QNX: Move screen event retrieval to the GUI thread

Instead of retrieving screen events itself, the screen event thread
now turns screen event notification into a Qt signal.  In response to
the signal, the GUI thread processes screen events.  Eliminates the
need to coordinate access to a screen event queue.  Also prepares the
way for getting rid of the screen event thread.  This could be done if
the QNX event dispatcher were switched from poll to MsgReceive
(dispatch).

Change-Id: If5892466d04d67f00828fddaea38b20da5fb18a3
Reviewed-by: Janne Koskinen <janne.p.koskinen@qt.io>
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>

src/plugins/platforms/qnx/qqnxintegration.cpp

@@ -164,7 +164,8 @@ QQnxIntegration::QQnxIntegration(const QStringList &paramList)
 #endif
 
     // Create/start event thread
-    m_screenEventThread = new QQnxScreenEventThread(ms_screenContext, m_screenEventHandler);
+    m_screenEventThread = new QQnxScreenEventThread(ms_screenContext);
+    m_screenEventHandler->setScreenEventThread(m_screenEventThread);
     m_screenEventThread->start();
 
 #if QT_CONFIG(qqnx_pps)

src/plugins/platforms/qnx/qqnxscreeneventhandler.cpp

@@ -197,36 +197,39 @@ void QQnxScreenEventHandler::injectKeyboardEvent(int flags, int sym, int modifie
 void QQnxScreenEventHandler::setScreenEventThread(QQnxScreenEventThread *eventThread)
 {
     m_eventThread = eventThread;
+    connect(m_eventThread, &QQnxScreenEventThread::eventsPending,
+            this, &QQnxScreenEventHandler::processEvents);
 }
 
-void QQnxScreenEventHandler::processEventsFromScreenThread()
+void QQnxScreenEventHandler::processEvents()
 {
     if (!m_eventThread)
         return;
 
-    QQnxScreenEventArray *events = m_eventThread->lock();
+    screen_event_t event = nullptr;
+    if (screen_create_event(&event) != 0)
+        return;
 
-    for (int i = 0; i < events->size(); ++i) {
-        screen_event_t event = events->at(i);
-        if (!event)
-            continue;
-        (*events)[i] = 0;
+    int count = 0;
+    for (;;) {
+        if (screen_get_event(m_eventThread->context(), event, 0) != 0)
+            break;
 
-        m_eventThread->unlock();
+        int type = SCREEN_EVENT_NONE;
+        screen_get_event_property_iv(event, SCREEN_PROPERTY_TYPE, &type);
+        if (type == SCREEN_EVENT_NONE)
+            break;
 
+        ++count;
         long result = 0;
         QAbstractEventDispatcher* dispatcher = QAbstractEventDispatcher::instance();
         bool handled = dispatcher && dispatcher->filterNativeEvent(QByteArrayLiteral("screen_event_t"), event, &result);
         if (!handled)
             handleEvent(event);
-        screen_destroy_event(event);
-
-        m_eventThread->lock();
     }
 
-    events->clear();
-
-    m_eventThread->unlock();
+    m_eventThread->armEventsPending(count);
+    screen_destroy_event(event);
 }
 
 void QQnxScreenEventHandler::handleKeyboardEvent(screen_event_t event)

src/plugins/platforms/qnx/qqnxscreeneventhandler.h

@@ -74,7 +74,7 @@ protected:
     void timerEvent(QTimerEvent *event) override;
 
 private Q_SLOTS:
-    void processEventsFromScreenThread();
+    void processEvents();
 
 private:
     void handleKeyboardEvent(screen_event_t event);

src/plugins/platforms/qnx/qqnxscreeneventthread.cpp

@@ -1,5 +1,6 @@
 /***************************************************************************
 **
+** Copyright (C) 2017 QNX Software Systems. All rights reserved.
 ** Copyright (C) 2011 - 2012 Research In Motion
 ** Contact: https://www.qt.io/licensing/
 **
@@ -55,116 +56,101 @@
 #define qScreenEventThreadDebug QT_NO_QDEBUG_MACRO
 #endif
 
-QQnxScreenEventThread::QQnxScreenEventThread(screen_context_t context, QQnxScreenEventHandler *screenEventHandler)
-    : QThread(),
-      m_screenContext(context),
-      m_screenEventHandler(screenEventHandler),
-      m_quit(false)
+static const int c_screenCode = _PULSE_CODE_MINAVAIL + 0;
+static const int c_armCode = _PULSE_CODE_MINAVAIL + 1;
+static const int c_quitCode = _PULSE_CODE_MINAVAIL + 2;
+
+QQnxScreenEventThread::QQnxScreenEventThread(screen_context_t context)
+    : QThread()
+    , m_screenContext(context)
 {
-    screenEventHandler->setScreenEventThread(this);
-    connect(this, SIGNAL(eventPending()), screenEventHandler, SLOT(processEventsFromScreenThread()), Qt::QueuedConnection);
-    connect(this, SIGNAL(finished()), screenEventHandler, SLOT(processEventsFromScreenThread()), Qt::QueuedConnection);
+    m_channelId = ChannelCreate(_NTO_CHF_DISCONNECT | _NTO_CHF_UNBLOCK | _NTO_CHF_PRIVATE);
+    if (m_channelId == -1) {
+        qFatal("QQnxScreenEventThread: Can't continue without a channel");
+    }
+
+    m_connectionId = ConnectAttach(0, 0, m_channelId, _NTO_SIDE_CHANNEL, 0);
+    if (m_connectionId == -1) {
+        ChannelDestroy(m_channelId);
+        qFatal("QQnxScreenEventThread: Can't continue without a channel connection");
+    }
+
+    struct sigevent screenEvent;
+    SIGEV_PULSE_INIT(&screenEvent, m_connectionId, SIGEV_PULSE_PRIO_INHERIT, c_screenCode, 0);
+
+    screen_notify(m_screenContext, SCREEN_NOTIFY_EVENT, nullptr, &screenEvent);
 }
 
 QQnxScreenEventThread::~QQnxScreenEventThread()
 {
     // block until thread terminates
     shutdown();
-}
 
-void QQnxScreenEventThread::injectKeyboardEvent(int flags, int sym, int mod, int scan, int cap)
-{
-    QQnxScreenEventHandler::injectKeyboardEvent(flags, sym, mod, scan, cap);
-}
-
-QQnxScreenEventArray *QQnxScreenEventThread::lock()
-{
-    m_mutex.lock();
-    return &m_events;
-}
-
-void QQnxScreenEventThread::unlock()
-{
-    m_mutex.unlock();
+    ConnectDetach(m_connectionId);
+    ChannelDestroy(m_channelId);
 }
 
 void QQnxScreenEventThread::run()
 {
     qScreenEventThreadDebug("screen event thread started");
 
-    int errorCounter = 0;
-    // loop indefinitely
-    while (!m_quit) {
-        screen_event_t event;
-
-        // create screen event
-        Q_SCREEN_CHECKERROR(screen_create_event(&event), "Failed to create screen event");
-
-        // block until screen event is available
-        const int error = screen_get_event(m_screenContext, event, -1);
-        Q_SCREEN_CRITICALERROR(error, "Failed to get screen event");
-        // Only allow 50 consecutive errors before we exit the thread
-        if (error) {
-            errorCounter++;
-            if (errorCounter > 50)
-                m_quit = true;
-
-            screen_destroy_event(event);
-            continue;
-        } else {
-            errorCounter = 0;
-        }
-
-        // process received event
-        // get the event type
-        int qnxType;
-        Q_SCREEN_CHECKERROR(screen_get_event_property_iv(event, SCREEN_PROPERTY_TYPE, &qnxType),
-                            "Failed to query screen event type");
-
-        if (qnxType == SCREEN_EVENT_USER) {
-            // treat all user events as shutdown requests
-            qScreenEventThreadDebug("QNX user screen event");
-            m_quit = true;
-        } else {
-            m_mutex.lock();
-            m_events << event;
-            m_mutex.unlock();
-            emit eventPending();
-        }
+    while (1) {
+        struct _pulse msg;
+        memset(&msg, 0, sizeof(msg));
+        int receiveId = MsgReceive(m_channelId, &msg, sizeof(msg), nullptr);
+        if (receiveId == 0 && msg.code == c_quitCode)
+            break;
+        else if (receiveId == 0)
+            handlePulse(msg);
+        else if (receiveId > 0)
+            qWarning() << "Unexpected message" << msg.code;
+        else
+            qWarning() << "MsgReceive error" << strerror(errno);
     }
 
     qScreenEventThreadDebug("screen event thread stopped");
+}
 
-    // cleanup
-    m_mutex.lock();
-    Q_FOREACH (screen_event_t event, m_events) {
-        screen_destroy_event(event);
+void QQnxScreenEventThread::armEventsPending(int count)
+{
+    MsgSendPulse(m_connectionId, SIGEV_PULSE_PRIO_INHERIT, c_armCode, count);
+}
+
+void QQnxScreenEventThread::handleScreenPulse(const struct _pulse &msg)
+{
+    Q_UNUSED(msg);
+
+    ++m_screenPulsesSinceLastArmPulse;
+    if (m_emitNeededOnNextScreenPulse) {
+        m_emitNeededOnNextScreenPulse = false;
+        Q_EMIT eventsPending();
     }
-    m_events.clear();
-    m_mutex.unlock();
+}
+
+void QQnxScreenEventThread::handleArmPulse(const struct _pulse &msg)
+{
+    if (msg.value.sival_int == 0 && m_screenPulsesSinceLastArmPulse == 0) {
+        m_emitNeededOnNextScreenPulse = true;
+    } else {
+        m_screenPulsesSinceLastArmPulse = 0;
+        m_emitNeededOnNextScreenPulse = false;
+        Q_EMIT eventsPending();
+    }
+}
+
+void QQnxScreenEventThread::handlePulse(const struct _pulse &msg)
+{
+    if (msg.code == c_screenCode)
+        handleScreenPulse(msg);
+    else if (msg.code == c_armCode)
+        handleArmPulse(msg);
+    else
+        qWarning() << "Unexpected pulse" << msg.code;
 }
 
 void QQnxScreenEventThread::shutdown()
 {
-    screen_event_t event;
-
-    // create screen event
-    Q_SCREEN_CHECKERROR(screen_create_event(&event),
-                        "Failed to create screen event");
-
-    // set the event type as user
-    int type = SCREEN_EVENT_USER;
-    Q_SCREEN_CHECKERROR(screen_set_event_property_iv(event, SCREEN_PROPERTY_TYPE, &type),
-                        "Failed to set screen type");
-
-    // NOTE: ignore SCREEN_PROPERTY_USER_DATA; treat all user events as shutdown events
-
-    // post event to event loop so it will wake up and die
-    Q_SCREEN_CHECKERROR(screen_send_event(m_screenContext, event, getpid()),
-                        "Failed to set screen event type");
-
-    // cleanup
-    screen_destroy_event(event);
+    MsgSendPulse(m_connectionId, SIGEV_PULSE_PRIO_INHERIT, c_quitCode, 0);
 
     qScreenEventThreadDebug("screen event thread shutdown begin");
 

src/plugins/platforms/qnx/qqnxscreeneventthread.h

@@ -1,5 +1,6 @@
 /***************************************************************************
 **
+** Copyright (C) 2017 QNX Software Systems. All rights reserved.
 ** Copyright (C) 2011 - 2012 Research In Motion
 ** Contact: https://www.qt.io/licensing/
 **
@@ -47,37 +48,34 @@
 
 QT_BEGIN_NAMESPACE
 
-class QQnxScreenEventHandler;
-
-typedef QVarLengthArray<screen_event_t, 64> QQnxScreenEventArray;
-
 class QQnxScreenEventThread : public QThread
 {
     Q_OBJECT
 
 public:
-    QQnxScreenEventThread(screen_context_t context, QQnxScreenEventHandler *screenEventHandler);
+    QQnxScreenEventThread(screen_context_t context);
     ~QQnxScreenEventThread();
 
-    static void injectKeyboardEvent(int flags, int sym, int mod, int scan, int cap);
-
-    QQnxScreenEventArray *lock();
-    void unlock();
+    screen_context_t context() const { return m_screenContext; }
+    void armEventsPending(int count);
 
 protected:
     void run() override;
 
 Q_SIGNALS:
-    void eventPending();
+    void eventsPending();
 
 private:
+    void handleScreenPulse(const struct _pulse &msg);
+    void handleArmPulse(const struct _pulse &msg);
+    void handlePulse(const struct _pulse &msg);
     void shutdown();
 
+    int m_channelId;
+    int m_connectionId;
     screen_context_t m_screenContext;
-    QMutex m_mutex;
-    QQnxScreenEventArray m_events;
-    QQnxScreenEventHandler *m_screenEventHandler;
-    bool m_quit;
+    bool m_emitNeededOnNextScreenPulse = true;
+    int m_screenPulsesSinceLastArmPulse = 0;
 };
 
 QT_END_NAMESPACE