macOS event dispatcher in Qt 5.8

qeventdispatcher_cf_p.cpp

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** ensure the GNU Lesser General Public License version 3 requirements
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** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
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** included in the packaging of this file. Please review the following
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#include "qeventdispatcher_cf_p.h"

#include <QtCore/qdebug.h>
#include <QtCore/qmetaobject.h>
#include <QtCore/qthread.h>
#include <QtCore/private/qcoreapplication_p.h>
#include <QtCore/private/qcore_unix_p.h>
#include <QtCore/private/qcore_mac_p.h>
#include <QtCore/private/qthread_p.h>

#include <limits>

#ifdef Q_OS_OSX
#  include <AppKit/NSApplication.h>
#elif defined(Q_OS_WATCHOS)
#  include <WatchKit/WatchKit.h>
#else
#  include <UIKit/UIApplication.h>
#endif

QT_USE_NAMESPACE

@interface RunLoopModeTracker : NSObject {
    QStack<CFStringRef> m_runLoopModes;
}
@end

@implementation RunLoopModeTracker

- (id) init
{
    if (self = [super init]) {
        m_runLoopModes.push(kCFRunLoopDefaultMode);

        [[NSNotificationCenter defaultCenter]
            addObserver:self
            selector:@selector(receivedNotification:)
            name:nil
#ifdef Q_OS_OSX
            object:[NSApplication sharedApplication]];
#elif defined(Q_OS_WATCHOS)
            object:[WKExtension sharedExtension]];
#else
            object:[UIApplication sharedApplication]];
#endif
    }

    return self;
}

- (void) dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];

    [super dealloc];
}

static CFStringRef runLoopMode(NSDictionary *dictionary)
{
    for (NSString *key in dictionary) {
        if (CFStringHasSuffix((CFStringRef)key, CFSTR("RunLoopMode")))
            return (CFStringRef)[dictionary objectForKey: key];
    }

    return nil;
}

- (void) receivedNotification:(NSNotification *) notification
{
     if (CFStringHasSuffix((CFStringRef)notification.name, CFSTR("RunLoopModePushNotification"))) {
        if (CFStringRef mode = runLoopMode(notification.userInfo))
            m_runLoopModes.push(mode);
        else
            qWarning("Encountered run loop push notification without run loop mode!");

     } else if (CFStringHasSuffix((CFStringRef)notification.name, CFSTR("RunLoopModePopNotification"))) {
        CFStringRef mode = runLoopMode(notification.userInfo);
        if (CFStringCompare(mode, [self currentMode], 0) == kCFCompareEqualTo)
            m_runLoopModes.pop();
        else
            qWarning("Tried to pop run loop mode '%s' that was never pushed!", qPrintable(QString::fromCFString(mode)));

        Q_ASSERT(m_runLoopModes.size() >= 1);
     }
}

- (CFStringRef) currentMode
{
    return m_runLoopModes.top();
}

@end

QT_BEGIN_NAMESPACE

class RunLoopDebugger : public QObject
{
    Q_OBJECT

    Q_ENUMS(Activity)
    Q_ENUMS(Result)

public:

    #define Q_MIRROR_ENUM(name) name = name

    enum Activity {
        Q_MIRROR_ENUM(kCFRunLoopEntry),
        Q_MIRROR_ENUM(kCFRunLoopBeforeTimers),
        Q_MIRROR_ENUM(kCFRunLoopBeforeSources),
        Q_MIRROR_ENUM(kCFRunLoopBeforeWaiting),
        Q_MIRROR_ENUM(kCFRunLoopAfterWaiting),
        Q_MIRROR_ENUM(kCFRunLoopExit)
    };

    enum Result {
        Q_MIRROR_ENUM(kCFRunLoopRunFinished),
        Q_MIRROR_ENUM(kCFRunLoopRunStopped),
        Q_MIRROR_ENUM(kCFRunLoopRunTimedOut),
        Q_MIRROR_ENUM(kCFRunLoopRunHandledSource)
    };
};

#define Q_ENUM_PRINTER(enumName) \
    static const char* qPrintable##enumName(int value) \
    { \
        return RunLoopDebugger::staticMetaObject.enumerator(RunLoopDebugger::staticMetaObject.indexOfEnumerator(#enumName)).valueToKey(value); \
    }

Q_ENUM_PRINTER(Activity);
Q_ENUM_PRINTER(Result);

QDebug operator<<(QDebug s, timespec tv)
{
    s << tv.tv_sec << "." << qSetFieldWidth(9) << qSetPadChar(QChar(48)) << tv.tv_nsec << reset;
    return s;
}

#if DEBUG_EVENT_DISPATCHER
uint g_eventDispatcherIndentationLevel = 0;
#endif

static const CFTimeInterval kCFTimeIntervalMinimum = 0;
static const CFTimeInterval kCFTimeIntervalDistantFuture = std::numeric_limits<CFTimeInterval>::max();

#pragma mark - Class definition

QEventDispatcherCoreFoundation::QEventDispatcherCoreFoundation(QObject *parent)
    : QAbstractEventDispatcher(parent)
    , m_processEvents(QEventLoop::EventLoopExec)
    , m_postedEventsRunLoopSource(this, &QEventDispatcherCoreFoundation::processPostedEvents)
    , m_runLoopActivityObserver(this, &QEventDispatcherCoreFoundation::handleRunLoopActivity,
#if DEBUG_EVENT_DISPATCHER
        kCFRunLoopAllActivities
#else
        kCFRunLoopBeforeWaiting | kCFRunLoopAfterWaiting
#endif
    )
    , m_runLoopModeTracker([[RunLoopModeTracker alloc] init])
    , m_runLoopTimer(0)
    , m_blockedRunLoopTimer(0)
    , m_overdueTimerScheduled(false)
{
    m_cfSocketNotifier.setHostEventDispatcher(this);

    m_postedEventsRunLoopSource.addToMode(kCFRunLoopCommonModes);
    m_runLoopActivityObserver.addToMode(kCFRunLoopCommonModes);
}

QEventDispatcherCoreFoundation::~QEventDispatcherCoreFoundation()
{
    invalidateTimer();
    qDeleteAll(m_timerInfoList);

    m_cfSocketNotifier.removeSocketNotifiers();
}

QEventLoop *QEventDispatcherCoreFoundation::currentEventLoop() const
{
    QEventLoop *eventLoop = QThreadData::current()->eventLoops.top();
    Q_ASSERT(eventLoop);
    return eventLoop;
}

/*!
    Processes all pending events that match \a flags until there are no
    more events to process. Returns \c true if pending events were handled;
    otherwise returns \c false.

    Note:

      - All events are considered equal. This function should process
        both system/native events (that we may or may not care about),
        as well as Qt-events (posted events and timers).

      - The function should not return until all queued/available events
        have been processed. If the WaitForMoreEvents is set, the
        function should wait only if there were no events ready,
        and _then_ process all newly queued/available events.

    These notes apply to other function in this class as well, such as
    hasPendingEvents().
*/
bool QEventDispatcherCoreFoundation::processEvents(QEventLoop::ProcessEventsFlags flags)
{
    bool eventsProcessed = false;

    if (flags & (QEventLoop::ExcludeUserInputEvents | QEventLoop::ExcludeSocketNotifiers))
        qWarning() << "processEvents() flags" << flags << "not supported on iOS";

    qEventDispatcherDebug() << "Entering with " << flags; qIndent();

    if (m_blockedRunLoopTimer) {
        Q_ASSERT(m_blockedRunLoopTimer == m_runLoopTimer);

        qEventDispatcherDebug() << "Recursing from blocked timer " << m_blockedRunLoopTimer;
        m_runLoopTimer = 0; // Unset current timer to force creation of new timer
        updateTimers();
    }

    if (m_processEvents.deferredWakeUp) {
        // We may be processing events recursivly as a result of processing a posted event,
        // in which case we need to signal the run-loop source so that this iteration of
        // processEvents will take care of the newly posted events.
        m_postedEventsRunLoopSource.signal();
        m_processEvents.deferredWakeUp = false;

        qEventDispatcherDebug() << "Processed deferred wake-up";
    }

    // The documentation states that this signal is emitted after the event
    // loop returns from a function that could block, which is not the case
    // here, but all the other event dispatchers emit awake at the start of
    // processEvents, and the QEventLoop auto-test has an explicit check for
    // this behavior, so we assume it's for a good reason and do it as well.
    emit awake();

    ProcessEventsState previousState = m_processEvents;
    m_processEvents = ProcessEventsState(flags);

    bool returnAfterSingleSourceHandled = !(m_processEvents.flags & QEventLoop::EventLoopExec);

    Q_FOREVER {
        CFStringRef mode = [m_runLoopModeTracker currentMode];

        CFTimeInterval duration = (m_processEvents.flags & QEventLoop::WaitForMoreEvents) ?
            kCFTimeIntervalDistantFuture : kCFTimeIntervalMinimum;

        qEventDispatcherDebug() << "Calling CFRunLoopRunInMode = " << qPrintable(QString::fromCFString(mode))
            << " for " << duration << " ms, processing single source = " << returnAfterSingleSourceHandled; qIndent();

        SInt32 result = CFRunLoopRunInMode(mode, duration, returnAfterSingleSourceHandled);

        qUnIndent(); qEventDispatcherDebug() << "result = " << qPrintableResult(result);

        eventsProcessed |= (result == kCFRunLoopRunHandledSource
                            || m_processEvents.processedPostedEvents
                            || m_processEvents.processedTimers);

        if (result == kCFRunLoopRunFinished) {
            // This should only happen at application shutdown, as the main runloop
            // will presumably always have sources registered.
            break;
        } else if (m_processEvents.wasInterrupted) {

            if (m_processEvents.flags & QEventLoop::EventLoopExec) {
                Q_ASSERT(result == kCFRunLoopRunStopped);

                // The runloop was potentially stopped (interrupted) by us, as a response to
                // a Qt event loop being asked to exit. We check that the topmost eventloop
                // is still supposed to keep going and return if not. Note that the runloop
                // might get stopped as a result of a non-top eventloop being asked to exit,
                // in which case we continue running the top event loop until that is asked
                // to exit, and then unwind back to the previous event loop which will break
                // immediately, since it has already been exited.

                if (!currentEventLoop()->isRunning()) {
                    qEventDispatcherDebug() << "Top level event loop was exited";
                    break;
                } else {
                    qEventDispatcherDebug() << "Top level event loop still running, making another pass";
                }
            } else {
                // We were called manually, through processEvents(), and should stop processing
                // events, even if we didn't finish processing all the queued events.
                qEventDispatcherDebug() << "Top level processEvents was interrupted";
                break;
            }
        }

        if (m_processEvents.flags & QEventLoop::EventLoopExec) {
            // We were called from QEventLoop's exec(), which blocks until the event
            // loop is asked to exit by calling processEvents repeatedly. Instead of
            // re-entering this method again and again from QEventLoop, we can block
            // here,  one lever closer to CFRunLoopRunInMode, by running the native
            // event loop again and again until we're interrupted by QEventLoop.
            continue;
        } else {
            // We were called 'manually', through processEvents()

            if (result == kCFRunLoopRunHandledSource) {
                // We processed one or more sources, but there might still be other
                // sources that did not get a chance to process events, so we need
                // to do another pass.

                // But we should only wait for more events the first time
                m_processEvents.flags &= ~QEventLoop::WaitForMoreEvents;
                continue;

            } else if (m_overdueTimerScheduled && !m_processEvents.processedTimers) {
                // CFRunLoopRunInMode does not guarantee that a scheduled timer with a fire
                // date in the past (overdue) will fire on the next run loop pass. The Qt
                // APIs on the other hand document eg. zero-interval timers to always be
                // handled after processing all available window-system events.
                qEventDispatcherDebug() << "Manually processing timers due to overdue timer";
                processTimers(0);
                eventsProcessed = true;
            }
        }

        break;
    }

    if (m_blockedRunLoopTimer) {
        invalidateTimer();
        m_runLoopTimer = m_blockedRunLoopTimer;
    }

    if (m_processEvents.deferredUpdateTimers)
        updateTimers();

    if (m_processEvents.deferredWakeUp) {
        m_postedEventsRunLoopSource.signal();
        qEventDispatcherDebug() << "Processed deferred wake-up";
    }

    bool wasInterrupted = m_processEvents.wasInterrupted;

    // Restore state of previous processEvents() call
    m_processEvents = previousState;

    if (wasInterrupted) {
        // The current processEvents run has been interrupted, but there may still be
        // others below it (eg, in the case of nested event loops). We need to trigger
        // another interrupt so that the parent processEvents call has a chance to check
        // if it should continue.
        qEventDispatcherDebug() << "Forwarding interrupt in case of nested processEvents";
        interrupt();
    }

    qEventDispatcherDebug() << "Returning with eventsProcessed = " << eventsProcessed; qUnIndent();

    return eventsProcessed;
}

bool QEventDispatcherCoreFoundation::processPostedEvents()
{
    if (m_processEvents.processedPostedEvents && !(m_processEvents.flags & QEventLoop::EventLoopExec)) {
        qEventDispatcherDebug() << "Already processed events this pass";
        return false;
    }

    m_processEvents.processedPostedEvents = true;

    qEventDispatcherDebug() << "Sending posted events for " << m_processEvents.flags; qIndent();
    QCoreApplication::sendPostedEvents();
    qUnIndent();

    return true;
}

void QEventDispatcherCoreFoundation::processTimers(CFRunLoopTimerRef timer)
{
    if (m_processEvents.processedTimers && !(m_processEvents.flags & QEventLoop::EventLoopExec)) {
        qEventDispatcherDebug() << "Already processed timers this pass";
        m_processEvents.deferredUpdateTimers = true;
        return;
    }

    qEventDispatcherDebug() << "CFRunLoopTimer " << timer << " fired, activating Qt timers"; qIndent();

    // Activating Qt timers might recurse into processEvents() if a timer-callback
    // brings up a new event-loop or tries to processes events manually. Although
    // a CFRunLoop can recurse inside its callbacks, a single CFRunLoopTimer can
    // not. So, for each recursion into processEvents() from a timer-callback we
    // need to set up a new timer-source. Instead of doing it preemtivly each
    // time we activate Qt timers, we set a flag here, and let processEvents()
    // decide whether or not it needs to bring up a new timer source.

    // We may have multiple recused timers, so keep track of the previous blocked timer
    CFRunLoopTimerRef previouslyBlockedRunLoopTimer = m_blockedRunLoopTimer;

    m_blockedRunLoopTimer = timer;
    m_timerInfoList.activateTimers();
    m_blockedRunLoopTimer = previouslyBlockedRunLoopTimer;
    m_processEvents.processedTimers = true;

    qUnIndent();

    // Now that the timer source is unblocked we may need to schedule it again
    updateTimers();
}

void QEventDispatcherCoreFoundation::handleRunLoopActivity(CFRunLoopActivity activity)
{
    qEventDispatcherDebug() << qPrintableActivity(activity);

    switch (activity) {
    case kCFRunLoopBeforeWaiting:
        if (m_processEvents.processedTimers
                && !(m_processEvents.flags & QEventLoop::EventLoopExec)
                && m_processEvents.flags & QEventLoop::WaitForMoreEvents) {
            // CoreFoundation does not treat a timer as a reason to exit CFRunLoopRunInMode
            // when asked to only process a single source, so we risk waiting a long time for
            // a 'proper' source to fire (typically a system source that we don't control).
            // To fix this we do an explicit interrupt after processing our timer, so that
            // processEvents() gets a chance to re-evaluate the state of things.
            interrupt();
        }
        emit aboutToBlock();
        break;
    case kCFRunLoopAfterWaiting:
        emit awake();
        break;
#if DEBUG_EVENT_DISPATCHER
    case kCFRunLoopEntry:
    case kCFRunLoopBeforeTimers:
    case kCFRunLoopBeforeSources:
    case kCFRunLoopExit:
        break;
#endif
    default:
        Q_UNREACHABLE();
    }
}

bool QEventDispatcherCoreFoundation::hasPendingEvents()
{
    // There doesn't seem to be any API on iOS to peek into the other sources
    // to figure out if there are pending non-Qt events. As a workaround, we
    // assume that if the run-loop is currently blocking and waiting for a
    // source to signal then there are no system-events pending. If this
    // function is called from the main thread then the second clause
    // of the condition will always be true, as the run loop is
    // never waiting in that case. The function would be more aptly named
    // 'maybeHasPendingEvents' in our case.

    extern uint qGlobalPostedEventsCount();
    return qGlobalPostedEventsCount() || !CFRunLoopIsWaiting(CFRunLoopGetMain());
}

void QEventDispatcherCoreFoundation::wakeUp()
{
    if (m_processEvents.processedPostedEvents && !(m_processEvents.flags & QEventLoop::EventLoopExec)) {
        // A manual processEvents call should only result in processing the events posted
        // up until then. Any newly posted events as result of processing existing posted
        // events should be handled in the next call to processEvents(). Since we're using
        // a run-loop source to process our posted events we need to prevent it from being
        // signaled as a result of posting new events, otherwise we end up in an infinite
        // loop. We do however need to signal the source at some point, so that the newly
        // posted event gets processed on the next processEvents() call, so we flag the
        // need to do a deferred wake-up.
        m_processEvents.deferredWakeUp = true;
        qEventDispatcherDebug() << "Already processed posted events, deferring wakeUp";
        return;
    }

    m_postedEventsRunLoopSource.signal();
    CFRunLoopWakeUp(CFRunLoopGetMain());

    qEventDispatcherDebug() << "Signaled posted event run-loop source";
}

void QEventDispatcherCoreFoundation::interrupt()
{
    qEventDispatcherDebug() << "Marking current processEvent as interrupted";
    m_processEvents.wasInterrupted = true;
    CFRunLoopStop(CFRunLoopGetMain());
}

void QEventDispatcherCoreFoundation::flush()
{
    // X11 only.
}

#pragma mark - Socket notifiers

void QEventDispatcherCoreFoundation::registerSocketNotifier(QSocketNotifier *notifier)
{
    m_cfSocketNotifier.registerSocketNotifier(notifier);
}

void QEventDispatcherCoreFoundation::unregisterSocketNotifier(QSocketNotifier *notifier)
{
    m_cfSocketNotifier.unregisterSocketNotifier(notifier);
}

#pragma mark - Timers

void QEventDispatcherCoreFoundation::registerTimer(int timerId, int interval, Qt::TimerType timerType, QObject *object)
{
    qEventDispatcherDebug() << "id = " << timerId << ", interval = " << interval
        << ", type = " << timerType << ", object = " << object;

    Q_ASSERT(timerId > 0 && interval >= 0 && object);
    Q_ASSERT(object->thread() == thread() && thread() == QThread::currentThread());

    m_timerInfoList.registerTimer(timerId, interval, timerType, object);
    updateTimers();
}

bool QEventDispatcherCoreFoundation::unregisterTimer(int timerId)
{
    Q_ASSERT(timerId > 0);
    Q_ASSERT(thread() == QThread::currentThread());

    bool returnValue = m_timerInfoList.unregisterTimer(timerId);

    qEventDispatcherDebug() << "id = " << timerId << ", timers left: " << m_timerInfoList.size();

    updateTimers();
    return returnValue;
}

bool QEventDispatcherCoreFoundation::unregisterTimers(QObject *object)
{
    Q_ASSERT(object && object->thread() == thread() && thread() == QThread::currentThread());

    bool returnValue = m_timerInfoList.unregisterTimers(object);

    qEventDispatcherDebug() << "object = " << object << ", timers left: " << m_timerInfoList.size();

    updateTimers();
    return returnValue;
}

QList<QAbstractEventDispatcher::TimerInfo> QEventDispatcherCoreFoundation::registeredTimers(QObject *object) const
{
    Q_ASSERT(object);
    return m_timerInfoList.registeredTimers(object);
}

int QEventDispatcherCoreFoundation::remainingTime(int timerId)
{
    Q_ASSERT(timerId > 0);
    return m_timerInfoList.timerRemainingTime(timerId);
}

static double timespecToSeconds(const timespec &spec)
{
    static double nanosecondsPerSecond = 1.0 * 1000 * 1000 * 1000;
    return spec.tv_sec + (spec.tv_nsec / nanosecondsPerSecond);
}

void QEventDispatcherCoreFoundation::updateTimers()
{
    if (m_timerInfoList.size() > 0) {
        // We have Qt timers registered, so create or reschedule CF timer to match

        timespec tv = { -1, -1 };
        CFAbsoluteTime timeToFire = m_timerInfoList.timerWait(tv) ?
            // We have a timer ready to fire right now, or some time in the future
            CFAbsoluteTimeGetCurrent() + timespecToSeconds(tv)
            // We have timers, but they are all currently blocked by callbacks
            : kCFTimeIntervalDistantFuture;

        if (!m_runLoopTimer) {
            m_runLoopTimer = CFRunLoopTimerCreateWithHandler(kCFAllocatorDefault,
                timeToFire, kCFTimeIntervalDistantFuture, 0, 0, ^(CFRunLoopTimerRef timer) {
                processTimers(timer);
            });

            CFRunLoopAddTimer(CFRunLoopGetMain(), m_runLoopTimer, kCFRunLoopCommonModes);
            qEventDispatcherDebug() << "Created new CFRunLoopTimer " << m_runLoopTimer;

        } else {
            CFRunLoopTimerSetNextFireDate(m_runLoopTimer, timeToFire);
            qEventDispatcherDebug() << "Re-scheduled CFRunLoopTimer " << m_runLoopTimer;
        }

        m_overdueTimerScheduled = !timespecToSeconds(tv);

        qEventDispatcherDebug() << "Next timeout in " << tv << " seconds";

    } else {
        // No Qt timers are registered, so make sure we're not running any CF timers
        invalidateTimer();

        m_overdueTimerScheduled = false;
    }
}

void QEventDispatcherCoreFoundation::invalidateTimer()
{
    if (!m_runLoopTimer || (m_runLoopTimer == m_blockedRunLoopTimer))
        return;

    CFRunLoopTimerInvalidate(m_runLoopTimer);
    qEventDispatcherDebug() << "Invalidated CFRunLoopTimer " << m_runLoopTimer;

    CFRelease(m_runLoopTimer);
    m_runLoopTimer = 0;
}

#include "qeventdispatcher_cf.moc"
#include "moc_qeventdispatcher_cf_p.cpp"

QT_END_NAMESPACE