The Tor Browser: widget/xpwidgets/nsBaseAppShell.cpp@44a2da4a2ab2 (annotated)

widget/xpwidgets/nsBaseAppShell.cpp@44a2da4a2ab2 (annotated)

widget/xpwidgets/nsBaseAppShell.cpp

Fri, 16 Jan 2015 04:50:19 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Fri, 16 Jan 2015 04:50:19 +0100
branch: TOR_BUG_9701
changeset 13: 44a2da4a2ab2
permissions: -rw-r--r--

Replace accessor implementation with direct member state manipulation, by
request https://trac.torproject.org/projects/tor/ticket/9701#comment:32

 /* -*- 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"
 #if defined(MOZ_CRASHREPORTER)
 #include "nsExceptionHandler.h"
 #endif
 #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(20)
 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()
 {
   NS_ASSERTION(mSyncSections.IsEmpty(), "Must have run all sync sections");
 }
 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, uint32_t recursionDepth)
 {
   // 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);
   // Make sure that any sync sections registered during this most recent event
   // are run now. This is not considered a stable state because we're not back
   // to the event loop yet.
   RunSyncSections(false, recursionDepth);
   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,
                                    uint32_t recursionDepth)
 {
   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, recursionDepth);
     } 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, recursionDepth);
     }
   }
   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, recursionDepth) || !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);
   }
   // We're about to run an event, so we're in a stable state.
   RunSyncSections(true, recursionDepth);
   return NS_OK;
 }
 bool
 nsBaseAppShell::DispatchDummyEvent(nsIThread* aTarget)
 {
   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
   if (!mDummyEvent)
     mDummyEvent = new nsRunnable();
   return NS_SUCCEEDED(aTarget->Dispatch(mDummyEvent, NS_DISPATCH_NORMAL));
 }
 void
 nsBaseAppShell::IncrementEventloopNestingLevel()
 {
   ++mEventloopNestingLevel;
 #if defined(MOZ_CRASHREPORTER)
   CrashReporter::SetEventloopNestingLevel(mEventloopNestingLevel);
 #endif
 }
 void
 nsBaseAppShell::DecrementEventloopNestingLevel()
 {
   --mEventloopNestingLevel;
 #if defined(MOZ_CRASHREPORTER)
   CrashReporter::SetEventloopNestingLevel(mEventloopNestingLevel);
 #endif
 }
 void
 nsBaseAppShell::RunSyncSectionsInternal(bool aStable,
                                         uint32_t aThreadRecursionLevel)
 {
   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
   NS_ASSERTION(!mSyncSections.IsEmpty(), "Nothing to do!");
   // We've got synchronous sections. Run all of them that are are awaiting a
   // stable state if aStable is true (i.e. we really are in a stable state).
   // Also run the synchronous sections that are simply waiting for the right
   // combination of event loop nesting level and thread recursion level.
   // Note that a synchronous section could add another synchronous section, so
   // we don't remove elements from mSyncSections until all sections have been
   // run, or else we'll screw up our iteration. Any sync sections that are not
   // ready to be run are saved for later.
   nsTArray<SyncSection> pendingSyncSections;
   for (uint32_t i = 0; i < mSyncSections.Length(); i++) {
     SyncSection& section = mSyncSections[i];
     if ((aStable && section.mStable) ||
         (!section.mStable &&
          section.mEventloopNestingLevel == mEventloopNestingLevel &&
          section.mThreadRecursionLevel == aThreadRecursionLevel)) {
       section.mRunnable->Run();
     }
     else {
       // Add to pending list.
       SyncSection* pending = pendingSyncSections.AppendElement();
       section.Forget(pending);
     }
   }
   mSyncSections.SwapElements(pendingSyncSections);
 }
 void
 nsBaseAppShell::ScheduleSyncSection(nsIRunnable* aRunnable, bool aStable)
 {
   NS_ASSERTION(NS_IsMainThread(), "Should be on main thread.");
   nsIThread* thread = NS_GetCurrentThread();
   // Add this runnable to our list of synchronous sections.
   SyncSection* section = mSyncSections.AppendElement();
   section->mStable = aStable;
   section->mRunnable = aRunnable;
   // If aStable is false then this synchronous section is supposed to run before
   // the next event at the current nesting level. Record the event loop nesting
   // level and the thread recursion level so that the synchronous section will
   // run at the proper time.
   if (!aStable) {
     section->mEventloopNestingLevel = mEventloopNestingLevel;
     nsCOMPtr<nsIThreadInternal> threadInternal = do_QueryInterface(thread);
     NS_ASSERTION(threadInternal, "This should never fail!");
     uint32_t recursionLevel;
     if (NS_FAILED(threadInternal->GetRecursionDepth(&recursionLevel))) {
       NS_ERROR("This should never fail!");
     }
     // Due to the weird way that the thread recursion counter is implemented we
     // subtract one from the recursion level if we have one.
     section->mThreadRecursionLevel = recursionLevel ? recursionLevel - 1 : 0;
   }
   // Ensure we've got a pending event, else the callbacks will never run.
   if (!NS_HasPendingEvents(thread) && !DispatchDummyEvent(thread)) {
     RunSyncSections(true, 0);
   }
 }
 // Called from the main thread
 NS_IMETHODIMP
 nsBaseAppShell::AfterProcessNextEvent(nsIThreadInternal *thr,
                                       uint32_t recursionDepth,
                                       bool eventWasProcessed)
 {
   // We've just finished running an event, so we're in a stable state.
   RunSyncSections(true, recursionDepth);
   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;
 }
 NS_IMETHODIMP
 nsBaseAppShell::RunInStableState(nsIRunnable* aRunnable)
 {
   ScheduleSyncSection(aRunnable, true);
   return NS_OK;
 }
 NS_IMETHODIMP
 nsBaseAppShell::RunBeforeNextEvent(nsIRunnable* aRunnable)
 {
   ScheduleSyncSection(aRunnable, false);
   return NS_OK;
 }

The Tor Browser / annotate

widget/xpwidgets/nsBaseAppShell.cpp@44a2da4a2ab2 (annotated)

widget/xpwidgets/nsBaseAppShell.cpp