layout/build/nsLayoutStatics.h

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #ifndef nsLayoutStatics_h__
   6 #define nsLayoutStatics_h__
   7
   8 #include "nscore.h"
   9 #include "MainThreadUtils.h"
  10 #include "nsISupportsImpl.h"
  11 #include "nsDebug.h"
  12
  13 // This isn't really a class, it's a namespace for static methods.
  14 // Documents and other objects can hold a reference to the layout static
  15 // objects so that they last past the xpcom-shutdown notification.
  16
  17 class nsLayoutStatics
  18 {
  19 public:
  20   // Called by the layout module constructor. This call performs an AddRef()
  21   // internally.
  22   static nsresult Initialize();
  23
  24   static void AddRef()
  25   {
  26     NS_ASSERTION(NS_IsMainThread(),
  27                  "nsLayoutStatics reference counting must be on main thread");
  28
  29     NS_ASSERTION(sLayoutStaticRefcnt,
  30                  "nsLayoutStatics already dropped to zero!");
  31
  32     ++sLayoutStaticRefcnt;
  33     NS_LOG_ADDREF(&sLayoutStaticRefcnt, sLayoutStaticRefcnt,
  34                   "nsLayoutStatics", 1);
  35   }
  36   static void Release()
  37   {
  38     NS_ASSERTION(NS_IsMainThread(),
  39                  "nsLayoutStatics reference counting must be on main thread");
  40
  41     --sLayoutStaticRefcnt;
  42     NS_LOG_RELEASE(&sLayoutStaticRefcnt, sLayoutStaticRefcnt,
  43                    "nsLayoutStatics");
  44
  45     if (!sLayoutStaticRefcnt)
  46       Shutdown();
  47   }
  48
  49 private:
  50   // not to be called!
  51   nsLayoutStatics();
  52
  53   static void Shutdown();
  54
  55   static nsrefcnt sLayoutStaticRefcnt;
  56 };
  57
  58 class nsLayoutStaticsRef
  59 {
  60 public:
  61   nsLayoutStaticsRef()
  62   {
  63     nsLayoutStatics::AddRef();
  64   }
  65   ~nsLayoutStaticsRef()
  66   {
  67     nsLayoutStatics::Release();
  68   }
  69 };
  70
  71 #endif // nsLayoutStatics_h__