Source/WebCore/platform/gtk/ScrollbarThemeGtk.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2008 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 "config.h"
 #include "ScrollbarThemeGtk.h"

 #include "PlatformMouseEvent.h"
 #include "RenderThemeGtk.h"
 #include "ScrollView.h"
 #include "Scrollbar.h"

 namespace WebCore {

 static HashSet<ScrollbarThemeClient*>* gScrollbars;

 ScrollbarTheme* ScrollbarTheme::nativeTheme()
 {
     static ScrollbarThemeGtk theme;
     return &theme;
 }

 ScrollbarThemeGtk::~ScrollbarThemeGtk()
 {
 }

 void ScrollbarThemeGtk::registerScrollbar(ScrollbarThemeClient* scrollbar)
 {
     if (!gScrollbars)
         gScrollbars = new HashSet<ScrollbarThemeClient*>;
     gScrollbars->add(scrollbar);
 }

 void ScrollbarThemeGtk::unregisterScrollbar(ScrollbarThemeClient* scrollbar)
 {
     gScrollbars->remove(scrollbar);
     if (gScrollbars->isEmpty()) {
         delete gScrollbars;
         gScrollbars = 0;
     }
 }

 void ScrollbarThemeGtk::updateScrollbarsFrameThickness()
 {
     if (!gScrollbars)
         return;

     // Update the thickness of every interior frame scrollbar widget. The
     // platform-independent scrollbar them code isn't yet smart enough to get
     // this information when it paints.
     HashSet<ScrollbarThemeClient*>::iterator end = gScrollbars->end();
     for (HashSet<ScrollbarThemeClient*>::iterator it = gScrollbars->begin(); it != end; ++it) {
         ScrollbarThemeClient* scrollbar = (*it);

         // Top-level scrollbar i.e. scrollbars who have a parent ScrollView
         // with no parent are native, and thus do not need to be resized.
         if (!scrollbar->parent() || !scrollbar->parent()->parent())
             return;

         int thickness = scrollbarThickness(scrollbar->controlSize());
         if (scrollbar->orientation() == HorizontalScrollbar)
             scrollbar->setFrameRect(IntRect(0, scrollbar->parent()->height() - thickness, scrollbar->width(), thickness));
         else
             scrollbar->setFrameRect(IntRect(scrollbar->parent()->width() - thickness, 0, thickness, scrollbar->height()));
     }
 }

 bool ScrollbarThemeGtk::hasThumb(ScrollbarThemeClient* scrollbar)
 {
     // This method is just called as a paint-time optimization to see if
     // painting the thumb can be skipped.  We don't have to be exact here.
     return thumbLength(scrollbar) > 0;
 }

 IntRect ScrollbarThemeGtk::backButtonRect(ScrollbarThemeClient* scrollbar, ScrollbarPart part, bool)
 {
     if (part == BackButtonEndPart && !m_hasBackButtonEndPart)
         return IntRect();
     if (part == BackButtonStartPart && !m_hasBackButtonStartPart)
         return IntRect();

     int x = scrollbar->x() + m_troughBorderWidth;
     int y = scrollbar->y() + m_troughBorderWidth;
     IntSize size = buttonSize(scrollbar);
     if (part == BackButtonStartPart)
         return IntRect(x, y, size.width(), size.height());

     // BackButtonEndPart (alternate button)
     if (scrollbar->orientation() == HorizontalScrollbar)
         return IntRect(scrollbar->x() + scrollbar->width() - m_troughBorderWidth - (2 * size.width()), y, size.width(), size.height());

     // VerticalScrollbar alternate button
     return IntRect(x, scrollbar->y() + scrollbar->height() - m_troughBorderWidth - (2 * size.height()), size.width(), size.height());
 }

 IntRect ScrollbarThemeGtk::forwardButtonRect(ScrollbarThemeClient* scrollbar, ScrollbarPart part, bool)
 {
     if (part == ForwardButtonStartPart && !m_hasForwardButtonStartPart)
         return IntRect();
     if (part == ForwardButtonEndPart && !m_hasForwardButtonEndPart)
         return IntRect();

     IntSize size = buttonSize(scrollbar);
     if (scrollbar->orientation() == HorizontalScrollbar) {
         int y = scrollbar->y() + m_troughBorderWidth;
         if (part == ForwardButtonEndPart)
             return IntRect(scrollbar->x() + scrollbar->width() - size.width() - m_troughBorderWidth, y, size.width(), size.height());

         // ForwardButtonStartPart (alternate button)
         return IntRect(scrollbar->x() + m_troughBorderWidth + size.width(), y, size.width(), size.height());
     }

     // VerticalScrollbar
     int x = scrollbar->x() + m_troughBorderWidth;
     if (part == ForwardButtonEndPart)
         return IntRect(x, scrollbar->y() + scrollbar->height() - size.height() - m_troughBorderWidth, size.width(), size.height());

     // ForwardButtonStartPart (alternate button)
     return IntRect(x, scrollbar->y() + m_troughBorderWidth + size.height(), size.width(), size.height());
 }

 IntRect ScrollbarThemeGtk::trackRect(ScrollbarThemeClient* scrollbar, bool)
 {
     // The padding along the thumb movement axis includes the trough border
     // plus the size of stepper spacing (the space between the stepper and
     // the place where the thumb stops). There is often no stepper spacing.
     int movementAxisPadding = m_troughBorderWidth + m_stepperSpacing;

     // The fatness of the scrollbar on the non-movement axis.
     int thickness = scrollbarThickness(scrollbar->controlSize());

     int startButtonsOffset = 0;
     int buttonsWidth = 0;
     if (m_hasForwardButtonStartPart) {
         startButtonsOffset += m_stepperSize;
         buttonsWidth += m_stepperSize;
     }
     if (m_hasBackButtonStartPart) {
         startButtonsOffset += m_stepperSize;
         buttonsWidth += m_stepperSize;
     }
     if (m_hasBackButtonEndPart)
         buttonsWidth += m_stepperSize;
     if (m_hasForwardButtonEndPart)
         buttonsWidth += m_stepperSize;

     if (scrollbar->orientation() == HorizontalScrollbar) {
         // Once the scrollbar becomes smaller than the natural size of the
         // two buttons, the track disappears.
         if (scrollbar->width() < 2 * thickness)
             return IntRect();
         return IntRect(scrollbar->x() + movementAxisPadding + startButtonsOffset, scrollbar->y(),
                        scrollbar->width() - (2 * movementAxisPadding) - buttonsWidth, thickness);
     }

     if (scrollbar->height() < 2 * thickness)
         return IntRect();
     return IntRect(scrollbar->x(), scrollbar->y() + movementAxisPadding + startButtonsOffset,
                    thickness, scrollbar->height() - (2 * movementAxisPadding) - buttonsWidth);
 }

 IntRect ScrollbarThemeGtk::thumbRect(ScrollbarThemeClient* scrollbar, const IntRect& unconstrainedTrackRect)
 {
     IntRect trackRect = constrainTrackRectToTrackPieces(scrollbar, unconstrainedTrackRect);
     int thumbPos = thumbPosition(scrollbar);
     if (scrollbar->orientation() == HorizontalScrollbar)
         return IntRect(trackRect.x() + thumbPos, trackRect.y() + (trackRect.height() - m_thumbFatness) / 2, thumbLength(scrollbar), m_thumbFatness);

     // VerticalScrollbar
     return IntRect(trackRect.x() + (trackRect.width() - m_thumbFatness) / 2, trackRect.y() + thumbPos, m_thumbFatness, thumbLength(scrollbar));
 }

 bool ScrollbarThemeGtk::paint(ScrollbarThemeClient* scrollbar, GraphicsContext* graphicsContext, const IntRect& damageRect)
 {
     if (graphicsContext->paintingDisabled())
         return false;

     // Create the ScrollbarControlPartMask based on the damageRect
     ScrollbarControlPartMask scrollMask = NoPart;

     IntRect backButtonStartPaintRect;
     IntRect backButtonEndPaintRect;
     IntRect forwardButtonStartPaintRect;
     IntRect forwardButtonEndPaintRect;
     if (hasButtons(scrollbar)) {
         backButtonStartPaintRect = backButtonRect(scrollbar, BackButtonStartPart, true);
         if (damageRect.intersects(backButtonStartPaintRect))
             scrollMask |= BackButtonStartPart;
         backButtonEndPaintRect = backButtonRect(scrollbar, BackButtonEndPart, true);
         if (damageRect.intersects(backButtonEndPaintRect))
             scrollMask |= BackButtonEndPart;
         forwardButtonStartPaintRect = forwardButtonRect(scrollbar, ForwardButtonStartPart, true);
         if (damageRect.intersects(forwardButtonStartPaintRect))
             scrollMask |= ForwardButtonStartPart;
         forwardButtonEndPaintRect = forwardButtonRect(scrollbar, ForwardButtonEndPart, true);
         if (damageRect.intersects(forwardButtonEndPaintRect))
             scrollMask |= ForwardButtonEndPart;
     }

     IntRect trackPaintRect = trackRect(scrollbar, true);
     if (damageRect.intersects(trackPaintRect))
         scrollMask |= TrackBGPart;

     if (m_troughUnderSteppers && (scrollMask & BackButtonStartPart
             || scrollMask & BackButtonEndPart
             || scrollMask & ForwardButtonStartPart
             || scrollMask & ForwardButtonEndPart))
         scrollMask |= TrackBGPart;

     bool thumbPresent = hasThumb(scrollbar);
     IntRect currentThumbRect;
     if (thumbPresent) {
         IntRect track = trackRect(scrollbar, false);
         currentThumbRect = thumbRect(scrollbar, track);
         if (damageRect.intersects(currentThumbRect))
             scrollMask |= ThumbPart;
     }

     ScrollbarControlPartMask allButtons = BackButtonStartPart | BackButtonEndPart
                                          | ForwardButtonStartPart | ForwardButtonEndPart;
     if (scrollMask & TrackBGPart || scrollMask & ThumbPart || scrollMask & allButtons)
         paintScrollbarBackground(graphicsContext, scrollbar);
         paintTrackBackground(graphicsContext, scrollbar, trackPaintRect);

     // Paint the back and forward buttons.
     if (scrollMask & BackButtonStartPart)
         paintButton(graphicsContext, scrollbar, backButtonStartPaintRect, BackButtonStartPart);
     if (scrollMask & BackButtonEndPart)
         paintButton(graphicsContext, scrollbar, backButtonEndPaintRect, BackButtonEndPart);
     if (scrollMask & ForwardButtonStartPart)
         paintButton(graphicsContext, scrollbar, forwardButtonStartPaintRect, ForwardButtonStartPart);
     if (scrollMask & ForwardButtonEndPart)
         paintButton(graphicsContext, scrollbar, forwardButtonEndPaintRect, ForwardButtonEndPart);

     // Paint the thumb.
     if (scrollMask & ThumbPart)
         paintThumb(graphicsContext, scrollbar, currentThumbRect);

     return true;
 }

 bool ScrollbarThemeGtk::shouldCenterOnThumb(ScrollbarThemeClient*, const PlatformMouseEvent& event)
 {
     return (event.shiftKey() && event.button() == LeftButton) || (event.button() == MiddleButton);
 }

 int ScrollbarThemeGtk::scrollbarThickness(ScrollbarControlSize)
 {
     return m_thumbFatness + (m_troughBorderWidth * 2);
 }

 IntSize ScrollbarThemeGtk::buttonSize(ScrollbarThemeClient* scrollbar)
 {
     if (scrollbar->orientation() == VerticalScrollbar)
         return IntSize(m_thumbFatness, m_stepperSize);

     // HorizontalScrollbar
     return IntSize(m_stepperSize, m_thumbFatness);
 }

 int ScrollbarThemeGtk::minimumThumbLength(ScrollbarThemeClient* scrollbar)
 {
     return m_minThumbLength;
 }

 }
	/*
	* Copyright (C) 2008 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 "config.h"
	#include "ScrollbarThemeGtk.h"

	#include "PlatformMouseEvent.h"
	#include "RenderThemeGtk.h"
	#include "ScrollView.h"
	#include "Scrollbar.h"

	namespace WebCore {

	static HashSet<ScrollbarThemeClient> gScrollbars;

	ScrollbarTheme* ScrollbarTheme::nativeTheme()
	{
	static ScrollbarThemeGtk theme;
	return &theme;
	}

	ScrollbarThemeGtk::~ScrollbarThemeGtk()
	{
	}

	void ScrollbarThemeGtk::registerScrollbar(ScrollbarThemeClient* scrollbar)
	{
	if (!gScrollbars)
	gScrollbars = new HashSet<ScrollbarThemeClient*>;
	gScrollbars->add(scrollbar);
	}

	void ScrollbarThemeGtk::unregisterScrollbar(ScrollbarThemeClient* scrollbar)
	{
	gScrollbars->remove(scrollbar);
	if (gScrollbars->isEmpty()) {
	delete gScrollbars;
	gScrollbars = 0;
	}
	}

	void ScrollbarThemeGtk::updateScrollbarsFrameThickness()
	{
	if (!gScrollbars)
	return;

	// Update the thickness of every interior frame scrollbar widget. The
	// platform-independent scrollbar them code isn't yet smart enough to get
	// this information when it paints.
	HashSet<ScrollbarThemeClient*>::iterator end = gScrollbars->end();
	for (HashSet<ScrollbarThemeClient*>::iterator it = gScrollbars->begin(); it != end; ++it) {
	ScrollbarThemeClient* scrollbar = (*it);

	// Top-level scrollbar i.e. scrollbars who have a parent ScrollView
	// with no parent are native, and thus do not need to be resized.
	if (!scrollbar->parent() \|\| !scrollbar->parent()->parent())
	return;

	int thickness = scrollbarThickness(scrollbar->controlSize());
	if (scrollbar->orientation() == HorizontalScrollbar)
	scrollbar->setFrameRect(IntRect(0, scrollbar->parent()->height() - thickness, scrollbar->width(), thickness));
	else
	scrollbar->setFrameRect(IntRect(scrollbar->parent()->width() - thickness, 0, thickness, scrollbar->height()));
	}
	}

	bool ScrollbarThemeGtk::hasThumb(ScrollbarThemeClient* scrollbar)
	{
	// This method is just called as a paint-time optimization to see if
	// painting the thumb can be skipped. We don't have to be exact here.
	return thumbLength(scrollbar) > 0;
	}

	IntRect ScrollbarThemeGtk::backButtonRect(ScrollbarThemeClient* scrollbar, ScrollbarPart part, bool)
	{
	if (part == BackButtonEndPart && !m_hasBackButtonEndPart)
	return IntRect();
	if (part == BackButtonStartPart && !m_hasBackButtonStartPart)
	return IntRect();

	int x = scrollbar->x() + m_troughBorderWidth;
	int y = scrollbar->y() + m_troughBorderWidth;
	IntSize size = buttonSize(scrollbar);
	if (part == BackButtonStartPart)
	return IntRect(x, y, size.width(), size.height());

	// BackButtonEndPart (alternate button)
	if (scrollbar->orientation() == HorizontalScrollbar)
	return IntRect(scrollbar->x() + scrollbar->width() - m_troughBorderWidth - (2 * size.width()), y, size.width(), size.height());

	// VerticalScrollbar alternate button
	return IntRect(x, scrollbar->y() + scrollbar->height() - m_troughBorderWidth - (2 * size.height()), size.width(), size.height());
	}

	IntRect ScrollbarThemeGtk::forwardButtonRect(ScrollbarThemeClient* scrollbar, ScrollbarPart part, bool)
	{
	if (part == ForwardButtonStartPart && !m_hasForwardButtonStartPart)
	return IntRect();
	if (part == ForwardButtonEndPart && !m_hasForwardButtonEndPart)
	return IntRect();

	IntSize size = buttonSize(scrollbar);
	if (scrollbar->orientation() == HorizontalScrollbar) {
	int y = scrollbar->y() + m_troughBorderWidth;
	if (part == ForwardButtonEndPart)
	return IntRect(scrollbar->x() + scrollbar->width() - size.width() - m_troughBorderWidth, y, size.width(), size.height());

	// ForwardButtonStartPart (alternate button)
	return IntRect(scrollbar->x() + m_troughBorderWidth + size.width(), y, size.width(), size.height());
	}

	// VerticalScrollbar
	int x = scrollbar->x() + m_troughBorderWidth;
	if (part == ForwardButtonEndPart)
	return IntRect(x, scrollbar->y() + scrollbar->height() - size.height() - m_troughBorderWidth, size.width(), size.height());

	// ForwardButtonStartPart (alternate button)
	return IntRect(x, scrollbar->y() + m_troughBorderWidth + size.height(), size.width(), size.height());
	}

	IntRect ScrollbarThemeGtk::trackRect(ScrollbarThemeClient* scrollbar, bool)
	{
	// The padding along the thumb movement axis includes the trough border
	// plus the size of stepper spacing (the space between the stepper and
	// the place where the thumb stops). There is often no stepper spacing.
	int movementAxisPadding = m_troughBorderWidth + m_stepperSpacing;

	// The fatness of the scrollbar on the non-movement axis.
	int thickness = scrollbarThickness(scrollbar->controlSize());

	int startButtonsOffset = 0;
	int buttonsWidth = 0;
	if (m_hasForwardButtonStartPart) {
	startButtonsOffset += m_stepperSize;
	buttonsWidth += m_stepperSize;
	}
	if (m_hasBackButtonStartPart) {
	startButtonsOffset += m_stepperSize;
	buttonsWidth += m_stepperSize;
	}
	if (m_hasBackButtonEndPart)
	buttonsWidth += m_stepperSize;
	if (m_hasForwardButtonEndPart)
	buttonsWidth += m_stepperSize;

	if (scrollbar->orientation() == HorizontalScrollbar) {
	// Once the scrollbar becomes smaller than the natural size of the
	// two buttons, the track disappears.
	if (scrollbar->width() < 2 * thickness)
	return IntRect();
	return IntRect(scrollbar->x() + movementAxisPadding + startButtonsOffset, scrollbar->y(),
	scrollbar->width() - (2 * movementAxisPadding) - buttonsWidth, thickness);
	}

	if (scrollbar->height() < 2 * thickness)
	return IntRect();
	return IntRect(scrollbar->x(), scrollbar->y() + movementAxisPadding + startButtonsOffset,
	thickness, scrollbar->height() - (2 * movementAxisPadding) - buttonsWidth);
	}

	IntRect ScrollbarThemeGtk::thumbRect(ScrollbarThemeClient* scrollbar, const IntRect& unconstrainedTrackRect)
	{
	IntRect trackRect = constrainTrackRectToTrackPieces(scrollbar, unconstrainedTrackRect);
	int thumbPos = thumbPosition(scrollbar);
	if (scrollbar->orientation() == HorizontalScrollbar)
	return IntRect(trackRect.x() + thumbPos, trackRect.y() + (trackRect.height() - m_thumbFatness) / 2, thumbLength(scrollbar), m_thumbFatness);

	// VerticalScrollbar
	return IntRect(trackRect.x() + (trackRect.width() - m_thumbFatness) / 2, trackRect.y() + thumbPos, m_thumbFatness, thumbLength(scrollbar));
	}

	bool ScrollbarThemeGtk::paint(ScrollbarThemeClient* scrollbar, GraphicsContext* graphicsContext, const IntRect& damageRect)
	{
	if (graphicsContext->paintingDisabled())
	return false;

	// Create the ScrollbarControlPartMask based on the damageRect
	ScrollbarControlPartMask scrollMask = NoPart;

	IntRect backButtonStartPaintRect;
	IntRect backButtonEndPaintRect;
	IntRect forwardButtonStartPaintRect;
	IntRect forwardButtonEndPaintRect;
	if (hasButtons(scrollbar)) {
	backButtonStartPaintRect = backButtonRect(scrollbar, BackButtonStartPart, true);
	if (damageRect.intersects(backButtonStartPaintRect))
	scrollMask \|= BackButtonStartPart;
	backButtonEndPaintRect = backButtonRect(scrollbar, BackButtonEndPart, true);
	if (damageRect.intersects(backButtonEndPaintRect))
	scrollMask \|= BackButtonEndPart;
	forwardButtonStartPaintRect = forwardButtonRect(scrollbar, ForwardButtonStartPart, true);
	if (damageRect.intersects(forwardButtonStartPaintRect))
	scrollMask \|= ForwardButtonStartPart;
	forwardButtonEndPaintRect = forwardButtonRect(scrollbar, ForwardButtonEndPart, true);
	if (damageRect.intersects(forwardButtonEndPaintRect))
	scrollMask \|= ForwardButtonEndPart;
	}

	IntRect trackPaintRect = trackRect(scrollbar, true);
	if (damageRect.intersects(trackPaintRect))
	scrollMask \|= TrackBGPart;

	if (m_troughUnderSteppers && (scrollMask & BackButtonStartPart
	\|\| scrollMask & BackButtonEndPart
	\|\| scrollMask & ForwardButtonStartPart
	\|\| scrollMask & ForwardButtonEndPart))
	scrollMask \|= TrackBGPart;

	bool thumbPresent = hasThumb(scrollbar);
	IntRect currentThumbRect;
	if (thumbPresent) {
	IntRect track = trackRect(scrollbar, false);
	currentThumbRect = thumbRect(scrollbar, track);
	if (damageRect.intersects(currentThumbRect))
	scrollMask \|= ThumbPart;
	}

	ScrollbarControlPartMask allButtons = BackButtonStartPart \| BackButtonEndPart
	\| ForwardButtonStartPart \| ForwardButtonEndPart;
	if (scrollMask & TrackBGPart \|\| scrollMask & ThumbPart \|\| scrollMask & allButtons)
	paintScrollbarBackground(graphicsContext, scrollbar);
	paintTrackBackground(graphicsContext, scrollbar, trackPaintRect);

	// Paint the back and forward buttons.
	if (scrollMask & BackButtonStartPart)
	paintButton(graphicsContext, scrollbar, backButtonStartPaintRect, BackButtonStartPart);
	if (scrollMask & BackButtonEndPart)
	paintButton(graphicsContext, scrollbar, backButtonEndPaintRect, BackButtonEndPart);
	if (scrollMask & ForwardButtonStartPart)
	paintButton(graphicsContext, scrollbar, forwardButtonStartPaintRect, ForwardButtonStartPart);
	if (scrollMask & ForwardButtonEndPart)
	paintButton(graphicsContext, scrollbar, forwardButtonEndPaintRect, ForwardButtonEndPart);

	// Paint the thumb.
	if (scrollMask & ThumbPart)
	paintThumb(graphicsContext, scrollbar, currentThumbRect);

	return true;
	}

	bool ScrollbarThemeGtk::shouldCenterOnThumb(ScrollbarThemeClient*, const PlatformMouseEvent& event)
	{
	return (event.shiftKey() && event.button() == LeftButton) \|\| (event.button() == MiddleButton);
	}

	int ScrollbarThemeGtk::scrollbarThickness(ScrollbarControlSize)
	{
	return m_thumbFatness + (m_troughBorderWidth * 2);
	}

	IntSize ScrollbarThemeGtk::buttonSize(ScrollbarThemeClient* scrollbar)
	{
	if (scrollbar->orientation() == VerticalScrollbar)
	return IntSize(m_thumbFatness, m_stepperSize);

	// HorizontalScrollbar
	return IntSize(m_stepperSize, m_thumbFatness);
	}

	int ScrollbarThemeGtk::minimumThumbLength(ScrollbarThemeClient* scrollbar)
	{
	return m_minThumbLength;
	}

	}