1 files changed, 349 insertions, 0 deletions
diff --git a/widget/nsBaseAppShell.cpp b/widget/nsBaseAppShell.cpp
new file mode 100644
index 0000000000..1557498b71
--- /dev/null
+++ b/widget/nsBaseAppShell.cpp
@@ -0,0 +1,349 @@
+/* -*- 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(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;
+#if defined(MOZ_CRASHREPORTER)
+  CrashReporter::SetEventloopNestingLevel(mEventloopNestingLevel);
+#endif
+}
+
+void
+nsBaseAppShell::DecrementEventloopNestingLevel()
+{
+  --mEventloopNestingLevel;
+#if defined(MOZ_CRASHREPORTER)
+  CrashReporter::SetEventloopNestingLevel(mEventloopNestingLevel);
+#endif
+}
+
+// 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;
+}