widget/nsAutoRollup.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5 #ifndef nsAutoRollup_h__
   6 #define nsAutoRollup_h__
   7
   8 #include "mozilla/Attributes.h"  // for MOZ_RAII
   9 #include "mozilla/StaticPtr.h"   // for StaticRefPtr
  10 #include "nsIContent.h"
  11
  12 namespace mozilla {
  13 namespace widget {
  14
  15 // A situation can occur when a mouse event occurs over a menu label while the
  16 // menu popup is already open. The expected behaviour is to close the popup.
  17 // This happens by calling nsIRollupListener::Rollup before the mouse event is
  18 // processed. However, in cases where the mouse event is not consumed, this
  19 // event will then get targeted at the menu label causing the menu to open
  20 // again. To prevent this, we store in sLastRollup a reference to the popup
  21 // that was closed during the Rollup call, and prevent this popup from
  22 // reopening while processing the mouse event.
  23 // sLastRollup can only be set while an nsAutoRollup is in scope;
  24 // when it goes out of scope sLastRollup is cleared automatically.
  25 // As sLastRollup is static, it can be retrieved by calling
  26 // nsAutoRollup::GetLastRollup.
  27 class MOZ_RAII nsAutoRollup {
  28  public:
  29   nsAutoRollup();
  30   ~nsAutoRollup();
  31
  32   // Convenience constructor that creates a nsAutoRollup and also sets
  33   // the last rollup.
  34   explicit nsAutoRollup(nsIContent* aRollup);
  35
  36   static void SetLastRollup(nsIContent* aLastRollup);
  37   // Return the popup that was last rolled up, or null if there isn't one.
  38   static nsIContent* GetLastRollup();
  39
  40  private:
  41   // Whether sLastRollup was clear when this nsAutoRollup
  42   // was created.
  43   bool mWasClear;
  44
  45   // The number of nsAutoRollup instances active.
  46   static uint32_t sCount;
  47   // The last rolled up popup.
  48   static StaticRefPtr<nsIContent> sLastRollup;
  49 };
  50
  51 }  // namespace widget
  52 }  // namespace mozilla
  53
  54 #endif  // nsAutoRollup_h__