third_party/WebKit/Source/core/layout/LayoutScrollbar.cpp - chromium/src - Git at Google

 /*
  * Copyright (C) 2008, 2009 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
  * 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 "core/layout/LayoutScrollbar.h"

 #include "core/css/PseudoStyleRequest.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/layout/LayoutPart.h"
 #include "core/layout/LayoutScrollbarPart.h"
 #include "core/layout/LayoutScrollbarTheme.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/api/LayoutAPIShim.h"
 #include "core/layout/api/LayoutPartItem.h"
 #include "core/paint/ObjectPaintInvalidator.h"
 #include "platform/graphics/GraphicsContext.h"

 namespace blink {

 Scrollbar* LayoutScrollbar::createCustomScrollbar(
     ScrollableArea* scrollableArea,
     ScrollbarOrientation orientation,
     Node* ownerNode,
     LocalFrame* owningFrame) {
   return new LayoutScrollbar(scrollableArea, orientation, ownerNode,
                              owningFrame);
 }

 LayoutScrollbar::LayoutScrollbar(ScrollableArea* scrollableArea,
                                  ScrollbarOrientation orientation,
                                  Node* ownerNode,
                                  LocalFrame* owningFrame)
     : Scrollbar(scrollableArea,
                 orientation,
                 RegularScrollbar,
                 nullptr,
                 LayoutScrollbarTheme::layoutScrollbarTheme()),
       m_owner(ownerNode),
       m_owningFrame(owningFrame) {
   ASSERT(ownerNode || owningFrame);

   // FIXME: We need to do this because LayoutScrollbar::styleChanged is called
   // as soon as the scrollbar is created.

   // Update the scrollbar size.
   IntRect rect(0, 0, 0, 0);
   updateScrollbarPart(ScrollbarBGPart);
   if (LayoutScrollbarPart* part = m_parts.get(ScrollbarBGPart)) {
     part->layout();
     rect.setSize(flooredIntSize(part->size()));
   } else if (this->orientation() == HorizontalScrollbar) {
     rect.setWidth(this->width());
   } else {
     rect.setHeight(this->height());
   }

   setFrameRect(rect);
 }

 LayoutScrollbar::~LayoutScrollbar() {
   if (m_parts.isEmpty())
     return;

   // When a scrollbar is detached from its parent (causing all parts removal)
   // and ready to be destroyed, its destruction can be delayed because of
   // RefPtr maintained in other classes such as EventHandler
   // (m_lastScrollbarUnderMouse).
   // Meanwhile, we can have a call to updateScrollbarPart which recreates the
   // scrollbar part. So, we need to destroy these parts since we don't want them
   // to call on a destroyed scrollbar. See webkit bug 68009.
   updateScrollbarParts(true);
 }

 DEFINE_TRACE(LayoutScrollbar) {
   visitor->trace(m_owner);
   visitor->trace(m_owningFrame);
   Scrollbar::trace(visitor);
 }

 LayoutBox* LayoutScrollbar::owningLayoutObject() const {
   if (m_owningFrame)
     return toLayoutBox(
         LayoutAPIShim::layoutObjectFrom(m_owningFrame->ownerLayoutItem()));
   return m_owner && m_owner->layoutObject()
              ? m_owner->layoutObject()->enclosingBox()
              : 0;
 }

 LayoutBox* LayoutScrollbar::owningLayoutObjectWithinFrame() const {
   if (m_owningFrame)
     return m_owningFrame->contentLayoutObject();
   return owningLayoutObject();
 }

 void LayoutScrollbar::setParent(Widget* parent) {
   Scrollbar::setParent(parent);
   if (!parent) {
     // Destroy all of the scrollbar's LayoutBoxes.
     updateScrollbarParts(true);
   }
 }

 void LayoutScrollbar::setEnabled(bool e) {
   bool wasEnabled = enabled();
   Scrollbar::setEnabled(e);
   if (wasEnabled != e)
     updateScrollbarParts();
 }

 void LayoutScrollbar::styleChanged() {
   updateScrollbarParts();
 }

 void LayoutScrollbar::setHoveredPart(ScrollbarPart part) {
   if (part == m_hoveredPart)
     return;

   ScrollbarPart oldPart = m_hoveredPart;
   m_hoveredPart = part;

   updateScrollbarPart(oldPart);
   updateScrollbarPart(m_hoveredPart);

   updateScrollbarPart(ScrollbarBGPart);
   updateScrollbarPart(TrackBGPart);
 }

 void LayoutScrollbar::setPressedPart(ScrollbarPart part) {
   ScrollbarPart oldPart = m_pressedPart;
   Scrollbar::setPressedPart(part);

   updateScrollbarPart(oldPart);
   updateScrollbarPart(part);

   updateScrollbarPart(ScrollbarBGPart);
   updateScrollbarPart(TrackBGPart);
 }

 PassRefPtr<ComputedStyle> LayoutScrollbar::getScrollbarPseudoStyle(
     ScrollbarPart partType,
     PseudoId pseudoId) {
   if (!owningLayoutObject())
     return nullptr;

   RefPtr<ComputedStyle> result = owningLayoutObject()->getUncachedPseudoStyle(
       PseudoStyleRequest(pseudoId, this, partType),
       owningLayoutObject()->style());
   // Scrollbars for root frames should always have background color
   // unless explicitly specified as transparent. So we force it.
   // This is because WebKit assumes scrollbar to be always painted and missing
   // background causes visual artifact like non-paint invalidated dirty region.
   if (result && m_owningFrame && m_owningFrame->view() &&
       !m_owningFrame->view()->isTransparent() && !result->hasBackground())
     result->setBackgroundColor(StyleColor(Color::white));

   return result;
 }

 void LayoutScrollbar::updateScrollbarParts(bool destroy) {
   updateScrollbarPart(ScrollbarBGPart, destroy);
   updateScrollbarPart(BackButtonStartPart, destroy);
   updateScrollbarPart(ForwardButtonStartPart, destroy);
   updateScrollbarPart(BackTrackPart, destroy);
   updateScrollbarPart(ThumbPart, destroy);
   updateScrollbarPart(ForwardTrackPart, destroy);
   updateScrollbarPart(BackButtonEndPart, destroy);
   updateScrollbarPart(ForwardButtonEndPart, destroy);
   updateScrollbarPart(TrackBGPart, destroy);

   if (destroy)
     return;

   // See if the scrollbar's thickness changed.  If so, we need to mark our
   // owning object as needing a layout.
   bool isHorizontal = orientation() == HorizontalScrollbar;
   int oldThickness = isHorizontal ? height() : width();
   int newThickness = 0;
   LayoutScrollbarPart* part = m_parts.get(ScrollbarBGPart);
   if (part) {
     part->layout();
     newThickness =
         (isHorizontal ? part->size().height() : part->size().width()).toInt();
   }

   if (newThickness != oldThickness) {
     setFrameRect(
         IntRect(location(), IntSize(isHorizontal ? width() : newThickness,
                                     isHorizontal ? newThickness : height())));
     if (LayoutBox* box = owningLayoutObjectWithinFrame()) {
       if (box->isLayoutBlock())
         toLayoutBlock(box)->notifyScrollbarThicknessChanged();
       box->setChildNeedsLayout();
       if (m_scrollableArea)
         m_scrollableArea->setScrollCornerNeedsPaintInvalidation();
     }
   }
 }

 static PseudoId pseudoForScrollbarPart(ScrollbarPart part) {
   switch (part) {
     case BackButtonStartPart:
     case ForwardButtonStartPart:
     case BackButtonEndPart:
     case ForwardButtonEndPart:
       return PseudoIdScrollbarButton;
     case BackTrackPart:
     case ForwardTrackPart:
       return PseudoIdScrollbarTrackPiece;
     case ThumbPart:
       return PseudoIdScrollbarThumb;
     case TrackBGPart:
       return PseudoIdScrollbarTrack;
     case ScrollbarBGPart:
       return PseudoIdScrollbar;
     case NoPart:
     case AllParts:
       break;
   }
   ASSERT_NOT_REACHED();
   return PseudoIdScrollbar;
 }

 void LayoutScrollbar::updateScrollbarPart(ScrollbarPart partType,
                                           bool destroy) {
   if (partType == NoPart)
     return;

   RefPtr<ComputedStyle> partStyle =
       !destroy
           ? getScrollbarPseudoStyle(partType, pseudoForScrollbarPart(partType))
           : PassRefPtr<ComputedStyle>(nullptr);

   bool needLayoutObject =
       !destroy && partStyle && partStyle->display() != EDisplay::None;

   if (needLayoutObject && partStyle->display() != EDisplay::Block) {
     // See if we are a button that should not be visible according to OS
     // settings.
     WebScrollbarButtonsPlacement buttonsPlacement = theme().buttonsPlacement();
     switch (partType) {
       case BackButtonStartPart:
         needLayoutObject =
             (buttonsPlacement == WebScrollbarButtonsPlacementSingle ||
              buttonsPlacement == WebScrollbarButtonsPlacementDoubleStart ||
              buttonsPlacement == WebScrollbarButtonsPlacementDoubleBoth);
         break;
       case ForwardButtonStartPart:
         needLayoutObject =
             (buttonsPlacement == WebScrollbarButtonsPlacementDoubleStart ||
              buttonsPlacement == WebScrollbarButtonsPlacementDoubleBoth);
         break;
       case BackButtonEndPart:
         needLayoutObject =
             (buttonsPlacement == WebScrollbarButtonsPlacementDoubleEnd ||
              buttonsPlacement == WebScrollbarButtonsPlacementDoubleBoth);
         break;
       case ForwardButtonEndPart:
         needLayoutObject =
             (buttonsPlacement == WebScrollbarButtonsPlacementSingle ||
              buttonsPlacement == WebScrollbarButtonsPlacementDoubleEnd ||
              buttonsPlacement == WebScrollbarButtonsPlacementDoubleBoth);
         break;
       default:
         break;
     }
   }

   LayoutScrollbarPart* partLayoutObject = m_parts.get(partType);
   if (!partLayoutObject && needLayoutObject && m_scrollableArea) {
     partLayoutObject = LayoutScrollbarPart::createAnonymous(
         &owningLayoutObject()->document(), m_scrollableArea, this, partType);
     m_parts.set(partType, partLayoutObject);
   } else if (partLayoutObject && !needLayoutObject) {
     m_parts.remove(partType);
     partLayoutObject->destroy();
     partLayoutObject = 0;
   }

   if (partLayoutObject)
     partLayoutObject->setStyleWithWritingModeOfParent(partStyle.release());
 }

 IntRect LayoutScrollbar::buttonRect(ScrollbarPart partType) const {
   LayoutScrollbarPart* partLayoutObject = m_parts.get(partType);
   if (!partLayoutObject)
     return IntRect();

   partLayoutObject->layout();

   bool isHorizontal = orientation() == HorizontalScrollbar;
   if (partType == BackButtonStartPart)
     return IntRect(
         location(),
         IntSize(
             isHorizontal ? partLayoutObject->pixelSnappedWidth() : width(),
             isHorizontal ? height() : partLayoutObject->pixelSnappedHeight()));
   if (partType == ForwardButtonEndPart) {
     return IntRect(
         isHorizontal ? x() + width() - partLayoutObject->pixelSnappedWidth()
                      : x(),
         isHorizontal ? y()
                      : y() + height() - partLayoutObject->pixelSnappedHeight(),
         isHorizontal ? partLayoutObject->pixelSnappedWidth() : width(),
         isHorizontal ? height() : partLayoutObject->pixelSnappedHeight());
   }

   if (partType == ForwardButtonStartPart) {
     IntRect previousButton = buttonRect(BackButtonStartPart);
     return IntRect(
         isHorizontal ? x() + previousButton.width() : x(),
         isHorizontal ? y() : y() + previousButton.height(),
         isHorizontal ? partLayoutObject->pixelSnappedWidth() : width(),
         isHorizontal ? height() : partLayoutObject->pixelSnappedHeight());
   }

   IntRect followingButton = buttonRect(ForwardButtonEndPart);
   return IntRect(
       isHorizontal
           ? x() + width() - followingButton.width() -
                 partLayoutObject->pixelSnappedWidth()
           : x(),
       isHorizontal ? y()
                    : y() + height() - followingButton.height() -
                          partLayoutObject->pixelSnappedHeight(),
       isHorizontal ? partLayoutObject->pixelSnappedWidth() : width(),
       isHorizontal ? height() : partLayoutObject->pixelSnappedHeight());
 }

 IntRect LayoutScrollbar::trackRect(int startLength, int endLength) const {
   LayoutScrollbarPart* part = m_parts.get(TrackBGPart);
   if (part)
     part->layout();

   if (orientation() == HorizontalScrollbar) {
     int marginLeft = part ? part->marginLeft().toInt() : 0;
     int marginRight = part ? part->marginRight().toInt() : 0;
     startLength += marginLeft;
     endLength += marginRight;
     int totalLength = startLength + endLength;
     return IntRect(x() + startLength, y(), width() - totalLength, height());
   }

   int marginTop = part ? part->marginTop().toInt() : 0;
   int marginBottom = part ? part->marginBottom().toInt() : 0;
   startLength += marginTop;
   endLength += marginBottom;
   int totalLength = startLength + endLength;

   return IntRect(x(), y() + startLength, width(), height() - totalLength);
 }

 IntRect LayoutScrollbar::trackPieceRectWithMargins(
     ScrollbarPart partType,
     const IntRect& oldRect) const {
   LayoutScrollbarPart* partLayoutObject = m_parts.get(partType);
   if (!partLayoutObject)
     return oldRect;

   partLayoutObject->layout();

   IntRect rect = oldRect;
   if (orientation() == HorizontalScrollbar) {
     rect.setX((rect.x() + partLayoutObject->marginLeft()).toInt());
     rect.setWidth((rect.width() - partLayoutObject->marginWidth()).toInt());
   } else {
     rect.setY((rect.y() + partLayoutObject->marginTop()).toInt());
     rect.setHeight((rect.height() - partLayoutObject->marginHeight()).toInt());
   }
   return rect;
 }

 int LayoutScrollbar::minimumThumbLength() const {
   LayoutScrollbarPart* partLayoutObject = m_parts.get(ThumbPart);
   if (!partLayoutObject)
     return 0;
   partLayoutObject->layout();
   return (orientation() == HorizontalScrollbar
               ? partLayoutObject->size().width()
               : partLayoutObject->size().height())
       .toInt();
 }

 void LayoutScrollbar::invalidateDisplayItemClientsOfScrollbarParts() {
   for (auto& part : m_parts)
     ObjectPaintInvalidator(*part.value)
         .invalidateDisplayItemClientsIncludingNonCompositingDescendants(
             PaintInvalidationScroll);
 }

 }  // namespace blink
	/*
	* Copyright (C) 2008, 2009 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
	* 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 "core/layout/LayoutScrollbar.h"

	#include "core/css/PseudoStyleRequest.h"
	#include "core/frame/FrameView.h"
	#include "core/frame/LocalFrame.h"
	#include "core/layout/LayoutPart.h"
	#include "core/layout/LayoutScrollbarPart.h"
	#include "core/layout/LayoutScrollbarTheme.h"
	#include "core/layout/LayoutView.h"
	#include "core/layout/api/LayoutAPIShim.h"
	#include "core/layout/api/LayoutPartItem.h"
	#include "core/paint/ObjectPaintInvalidator.h"
	#include "platform/graphics/GraphicsContext.h"

	namespace blink {

	Scrollbar* LayoutScrollbar::createCustomScrollbar(
	ScrollableArea* scrollableArea,
	ScrollbarOrientation orientation,
	Node* ownerNode,
	LocalFrame* owningFrame) {
	return new LayoutScrollbar(scrollableArea, orientation, ownerNode,
	owningFrame);
	}

	LayoutScrollbar::LayoutScrollbar(ScrollableArea* scrollableArea,
	ScrollbarOrientation orientation,
	Node* ownerNode,
	LocalFrame* owningFrame)
	: Scrollbar(scrollableArea,
	orientation,
	RegularScrollbar,
	nullptr,
	LayoutScrollbarTheme::layoutScrollbarTheme()),
	m_owner(ownerNode),
	m_owningFrame(owningFrame) {
	ASSERT(ownerNode \|\| owningFrame);

	// FIXME: We need to do this because LayoutScrollbar::styleChanged is called
	// as soon as the scrollbar is created.

	// Update the scrollbar size.
	IntRect rect(0, 0, 0, 0);
	updateScrollbarPart(ScrollbarBGPart);
	if (LayoutScrollbarPart* part = m_parts.get(ScrollbarBGPart)) {
	part->layout();
	rect.setSize(flooredIntSize(part->size()));
	} else if (this->orientation() == HorizontalScrollbar) {
	rect.setWidth(this->width());
	} else {
	rect.setHeight(this->height());
	}

	setFrameRect(rect);
	}

	LayoutScrollbar::~LayoutScrollbar() {
	if (m_parts.isEmpty())
	return;

	// When a scrollbar is detached from its parent (causing all parts removal)
	// and ready to be destroyed, its destruction can be delayed because of
	// RefPtr maintained in other classes such as EventHandler
	// (m_lastScrollbarUnderMouse).
	// Meanwhile, we can have a call to updateScrollbarPart which recreates the
	// scrollbar part. So, we need to destroy these parts since we don't want them
	// to call on a destroyed scrollbar. See webkit bug 68009.
	updateScrollbarParts(true);
	}

	DEFINE_TRACE(LayoutScrollbar) {
	visitor->trace(m_owner);
	visitor->trace(m_owningFrame);
	Scrollbar::trace(visitor);
	}

	LayoutBox* LayoutScrollbar::owningLayoutObject() const {
	if (m_owningFrame)
	return toLayoutBox(
	LayoutAPIShim::layoutObjectFrom(m_owningFrame->ownerLayoutItem()));
	return m_owner && m_owner->layoutObject()
	? m_owner->layoutObject()->enclosingBox()
	: 0;
	}

	LayoutBox* LayoutScrollbar::owningLayoutObjectWithinFrame() const {
	if (m_owningFrame)
	return m_owningFrame->contentLayoutObject();
	return owningLayoutObject();
	}

	void LayoutScrollbar::setParent(Widget* parent) {
	Scrollbar::setParent(parent);
	if (!parent) {
	// Destroy all of the scrollbar's LayoutBoxes.
	updateScrollbarParts(true);
	}
	}

	void LayoutScrollbar::setEnabled(bool e) {
	bool wasEnabled = enabled();
	Scrollbar::setEnabled(e);
	if (wasEnabled != e)
	updateScrollbarParts();
	}

	void LayoutScrollbar::styleChanged() {
	updateScrollbarParts();
	}

	void LayoutScrollbar::setHoveredPart(ScrollbarPart part) {
	if (part == m_hoveredPart)
	return;

	ScrollbarPart oldPart = m_hoveredPart;
	m_hoveredPart = part;

	updateScrollbarPart(oldPart);
	updateScrollbarPart(m_hoveredPart);

	updateScrollbarPart(ScrollbarBGPart);
	updateScrollbarPart(TrackBGPart);
	}

	void LayoutScrollbar::setPressedPart(ScrollbarPart part) {
	ScrollbarPart oldPart = m_pressedPart;
	Scrollbar::setPressedPart(part);

	updateScrollbarPart(oldPart);
	updateScrollbarPart(part);

	updateScrollbarPart(ScrollbarBGPart);
	updateScrollbarPart(TrackBGPart);
	}

	PassRefPtr<ComputedStyle> LayoutScrollbar::getScrollbarPseudoStyle(
	ScrollbarPart partType,
	PseudoId pseudoId) {
	if (!owningLayoutObject())
	return nullptr;

	RefPtr<ComputedStyle> result = owningLayoutObject()->getUncachedPseudoStyle(
	PseudoStyleRequest(pseudoId, this, partType),
	owningLayoutObject()->style());
	// Scrollbars for root frames should always have background color
	// unless explicitly specified as transparent. So we force it.
	// This is because WebKit assumes scrollbar to be always painted and missing
	// background causes visual artifact like non-paint invalidated dirty region.
	if (result && m_owningFrame && m_owningFrame->view() &&
	!m_owningFrame->view()->isTransparent() && !result->hasBackground())
	result->setBackgroundColor(StyleColor(Color::white));

	return result;
	}

	void LayoutScrollbar::updateScrollbarParts(bool destroy) {
	updateScrollbarPart(ScrollbarBGPart, destroy);
	updateScrollbarPart(BackButtonStartPart, destroy);
	updateScrollbarPart(ForwardButtonStartPart, destroy);
	updateScrollbarPart(BackTrackPart, destroy);
	updateScrollbarPart(ThumbPart, destroy);
	updateScrollbarPart(ForwardTrackPart, destroy);
	updateScrollbarPart(BackButtonEndPart, destroy);
	updateScrollbarPart(ForwardButtonEndPart, destroy);
	updateScrollbarPart(TrackBGPart, destroy);

	if (destroy)
	return;

	// See if the scrollbar's thickness changed. If so, we need to mark our
	// owning object as needing a layout.
	bool isHorizontal = orientation() == HorizontalScrollbar;
	int oldThickness = isHorizontal ? height() : width();
	int newThickness = 0;
	LayoutScrollbarPart* part = m_parts.get(ScrollbarBGPart);
	if (part) {
	part->layout();
	newThickness =
	(isHorizontal ? part->size().height() : part->size().width()).toInt();
	}

	if (newThickness != oldThickness) {
	setFrameRect(
	IntRect(location(), IntSize(isHorizontal ? width() : newThickness,
	isHorizontal ? newThickness : height())));
	if (LayoutBox* box = owningLayoutObjectWithinFrame()) {
	if (box->isLayoutBlock())
	toLayoutBlock(box)->notifyScrollbarThicknessChanged();
	box->setChildNeedsLayout();
	if (m_scrollableArea)
	m_scrollableArea->setScrollCornerNeedsPaintInvalidation();
	}
	}
	}

	static PseudoId pseudoForScrollbarPart(ScrollbarPart part) {
	switch (part) {
	case BackButtonStartPart:
	case ForwardButtonStartPart:
	case BackButtonEndPart:
	case ForwardButtonEndPart:
	return PseudoIdScrollbarButton;
	case BackTrackPart:
	case ForwardTrackPart:
	return PseudoIdScrollbarTrackPiece;
	case ThumbPart:
	return PseudoIdScrollbarThumb;
	case TrackBGPart:
	return PseudoIdScrollbarTrack;
	case ScrollbarBGPart:
	return PseudoIdScrollbar;
	case NoPart:
	case AllParts:
	break;
	}
	ASSERT_NOT_REACHED();
	return PseudoIdScrollbar;
	}

	void LayoutScrollbar::updateScrollbarPart(ScrollbarPart partType,
	bool destroy) {
	if (partType == NoPart)
	return;

	RefPtr<ComputedStyle> partStyle =
	!destroy
	? getScrollbarPseudoStyle(partType, pseudoForScrollbarPart(partType))
	: PassRefPtr<ComputedStyle>(nullptr);

	bool needLayoutObject =
	!destroy && partStyle && partStyle->display() != EDisplay::None;

	if (needLayoutObject && partStyle->display() != EDisplay::Block) {
	// See if we are a button that should not be visible according to OS
	// settings.
	WebScrollbarButtonsPlacement buttonsPlacement = theme().buttonsPlacement();
	switch (partType) {
	case BackButtonStartPart:
	needLayoutObject =
	(buttonsPlacement == WebScrollbarButtonsPlacementSingle \|\|
	buttonsPlacement == WebScrollbarButtonsPlacementDoubleStart \|\|
	buttonsPlacement == WebScrollbarButtonsPlacementDoubleBoth);
	break;
	case ForwardButtonStartPart:
	needLayoutObject =
	(buttonsPlacement == WebScrollbarButtonsPlacementDoubleStart \|\|
	buttonsPlacement == WebScrollbarButtonsPlacementDoubleBoth);
	break;
	case BackButtonEndPart:
	needLayoutObject =
	(buttonsPlacement == WebScrollbarButtonsPlacementDoubleEnd \|\|
	buttonsPlacement == WebScrollbarButtonsPlacementDoubleBoth);
	break;
	case ForwardButtonEndPart:
	needLayoutObject =
	(buttonsPlacement == WebScrollbarButtonsPlacementSingle \|\|
	buttonsPlacement == WebScrollbarButtonsPlacementDoubleEnd \|\|
	buttonsPlacement == WebScrollbarButtonsPlacementDoubleBoth);
	break;
	default:
	break;
	}
	}

	LayoutScrollbarPart* partLayoutObject = m_parts.get(partType);
	if (!partLayoutObject && needLayoutObject && m_scrollableArea) {
	partLayoutObject = LayoutScrollbarPart::createAnonymous(
	&owningLayoutObject()->document(), m_scrollableArea, this, partType);
	m_parts.set(partType, partLayoutObject);
	} else if (partLayoutObject && !needLayoutObject) {
	m_parts.remove(partType);
	partLayoutObject->destroy();
	partLayoutObject = 0;
	}

	if (partLayoutObject)
	partLayoutObject->setStyleWithWritingModeOfParent(partStyle.release());
	}

	IntRect LayoutScrollbar::buttonRect(ScrollbarPart partType) const {
	LayoutScrollbarPart* partLayoutObject = m_parts.get(partType);
	if (!partLayoutObject)
	return IntRect();

	partLayoutObject->layout();

	bool isHorizontal = orientation() == HorizontalScrollbar;
	if (partType == BackButtonStartPart)
	return IntRect(
	location(),
	IntSize(
	isHorizontal ? partLayoutObject->pixelSnappedWidth() : width(),
	isHorizontal ? height() : partLayoutObject->pixelSnappedHeight()));
	if (partType == ForwardButtonEndPart) {
	return IntRect(
	isHorizontal ? x() + width() - partLayoutObject->pixelSnappedWidth()
	: x(),
	isHorizontal ? y()
	: y() + height() - partLayoutObject->pixelSnappedHeight(),
	isHorizontal ? partLayoutObject->pixelSnappedWidth() : width(),
	isHorizontal ? height() : partLayoutObject->pixelSnappedHeight());
	}

	if (partType == ForwardButtonStartPart) {
	IntRect previousButton = buttonRect(BackButtonStartPart);
	return IntRect(
	isHorizontal ? x() + previousButton.width() : x(),
	isHorizontal ? y() : y() + previousButton.height(),
	isHorizontal ? partLayoutObject->pixelSnappedWidth() : width(),
	isHorizontal ? height() : partLayoutObject->pixelSnappedHeight());
	}

	IntRect followingButton = buttonRect(ForwardButtonEndPart);
	return IntRect(
	isHorizontal
	? x() + width() - followingButton.width() -
	partLayoutObject->pixelSnappedWidth()
	: x(),
	isHorizontal ? y()
	: y() + height() - followingButton.height() -
	partLayoutObject->pixelSnappedHeight(),
	isHorizontal ? partLayoutObject->pixelSnappedWidth() : width(),
	isHorizontal ? height() : partLayoutObject->pixelSnappedHeight());
	}

	IntRect LayoutScrollbar::trackRect(int startLength, int endLength) const {
	LayoutScrollbarPart* part = m_parts.get(TrackBGPart);
	if (part)
	part->layout();

	if (orientation() == HorizontalScrollbar) {
	int marginLeft = part ? part->marginLeft().toInt() : 0;
	int marginRight = part ? part->marginRight().toInt() : 0;
	startLength += marginLeft;
	endLength += marginRight;
	int totalLength = startLength + endLength;
	return IntRect(x() + startLength, y(), width() - totalLength, height());
	}

	int marginTop = part ? part->marginTop().toInt() : 0;
	int marginBottom = part ? part->marginBottom().toInt() : 0;
	startLength += marginTop;
	endLength += marginBottom;
	int totalLength = startLength + endLength;

	return IntRect(x(), y() + startLength, width(), height() - totalLength);
	}

	IntRect LayoutScrollbar::trackPieceRectWithMargins(
	ScrollbarPart partType,
	const IntRect& oldRect) const {
	LayoutScrollbarPart* partLayoutObject = m_parts.get(partType);
	if (!partLayoutObject)
	return oldRect;

	partLayoutObject->layout();

	IntRect rect = oldRect;
	if (orientation() == HorizontalScrollbar) {
	rect.setX((rect.x() + partLayoutObject->marginLeft()).toInt());
	rect.setWidth((rect.width() - partLayoutObject->marginWidth()).toInt());
	} else {
	rect.setY((rect.y() + partLayoutObject->marginTop()).toInt());
	rect.setHeight((rect.height() - partLayoutObject->marginHeight()).toInt());
	}
	return rect;
	}

	int LayoutScrollbar::minimumThumbLength() const {
	LayoutScrollbarPart* partLayoutObject = m_parts.get(ThumbPart);
	if (!partLayoutObject)
	return 0;
	partLayoutObject->layout();
	return (orientation() == HorizontalScrollbar
	? partLayoutObject->size().width()
	: partLayoutObject->size().height())
	.toInt();
	}

	void LayoutScrollbar::invalidateDisplayItemClientsOfScrollbarParts() {
	for (auto& part : m_parts)
	ObjectPaintInvalidator(*part.value)
	.invalidateDisplayItemClientsIncludingNonCompositingDescendants(
	PaintInvalidationScroll);
	}

	} // namespace blink