Source/WebCore/platform/win/ScrollbarThemeWin.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2008, 2013 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 "ScrollbarThemeWin.h"

 #include "GDIUtilities.h"
 #include "GraphicsContext.h"
 #include "HWndDC.h"
 #include "LocalWindowsContext.h"
 #include "PlatformMouseEvent.h"
 #include "Scrollbar.h"
 #include "SystemInfo.h"
 #include <wtf/SoftLinking.h>
 #include <wtf/win/GDIObject.h>

 // Generic state constants
 #define TS_NORMAL    1
 #define TS_HOVER     2
 #define TS_ACTIVE    3
 #define TS_DISABLED  4

 #define SP_BUTTON          1
 #define SP_THUMBHOR        2
 #define SP_THUMBVERT       3
 #define SP_TRACKSTARTHOR   4
 #define SP_TRACKENDHOR     5
 #define SP_TRACKSTARTVERT  6
 #define SP_TRACKENDVERT    7
 #define SP_GRIPPERHOR      8
 #define SP_GRIPPERVERT     9

 #define TS_UP_BUTTON       0
 #define TS_DOWN_BUTTON     4
 #define TS_LEFT_BUTTON     8
 #define TS_RIGHT_BUTTON    12
 #define TS_UP_BUTTON_HOVER   17
 #define TS_DOWN_BUTTON_HOVER  18
 #define TS_LEFT_BUTTON_HOVER  19
 #define TS_RIGHT_BUTTON_HOVER   20


 namespace WebCore {

 static HANDLE scrollbarTheme;
 static bool runningVista;

 // FIXME:  Refactor the soft-linking code so that it can be shared with RenderThemeWin
 SOFT_LINK_LIBRARY(uxtheme)
 SOFT_LINK(uxtheme, OpenThemeData, HANDLE, WINAPI, (HWND hwnd, LPCWSTR pszClassList), (hwnd, pszClassList))
 SOFT_LINK(uxtheme, CloseThemeData, HRESULT, WINAPI, (HANDLE hTheme), (hTheme))
 SOFT_LINK(uxtheme, DrawThemeBackground, HRESULT, WINAPI, (HANDLE hTheme, HDC hdc, int iPartId, int iStateId, const RECT* pRect, const RECT* pClipRect), (hTheme, hdc, iPartId, iStateId, pRect, pClipRect))
 SOFT_LINK(uxtheme, IsThemeActive, BOOL, WINAPI, (), ())
 SOFT_LINK(uxtheme, IsThemeBackgroundPartiallyTransparent, BOOL, WINAPI, (HANDLE hTheme, int iPartId, int iStateId), (hTheme, iPartId, iStateId))

 // Constants used to figure the drag rect outside which we should snap the
 // scrollbar thumb back to its origin.  These calculations are based on
 // observing the behavior of the MSVC8 main window scrollbar + some
 // guessing/extrapolation.
 static const int kOffEndMultiplier = 3;
 static const int kOffSideMultiplier = 8;

 static void checkAndInitScrollbarTheme()
 {
     if (uxthemeLibrary() && !scrollbarTheme && IsThemeActive())
         scrollbarTheme = OpenThemeData(0, L"Scrollbar");
 }

 ScrollbarTheme& ScrollbarTheme::nativeTheme()
 {
     static ScrollbarThemeWin winTheme;
     return winTheme;
 }

 ScrollbarThemeWin::ScrollbarThemeWin()
 {
     static bool initialized;
     if (!initialized) {
         initialized = true;
         checkAndInitScrollbarTheme();
         runningVista = (windowsVersion() >= WindowsVista);
     }
 }

 ScrollbarThemeWin::~ScrollbarThemeWin() = default;

 static int scrollbarThicknessInPixels()
 {
     static int thickness = ::GetSystemMetrics(SM_CXVSCROLL);
     return thickness;
 }

 int ScrollbarThemeWin::scrollbarThickness(ScrollbarControlSize, ScrollbarExpansionState)
 {
     float inverseScaleFactor = 1.0f / deviceScaleFactorForWindow(0);
     return clampTo<int>(inverseScaleFactor * scrollbarThicknessInPixels());
 }

 void ScrollbarThemeWin::themeChanged()
 {
     if (!scrollbarTheme)
         return;

     CloseThemeData(scrollbarTheme);
     scrollbarTheme = 0;
 }

 bool ScrollbarThemeWin::invalidateOnMouseEnterExit()
 {
     return runningVista;
 }

 bool ScrollbarThemeWin::hasThumb(Scrollbar& scrollbar)
 {
     return thumbLength(scrollbar) > 0;
 }

 IntRect ScrollbarThemeWin::backButtonRect(Scrollbar& scrollbar, ScrollbarPart part, bool)
 {
     // Windows just has single arrows.
     if (part == BackButtonEndPart)
         return IntRect();

     // Our desired rect is essentially 17x17.

     // Our actual rect will shrink to half the available space when
     // we have < 34 pixels left.  This allows the scrollbar
     // to scale down and function even at tiny sizes.
     int thickness = scrollbarThickness();
     if (scrollbar.orientation() == HorizontalScrollbar)
         return IntRect(scrollbar.x(), scrollbar.y(),
                        scrollbar.width() < 2 * thickness ? scrollbar.width() / 2 : thickness, thickness);
     return IntRect(scrollbar.x(), scrollbar.y(),
                    thickness, scrollbar.height() < 2 * thickness ? scrollbar.height() / 2 : thickness);
 }

 IntRect ScrollbarThemeWin::forwardButtonRect(Scrollbar& scrollbar, ScrollbarPart part, bool)
 {
     // Windows just has single arrows.
     if (part == ForwardButtonStartPart)
         return IntRect();

     // Our desired rect is essentially 17x17.

     // Our actual rect will shrink to half the available space when
     // we have < 34 pixels left.  This allows the scrollbar
     // to scale down and function even at tiny sizes.
     int thickness = scrollbarThickness();
     if (scrollbar.orientation() == HorizontalScrollbar) {
         int w = scrollbar.width() < 2 * thickness ? scrollbar.width() / 2 : thickness;
         return IntRect(scrollbar.x() + scrollbar.width() - w, scrollbar.y(), w, thickness);
     }

     int h = scrollbar.height() < 2 * thickness ? scrollbar.height() / 2 : thickness;
     return IntRect(scrollbar.x(), scrollbar.y() + scrollbar.height() - h, thickness, h);
 }

 IntRect ScrollbarThemeWin::trackRect(Scrollbar& scrollbar, bool)
 {
     int thickness = scrollbarThickness();
     if (scrollbar.orientation() == HorizontalScrollbar) {
         if (scrollbar.width() < 2 * thickness)
             return IntRect();
         return IntRect(scrollbar.x() + thickness, scrollbar.y(), scrollbar.width() - 2 * thickness, thickness);
     }
     if (scrollbar.height() < 2 * thickness)
         return IntRect();
     return IntRect(scrollbar.x(), scrollbar.y() + thickness, thickness, scrollbar.height() - 2 * thickness);
 }

 ScrollbarButtonPressAction ScrollbarThemeWin::handleMousePressEvent(Scrollbar&, const PlatformMouseEvent& event, ScrollbarPart pressedPart)
 {
     if (event.button() == RightButton)
         return ScrollbarButtonPressAction::None;

     switch (pressedPart) {
     case BackTrackPart:
     case ForwardTrackPart:
         if (event.shiftKey() && event.button() == LeftButton)
             return ScrollbarButtonPressAction::CenterOnThumb;
         break;
     case ThumbPart:
         return ScrollbarButtonPressAction::StartDrag;
     default:
         break;
     }

     return ScrollbarButtonPressAction::Scroll;
 }

 bool ScrollbarThemeWin::shouldSnapBackToDragOrigin(Scrollbar& scrollbar, const PlatformMouseEvent& evt)
 {
     // Find the rect within which we shouldn't snap, by expanding the track rect
     // in both dimensions.
     IntRect rect = trackRect(scrollbar);
     const bool horz = scrollbar.orientation() == HorizontalScrollbar;
     const int thickness = scrollbarThickness(scrollbar.controlSize());
     rect.inflateX((horz ? kOffEndMultiplier : kOffSideMultiplier) * thickness);
     rect.inflateY((horz ? kOffSideMultiplier : kOffEndMultiplier) * thickness);

     // Convert the event to local coordinates.
     IntPoint mousePosition = scrollbar.convertFromContainingWindow(evt.position());
     mousePosition.move(scrollbar.x(), scrollbar.y());

     // We should snap iff the event is outside our calculated rect.
     return !rect.contains(mousePosition);
 }

 void ScrollbarThemeWin::paintTrackBackground(GraphicsContext& context, Scrollbar& scrollbar, const IntRect& rect)
 {
     // Just assume a forward track part.  We only paint the track as a single piece when there is no thumb.
     if (!hasThumb(scrollbar))
         paintTrackPiece(context, scrollbar, rect, ForwardTrackPart);
 }

 void ScrollbarThemeWin::paintTrackPiece(GraphicsContext& context, Scrollbar& scrollbar, const IntRect& rect, ScrollbarPart partType)
 {
     checkAndInitScrollbarTheme();

     bool start = partType == BackTrackPart;
     int part;
     if (scrollbar.orientation() == HorizontalScrollbar)
         part = start ? SP_TRACKSTARTHOR : SP_TRACKENDHOR;
     else
         part = start ? SP_TRACKSTARTVERT : SP_TRACKENDVERT;

     int state;
     if (!scrollbar.enabled())
         state = TS_DISABLED;
     else if ((scrollbar.hoveredPart() == BackTrackPart && start) ||
              (scrollbar.hoveredPart() == ForwardTrackPart && !start))
         state = (scrollbar.pressedPart() == scrollbar.hoveredPart() ? TS_ACTIVE : TS_HOVER);
     else
         state = TS_NORMAL;

     bool alphaBlend = false;
     if (scrollbarTheme)
         alphaBlend = IsThemeBackgroundPartiallyTransparent(scrollbarTheme, part, state);

     LocalWindowsContext windowsContext(context, rect, alphaBlend);
     RECT themeRect(rect);

     if (scrollbarTheme)
         DrawThemeBackground(scrollbarTheme, windowsContext.hdc(), part, state, &themeRect, 0);
     else {
         DWORD color3DFace = ::GetSysColor(COLOR_3DFACE);
         DWORD colorScrollbar = ::GetSysColor(COLOR_SCROLLBAR);
         DWORD colorWindow = ::GetSysColor(COLOR_WINDOW);
         HDC hdc = windowsContext.hdc();
         if ((color3DFace != colorScrollbar) && (colorWindow != colorScrollbar))
             ::FillRect(hdc, &themeRect, HBRUSH(COLOR_SCROLLBAR+1));
         else {
             static WORD patternBits[8] = { 0xaa, 0x55, 0xaa, 0x55, 0xaa, 0x55, 0xaa, 0x55 };
             auto patternBitmap = adoptGDIObject(::CreateBitmap(8, 8, 1, 1, patternBits));
             auto brush = adoptGDIObject(::CreatePatternBrush(patternBitmap.get()));
             SaveDC(hdc);
             ::SetTextColor(hdc, ::GetSysColor(COLOR_3DHILIGHT));
             ::SetBkColor(hdc, ::GetSysColor(COLOR_3DFACE));
             ::SetBrushOrgEx(hdc, rect.x(), rect.y(), NULL);
             ::SelectObject(hdc, brush.get());
             ::FillRect(hdc, &themeRect, brush.get());
             ::RestoreDC(hdc, -1);
         }
     }

     if (!alphaBlend && !context.isInTransparencyLayer())
         DIBPixelData::setRGBABitmapAlpha(windowsContext.hdc(), rect, 255);
 }

 void ScrollbarThemeWin::paintButton(GraphicsContext& context, Scrollbar& scrollbar, const IntRect& rect, ScrollbarPart part)
 {
     checkAndInitScrollbarTheme();

     bool start = (part == BackButtonStartPart);
     int xpState = 0;
     int classicState = 0;
     if (scrollbar.orientation() == HorizontalScrollbar)
         xpState = start ? TS_LEFT_BUTTON : TS_RIGHT_BUTTON;
     else
         xpState = start ? TS_UP_BUTTON : TS_DOWN_BUTTON;
     classicState = xpState / 4;

     if (!scrollbar.enabled()) {
         xpState += TS_DISABLED;
         classicState |= DFCS_INACTIVE;
     } else if ((scrollbar.hoveredPart() == BackButtonStartPart && start) ||
                (scrollbar.hoveredPart() == ForwardButtonEndPart && !start)) {
         if (scrollbar.pressedPart() == scrollbar.hoveredPart()) {
             xpState += TS_ACTIVE;
             classicState |= DFCS_PUSHED;
             classicState |= DFCS_FLAT;
         } else
             xpState += TS_HOVER;
     } else {
         if (scrollbar.hoveredPart() == NoPart || !runningVista)
             xpState += TS_NORMAL;
         else {
             if (scrollbar.orientation() == HorizontalScrollbar)
                 xpState = start ? TS_LEFT_BUTTON_HOVER : TS_RIGHT_BUTTON_HOVER;
             else
                 xpState = start ? TS_UP_BUTTON_HOVER : TS_DOWN_BUTTON_HOVER;
         }
     }

     bool alphaBlend = false;
     if (scrollbarTheme)
         alphaBlend = IsThemeBackgroundPartiallyTransparent(scrollbarTheme, SP_BUTTON, xpState);

     // There seems to be a bug in DrawThemeBackground when the device context is scaled.
     // We can work around this by scaling the drawing rectangle instead.
     auto scaleFactor = context.scaleFactor().width();
     auto scaledRect = rect;
     scaledRect.scale(scaleFactor);
     context.save();
     context.scale(FloatSize(1.0f / scaleFactor, 1.0f / scaleFactor));

     {
         LocalWindowsContext windowsContext(context, scaledRect, alphaBlend);
         RECT themeRect(scaledRect);
         if (scrollbarTheme)
             DrawThemeBackground(scrollbarTheme, windowsContext.hdc(), SP_BUTTON, xpState, &themeRect, 0);
         else
             ::DrawFrameControl(windowsContext.hdc(), &themeRect, DFC_SCROLL, classicState);

         if (!alphaBlend && !context.isInTransparencyLayer())
             DIBPixelData::setRGBABitmapAlpha(windowsContext.hdc(), scaledRect, 255);
     }
     context.restore();
 }

 static IntRect gripperRect(int thickness, const IntRect& thumbRect)
 {
     // Center in the thumb.
     int gripperThickness = thickness / 2;
     return IntRect(thumbRect.x() + (thumbRect.width() - gripperThickness) / 2,
                    thumbRect.y() + (thumbRect.height() - gripperThickness) / 2,
                    gripperThickness, gripperThickness);
 }

 static void paintGripper(Scrollbar& scrollbar, HDC hdc, const IntRect& rect)
 {
     if (!scrollbarTheme)
         return;  // Classic look has no gripper.

     int state;
     if (!scrollbar.enabled())
         state = TS_DISABLED;
     else if (scrollbar.pressedPart() == ThumbPart)
         state = TS_ACTIVE; // Thumb always stays active once pressed.
     else if (scrollbar.hoveredPart() == ThumbPart)
         state = TS_HOVER;
     else
         state = TS_NORMAL;

     RECT themeRect(rect);
     DrawThemeBackground(scrollbarTheme, hdc, scrollbar.orientation() == HorizontalScrollbar ? SP_GRIPPERHOR : SP_GRIPPERVERT, state, &themeRect, 0);
 }

 void ScrollbarThemeWin::paintThumb(GraphicsContext& context, Scrollbar& scrollbar, const IntRect& rect)
 {
     checkAndInitScrollbarTheme();

     int state;
     if (!scrollbar.enabled())
         state = TS_DISABLED;
     else if (scrollbar.pressedPart() == ThumbPart)
         state = TS_ACTIVE; // Thumb always stays active once pressed.
     else if (scrollbar.hoveredPart() == ThumbPart)
         state = TS_HOVER;
     else
         state = TS_NORMAL;

     bool alphaBlend = false;
     if (scrollbarTheme)
         alphaBlend = IsThemeBackgroundPartiallyTransparent(scrollbarTheme, scrollbar.orientation() == HorizontalScrollbar ? SP_THUMBHOR : SP_THUMBVERT, state);
     LocalWindowsContext windowsContext(context, rect, alphaBlend);
     RECT themeRect(rect);
     if (scrollbarTheme) {
         DrawThemeBackground(scrollbarTheme, windowsContext.hdc(), scrollbar.orientation() == HorizontalScrollbar ? SP_THUMBHOR : SP_THUMBVERT, state, &themeRect, 0);
         paintGripper(scrollbar, windowsContext.hdc(), gripperRect(scrollbarThickness(), rect));
     } else
         ::DrawEdge(windowsContext.hdc(), &themeRect, EDGE_RAISED, BF_RECT | BF_MIDDLE);

     if (!alphaBlend && !context.isInTransparencyLayer())
         DIBPixelData::setRGBABitmapAlpha(windowsContext.hdc(), rect, 255);
 }

 }
	/*
	* Copyright (C) 2008, 2013 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 "ScrollbarThemeWin.h"

	#include "GDIUtilities.h"
	#include "GraphicsContext.h"
	#include "HWndDC.h"
	#include "LocalWindowsContext.h"
	#include "PlatformMouseEvent.h"
	#include "Scrollbar.h"
	#include "SystemInfo.h"
	#include <wtf/SoftLinking.h>
	#include <wtf/win/GDIObject.h>

	// Generic state constants
	#define TS_NORMAL 1
	#define TS_HOVER 2
	#define TS_ACTIVE 3
	#define TS_DISABLED 4

	#define SP_BUTTON 1
	#define SP_THUMBHOR 2
	#define SP_THUMBVERT 3
	#define SP_TRACKSTARTHOR 4
	#define SP_TRACKENDHOR 5
	#define SP_TRACKSTARTVERT 6
	#define SP_TRACKENDVERT 7
	#define SP_GRIPPERHOR 8
	#define SP_GRIPPERVERT 9

	#define TS_UP_BUTTON 0
	#define TS_DOWN_BUTTON 4
	#define TS_LEFT_BUTTON 8
	#define TS_RIGHT_BUTTON 12
	#define TS_UP_BUTTON_HOVER 17
	#define TS_DOWN_BUTTON_HOVER 18
	#define TS_LEFT_BUTTON_HOVER 19
	#define TS_RIGHT_BUTTON_HOVER 20


	namespace WebCore {

	static HANDLE scrollbarTheme;
	static bool runningVista;

	// FIXME: Refactor the soft-linking code so that it can be shared with RenderThemeWin
	SOFT_LINK_LIBRARY(uxtheme)
	SOFT_LINK(uxtheme, OpenThemeData, HANDLE, WINAPI, (HWND hwnd, LPCWSTR pszClassList), (hwnd, pszClassList))
	SOFT_LINK(uxtheme, CloseThemeData, HRESULT, WINAPI, (HANDLE hTheme), (hTheme))
	SOFT_LINK(uxtheme, DrawThemeBackground, HRESULT, WINAPI, (HANDLE hTheme, HDC hdc, int iPartId, int iStateId, const RECT* pRect, const RECT* pClipRect), (hTheme, hdc, iPartId, iStateId, pRect, pClipRect))
	SOFT_LINK(uxtheme, IsThemeActive, BOOL, WINAPI, (), ())
	SOFT_LINK(uxtheme, IsThemeBackgroundPartiallyTransparent, BOOL, WINAPI, (HANDLE hTheme, int iPartId, int iStateId), (hTheme, iPartId, iStateId))

	// Constants used to figure the drag rect outside which we should snap the
	// scrollbar thumb back to its origin. These calculations are based on
	// observing the behavior of the MSVC8 main window scrollbar + some
	// guessing/extrapolation.
	static const int kOffEndMultiplier = 3;
	static const int kOffSideMultiplier = 8;

	static void checkAndInitScrollbarTheme()
	{
	if (uxthemeLibrary() && !scrollbarTheme && IsThemeActive())
	scrollbarTheme = OpenThemeData(0, L"Scrollbar");
	}

	ScrollbarTheme& ScrollbarTheme::nativeTheme()
	{
	static ScrollbarThemeWin winTheme;
	return winTheme;
	}

	ScrollbarThemeWin::ScrollbarThemeWin()
	{
	static bool initialized;
	if (!initialized) {
	initialized = true;
	checkAndInitScrollbarTheme();
	runningVista = (windowsVersion() >= WindowsVista);
	}
	}

	ScrollbarThemeWin::~ScrollbarThemeWin() = default;

	static int scrollbarThicknessInPixels()
	{
	static int thickness = ::GetSystemMetrics(SM_CXVSCROLL);
	return thickness;
	}

	int ScrollbarThemeWin::scrollbarThickness(ScrollbarControlSize, ScrollbarExpansionState)
	{
	float inverseScaleFactor = 1.0f / deviceScaleFactorForWindow(0);
	return clampTo<int>(inverseScaleFactor * scrollbarThicknessInPixels());
	}

	void ScrollbarThemeWin::themeChanged()
	{
	if (!scrollbarTheme)
	return;

	CloseThemeData(scrollbarTheme);
	scrollbarTheme = 0;
	}

	bool ScrollbarThemeWin::invalidateOnMouseEnterExit()
	{
	return runningVista;
	}

	bool ScrollbarThemeWin::hasThumb(Scrollbar& scrollbar)
	{
	return thumbLength(scrollbar) > 0;
	}

	IntRect ScrollbarThemeWin::backButtonRect(Scrollbar& scrollbar, ScrollbarPart part, bool)
	{
	// Windows just has single arrows.
	if (part == BackButtonEndPart)
	return IntRect();

	// Our desired rect is essentially 17x17.

	// Our actual rect will shrink to half the available space when
	// we have < 34 pixels left. This allows the scrollbar
	// to scale down and function even at tiny sizes.
	int thickness = scrollbarThickness();
	if (scrollbar.orientation() == HorizontalScrollbar)
	return IntRect(scrollbar.x(), scrollbar.y(),
	scrollbar.width() < 2 * thickness ? scrollbar.width() / 2 : thickness, thickness);
	return IntRect(scrollbar.x(), scrollbar.y(),
	thickness, scrollbar.height() < 2 * thickness ? scrollbar.height() / 2 : thickness);
	}

	IntRect ScrollbarThemeWin::forwardButtonRect(Scrollbar& scrollbar, ScrollbarPart part, bool)
	{
	// Windows just has single arrows.
	if (part == ForwardButtonStartPart)
	return IntRect();

	// Our desired rect is essentially 17x17.

	// Our actual rect will shrink to half the available space when
	// we have < 34 pixels left. This allows the scrollbar
	// to scale down and function even at tiny sizes.
	int thickness = scrollbarThickness();
	if (scrollbar.orientation() == HorizontalScrollbar) {
	int w = scrollbar.width() < 2 * thickness ? scrollbar.width() / 2 : thickness;
	return IntRect(scrollbar.x() + scrollbar.width() - w, scrollbar.y(), w, thickness);
	}

	int h = scrollbar.height() < 2 * thickness ? scrollbar.height() / 2 : thickness;
	return IntRect(scrollbar.x(), scrollbar.y() + scrollbar.height() - h, thickness, h);
	}

	IntRect ScrollbarThemeWin::trackRect(Scrollbar& scrollbar, bool)
	{
	int thickness = scrollbarThickness();
	if (scrollbar.orientation() == HorizontalScrollbar) {
	if (scrollbar.width() < 2 * thickness)
	return IntRect();
	return IntRect(scrollbar.x() + thickness, scrollbar.y(), scrollbar.width() - 2 * thickness, thickness);
	}
	if (scrollbar.height() < 2 * thickness)
	return IntRect();
	return IntRect(scrollbar.x(), scrollbar.y() + thickness, thickness, scrollbar.height() - 2 * thickness);
	}

	ScrollbarButtonPressAction ScrollbarThemeWin::handleMousePressEvent(Scrollbar&, const PlatformMouseEvent& event, ScrollbarPart pressedPart)
	{
	if (event.button() == RightButton)
	return ScrollbarButtonPressAction::None;

	switch (pressedPart) {
	case BackTrackPart:
	case ForwardTrackPart:
	if (event.shiftKey() && event.button() == LeftButton)
	return ScrollbarButtonPressAction::CenterOnThumb;
	break;
	case ThumbPart:
	return ScrollbarButtonPressAction::StartDrag;
	default:
	break;
	}

	return ScrollbarButtonPressAction::Scroll;
	}

	bool ScrollbarThemeWin::shouldSnapBackToDragOrigin(Scrollbar& scrollbar, const PlatformMouseEvent& evt)
	{
	// Find the rect within which we shouldn't snap, by expanding the track rect
	// in both dimensions.
	IntRect rect = trackRect(scrollbar);
	const bool horz = scrollbar.orientation() == HorizontalScrollbar;
	const int thickness = scrollbarThickness(scrollbar.controlSize());
	rect.inflateX((horz ? kOffEndMultiplier : kOffSideMultiplier) * thickness);
	rect.inflateY((horz ? kOffSideMultiplier : kOffEndMultiplier) * thickness);

	// Convert the event to local coordinates.
	IntPoint mousePosition = scrollbar.convertFromContainingWindow(evt.position());
	mousePosition.move(scrollbar.x(), scrollbar.y());

	// We should snap iff the event is outside our calculated rect.
	return !rect.contains(mousePosition);
	}

	void ScrollbarThemeWin::paintTrackBackground(GraphicsContext& context, Scrollbar& scrollbar, const IntRect& rect)
	{
	// Just assume a forward track part. We only paint the track as a single piece when there is no thumb.
	if (!hasThumb(scrollbar))
	paintTrackPiece(context, scrollbar, rect, ForwardTrackPart);
	}

	void ScrollbarThemeWin::paintTrackPiece(GraphicsContext& context, Scrollbar& scrollbar, const IntRect& rect, ScrollbarPart partType)
	{
	checkAndInitScrollbarTheme();

	bool start = partType == BackTrackPart;
	int part;
	if (scrollbar.orientation() == HorizontalScrollbar)
	part = start ? SP_TRACKSTARTHOR : SP_TRACKENDHOR;
	else
	part = start ? SP_TRACKSTARTVERT : SP_TRACKENDVERT;

	int state;
	if (!scrollbar.enabled())
	state = TS_DISABLED;
	else if ((scrollbar.hoveredPart() == BackTrackPart && start) \|\|
	(scrollbar.hoveredPart() == ForwardTrackPart && !start))
	state = (scrollbar.pressedPart() == scrollbar.hoveredPart() ? TS_ACTIVE : TS_HOVER);
	else
	state = TS_NORMAL;

	bool alphaBlend = false;
	if (scrollbarTheme)
	alphaBlend = IsThemeBackgroundPartiallyTransparent(scrollbarTheme, part, state);

	LocalWindowsContext windowsContext(context, rect, alphaBlend);
	RECT themeRect(rect);

	if (scrollbarTheme)
	DrawThemeBackground(scrollbarTheme, windowsContext.hdc(), part, state, &themeRect, 0);
	else {
	DWORD color3DFace = ::GetSysColor(COLOR_3DFACE);
	DWORD colorScrollbar = ::GetSysColor(COLOR_SCROLLBAR);
	DWORD colorWindow = ::GetSysColor(COLOR_WINDOW);
	HDC hdc = windowsContext.hdc();
	if ((color3DFace != colorScrollbar) && (colorWindow != colorScrollbar))
	::FillRect(hdc, &themeRect, HBRUSH(COLOR_SCROLLBAR+1));
	else {
	static WORD patternBits[8] = { 0xaa, 0x55, 0xaa, 0x55, 0xaa, 0x55, 0xaa, 0x55 };
	auto patternBitmap = adoptGDIObject(::CreateBitmap(8, 8, 1, 1, patternBits));
	auto brush = adoptGDIObject(::CreatePatternBrush(patternBitmap.get()));
	SaveDC(hdc);
	::SetTextColor(hdc, ::GetSysColor(COLOR_3DHILIGHT));
	::SetBkColor(hdc, ::GetSysColor(COLOR_3DFACE));
	::SetBrushOrgEx(hdc, rect.x(), rect.y(), NULL);
	::SelectObject(hdc, brush.get());
	::FillRect(hdc, &themeRect, brush.get());
	::RestoreDC(hdc, -1);
	}
	}

	if (!alphaBlend && !context.isInTransparencyLayer())
	DIBPixelData::setRGBABitmapAlpha(windowsContext.hdc(), rect, 255);
	}

	void ScrollbarThemeWin::paintButton(GraphicsContext& context, Scrollbar& scrollbar, const IntRect& rect, ScrollbarPart part)
	{
	checkAndInitScrollbarTheme();

	bool start = (part == BackButtonStartPart);
	int xpState = 0;
	int classicState = 0;
	if (scrollbar.orientation() == HorizontalScrollbar)
	xpState = start ? TS_LEFT_BUTTON : TS_RIGHT_BUTTON;
	else
	xpState = start ? TS_UP_BUTTON : TS_DOWN_BUTTON;
	classicState = xpState / 4;

	if (!scrollbar.enabled()) {
	xpState += TS_DISABLED;
	classicState \|= DFCS_INACTIVE;
	} else if ((scrollbar.hoveredPart() == BackButtonStartPart && start) \|\|
	(scrollbar.hoveredPart() == ForwardButtonEndPart && !start)) {
	if (scrollbar.pressedPart() == scrollbar.hoveredPart()) {
	xpState += TS_ACTIVE;
	classicState \|= DFCS_PUSHED;
	classicState \|= DFCS_FLAT;
	} else
	xpState += TS_HOVER;
	} else {
	if (scrollbar.hoveredPart() == NoPart \|\| !runningVista)
	xpState += TS_NORMAL;
	else {
	if (scrollbar.orientation() == HorizontalScrollbar)
	xpState = start ? TS_LEFT_BUTTON_HOVER : TS_RIGHT_BUTTON_HOVER;
	else
	xpState = start ? TS_UP_BUTTON_HOVER : TS_DOWN_BUTTON_HOVER;
	}
	}

	bool alphaBlend = false;
	if (scrollbarTheme)
	alphaBlend = IsThemeBackgroundPartiallyTransparent(scrollbarTheme, SP_BUTTON, xpState);

	// There seems to be a bug in DrawThemeBackground when the device context is scaled.
	// We can work around this by scaling the drawing rectangle instead.
	auto scaleFactor = context.scaleFactor().width();
	auto scaledRect = rect;
	scaledRect.scale(scaleFactor);
	context.save();
	context.scale(FloatSize(1.0f / scaleFactor, 1.0f / scaleFactor));

	{
	LocalWindowsContext windowsContext(context, scaledRect, alphaBlend);
	RECT themeRect(scaledRect);
	if (scrollbarTheme)
	DrawThemeBackground(scrollbarTheme, windowsContext.hdc(), SP_BUTTON, xpState, &themeRect, 0);
	else
	::DrawFrameControl(windowsContext.hdc(), &themeRect, DFC_SCROLL, classicState);

	if (!alphaBlend && !context.isInTransparencyLayer())
	DIBPixelData::setRGBABitmapAlpha(windowsContext.hdc(), scaledRect, 255);
	}
	context.restore();
	}

	static IntRect gripperRect(int thickness, const IntRect& thumbRect)
	{
	// Center in the thumb.
	int gripperThickness = thickness / 2;
	return IntRect(thumbRect.x() + (thumbRect.width() - gripperThickness) / 2,
	thumbRect.y() + (thumbRect.height() - gripperThickness) / 2,
	gripperThickness, gripperThickness);
	}

	static void paintGripper(Scrollbar& scrollbar, HDC hdc, const IntRect& rect)
	{
	if (!scrollbarTheme)
	return; // Classic look has no gripper.

	int state;
	if (!scrollbar.enabled())
	state = TS_DISABLED;
	else if (scrollbar.pressedPart() == ThumbPart)
	state = TS_ACTIVE; // Thumb always stays active once pressed.
	else if (scrollbar.hoveredPart() == ThumbPart)
	state = TS_HOVER;
	else
	state = TS_NORMAL;

	RECT themeRect(rect);
	DrawThemeBackground(scrollbarTheme, hdc, scrollbar.orientation() == HorizontalScrollbar ? SP_GRIPPERHOR : SP_GRIPPERVERT, state, &themeRect, 0);
	}

	void ScrollbarThemeWin::paintThumb(GraphicsContext& context, Scrollbar& scrollbar, const IntRect& rect)
	{
	checkAndInitScrollbarTheme();

	int state;
	if (!scrollbar.enabled())
	state = TS_DISABLED;
	else if (scrollbar.pressedPart() == ThumbPart)
	state = TS_ACTIVE; // Thumb always stays active once pressed.
	else if (scrollbar.hoveredPart() == ThumbPart)
	state = TS_HOVER;
	else
	state = TS_NORMAL;

	bool alphaBlend = false;
	if (scrollbarTheme)
	alphaBlend = IsThemeBackgroundPartiallyTransparent(scrollbarTheme, scrollbar.orientation() == HorizontalScrollbar ? SP_THUMBHOR : SP_THUMBVERT, state);
	LocalWindowsContext windowsContext(context, rect, alphaBlend);
	RECT themeRect(rect);
	if (scrollbarTheme) {
	DrawThemeBackground(scrollbarTheme, windowsContext.hdc(), scrollbar.orientation() == HorizontalScrollbar ? SP_THUMBHOR : SP_THUMBVERT, state, &themeRect, 0);
	paintGripper(scrollbar, windowsContext.hdc(), gripperRect(scrollbarThickness(), rect));
	} else
	::DrawEdge(windowsContext.hdc(), &themeRect, EDGE_RAISED, BF_RECT \| BF_MIDDLE);

	if (!alphaBlend && !context.isInTransparencyLayer())
	DIBPixelData::setRGBABitmapAlpha(windowsContext.hdc(), rect, 255);
	}

	}