widget/nsBaseAppShell.h
author Chris H-C <chutten@mozilla.com>
Mon, 04 Jul 2016 11:16:05 -0400
changeset 312997 df28918fe2361f0b54ca9ce4773a29c4c0675d06
parent 257286 a13c1f26e351dd6251da641fe7a9eb53790fc2d0
permissions -rw-r--r--
bug 1218576 - Support remote accumulation via JS histograms. r=gfritzsche The JS histograms, too, need to dispatch their accumulations from child to parent. JSHistograms_Add now only supports histograms that are in gHistogramsMap or that were created in the parent process. After bug 1288745, maybe we'll be able to change this to be less convoluted. MozReview-Commit-ID: 3qTH89YKbGP

/* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef nsBaseAppShell_h__
#define nsBaseAppShell_h__

#include "mozilla/Atomics.h"
#include "nsIAppShell.h"
#include "nsIThreadInternal.h"
#include "nsIObserver.h"
#include "nsIRunnable.h"
#include "nsCOMPtr.h"
#include "nsTArray.h"
#include "prinrval.h"

/**
 * A singleton that manages the UI thread's event queue.  Subclass this class
 * to enable platform-specific event queue support.
 */
class nsBaseAppShell : public nsIAppShell, public nsIThreadObserver,
                       public nsIObserver
{
public:
  NS_DECL_THREADSAFE_ISUPPORTS
  NS_DECL_NSIAPPSHELL

  NS_DECL_NSITHREADOBSERVER
  NS_DECL_NSIOBSERVER

  nsBaseAppShell();

protected:
  virtual ~nsBaseAppShell();

  /**
   * This method is called by subclasses when the app shell singleton is
   * instantiated.
   */
  nsresult Init();

  /**
   * Called by subclasses from a native event. See ScheduleNativeEventCallback.
   */
  void NativeEventCallback();

  /**
   * Make a decision as to whether or not NativeEventCallback will
   * trigger gecko event processing when there are pending gecko
   * events.
   */
  virtual void DoProcessMoreGeckoEvents();

  /**
   * Implemented by subclasses.  Invoke NativeEventCallback from a native
   * event.  This method may be called on any thread.
   */
  virtual void ScheduleNativeEventCallback() = 0;

  /**
   * Implemented by subclasses.  Process the next native event.  Only wait for
   * the next native event if mayWait is true.  This method is only called on
   * the main application thread.
   *
   * @param mayWait
   *   If "true", then this method may wait if necessary for the next available
   *   native event.  DispatchNativeEvent may be called to unblock a call to
   *   ProcessNextNativeEvent that is waiting.
   * @return
   *   This method returns "true" if a native event was processed.
   */
  virtual bool ProcessNextNativeEvent(bool mayWait) = 0;

  int32_t mSuspendNativeCount;
  uint32_t mEventloopNestingLevel;

private:
  bool DoProcessNextNativeEvent(bool mayWait);

  bool DispatchDummyEvent(nsIThread* target);

  void IncrementEventloopNestingLevel();
  void DecrementEventloopNestingLevel();

  nsCOMPtr<nsIRunnable> mDummyEvent;
  /**
   * mBlockedWait points back to a slot that controls the wait loop in
   * an outer OnProcessNextEvent invocation.  Nested calls always set
   * it to false to unblock an outer loop, since all events may
   * have been consumed by the inner event loop(s).
   */
  bool *mBlockedWait;
  int32_t mFavorPerf;
  mozilla::Atomic<bool> mNativeEventPending;
  PRIntervalTime mStarvationDelay;
  PRIntervalTime mSwitchTime;
  PRIntervalTime mLastNativeEventTime;
  enum EventloopNestingState {
    eEventloopNone,  // top level thread execution
    eEventloopXPCOM, // innermost native event loop is ProcessNextNativeEvent
    eEventloopOther  // innermost native event loop is a native library/plugin etc
  };
  EventloopNestingState mEventloopNestingState;
  bool mRunning;
  bool mExiting;
  /**
   * mBlockNativeEvent blocks the appshell from processing native events.
   * It is set to true while a nested native event loop (eEventloopOther)
   * is processing gecko events in NativeEventCallback(), thus queuing up
   * native events until we return to that loop (bug 420148).
   * We force mBlockNativeEvent to false in case handling one of the gecko
   * events spins up a nested XPCOM event loop (eg. modal window) which would
   * otherwise lead to a "deadlock" where native events aren't processed at all.
   */
  bool mBlockNativeEvent;
  /**
   * Tracks whether we have processed any gecko events in NativeEventCallback so
   * that we can avoid erroneously entering a blocking loop waiting for gecko
   * events to show up during OnProcessNextEvent.  This is required because on
   * OS X ProcessGeckoEvents may be invoked inside the context of
   * ProcessNextNativeEvent and may result in NativeEventCallback being invoked
   * and in turn invoking NS_ProcessPendingEvents.  Because
   * ProcessNextNativeEvent may be invoked prior to the NS_HasPendingEvents
   * waiting loop, this is the only way to make the loop aware that events may
   * have been processed.
   *
   * This variable is set to false in OnProcessNextEvent prior to the first
   * call to DoProcessNextNativeEvent.  It is set to true by
   * NativeEventCallback after calling NS_ProcessPendingEvents.
   */
  bool mProcessedGeckoEvents;
};

#endif // nsBaseAppShell_h__