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  protected:
  35   virtual ~nsBaseAppShell();
  36
  37   /**
  38    * This method is called by subclasses when the app shell singleton is
  39    * instantiated.
  40    */
  41   nsresult Init();
  42
  43   /**
  44    * Called by subclasses from a native event. See ScheduleNativeEventCallback.
  45    */
  46   void NativeEventCallback();
  47
  48   /**
  49    * Make a decision as to whether or not NativeEventCallback will
  50    * trigger gecko event processing when there are pending gecko
  51    * events.
  52    */
  53   virtual void DoProcessMoreGeckoEvents();
  54
  55   /**
  56    * Implemented by subclasses.  Invoke NativeEventCallback from a native
  57    * event.  This method may be called on any thread.
  58    */
  59   virtual void ScheduleNativeEventCallback() = 0;
  60
  61   /**
  62    * Implemented by subclasses.  Process the next native event.  Only wait for
  63    * the next native event if mayWait is true.  This method is only called on
  64    * the main application thread.
  65    *
  66    * @param mayWait
  67    *   If "true", then this method may wait if necessary for the next available
  68    *   native event.  DispatchNativeEvent may be called to unblock a call to
  69    *   ProcessNextNativeEvent that is waiting.
  70    * @return
  71    *   This method returns "true" if a native event was processed.
  72    */
  73   virtual bool ProcessNextNativeEvent(bool mayWait) = 0;
  74
  75   int32_t mSuspendNativeCount;
  76   uint32_t mEventloopNestingLevel;
  77
  78  private:
  79   bool DoProcessNextNativeEvent(bool mayWait);
  80
  81   bool DispatchDummyEvent(nsIThread* target);
  82
  83   void IncrementEventloopNestingLevel();
  84   void DecrementEventloopNestingLevel();
  85
  86   nsCOMPtr<nsIRunnable> mDummyEvent;
  87   /**
  88    * mBlockedWait points back to a slot that controls the wait loop in
  89    * an outer OnProcessNextEvent invocation.  Nested calls always set
  90    * it to false to unblock an outer loop, since all events may
  91    * have been consumed by the inner event loop(s).
  92    */
  93   bool* mBlockedWait;
  94   int32_t mFavorPerf;
  95   mozilla::Atomic<bool> mNativeEventPending;
  96   PRIntervalTime mStarvationDelay;
  97   PRIntervalTime mSwitchTime;
  98   PRIntervalTime mLastNativeEventTime;
  99   enum EventloopNestingState {
 100     eEventloopNone,   // top level thread execution
 101     eEventloopXPCOM,  // innermost native event loop is ProcessNextNativeEvent
 102     eEventloopOther   // innermost native event loop is a native library/plugin
 103                       // etc
 104   };
 105   EventloopNestingState mEventloopNestingState;
 106   bool mRunning;
 107   bool mExiting;
 108   /**
 109    * mBlockNativeEvent blocks the appshell from processing native events.
 110    * It is set to true while a nested native event loop (eEventloopOther)
 111    * is processing gecko events in NativeEventCallback(), thus queuing up
 112    * native events until we return to that loop (bug 420148).
 113    * We force mBlockNativeEvent to false in case handling one of the gecko
 114    * events spins up a nested XPCOM event loop (eg. modal window) which would
 115    * otherwise lead to a "deadlock" where native events aren't processed at all.
 116    */
 117   bool mBlockNativeEvent;
 118   /**
 119    * Tracks whether we have processed any gecko events in NativeEventCallback so
 120    * that we can avoid erroneously entering a blocking loop waiting for gecko
 121    * events to show up during OnProcessNextEvent.  This is required because on
 122    * OS X ProcessGeckoEvents may be invoked inside the context of
 123    * ProcessNextNativeEvent and may result in NativeEventCallback being invoked
 124    * and in turn invoking NS_ProcessPendingEvents.  Because
 125    * ProcessNextNativeEvent may be invoked prior to the NS_HasPendingEvents
 126    * waiting loop, this is the only way to make the loop aware that events may
 127    * have been processed.
 128    *
 129    * This variable is set to false in OnProcessNextEvent prior to the first
 130    * call to DoProcessNextNativeEvent.  It is set to true by
 131    * NativeEventCallback after calling NS_ProcessPendingEvents.
 132    */
 133   bool mProcessedGeckoEvents;
 134 };
 135
 136 #endif  // nsBaseAppShell_h__