Bug 1893918 - A not-yet-loaded browser window shouldn't stop being an early blank window. r=win-reviewers,rkraesig

Otherwise we start painting the window too early, which after
bug 1891063 causes the non-client area to be filled, but we don't paint
anything on top.

Differential Revision: https://phabricator.services.mozilla.com/D208898

widget/nsIWidget.h

@@ -1397,6 +1397,8 @@ class nsIWidget : public nsISupports {
                               const nsAString& xulWinClass,
                               const nsAString& xulWinName) = 0;
 
+  virtual void SetIsEarlyBlankWindow(bool) {}
+
   /**
    * Enables/Disables system capture of any and all events that would cause a
    * popup to be rolled up. aListener should be set to a non-null value for

widget/windows/nsWindow.cpp

@@ -3951,10 +3951,8 @@ uint32_t nsWindow::GetMaxTouchPoints() const {
   return WinUtils::GetMaxTouchPoints();
 }
 
-void nsWindow::SetWindowClass(const nsAString& xulWinType,
-                              const nsAString& xulWinClass,
-                              const nsAString& xulWinName) {
-  mIsEarlyBlankWindow = xulWinType.EqualsLiteral("navigator:blank");
+void nsWindow::SetIsEarlyBlankWindow(bool aIsEarlyBlankWindow) {
+  mIsEarlyBlankWindow = aIsEarlyBlankWindow;
 }
 
 /**************************************************************

widget/windows/nsWindow.h

@@ -261,8 +261,7 @@ class nsWindow final : public nsBaseWidget {
       const LayoutDeviceIntRegion& aRegion) override;
 
   uint32_t GetMaxTouchPoints() const override;
-  void SetWindowClass(const nsAString& xulWinType, const nsAString& xulWinClass,
-                      const nsAString& xulWinName) override;
+  void SetIsEarlyBlankWindow(bool) override;
 
   /**
    * Event helpers

xpfe/appshell/AppWindow.cpp

@@ -1631,30 +1631,33 @@ void AppWindow::SyncAttributesToWidget() {
 
   NS_ENSURE_TRUE_VOID(mWindow);
 
+  // Only change blank window status once we're loaded, so that a
+  // partially-loaded browser window doesn't start painting early.
+  if (mChromeLoaded) {
+    mWindow->SetIsEarlyBlankWindow(attr.EqualsLiteral("navigator:blank"));
+    NS_ENSURE_TRUE_VOID(mWindow);
+  }
+
   // "icon" attribute
   windowElement->GetAttribute(u"icon"_ns, attr);
   if (!attr.IsEmpty()) {
     mWindow->SetIcon(attr);
-
     NS_ENSURE_TRUE_VOID(mWindow);
   }
 
   // "drawtitle" attribute
   windowElement->GetAttribute(u"drawtitle"_ns, attr);
   mWindow->SetDrawsTitle(attr.LowerCaseEqualsLiteral("true"));
-
   NS_ENSURE_TRUE_VOID(mWindow);
 
   // "toggletoolbar" attribute
   windowElement->GetAttribute(u"toggletoolbar"_ns, attr);
   mWindow->SetShowsToolbarButton(attr.LowerCaseEqualsLiteral("true"));
-
   NS_ENSURE_TRUE_VOID(mWindow);
 
   // "macnativefullscreen" attribute
   windowElement->GetAttribute(u"macnativefullscreen"_ns, attr);
   mWindow->SetSupportsNativeFullscreen(attr.LowerCaseEqualsLiteral("true"));
-
   NS_ENSURE_TRUE_VOID(mWindow);
 
   // "macanimationtype" attribute