(startOverhang, std::min<int>(toRenderText(startRenderer)->minLogicalWidth(), halfWidthOfFontSize));
	if (endOverhang)
	endOverhang = std::min<int>(endOverhang, std::min<int>(toRenderText(endRenderer)->minLogicalWidth(), halfWidthOfFontSize));
	}

	} // namespace WebCore