widget/nsBaseAppShell.h

   1 /* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; -*- */
   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 #ifndef nsBaseAppShell_h__
   7 #define nsBaseAppShell_h__
   8
   9 #include "mozilla/Atomics.h"
  10 #include "nsIAppShell.h"
  11 #include "nsIThreadInternal.h"
  12 #include "nsIObserver.h"
  13 #include "nsIRunnable.h"
  14 #include "nsCOMPtr.h"
  15 #include "nsTArray.h"
  16 #include "prinrval.h"
  17
  18 /**
  19  * A singleton that manages the UI thread's event queue.  Subclass this class
  20  * to enable platform-specific event queue support.
  21  */
  22 class nsBaseAppShell : public nsIAppShell,
  23                        public nsIThreadObserver,
  24                        public nsIObserver {
  25  public:
  26   NS_DECL_THREADSAFE_ISUPPORTS
  27   NS_DECL_NSIAPPSHELL
  28
  29   NS_DECL_NSITHREADOBSERVER
  30   NS_DECL_NSIOBSERVER
  31
  32   nsBaseAppShell();
  33
  34   /**
  35    * Called by subclasses. Reset the internal timezone when the user's system
  36    * timezone changes.
  37    */
  38   static void OnSystemTimezoneChange();
  39
  40  protected:
  41   virtual ~nsBaseAppShell();
  42
  43   /**
  44    * This method is called by subclasses when the app shell singleton is
  45    * instantiated.
  46    */
  47   nsresult Init();
  48
  49   /**
  50    * Called by subclasses from a native event. See ScheduleNativeEventCallback.
  51    */
  52   void NativeEventCallback();
  53
  54   /**
  55    * Make a decision as to whether or not NativeEventCallback will
  56    * trigger gecko event processing when there are pending gecko
  57    * events.
  58    */
  59   virtual void DoProcessMoreGeckoEvents();
  60
  61   /**
  62    * Implemented by subclasses.  Invoke NativeEventCallback from a native
  63    * event.  This method may be called on any thread.
  64    */
  65   virtual void ScheduleNativeEventCallback() = 0;
  66
  67   /**
  68    * Implemented by subclasses.  Process the next native event.  Only wait for
  69    * the next native event if mayWait is true.  This method is only called on
  70    * the main application thread.
  71    *
  72    * @param mayWait
  73    *   If "true", then this method may wait if necessary for the next available
  74    *   native event.  DispatchNativeEvent may be called to unblock a call to
  75    *   ProcessNextNativeEvent that is waiting.
  76    * @return
  77    *   This method returns "true" if a native event was processed.
  78    */
  79   virtual bool ProcessNextNativeEvent(bool mayWait) = 0;
  80
  81   int32_t mSuspendNativeCount;
  82   uint32_t mEventloopNestingLevel;
  83
  84  private:
  85   bool DoProcessNextNativeEvent(bool mayWait);
  86
  87   bool DispatchDummyEvent(nsIThread* target);
  88
  89   void IncrementEventloopNestingLevel();
  90   void DecrementEventloopNestingLevel();
  91
  92   nsCOMPtr<nsIRunnable> mDummyEvent;
  93   /**
  94    * mBlockedWait points back to a slot that controls the wait loop in
  95    * an outer OnProcessNextEvent invocation.  Nested calls always set
  96    * it to false to unblock an outer loop, since all events may
  97    * have been consumed by the inner event loop(s).
  98    */
  99   bool* mBlockedWait;
 100   mozilla::Atomic<bool> mNativeEventPending;
 101   PRIntervalTime mGeckoTaskBurstStartTime;
 102   PRIntervalTime mLastNativeEventTime;
 103   enum EventloopNestingState {
 104     eEventloopNone,   // top level thread execution
 105     eEventloopXPCOM,  // innermost native event loop is ProcessNextNativeEvent
 106     eEventloopOther   // innermost native event loop is a native library/plugin
 107                       // etc
 108   };
 109   EventloopNestingState mEventloopNestingState;
 110   bool mRunning;
 111   bool mExiting;
 112   /**
 113    * mBlockNativeEvent blocks the appshell from processing native events.
 114    * It is set to true while a nested native event loop (eEventloopOther)
 115    * is processing gecko events in NativeEventCallback(), thus queuing up
 116    * native events until we return to that loop (bug 420148).
 117    * We force mBlockNativeEvent to false in case handling one of the gecko
 118    * events spins up a nested XPCOM event loop (eg. modal window) which would
 119    * otherwise lead to a "deadlock" where native events aren't processed at all.
 120    */
 121   bool mBlockNativeEvent;
 122   /**
 123    * Tracks whether we have processed any gecko events in NativeEventCallback so
 124    * that we can avoid erroneously entering a blocking loop waiting for gecko
 125    * events to show up during OnProcessNextEvent.  This is required because on
 126    * OS X ProcessGeckoEvents may be invoked inside the context of
 127    * ProcessNextNativeEvent and may result in NativeEventCallback being invoked
 128    * and in turn invoking NS_ProcessPendingEvents.  Because
 129    * ProcessNextNativeEvent may be invoked prior to the NS_HasPendingEvents
 130    * waiting loop, this is the only way to make the loop aware that events may
 131    * have been processed.
 132    *
 133    * This variable is set to false in OnProcessNextEvent prior to the first
 134    * call to DoProcessNextNativeEvent.  It is set to true by
 135    * NativeEventCallback after calling NS_ProcessPendingEvents.
 136    */
 137   bool mProcessedGeckoEvents;
 138 };
 139
 140 #endif  // nsBaseAppShell_h__