Add a '-moz-win-accentcolor' color keyword to expose the Win10 accent color.

layout/style/nsCSSKeywordList.h

@@ -685,6 +685,7 @@ CSS_KEY(button-focus, button_focus)
 CSS_KEY(-moz-win-media-toolbox, _moz_win_media_toolbox)
 CSS_KEY(-moz-win-communications-toolbox, _moz_win_communications_toolbox)
 CSS_KEY(-moz-win-browsertabbar-toolbox, _moz_win_browsertabbar_toolbox)
+CSS_KEY(-moz-win-accentcolor, _moz_win_accentcolor)
 CSS_KEY(-moz-win-mediatext, _moz_win_mediatext)
 CSS_KEY(-moz-win-communicationstext, _moz_win_communicationstext)
 CSS_KEY(-moz-win-glass, _moz_win_glass)

layout/style/nsCSSProps.cpp

@@ -971,6 +971,7 @@ const KTableValue nsCSSProps::kColorKTable[] = {
   eCSSKeyword__moz_oddtreerow, LookAndFeel::eColorID__moz_oddtreerow,
   eCSSKeyword__moz_visitedhyperlinktext, NS_COLOR_MOZ_VISITEDHYPERLINKTEXT,
   eCSSKeyword_currentcolor, NS_COLOR_CURRENTCOLOR,
+  eCSSKeyword__moz_win_accentcolor, LookAndFeel::eColorID__moz_win_accentcolor,
   eCSSKeyword__moz_win_mediatext, LookAndFeel::eColorID__moz_win_mediatext,
   eCSSKeyword__moz_win_communicationstext, LookAndFeel::eColorID__moz_win_communicationstext,
   eCSSKeyword__moz_nativehyperlinktext, LookAndFeel::eColorID__moz_nativehyperlinktext,

widget/LookAndFeel.h

@@ -151,6 +151,8 @@ public:
 
     // vista rebars
 
+    // accent color for title bar
+    eColorID__moz_win_accentcolor,
     // media rebar text
     eColorID__moz_win_mediatext,
     // communications rebar text

widget/nsXPLookAndFeel.cpp

@@ -226,6 +226,7 @@ const char nsXPLookAndFeel::sColorPrefs[][38] =
   "ui.-moz-mac-menutextselect",
   "ui.-moz_mac_disabledtoolbartext",
   "ui.-moz-mac-secondaryhighlight",
+  "ui.-moz-win-accentcolor",
   "ui.-moz-win-mediatext",
   "ui.-moz-win-communicationstext",
   "ui.-moz-nativehyperlinktext",

widget/windows/nsLookAndFeel.cpp

@@ -277,6 +277,16 @@ nsLookAndFeel::NativeGetColor(ColorID aID, nscolor &aColor)
     case eColorID__moz_cellhighlight:
       idx = COLOR_3DFACE;
       break;
+    case eColorID__moz_win_accentcolor:
+      res = GetAccentColor(aColor);
+      if (NS_SUCCEEDED(res)) {
+        return res;
+      }
+      NS_WARNING("Using fallback for accent color - UI code failed to use the "
+                 "-moz-windows-accent-color-applies media query properly");
+      // Seems to be the default color (hardcoded because of bug 1065998)
+      aColor = NS_RGB(158, 158, 158);
+      return NS_OK;
     case eColorID__moz_win_mediatext:
       if (IsVistaOrLater() && IsAppThemed()) {
         res = ::GetColorFromTheme(eUXMediaToolbar,
@@ -677,3 +687,43 @@ nsLookAndFeel::GetPasswordCharacterImpl()
 #define UNICODE_BLACK_CIRCLE_CHAR 0x25cf
   return UNICODE_BLACK_CIRCLE_CHAR;
 }
+
+/* static */ nsresult
+nsLookAndFeel::GetAccentColor(nscolor& aColor)
+{
+  nsresult rv;
+
+  if (!mDwmKey) {
+    mDwmKey = do_CreateInstance("@mozilla.org/windows-registry-key;1", &rv);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  rv = mDwmKey->Open(nsIWindowsRegKey::ROOT_KEY_CURRENT_USER,
+                     NS_LITERAL_STRING("SOFTWARE\\Microsoft\\Windows\\DWM"),
+                     nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  // The ColorPrevalence value is set to 1 when the "Show color on title bar"
+  // setting in the Color section of Window's Personalization settings is
+  // turned on.
+  uint32_t accentColor, colorPrevalence;
+  if (NS_SUCCEEDED(mDwmKey->ReadIntValue(NS_LITERAL_STRING("AccentColor"), &accentColor)) &&
+      NS_SUCCEEDED(mDwmKey->ReadIntValue(NS_LITERAL_STRING("ColorPrevalence"), &colorPrevalence)) &&
+      colorPrevalence == 1) {
+    // The order of the color components in the DWORD stored in the registry
+    // happens to be the same order as we store the components in nscolor
+    // so we can just assign directly here.
+    aColor = accentColor;
+    rv = NS_OK;
+  } else {
+    rv = NS_ERROR_NOT_AVAILABLE;
+  }
+
+  mDwmKey->Close();
+
+  return rv;
+}

widget/windows/nsLookAndFeel.h

@@ -5,7 +5,9 @@
 
 #ifndef __nsLookAndFeel
 #define __nsLookAndFeel
+
 #include "nsXPLookAndFeel.h"
+#include "nsIWindowsRegKey.h"
 
 /*
  * Gesture System Metrics
@@ -34,6 +36,15 @@ public:
                            gfxFontStyle& aFontStyle,
                            float aDevPixPerCSSPixel);
   virtual char16_t GetPasswordCharacterImpl();
+private:
+  /**
+   * Fetches the Windows accent color from the Windows settings if
+   * the accent color is set to apply to the title bar, otherwise
+   * returns an error code.
+   */
+  nsresult GetAccentColor(nscolor& aColor);
+  
+  nsCOMPtr<nsIWindowsRegKey> mDwmKey;
 };
 
 #endif

widget/windows/nsWindow.cpp

@@ -4630,6 +4630,19 @@ nsWindow::ProcessMessage(UINT msg, WPARAM& wParam, LPARAM& lParam,
     }
     break;
 
+    case WM_SETTINGCHANGE:
+    {
+      if (lParam) {
+        auto lParamString = reinterpret_cast<const wchar_t*>(lParam);
+        if (!wcscmp(lParamString, L"ImmersiveColorSet")) {
+          // WM_SYSCOLORCHANGE is not dispatched for accent color changes
+          OnSysColorChanged();
+          break;
+        }
+      }
+    }
+    break;
+
     case WM_NCCALCSIZE:
     {
       if (mCustomNonClient) {