1 files changed, 54 insertions, 0 deletions
diff --git a/widget/nsAutoRollup.h b/widget/nsAutoRollup.h
new file mode 100644
index 0000000000..f6f3685887
--- /dev/null
+++ b/widget/nsAutoRollup.h
@@ -0,0 +1,54 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef nsAutoRollup_h__
+#define nsAutoRollup_h__
+
+#include "mozilla/Attributes.h"  // for MOZ_RAII
+#include "mozilla/StaticPtr.h"   // for StaticRefPtr
+#include "nsIContent.h"
+
+namespace mozilla {
+namespace widget {
+
+// A situation can occur when a mouse event occurs over a menu label while the
+// menu popup is already open. The expected behaviour is to close the popup.
+// This happens by calling nsIRollupListener::Rollup before the mouse event is
+// processed. However, in cases where the mouse event is not consumed, this
+// event will then get targeted at the menu label causing the menu to open
+// again. To prevent this, we store in sLastRollup a reference to the popup
+// that was closed during the Rollup call, and prevent this popup from
+// reopening while processing the mouse event.
+// sLastRollup can only be set while an nsAutoRollup is in scope;
+// when it goes out of scope sLastRollup is cleared automatically.
+// As sLastRollup is static, it can be retrieved by calling
+// nsAutoRollup::GetLastRollup.
+class MOZ_RAII nsAutoRollup {
+ public:
+  nsAutoRollup();
+  ~nsAutoRollup();
+
+  // Convenience constructor that creates a nsAutoRollup and also sets
+  // the last rollup.
+  explicit nsAutoRollup(nsIContent* aRollup);
+
+  static void SetLastRollup(nsIContent* aLastRollup);
+  // Return the popup that was last rolled up, or null if there isn't one.
+  static nsIContent* GetLastRollup();
+
+ private:
+  // Whether sLastRollup was clear when this nsAutoRollup
+  // was created.
+  bool mWasClear;
+
+  // The number of nsAutoRollup instances active.
+  static uint32_t sCount;
+  // The last rolled up popup.
+  static StaticRefPtr<nsIContent> sLastRollup;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // nsAutoRollup_h__