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/* -*- 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 "nsExceptionHandler.h"
#include "nsThreadUtils.h"
#include "nsIObserverService.h"
#include "nsServiceManagerUtils.h"
#include "mozilla/Services.h"
#include "nsXULAppAPI.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),
mProcessedGeckoEvents(false) {}
nsBaseAppShell::~nsBaseAppShell() = default;
nsresult nsBaseAppShell::Init() {
// Configure ourselves as an observer for the current thread:
if (XRE_UseNativeEventProcessing()) {
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(); }
// 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() {
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(); // 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("DummyEvent");
return NS_SUCCEEDED(aTarget->Dispatch(mDummyEvent, NS_DISPATCH_NORMAL));
}
void nsBaseAppShell::IncrementEventloopNestingLevel() {
++mEventloopNestingLevel;
CrashReporter::SetEventloopNestingLevel(mEventloopNestingLevel);
}
void nsBaseAppShell::DecrementEventloopNestingLevel() {
--mEventloopNestingLevel;
CrashReporter::SetEventloopNestingLevel(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;
}