Bug 946595 - High contrast themes on Windows 8 shouldn't be considered the default theme in CSS, r=jimm

widget/windows/nsLookAndFeel.cpp

@@ -369,11 +369,7 @@ nsLookAndFeel::GetIntImpl(IntID aID, int32_t &aResult)
         // High contrast is a misnomer under Win32 -- any theme can be used with it, 
         // e.g. normal contrast with large fonts, low contrast, etc.
         // The high contrast flag really means -- use this theme and don't override it.
-        HIGHCONTRAST contrastThemeInfo;
-        contrastThemeInfo.cbSize = sizeof(contrastThemeInfo);
-        ::SystemParametersInfo(SPI_GETHIGHCONTRAST, 0, &contrastThemeInfo, 0);
-
-        aResult = ((contrastThemeInfo.dwFlags & HCF_HIGHCONTRASTON) != 0);
+        aResult = nsUXThemeData::IsHighContrastOn();
         break;
     case eIntID_ScrollArrowStyle:
         aResult = eScrollArrowStyle_Single;

widget/windows/nsUXThemeData.cpp

@@ -253,6 +253,8 @@ nsUXThemeData::sThemeId = LookAndFeel::eWindowsTheme_Generic;
 
 bool
 nsUXThemeData::sIsDefaultWindowsTheme = false;
+bool
+nsUXThemeData::sIsHighContrastOn = false;
 
 // static
 LookAndFeel::WindowsTheme
@@ -267,6 +269,11 @@ bool nsUXThemeData::IsDefaultWindowTheme()
   return sIsDefaultWindowsTheme;
 }
 
+bool nsUXThemeData::IsHighContrastOn()
+{
+  return sIsHighContrastOn;
+}
+
 // static
 bool nsUXThemeData::CheckForCompositor(bool aUpdateCache)
 {
@@ -292,6 +299,14 @@ nsUXThemeData::UpdateNativeThemeInfo()
     return;
   }
 
+  HIGHCONTRAST highContrastInfo;
+  highContrastInfo.cbSize = sizeof(HIGHCONTRAST);
+  if (SystemParametersInfo(SPI_GETHIGHCONTRAST, 0, &highContrastInfo, 0)) {
+    sIsHighContrastOn = ((highContrastInfo.dwFlags & HCF_HIGHCONTRASTON) != 0);
+  } else {
+    sIsHighContrastOn = false;
+  }
+
   WCHAR themeFileName[MAX_PATH + 1];
   WCHAR themeColor[MAX_PATH + 1];
   if (FAILED(GetCurrentThemeName(themeFileName,
@@ -317,9 +332,16 @@ nsUXThemeData::UpdateNativeThemeInfo()
   if (theme == WINTHEME_UNRECOGNIZED)
     return;
 
-  if (theme == WINTHEME_AERO || theme == WINTHEME_AERO_LITE || theme == WINTHEME_LUNA)
+  // We're using the default theme if we're using any of Aero, Aero Lite, or
+  // luna. However, on Win8, GetCurrentThemeName (see above) returns
+  // AeroLite.msstyles for the 4 builtin highcontrast themes as well. Those
+  // themes "don't count" as default themes, so we specifically check for high
+  // contrast mode in that situation.
+  if (!(IsWin8OrLater() && sIsHighContrastOn) &&
+      (theme == WINTHEME_AERO || theme == WINTHEME_AERO_LITE || theme == WINTHEME_LUNA)) {
     sIsDefaultWindowsTheme = true;
-  
+  }
+
   if (theme != WINTHEME_LUNA) {
     switch(theme) {
       case WINTHEME_AERO:

widget/windows/nsUXThemeData.h

@@ -92,6 +92,7 @@ public:
   static SIZE sCommandButtons[4];
   static mozilla::LookAndFeel::WindowsTheme sThemeId;
   static bool sIsDefaultWindowsTheme;
+  static bool sIsHighContrastOn;
 
   static void Initialize();
   static void Teardown();
@@ -106,6 +107,7 @@ public:
   static void UpdateNativeThemeInfo();
   static mozilla::LookAndFeel::WindowsTheme GetNativeThemeId();
   static bool IsDefaultWindowTheme();
+  static bool IsHighContrastOn();
 
   // This method returns the cached compositor state. Most
   // callers should call without the argument. The cache