summaryrefslogtreecommitdiffstats
path: root/widget/nsBaseAppShell.cpp
blob: c6b88cba036e69493930b8488a2bcb4003a6fa4f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
/* -*- 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/. */

#include "base/message_loop.h"

#include "nsBaseAppShell.h"
#include "nsThreadUtils.h"
#include "nsIObserverService.h"
#include "nsServiceManagerUtils.h"
#include "mozilla/Services.h"

// When processing the next thread event, the appshell may process native
// events (if not in performance mode), which can result in suppressing the
// next thread event for at most this many ticks:
#define THREAD_EVENT_STARVATION_LIMIT PR_MillisecondsToInterval(10)

NS_IMPL_ISUPPORTS(nsBaseAppShell, nsIAppShell, nsIThreadObserver, nsIObserver)

nsBaseAppShell::nsBaseAppShell()
  : mSuspendNativeCount(0)
  , mEventloopNestingLevel(0)
  , mBlockedWait(nullptr)
  , mFavorPerf(0)
  , mNativeEventPending(false)
  , mStarvationDelay(0)
  , mSwitchTime(0)
  , mLastNativeEventTime(0)
  , mEventloopNestingState(eEventloopNone)
  , mRunning(false)
  , mExiting(false)
  , mBlockNativeEvent(false)
{
}

nsBaseAppShell::~nsBaseAppShell()
{
}

nsresult
nsBaseAppShell::Init()
{
  // Configure ourselves as an observer for the current thread:

  nsCOMPtr<nsIThreadInternal> threadInt =
      do_QueryInterface(NS_GetCurrentThread());
  NS_ENSURE_STATE(threadInt);

  threadInt->SetObserver(this);

  nsCOMPtr<nsIObserverService> obsSvc =
    mozilla::services::GetObserverService();
  if (obsSvc)
    obsSvc->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
  return NS_OK;
}

// Called by nsAppShell's native event callback
void
nsBaseAppShell::NativeEventCallback()
{
  if (!mNativeEventPending.exchange(false))
    return;

  // If DoProcessNextNativeEvent is on the stack, then we assume that we can
  // just unwind and let nsThread::ProcessNextEvent process the next event.
  // However, if we are called from a nested native event loop (maybe via some
  // plug-in or library function), then go ahead and process Gecko events now.
  if (mEventloopNestingState == eEventloopXPCOM) {
    mEventloopNestingState = eEventloopOther;
    // XXX there is a tiny risk we will never get a new NativeEventCallback,
    // XXX see discussion in bug 389931.
    return;
  }

  // nsBaseAppShell::Run is not being used to pump events, so this may be
  // our only opportunity to process pending gecko events.

  nsIThread *thread = NS_GetCurrentThread();
  bool prevBlockNativeEvent = mBlockNativeEvent;
  if (mEventloopNestingState == eEventloopOther) {
    if (!NS_HasPendingEvents(thread))
      return;
    // We're in a nested native event loop and have some gecko events to
    // process.  While doing that we block processing native events from the
    // appshell - instead, we want to get back to the nested native event
    // loop ASAP (bug 420148).
    mBlockNativeEvent = true;
  }

  IncrementEventloopNestingLevel();
  EventloopNestingState prevVal = mEventloopNestingState;
  NS_ProcessPendingEvents(thread, THREAD_EVENT_STARVATION_LIMIT);
  mProcessedGeckoEvents = true;
  mEventloopNestingState = prevVal;
  mBlockNativeEvent = prevBlockNativeEvent;

  // Continue processing pending events later (we don't want to starve the
  // embedders event loop).
  if (NS_HasPendingEvents(thread))
    DoProcessMoreGeckoEvents();

  DecrementEventloopNestingLevel();
}

// Note, this is currently overidden on windows, see comments in nsAppShell for
// details.
void
nsBaseAppShell::DoProcessMoreGeckoEvents()
{
  OnDispatchedEvent(nullptr);
}


// Main thread via OnProcessNextEvent below
bool
nsBaseAppShell::DoProcessNextNativeEvent(bool mayWait)
{
  // The next native event to be processed may trigger our NativeEventCallback,
  // in which case we do not want it to process any thread events since we'll
  // do that when this function returns.
  //
  // If the next native event is not our NativeEventCallback, then we may end
  // up recursing into this function.
  //
  // However, if the next native event is not our NativeEventCallback, but it
  // results in another native event loop, then our NativeEventCallback could
  // fire and it will see mEventloopNestingState as eEventloopOther.
  //
  EventloopNestingState prevVal = mEventloopNestingState;
  mEventloopNestingState = eEventloopXPCOM;

  IncrementEventloopNestingLevel();
  bool result = ProcessNextNativeEvent(mayWait);
  DecrementEventloopNestingLevel();

  mEventloopNestingState = prevVal;
  return result;
}

//-------------------------------------------------------------------------
// nsIAppShell methods:

NS_IMETHODIMP
nsBaseAppShell::Run(void)
{
  NS_ENSURE_STATE(!mRunning);  // should not call Run twice
  mRunning = true;

  nsIThread *thread = NS_GetCurrentThread();

  MessageLoop::current()->Run();

  NS_ProcessPendingEvents(thread);

  mRunning = false;
  return NS_OK;
}

NS_IMETHODIMP
nsBaseAppShell::Exit(void)
{
  if (mRunning && !mExiting) {
    MessageLoop::current()->Quit();
  }
  mExiting = true;
  return NS_OK;
}

NS_IMETHODIMP
nsBaseAppShell::FavorPerformanceHint(bool favorPerfOverStarvation,
                                     uint32_t starvationDelay)
{
  mStarvationDelay = PR_MillisecondsToInterval(starvationDelay);
  if (favorPerfOverStarvation) {
    ++mFavorPerf;
  } else {
    --mFavorPerf;
    mSwitchTime = PR_IntervalNow();
  }
  return NS_OK;
}

NS_IMETHODIMP
nsBaseAppShell::SuspendNative()
{
  ++mSuspendNativeCount;
  return NS_OK;
}

NS_IMETHODIMP
nsBaseAppShell::ResumeNative()
{
  --mSuspendNativeCount;
  NS_ASSERTION(mSuspendNativeCount >= 0, "Unbalanced call to nsBaseAppShell::ResumeNative!");
  return NS_OK;
}

NS_IMETHODIMP
nsBaseAppShell::GetEventloopNestingLevel(uint32_t* aNestingLevelResult)
{
  NS_ENSURE_ARG_POINTER(aNestingLevelResult);

  *aNestingLevelResult = mEventloopNestingLevel;

  return NS_OK;
}

//-------------------------------------------------------------------------
// nsIThreadObserver methods:

// Called from any thread
NS_IMETHODIMP
nsBaseAppShell::OnDispatchedEvent(nsIThreadInternal *thr)
{
  if (mBlockNativeEvent)
    return NS_OK;

  if (mNativeEventPending.exchange(true))
    return NS_OK;

  // Returns on the main thread in NativeEventCallback above
  ScheduleNativeEventCallback();
  return NS_OK;
}

// Called from the main thread
NS_IMETHODIMP
nsBaseAppShell::OnProcessNextEvent(nsIThreadInternal *thr, bool mayWait)
{
  if (mBlockNativeEvent) {
    if (!mayWait)
      return NS_OK;
    // Hmm, we're in a nested native event loop and would like to get
    // back to it ASAP, but it seems a gecko event has caused us to
    // spin up a nested XPCOM event loop (eg. modal window), so we
    // really must start processing native events here again.
    mBlockNativeEvent = false;
    if (NS_HasPendingEvents(thr))
      OnDispatchedEvent(thr); // in case we blocked it earlier
  }

  PRIntervalTime start = PR_IntervalNow();
  PRIntervalTime limit = THREAD_EVENT_STARVATION_LIMIT;

  // Unblock outer nested wait loop (below).
  if (mBlockedWait)
    *mBlockedWait = false;

  bool *oldBlockedWait = mBlockedWait;
  mBlockedWait = &mayWait;

  // When mayWait is true, we need to make sure that there is an event in the
  // thread's event queue before we return.  Otherwise, the thread will block
  // on its event queue waiting for an event.
  bool needEvent = mayWait;
  // Reset prior to invoking DoProcessNextNativeEvent which might cause
  // NativeEventCallback to process gecko events.
  mProcessedGeckoEvents = false;

  if (mFavorPerf <= 0 && start > mSwitchTime + mStarvationDelay) {
    // Favor pending native events
    PRIntervalTime now = start;
    bool keepGoing;
    do {
      mLastNativeEventTime = now;
      keepGoing = DoProcessNextNativeEvent(false);
    } while (keepGoing && ((now = PR_IntervalNow()) - start) < limit);
  } else {
    // Avoid starving native events completely when in performance mode
    if (start - mLastNativeEventTime > limit) {
      mLastNativeEventTime = start;
      DoProcessNextNativeEvent(false);
    }
  }

  while (!NS_HasPendingEvents(thr) && !mProcessedGeckoEvents) {
    // If we have been asked to exit from Run, then we should not wait for
    // events to process.  Note that an inner nested event loop causes
    // 'mayWait' to become false too, through 'mBlockedWait'.
    if (mExiting)
      mayWait = false;

    mLastNativeEventTime = PR_IntervalNow();
    if (!DoProcessNextNativeEvent(mayWait) || !mayWait)
      break;
  }

  mBlockedWait = oldBlockedWait;

  // Make sure that the thread event queue does not block on its monitor, as
  // it normally would do if it did not have any pending events.  To avoid
  // that, we simply insert a dummy event into its queue during shutdown.
  if (needEvent && !mExiting && !NS_HasPendingEvents(thr)) {
    DispatchDummyEvent(thr);
  }

  return NS_OK;
}

bool
nsBaseAppShell::DispatchDummyEvent(nsIThread* aTarget)
{
  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");

  if (!mDummyEvent)
    mDummyEvent = new mozilla::Runnable();

  return NS_SUCCEEDED(aTarget->Dispatch(mDummyEvent, NS_DISPATCH_NORMAL));
}

void
nsBaseAppShell::IncrementEventloopNestingLevel()
{
  ++mEventloopNestingLevel;
}

void
nsBaseAppShell::DecrementEventloopNestingLevel()
{
  --mEventloopNestingLevel;
}

// Called from the main thread
NS_IMETHODIMP
nsBaseAppShell::AfterProcessNextEvent(nsIThreadInternal *thr,
                                      bool eventWasProcessed)
{
  return NS_OK;
}

NS_IMETHODIMP
nsBaseAppShell::Observe(nsISupports *subject, const char *topic,
                        const char16_t *data)
{
  NS_ASSERTION(!strcmp(topic, NS_XPCOM_SHUTDOWN_OBSERVER_ID), "oops");
  Exit();
  return NS_OK;
}