widget/nsBaseAppShell.cpp

   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 #include "base/message_loop.h"
   7
   8 #include "nsBaseAppShell.h"
   9 #include "nsExceptionHandler.h"
  10 #include "nsThreadUtils.h"
  11 #include "nsIObserverService.h"
  12 #include "nsServiceManagerUtils.h"
  13 #include "mozilla/Services.h"
  14 #include "nsXULAppAPI.h"
  15
  16 // When processing the next thread event, the appshell may process native
  17 // events (if not in performance mode), which can result in suppressing the
  18 // next thread event for at most this many ticks:
  19 #define THREAD_EVENT_STARVATION_LIMIT PR_MillisecondsToInterval(10)
  20
  21 NS_IMPL_ISUPPORTS(nsBaseAppShell, nsIAppShell, nsIThreadObserver, nsIObserver)
  22
  23 nsBaseAppShell::nsBaseAppShell()
  24     : mSuspendNativeCount(0),
  25       mEventloopNestingLevel(0),
  26       mBlockedWait(nullptr),
  27       mFavorPerf(0),
  28       mNativeEventPending(false),
  29       mStarvationDelay(0),
  30       mSwitchTime(0),
  31       mLastNativeEventTime(0),
  32       mEventloopNestingState(eEventloopNone),
  33       mRunning(false),
  34       mExiting(false),
  35       mBlockNativeEvent(false),
  36       mProcessedGeckoEvents(false) {}
  37
  38 nsBaseAppShell::~nsBaseAppShell() = default;
  39
  40 nsresult nsBaseAppShell::Init() {
  41   // Configure ourselves as an observer for the current thread:
  42
  43   if (XRE_UseNativeEventProcessing()) {
  44     nsCOMPtr<nsIThreadInternal> threadInt =
  45         do_QueryInterface(NS_GetCurrentThread());
  46     NS_ENSURE_STATE(threadInt);
  47
  48     threadInt->SetObserver(this);
  49   }
  50
  51   nsCOMPtr<nsIObserverService> obsSvc = mozilla::services::GetObserverService();
  52   if (obsSvc) obsSvc->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
  53   return NS_OK;
  54 }
  55
  56 // Called by nsAppShell's native event callback
  57 void nsBaseAppShell::NativeEventCallback() {
  58   if (!mNativeEventPending.exchange(false)) return;
  59
  60   // If DoProcessNextNativeEvent is on the stack, then we assume that we can
  61   // just unwind and let nsThread::ProcessNextEvent process the next event.
  62   // However, if we are called from a nested native event loop (maybe via some
  63   // plug-in or library function), then go ahead and process Gecko events now.
  64   if (mEventloopNestingState == eEventloopXPCOM) {
  65     mEventloopNestingState = eEventloopOther;
  66     // XXX there is a tiny risk we will never get a new NativeEventCallback,
  67     // XXX see discussion in bug 389931.
  68     return;
  69   }
  70
  71   // nsBaseAppShell::Run is not being used to pump events, so this may be
  72   // our only opportunity to process pending gecko events.
  73
  74   nsIThread* thread = NS_GetCurrentThread();
  75   bool prevBlockNativeEvent = mBlockNativeEvent;
  76   if (mEventloopNestingState == eEventloopOther) {
  77     if (!NS_HasPendingEvents(thread)) return;
  78     // We're in a nested native event loop and have some gecko events to
  79     // process.  While doing that we block processing native events from the
  80     // appshell - instead, we want to get back to the nested native event
  81     // loop ASAP (bug 420148).
  82     mBlockNativeEvent = true;
  83   }
  84
  85   IncrementEventloopNestingLevel();
  86   EventloopNestingState prevVal = mEventloopNestingState;
  87   NS_ProcessPendingEvents(thread, THREAD_EVENT_STARVATION_LIMIT);
  88   mProcessedGeckoEvents = true;
  89   mEventloopNestingState = prevVal;
  90   mBlockNativeEvent = prevBlockNativeEvent;
  91
  92   // Continue processing pending events later (we don't want to starve the
  93   // embedders event loop).
  94   if (NS_HasPendingEvents(thread)) DoProcessMoreGeckoEvents();
  95
  96   DecrementEventloopNestingLevel();
  97 }
  98
  99 // Note, this is currently overidden on windows, see comments in nsAppShell for
 100 // details.
 101 void nsBaseAppShell::DoProcessMoreGeckoEvents() { OnDispatchedEvent(); }
 102
 103 // Main thread via OnProcessNextEvent below
 104 bool nsBaseAppShell::DoProcessNextNativeEvent(bool mayWait) {
 105   // The next native event to be processed may trigger our NativeEventCallback,
 106   // in which case we do not want it to process any thread events since we'll
 107   // do that when this function returns.
 108   //
 109   // If the next native event is not our NativeEventCallback, then we may end
 110   // up recursing into this function.
 111   //
 112   // However, if the next native event is not our NativeEventCallback, but it
 113   // results in another native event loop, then our NativeEventCallback could
 114   // fire and it will see mEventloopNestingState as eEventloopOther.
 115   //
 116   EventloopNestingState prevVal = mEventloopNestingState;
 117   mEventloopNestingState = eEventloopXPCOM;
 118
 119   IncrementEventloopNestingLevel();
 120   bool result = ProcessNextNativeEvent(mayWait);
 121   DecrementEventloopNestingLevel();
 122
 123   mEventloopNestingState = prevVal;
 124   return result;
 125 }
 126
 127 //-------------------------------------------------------------------------
 128 // nsIAppShell methods:
 129
 130 NS_IMETHODIMP
 131 nsBaseAppShell::Run(void) {
 132   NS_ENSURE_STATE(!mRunning);  // should not call Run twice
 133   mRunning = true;
 134
 135   nsIThread* thread = NS_GetCurrentThread();
 136
 137   MessageLoop::current()->Run();
 138
 139   NS_ProcessPendingEvents(thread);
 140
 141   mRunning = false;
 142   return NS_OK;
 143 }
 144
 145 NS_IMETHODIMP
 146 nsBaseAppShell::Exit(void) {
 147   if (mRunning && !mExiting) {
 148     MessageLoop::current()->Quit();
 149   }
 150   mExiting = true;
 151   return NS_OK;
 152 }
 153
 154 NS_IMETHODIMP
 155 nsBaseAppShell::FavorPerformanceHint(bool favorPerfOverStarvation,
 156                                      uint32_t starvationDelay) {
 157   mStarvationDelay = PR_MillisecondsToInterval(starvationDelay);
 158   if (favorPerfOverStarvation) {
 159     ++mFavorPerf;
 160   } else {
 161     --mFavorPerf;
 162     mSwitchTime = PR_IntervalNow();
 163   }
 164   return NS_OK;
 165 }
 166
 167 NS_IMETHODIMP
 168 nsBaseAppShell::SuspendNative() {
 169   ++mSuspendNativeCount;
 170   return NS_OK;
 171 }
 172
 173 NS_IMETHODIMP
 174 nsBaseAppShell::ResumeNative() {
 175   --mSuspendNativeCount;
 176   NS_ASSERTION(mSuspendNativeCount >= 0,
 177                "Unbalanced call to nsBaseAppShell::ResumeNative!");
 178   return NS_OK;
 179 }
 180
 181 NS_IMETHODIMP
 182 nsBaseAppShell::GetEventloopNestingLevel(uint32_t* aNestingLevelResult) {
 183   NS_ENSURE_ARG_POINTER(aNestingLevelResult);
 184
 185   *aNestingLevelResult = mEventloopNestingLevel;
 186
 187   return NS_OK;
 188 }
 189
 190 //-------------------------------------------------------------------------
 191 // nsIThreadObserver methods:
 192
 193 // Called from any thread
 194 NS_IMETHODIMP
 195 nsBaseAppShell::OnDispatchedEvent() {
 196   if (mBlockNativeEvent) return NS_OK;
 197
 198   if (mNativeEventPending.exchange(true)) return NS_OK;
 199
 200   // Returns on the main thread in NativeEventCallback above
 201   ScheduleNativeEventCallback();
 202   return NS_OK;
 203 }
 204
 205 // Called from the main thread
 206 NS_IMETHODIMP
 207 nsBaseAppShell::OnProcessNextEvent(nsIThreadInternal* thr, bool mayWait) {
 208   if (mBlockNativeEvent) {
 209     if (!mayWait) return NS_OK;
 210     // Hmm, we're in a nested native event loop and would like to get
 211     // back to it ASAP, but it seems a gecko event has caused us to
 212     // spin up a nested XPCOM event loop (eg. modal window), so we
 213     // really must start processing native events here again.
 214     mBlockNativeEvent = false;
 215     if (NS_HasPendingEvents(thr))
 216       OnDispatchedEvent();  // in case we blocked it earlier
 217   }
 218
 219   PRIntervalTime start = PR_IntervalNow();
 220   PRIntervalTime limit = THREAD_EVENT_STARVATION_LIMIT;
 221
 222   // Unblock outer nested wait loop (below).
 223   if (mBlockedWait) *mBlockedWait = false;
 224
 225   bool* oldBlockedWait = mBlockedWait;
 226   mBlockedWait = &mayWait;
 227
 228   // When mayWait is true, we need to make sure that there is an event in the
 229   // thread's event queue before we return.  Otherwise, the thread will block
 230   // on its event queue waiting for an event.
 231   bool needEvent = mayWait;
 232   // Reset prior to invoking DoProcessNextNativeEvent which might cause
 233   // NativeEventCallback to process gecko events.
 234   mProcessedGeckoEvents = false;
 235
 236   if (mFavorPerf <= 0 && start > mSwitchTime + mStarvationDelay) {
 237     // Favor pending native events
 238     PRIntervalTime now = start;
 239     bool keepGoing;
 240     do {
 241       mLastNativeEventTime = now;
 242       keepGoing = DoProcessNextNativeEvent(false);
 243     } while (keepGoing && ((now = PR_IntervalNow()) - start) < limit);
 244   } else {
 245     // Avoid starving native events completely when in performance mode
 246     if (start - mLastNativeEventTime > limit) {
 247       mLastNativeEventTime = start;
 248       DoProcessNextNativeEvent(false);
 249     }
 250   }
 251
 252   while (!NS_HasPendingEvents(thr) && !mProcessedGeckoEvents) {
 253     // If we have been asked to exit from Run, then we should not wait for
 254     // events to process.  Note that an inner nested event loop causes
 255     // 'mayWait' to become false too, through 'mBlockedWait'.
 256     if (mExiting) mayWait = false;
 257
 258     mLastNativeEventTime = PR_IntervalNow();
 259     if (!DoProcessNextNativeEvent(mayWait) || !mayWait) break;
 260   }
 261
 262   mBlockedWait = oldBlockedWait;
 263
 264   // Make sure that the thread event queue does not block on its monitor, as
 265   // it normally would do if it did not have any pending events.  To avoid
 266   // that, we simply insert a dummy event into its queue during shutdown.
 267   if (needEvent && !mExiting && !NS_HasPendingEvents(thr)) {
 268     DispatchDummyEvent(thr);
 269   }
 270
 271   return NS_OK;
 272 }
 273
 274 bool nsBaseAppShell::DispatchDummyEvent(nsIThread* aTarget) {
 275   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
 276
 277   if (!mDummyEvent) mDummyEvent = new mozilla::Runnable("DummyEvent");
 278
 279   return NS_SUCCEEDED(aTarget->Dispatch(mDummyEvent, NS_DISPATCH_NORMAL));
 280 }
 281
 282 void nsBaseAppShell::IncrementEventloopNestingLevel() {
 283   ++mEventloopNestingLevel;
 284   CrashReporter::SetEventloopNestingLevel(mEventloopNestingLevel);
 285 }
 286
 287 void nsBaseAppShell::DecrementEventloopNestingLevel() {
 288   --mEventloopNestingLevel;
 289   CrashReporter::SetEventloopNestingLevel(mEventloopNestingLevel);
 290 }
 291
 292 // Called from the main thread
 293 NS_IMETHODIMP
 294 nsBaseAppShell::AfterProcessNextEvent(nsIThreadInternal* thr,
 295                                       bool eventWasProcessed) {
 296   return NS_OK;
 297 }
 298
 299 NS_IMETHODIMP
 300 nsBaseAppShell::Observe(nsISupports* subject, const char* topic,
 301                         const char16_t* data) {
 302   NS_ASSERTION(!strcmp(topic, NS_XPCOM_SHUTDOWN_OBSERVER_ID), "oops");
 303   Exit();
 304   return NS_OK;
 305 }