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__
137