--- a/gfx/public/nsITheme.h
+++ b/gfx/public/nsITheme.h
@@ -54,18 +54,17 @@ class nsIRenderingContext;
 class nsIDeviceContext;
 class nsIFrame;
 class nsIContent;
 class nsIAtom;
 
 // IID for the nsITheme interface
 // {887e8902-db6b-41b4-8481-a80f49c5a93a}
  #define NS_ITHEME_IID     \
-{ 0x887e8902, 0xdb6b, 0x41b4, { 0x84, 0x81, 0xa8, 0x0f, 0x49, 0xc5, 0xa9, 0x3a } }
-
+{ 0x23db7c13, 0x873d, 0x4fb5, { 0xaf, 0x29, 0xc1, 0xe9, 0xed, 0x91, 0x23, 0xf9 } }
 // {D930E29B-6909-44e5-AB4B-AF10D6923705}
 #define NS_THEMERENDERER_CID \
 { 0xd930e29b, 0x6909, 0x44e5, { 0xab, 0x4b, 0xaf, 0x10, 0xd6, 0x92, 0x37, 0x5 } }
 
 enum nsTransparencyMode {
   eTransparencyOpaque = 0,  // Fully opaque
   eTransparencyTransparent, // Parts of the window may be transparent
   eTransparencyGlass        // Transparent parts of the window have Vista AeroGlass effect applied
@@ -134,17 +133,28 @@ public:
    * widget.
    */
   NS_IMETHOD GetMinimumWidgetSize(nsIRenderingContext* aContext,
                                   nsIFrame* aFrame,
                                   PRUint8 aWidgetType,
                                   nsIntSize* aResult,
                                   PRBool* aIsOverridable)=0;
 
-  virtual nsTransparencyMode GetWidgetTransparency(PRUint8 aWidgetType)=0;
+
+  enum Transparency {
+    eOpaque = 0,
+    eTransparent,
+    eUnknownTransparency
+  };
+
+  /**
+   * Returns what we know about the transparency of the widget.
+   */
+  virtual Transparency GetWidgetTransparency(nsIFrame* aFrame, PRUint8 aWidgetType)
+  { return eUnknownTransparency; }
 
   NS_IMETHOD WidgetStateChanged(nsIFrame* aFrame, PRUint8 aWidgetType, 
                                 nsIAtom* aAttribute, PRBool* aShouldRepaint)=0;
 
   NS_IMETHOD ThemeChanged()=0;
 
   /**
    * Can the nsITheme implementation handle this widget?

--- a/layout/base/nsDisplayList.cpp
+++ b/layout/base/nsDisplayList.cpp
@@ -670,17 +670,17 @@ static PRBool RoundedRectContainsRect(co
 
   return PR_FALSE;
 }
 
 PRBool
 nsDisplayBackground::IsOpaque(nsDisplayListBuilder* aBuilder) {
   // theme background overrides any other background
   if (mIsThemed)
-    return PR_FALSE;
+    return mThemeTransparency == nsITheme::eOpaque;
 
   nsStyleContext *bgSC;
   if (!nsCSSRendering::FindBackground(mFrame->PresContext(), mFrame, &bgSC))
     return PR_FALSE;
   const nsStyleBackground* bg = bgSC->GetStyleBackground();
 
   const nsStyleBackground::Layer& bottomLayer = bg->BottomLayer();
 

--- a/layout/base/nsDisplayList.h
+++ b/layout/base/nsDisplayList.h
@@ -1252,17 +1252,17 @@ private:
 };
 
 /**
  * The standard display item to paint the CSS background of a frame.
  */
 class nsDisplayBackground : public nsDisplayItem {
 public:
   nsDisplayBackground(nsIFrame* aFrame) : nsDisplayItem(aFrame) {
-    mIsThemed = mFrame->IsThemed();
+    mIsThemed = mFrame->IsThemed(&mThemeTransparency);
     MOZ_COUNT_CTOR(nsDisplayBackground);
   }
 #ifdef NS_BUILD_REFCNT_LOGGING
   virtual ~nsDisplayBackground() {
     MOZ_COUNT_DTOR(nsDisplayBackground);
   }
 #endif
 
@@ -1273,18 +1273,19 @@ public:
   }
   virtual PRBool IsOpaque(nsDisplayListBuilder* aBuilder);
   virtual PRBool IsVaryingRelativeToMovingFrame(nsDisplayListBuilder* aBuilder);
   virtual PRBool IsUniform(nsDisplayListBuilder* aBuilder, nscolor* aColor);
   virtual nsRect GetBounds(nsDisplayListBuilder* aBuilder);
   virtual void Paint(nsDisplayListBuilder* aBuilder, nsIRenderingContext* aCtx);
   NS_DISPLAY_DECL_NAME("Background")
 private:
-    /* Used to cache mFrame->IsThemed() since it isn't a cheap call */
-    PRPackedBool mIsThemed;
+  /* Used to cache mFrame->IsThemed() since it isn't a cheap call */
+  PRPackedBool mIsThemed;
+  nsITheme::Transparency mThemeTransparency;
 };
 
 /**
  * The standard display item to paint the outer CSS box-shadows of a frame.
  */
 class nsDisplayBoxShadowOuter : public nsDisplayItem {
 public:
   nsDisplayBoxShadowOuter(nsIFrame* aFrame) : nsDisplayItem(aFrame) {

--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -3211,19 +3211,21 @@ nsLayoutUtils::HasNonZeroCornerOnSide(co
 nsLayoutUtils::GetFrameTransparency(nsIFrame* aBackgroundFrame,
                                     nsIFrame* aCSSRootFrame) {
   if (aCSSRootFrame->GetStyleContext()->GetStyleDisplay()->mOpacity < 1.0f)
     return eTransparencyTransparent;
 
   if (HasNonZeroCorner(aCSSRootFrame->GetStyleContext()->GetStyleBorder()->mBorderRadius))
     return eTransparencyTransparent;
 
-  nsTransparencyMode transparency;
+  nsITheme::Transparency transparency;
   if (aCSSRootFrame->IsThemed(&transparency))
-    return transparency;
+    return transparency == nsITheme::eTransparent
+         ? eTransparencyTransparent
+         : eTransparencyOpaque;
 
   if (aCSSRootFrame->GetStyleDisplay()->mAppearance == NS_THEME_WIN_GLASS)
     return eTransparencyGlass;
 
   // We need an uninitialized window to be treated as opaque because
   // doing otherwise breaks window display effects on some platforms,
   // specifically Vista. (bug 450322)
   if (aBackgroundFrame->GetType() == nsGkAtoms::viewportFrame &&

--- a/layout/generic/nsIFrame.h
+++ b/layout/generic/nsIFrame.h
@@ -992,29 +992,30 @@ public:
 
   /**
    * Get the preferred caret color at the offset.
    *
    * @param aOffset is offset of the content.
    */
   virtual nscolor GetCaretColorAt(PRInt32 aOffset);
 
-  PRBool IsThemed(nsTransparencyMode* aTransparencyMode = nsnull) {
-    return IsThemed(GetStyleDisplay(), aTransparencyMode);
+ 
+  PRBool IsThemed(nsITheme::Transparency* aTransparencyState = nsnull) {
+    return IsThemed(GetStyleDisplay(), aTransparencyState);
   }
   PRBool IsThemed(const nsStyleDisplay* aDisp,
-                  nsTransparencyMode* aTransparencyMode = nsnull) {
+                  nsITheme::Transparency* aTransparencyState = nsnull) {
     if (!aDisp->mAppearance)
       return PR_FALSE;
     nsPresContext* pc = PresContext();
     nsITheme *theme = pc->GetTheme();
     if(!theme || !theme->ThemeSupportsWidget(pc, this, aDisp->mAppearance))
       return PR_FALSE;
-    if (aTransparencyMode) {
-      *aTransparencyMode = theme->GetWidgetTransparency(aDisp->mAppearance);
+    if (aTransparencyState) {
+      *aTransparencyState = theme->GetWidgetTransparency(this, aDisp->mAppearance);
     }
     return PR_TRUE;
   }
   
   /**
    * Builds a display list for the content represented by this frame,
    * treating this frame as the root of a stacking context.
    * @param aDirtyRect content outside this rectangle can be ignored; the

--- a/widget/src/cocoa/nsNativeThemeCocoa.h
+++ b/widget/src/cocoa/nsNativeThemeCocoa.h
@@ -85,17 +85,17 @@ public:
                                   nsIntSize* aResult, PRBool* aIsOverridable);
   NS_IMETHOD WidgetStateChanged(nsIFrame* aFrame, PRUint8 aWidgetType, 
                                 nsIAtom* aAttribute, PRBool* aShouldRepaint);
   NS_IMETHOD ThemeChanged();
   PRBool ThemeSupportsWidget(nsPresContext* aPresContext, nsIFrame* aFrame, PRUint8 aWidgetType);
   PRBool WidgetIsContainer(PRUint8 aWidgetType);
   PRBool ThemeDrawsFocusForWidget(nsPresContext* aPresContext, nsIFrame* aFrame, PRUint8 aWidgetType);
   PRBool ThemeNeedsComboboxDropmarker();
-  virtual nsTransparencyMode GetWidgetTransparency(PRUint8 aWidgetType);
+  virtual Transparency GetWidgetTransparency(nsIFrame* aFrame, PRUint8 aWidgetType);
 
 protected:  
 
   nsresult GetSystemColor(PRUint8 aWidgetType, nsILookAndFeel::nsColorID& aColorID);
   nsresult GetSystemFont(PRUint8 aWidgetType, nsSystemFontID& aFont);
   nsIntMargin RTLAwareMargin(const nsIntMargin& aMargin, nsIFrame* aFrame);
 
   // HITheme drawing routines

--- a/widget/src/cocoa/nsNativeThemeCocoa.mm
+++ b/widget/src/cocoa/nsNativeThemeCocoa.mm
@@ -2475,17 +2475,17 @@ nsNativeThemeCocoa::ThemeDrawsFocusForWi
 }
 
 PRBool
 nsNativeThemeCocoa::ThemeNeedsComboboxDropmarker()
 {
   return PR_FALSE;
 }
 
-nsTransparencyMode
-nsNativeThemeCocoa::GetWidgetTransparency(PRUint8 aWidgetType)
+nsITheme::Transparency
+nsNativeThemeCocoa::GetWidgetTransparency(nsIFrame* aFrame, PRUint8 aWidgetType)
 {
   if (aWidgetType == NS_THEME_MENUPOPUP ||
       aWidgetType == NS_THEME_TOOLTIP)
-    return eTransparencyTransparent;
+    return eTransparent;
 
-  return eTransparencyOpaque;
+  return eUnknownTransparency;
 }

--- a/widget/src/gtk2/nsNativeThemeGTK.cpp
+++ b/widget/src/gtk2/nsNativeThemeGTK.cpp
@@ -1337,14 +1337,8 @@ nsNativeThemeGTK::ThemeDrawsFocusForWidg
   return PR_FALSE;
 }
 
 PRBool
 nsNativeThemeGTK::ThemeNeedsComboboxDropmarker()
 {
   return PR_FALSE;
 }
-
-nsTransparencyMode
-nsNativeThemeGTK::GetWidgetTransparency(PRUint8 aWidgetType)
-{
-  return eTransparencyOpaque;
-}

--- a/widget/src/gtk2/nsNativeThemeGTK.h
+++ b/widget/src/gtk2/nsNativeThemeGTK.h
@@ -87,18 +87,16 @@ public:
 
   NS_IMETHOD_(PRBool) WidgetIsContainer(PRUint8 aWidgetType);
   
   NS_IMETHOD_(PRBool) ThemeDrawsFocusForWidget(nsPresContext* aPresContext,
                                                nsIFrame* aFrame, PRUint8 aWidgetType);
 
   PRBool ThemeNeedsComboboxDropmarker();
 
-  virtual nsTransparencyMode GetWidgetTransparency(PRUint8 aWidgetType);
-
   nsNativeThemeGTK();
   virtual ~nsNativeThemeGTK();
 
 private:
   PRBool GetGtkWidgetAndState(PRUint8 aWidgetType, nsIFrame* aFrame,
                               GtkThemeWidgetType& aGtkWidgetType,
                               GtkWidgetState* aState, gint* aWidgetFlags);
 

--- a/widget/src/qt/nsNativeThemeQt.cpp
+++ b/widget/src/qt/nsNativeThemeQt.cpp
@@ -622,22 +622,16 @@ nsNativeThemeQt::ThemeDrawsFocusForWidge
 }
 
 PRBool
 nsNativeThemeQt::ThemeNeedsComboboxDropmarker()
 {
     return PR_TRUE;
 }
 
-nsTransparencyMode
-nsNativeThemeQt::GetWidgetTransparency(PRUint8 aWidgetType)
-{
-  return eTransparencyOpaque;
-}
-
 void
 nsNativeThemeQt::InitButtonStyle(PRUint8 aWidgetType,
                                  nsIFrame* aFrame,
                                  QRect rect,
                                  QStyleOptionButton &opt)
 {
     PRInt32 eventState = GetContentState(aFrame, aWidgetType);
 

--- a/widget/src/qt/nsNativeThemeQt.h
+++ b/widget/src/qt/nsNativeThemeQt.h
@@ -94,18 +94,16 @@ public:
                                               PRUint8 aWidgetType,
                                               nsIntMargin* aResult);
 
   NS_IMETHOD_(PRBool) ThemeDrawsFocusForWidget(nsPresContext* aPresContext,
                                                nsIFrame* aFrame, PRUint8 aWidgetType);
 
   PRBool ThemeNeedsComboboxDropmarker();
 
-  virtual nsTransparencyMode GetWidgetTransparency(PRUint8 aWidgetType);
-
   nsNativeThemeQt();
   virtual ~nsNativeThemeQt();
 
 private:
 
   inline nsresult DrawWidgetBackground(QPainter *qPainter,
                                        nsIRenderingContext* aContext,
                                        nsIFrame* aFrame,

--- a/widget/src/windows/nsNativeThemeWin.cpp
+++ b/widget/src/windows/nsNativeThemeWin.cpp
@@ -392,16 +392,23 @@ nsNativeThemeWin::IsMenuActive(nsIFrame 
   nsIContent* content = aFrame->GetContent();
   if (content->IsXUL() &&
       content->NodeInfo()->Equals(nsWidgetAtoms::richlistitem))
     return CheckBooleanAttr(aFrame, nsWidgetAtoms::selected);
 
   return CheckBooleanAttr(aFrame, nsWidgetAtoms::mozmenuactive);
 }
 
+/**
+ * aPart is filled in with the UXTheme part code. On return, values > 0
+ * are the actual UXTheme part code; -1 means the widget will be drawn by
+ * us; 0 means that we should use part code 0, which isn't a real part code
+ * but elicits some kind of default behaviour from UXTheme when drawing
+ * (but isThemeBackgroundPartiallyTransparent may not work).
+ */
 nsresult 
 nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType, 
                                        PRInt32& aPart, PRInt32& aState)
 {
   if (!nsUXThemeData::sIsVistaOrLater) {
     // See GetTheme
     if (aWidgetType == NS_THEME_DROPDOWN)
       aWidgetType = NS_THEME_TEXTFIELD;
@@ -1771,20 +1778,38 @@ nsNativeThemeWin::ThemeDrawsFocusForWidg
 }
 
 PRBool
 nsNativeThemeWin::ThemeNeedsComboboxDropmarker()
 {
   return PR_TRUE;
 }
 
-nsTransparencyMode
-nsNativeThemeWin::GetWidgetTransparency(PRUint8 aWidgetType)
+nsITheme::Transparency
+nsNativeThemeWin::GetWidgetTransparency(nsIFrame* aFrame, PRUint8 aWidgetType)
 {
-  return eTransparencyOpaque;
+  HANDLE theme = GetTheme(aWidgetType);
+  // For the classic theme we don't really have a way of knowing
+  if (!theme)
+    return eUnknownTransparency;
+
+  PRInt32 part, state;
+  nsresult rv = GetThemePartAndState(aFrame, aWidgetType, part, state);
+  // Fail conservatively
+  NS_ENSURE_SUCCESS(rv, eUnknownTransparency);
+
+  if (part <= 0) {
+    // Not a real part code, so isThemeBackgroundPartiallyTransparent may
+    // not work, so don't call it.
+    return eUnknownTransparency;
+  }
+
+  if (nsUXThemeData::isThemeBackgroundPartiallyTransparent(theme, part, state))
+    return eTransparent;
+  return eOpaque;
 }
 
 /* Windows 9x/NT/2000/Classic XP Theme Support */
 
 PRBool 
 nsNativeThemeWin::ClassicThemeSupportsWidget(nsPresContext* aPresContext,
                                       nsIFrame* aFrame,
                                       PRUint8 aWidgetType)

--- a/widget/src/windows/nsNativeThemeWin.h
+++ b/widget/src/windows/nsNativeThemeWin.h
@@ -73,17 +73,17 @@ public:
                                    PRUint8 aWidgetType,
                                    nsRect* aOverflowRect);
 
   NS_IMETHOD GetMinimumWidgetSize(nsIRenderingContext* aContext, nsIFrame* aFrame,
                                   PRUint8 aWidgetType,
                                   nsIntSize* aResult,
                                   PRBool* aIsOverridable);
 
-  virtual nsTransparencyMode GetWidgetTransparency(PRUint8 aWidgetType);
+  virtual Transparency GetWidgetTransparency(nsIFrame* aFrame, PRUint8 aWidgetType);
 
   NS_IMETHOD WidgetStateChanged(nsIFrame* aFrame, PRUint8 aWidgetType, 
                                 nsIAtom* aAttribute, PRBool* aShouldRepaint);
 
   NS_IMETHOD ThemeChanged();
 
   PRBool ThemeSupportsWidget(nsPresContext* aPresContext, 
                              nsIFrame* aFrame,

--- a/widget/src/windows/nsUXThemeData.cpp
+++ b/widget/src/windows/nsUXThemeData.cpp
@@ -78,16 +78,17 @@ nsUXThemeData::GetThemeContentRectPtr ns
 nsUXThemeData::GetThemeBackgroundRegionPtr nsUXThemeData::getThemeBackgroundRegion = NULL;
 nsUXThemeData::GetThemePartSizePtr nsUXThemeData::getThemePartSize = NULL;
 nsUXThemeData::GetThemeSysFontPtr nsUXThemeData::getThemeSysFont = NULL;
 nsUXThemeData::GetThemeColorPtr nsUXThemeData::getThemeColor = NULL;
 nsUXThemeData::GetThemeMarginsPtr nsUXThemeData::getThemeMargins = NULL;
 nsUXThemeData::IsAppThemedPtr nsUXThemeData::isAppThemed = NULL;
 nsUXThemeData::GetCurrentThemeNamePtr nsUXThemeData::getCurrentThemeName = NULL;
 nsUXThemeData::GetThemeSysColorPtr nsUXThemeData::getThemeSysColor = NULL;
+nsUXThemeData::IsThemeBackgroundPartiallyTransparentPtr nsUXThemeData::isThemeBackgroundPartiallyTransparent = NULL;
 
 #if MOZ_WINSDK_TARGETVER >= MOZ_NTDDI_LONGHORN
 nsUXThemeData::DwmExtendFrameIntoClientAreaProc nsUXThemeData::dwmExtendFrameIntoClientAreaPtr = NULL;
 nsUXThemeData::DwmIsCompositionEnabledProc nsUXThemeData::dwmIsCompositionEnabledPtr = NULL;
 nsUXThemeData::DwmSetIconicThumbnailProc nsUXThemeData::dwmSetIconicThumbnailPtr = NULL;
 nsUXThemeData::DwmSetIconicLivePreviewBitmapProc nsUXThemeData::dwmSetIconicLivePreviewBitmapPtr = NULL;
 nsUXThemeData::DwmSetWindowAttributeProc nsUXThemeData::dwmSetWindowAttributePtr = NULL;
 nsUXThemeData::DwmInvalidateIconicBitmapsProc nsUXThemeData::dwmInvalidateIconicBitmapsPtr = NULL;
@@ -119,16 +120,17 @@ nsUXThemeData::Initialize()
     getThemeBackgroundRegion = (GetThemeBackgroundRegionPtr)GetProcAddress(sThemeDLL, "GetThemeBackgroundRegion");
     getThemePartSize = (GetThemePartSizePtr)GetProcAddress(sThemeDLL, "GetThemePartSize");
     getThemeSysFont = (GetThemeSysFontPtr)GetProcAddress(sThemeDLL, "GetThemeSysFont");
     getThemeColor = (GetThemeColorPtr)GetProcAddress(sThemeDLL, "GetThemeColor");
     getThemeMargins = (GetThemeMarginsPtr)GetProcAddress(sThemeDLL, "GetThemeMargins");
     isAppThemed = (IsAppThemedPtr)GetProcAddress(sThemeDLL, "IsAppThemed");
     getCurrentThemeName = (GetCurrentThemeNamePtr)GetProcAddress(sThemeDLL, "GetCurrentThemeName");
     getThemeSysColor = (GetThemeSysColorPtr)GetProcAddress(sThemeDLL, "GetThemeSysColor");
+    isThemeBackgroundPartiallyTransparent = (IsThemeBackgroundPartiallyTransparentPtr)GetProcAddress(sThemeDLL, "IsThemeBackgroundPartiallyTransparent");
   }
 #if MOZ_WINSDK_TARGETVER >= MOZ_NTDDI_LONGHORN
    sDwmDLL = ::LoadLibraryW(kDwmLibraryName);
    if(sDwmDLL) {
      dwmExtendFrameIntoClientAreaPtr = (DwmExtendFrameIntoClientAreaProc)::GetProcAddress(sDwmDLL, "DwmExtendFrameIntoClientArea");
      dwmIsCompositionEnabledPtr = (DwmIsCompositionEnabledProc)::GetProcAddress(sDwmDLL, "DwmIsCompositionEnabled");
      dwmSetIconicThumbnailPtr = (DwmSetIconicThumbnailProc)::GetProcAddress(sDwmDLL, "DwmSetIconicThumbnail");
      dwmSetIconicLivePreviewBitmapPtr = (DwmSetIconicLivePreviewBitmapProc)::GetProcAddress(sDwmDLL, "DwmSetIconicLivePreviewBitmap");

--- a/widget/src/windows/nsUXThemeData.h
+++ b/widget/src/windows/nsUXThemeData.h
@@ -148,30 +148,32 @@ public:
   typedef HRESULT (WINAPI*GetThemeMarginsPtr)(HANDLE hTheme, HDC hdc, int iPartId,
                                            int iStateid, int iPropId,
                                            LPRECT prc, MARGINS *pMargins);
   typedef BOOL (WINAPI*IsAppThemedPtr)(VOID);
   typedef HRESULT (WINAPI*GetCurrentThemeNamePtr)(LPWSTR pszThemeFileName, int dwMaxNameChars,
                                                   LPWSTR pszColorBuff, int cchMaxColorChars,
                                                   LPWSTR pszSizeBuff, int cchMaxSizeChars);
   typedef COLORREF (WINAPI*GetThemeSysColorPtr)(HANDLE hTheme, int iColorID);
+  typedef BOOL (WINAPI*IsThemeBackgroundPartiallyTransparentPtr)(HANDLE hTheme, int iPartId, int iStateId);
 
   static OpenThemeDataPtr openTheme;
   static CloseThemeDataPtr closeTheme;
   static DrawThemeBackgroundPtr drawThemeBG;
   static DrawThemeEdgePtr drawThemeEdge;
   static GetThemeContentRectPtr getThemeContentRect;
   static GetThemeBackgroundRegionPtr getThemeBackgroundRegion;
   static GetThemePartSizePtr getThemePartSize;
   static GetThemeSysFontPtr getThemeSysFont;
   static GetThemeColorPtr getThemeColor;
   static GetThemeMarginsPtr getThemeMargins;
   static IsAppThemedPtr isAppThemed;
   static GetCurrentThemeNamePtr getCurrentThemeName;
   static GetThemeSysColorPtr getThemeSysColor;
+  static IsThemeBackgroundPartiallyTransparentPtr isThemeBackgroundPartiallyTransparent;
 
 #if MOZ_WINSDK_TARGETVER >= MOZ_NTDDI_LONGHORN
   // dwmapi.dll function typedefs and declarations
   typedef HRESULT (WINAPI*DwmExtendFrameIntoClientAreaProc)(HWND hWnd, const MARGINS *pMarInset);
   typedef HRESULT (WINAPI*DwmIsCompositionEnabledProc)(BOOL *pfEnabled);
   typedef HRESULT (WINAPI*DwmSetIconicThumbnailProc)(HWND hWnd, HBITMAP hBitmap, DWORD dwSITFlags);
   typedef HRESULT (WINAPI*DwmSetIconicLivePreviewBitmapProc)(HWND hWnd, HBITMAP hBitmap, POINT *pptClient, DWORD dwSITFlags);
   typedef HRESULT (WINAPI*DwmSetWindowAttributeProc)(HWND hWnd, DWORD dwAttribute, LPCVOID pvAttribute, DWORD cbAttribute);