widget/nsAutoRollup.cpp

   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
   6 #include "mozilla/widget/nsAutoRollup.h"
   7
   8 namespace mozilla {
   9 namespace widget {
  10
  11 /*static*/ uint32_t nsAutoRollup::sCount = 0;
  12 /*static*/ StaticRefPtr<nsIContent> nsAutoRollup::sLastRollup;
  13
  14 nsAutoRollup::nsAutoRollup()
  15 {
  16   // remember if sLastRollup was null, and only clear it upon destruction
  17   // if so. This prevents recursive usage of nsAutoRollup from clearing
  18   // sLastRollup when it shouldn't.
  19   mWasClear = !sLastRollup;
  20   sCount++;
  21 }
  22
  23 nsAutoRollup::nsAutoRollup(nsIContent* aRollup)
  24 {
  25   MOZ_ASSERT(!sLastRollup);
  26   mWasClear = true;
  27   sCount++;
  28   SetLastRollup(aRollup);
  29 }
  30
  31 nsAutoRollup::~nsAutoRollup()
  32 {
  33   if (sLastRollup && mWasClear) {
  34     sLastRollup = nullptr;
  35   }
  36   sCount--;
  37 }
  38
  39 /*static*/ void
  40 nsAutoRollup::SetLastRollup(nsIContent* aLastRollup)
  41 {
  42   // There must be at least one nsAutoRollup on the stack.
  43   MOZ_ASSERT(sCount);
  44
  45   sLastRollup = aLastRollup;
  46 }
  47
  48 /*static*/ nsIContent*
  49 nsAutoRollup::GetLastRollup()
  50 {
  51   return sLastRollup.get();
  52 }
  53
  54 } // namespace widget
  55 } // namespace mozilla