Bug 1751010: Use a unique icon for the Private Browsing taskbar pin r=mhowell

This is subject to the same issue as an earlier patch in this series -- the icon will be wrong briefly at first launch, before the code in `BrowserContentHandler.jsm` replaces the default icon with the correct one.

Differential Revision: https://phabricator.services.mozilla.com/D138601

browser/components/BrowserContentHandler.jsm

@@ -41,6 +41,9 @@ XPCOMUtils.defineLazyGlobalGetters(this, [URL]);
 const ONCE_DOMAINS = ["mozilla.org", "firefox.com"];
 const ONCE_PREF = "browser.startup.homepage_override.once";
 
+// Index of Private Browsing icon in firefox.exe
+// Must line up with the one in nsNativeAppSupportWin.h.
+const PRIVATE_BROWSING_ICON_INDEX = 5;
 const PRIVACY_SEGMENTATION_PREF = "browser.privacySegmentation.enabled";
 
 function shouldLoadURI(aURI) {
@@ -277,6 +280,13 @@ function openBrowserWindow(
           // This must stay pref'ed off until this is resolved.
           // https://bugzilla.mozilla.org/show_bug.cgi?id=1751010
           WinTaskbar.setGroupIdForWindow(win, WinTaskbar.defaultPrivateGroupId);
+          WindowsUIUtils.setWindowIconFromExe(
+            win,
+            Services.dirsvc.get("XREExeF", Ci.nsIFile).path,
+            // This corresponds to the definitions in
+            // nsNativeAppSupportWin.h
+            PRIVATE_BROWSING_ICON_INDEX
+          );
         }
       }
 

toolkit/xre/nsNativeAppSupportWin.h

@@ -17,6 +17,8 @@
 #define IDI_DOCUMENT 2
 #define IDI_NEWWINDOW 3
 #define IDI_NEWTAB 4
+// If IDI_PBMODE's index changes, PRIVATE_BROWSING_ICON_INDEX
+// in BrowserContentHandler.jsm must also be updated.
 #define IDI_PBMODE 5
 #ifndef IDI_APPLICATION
 #  define IDI_APPLICATION 32512

widget/nsIWindowsUIUtils.idl

@@ -17,6 +17,8 @@ interface nsIWindowsUIUtils : nsISupports
 
   void setWindowIcon(in mozIDOMWindowProxy aWindow, in imgIContainer aSmallIcon, in imgIContainer aLargeIcon);
 
+  void setWindowIconFromExe(in mozIDOMWindowProxy aWindow, in AString aExe, in unsigned short aIndex);
+
   void setWindowIconNoData(in mozIDOMWindowProxy aWindow);
 
   /**

widget/windows/WindowsUIUtils.cpp

@@ -198,6 +198,23 @@ WindowsUIUtils::SetWindowIcon(mozIDOMWindowProxy* aWindow,
   return NS_OK;
 }
 
+NS_IMETHODIMP
+WindowsUIUtils::SetWindowIconFromExe(mozIDOMWindowProxy* aWindow,
+                                     const nsAString& aExe, uint16_t aIndex) {
+  NS_ENSURE_ARG(aWindow);
+
+  nsCOMPtr<nsIWidget> widget =
+      nsGlobalWindowOuter::Cast(aWindow)->GetMainWidget();
+  nsWindow* window = static_cast<nsWindow*>(widget.get());
+
+  HICON icon = ::LoadIconW(::GetModuleHandleW(PromiseFlatString(aExe).get()),
+                           MAKEINTRESOURCEW(aIndex));
+  window->SetBigIcon(icon);
+  window->SetSmallIcon(icon);
+
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 WindowsUIUtils::SetWindowIconNoData(mozIDOMWindowProxy* aWindow) {
   NS_ENSURE_ARG(aWindow);

widget/windows/nsWindow.cpp

@@ -158,6 +158,7 @@
 #include "mozilla/StaticPrefs_dom.h"
 #include "mozilla/StaticPrefs_gfx.h"
 #include "mozilla/StaticPrefs_layout.h"
+#include "nsNativeAppSupportWin.h"
 
 #include "nsIGfxInfo.h"
 #include "nsUXThemeConstants.h"
@@ -994,6 +995,10 @@ nsresult nsWindow::Create(nsIWidget* aParent, nsNativeWidget aNativeParent,
         }
       }
     }
+    HICON icon =
+        ::LoadIconW(::GetModuleHandleW(nullptr), MAKEINTRESOURCEW(IDI_PBMODE));
+    SetBigIcon(icon);
+    SetSmallIcon(icon);
   }
 
   mDeviceNotifyHandle = InputDeviceUtils::RegisterNotification(mWnd);