iOS: Make the event dispatcher properly emit aboutToBlock() and awake()

This approach follows the same one used by the Cocoa event dispatcher.

Change-Id: I2813b09beae07d90477c9ca506924058ace13f34
Reviewed-by: Ian Dean <ian@mediator-software.com>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>

src/platformsupport/eventdispatchers/qeventdispatcher_cf.mm

@@ -134,6 +134,8 @@ QEventDispatcherCoreFoundation::QEventDispatcherCoreFoundation(QObject *parent)
     , m_interrupted(false)
     , m_postedEventsRunLoopSource(this, &QEventDispatcherCoreFoundation::processPostedEvents)
     , m_blockingTimerRunLoopSource(this, &QEventDispatcherCoreFoundation::processTimers)
+    , m_awakeAndBlockObserver(this, &QEventDispatcherCoreFoundation::handleRunLoopActivity,
+        kCFRunLoopBeforeWaiting | kCFRunLoopAfterWaiting)
     , m_runLoopTimerRef(0)
 {
     m_cfSocketNotifier.setHostEventDispatcher(this);
@@ -142,6 +144,8 @@ QEventDispatcherCoreFoundation::QEventDispatcherCoreFoundation(QObject *parent)
 
     m_blockingTimerRunLoopSource.addToMode(kCFRunLoopCommonModes);
     m_blockingTimerRunLoopSource.addToMode(CFStringRef(UITrackingRunLoopMode));
+
+    m_awakeAndBlockObserver.addToMode(kCFRunLoopCommonModes);
 }
 
 QEventDispatcherCoreFoundation::~QEventDispatcherCoreFoundation()
@@ -168,11 +172,32 @@ void QEventDispatcherCoreFoundation::processTimers()
     maybeStartCFRunLoopTimer();
 }
 
+void QEventDispatcherCoreFoundation::handleRunLoopActivity(CFRunLoopActivity activity)
+{
+    switch (activity) {
+    case kCFRunLoopBeforeWaiting:
+        emit aboutToBlock();
+        break;
+    case kCFRunLoopAfterWaiting:
+        emit awake();
+        break;
+    default:
+        Q_UNREACHABLE();
+    }
+}
+
 bool QEventDispatcherCoreFoundation::processEvents(QEventLoop::ProcessEventsFlags flags)
 {
     m_interrupted = false;
     bool eventsProcessed = false;
 
+    // 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();
+
     bool excludeUserEvents = flags & QEventLoop::ExcludeUserInputEvents;
     bool execFlagSet = (flags & QEventLoop::DialogExec) || (flags & QEventLoop::EventLoopExec);
     bool useExecMode = execFlagSet && !excludeUserEvents;

src/platformsupport/eventdispatchers/qeventdispatcher_cf_p.h

@@ -132,6 +132,48 @@ private:
     CFRunLoopSourceRef m_source;
 };
 
+template <class T = QEventDispatcherCoreFoundation>
+class RunLoopObserver
+{
+public:
+    typedef void (T::*CallbackFunction) (CFRunLoopActivity activity);
+
+    RunLoopObserver(T *delegate, CallbackFunction callback, CFOptionFlags activities)
+        : m_delegate(delegate), m_callback(callback)
+    {
+        CFRunLoopObserverContext context = {};
+        context.info = this;
+
+        m_observer = CFRunLoopObserverCreate(kCFAllocatorDefault, activities, true, 0, process, &context);
+        Q_ASSERT(m_observer);
+    }
+
+    ~RunLoopObserver()
+    {
+        CFRunLoopObserverInvalidate(m_observer);
+        CFRelease(m_observer);
+    }
+
+    void addToMode(CFStringRef mode, CFRunLoopRef runLoop = 0)
+    {
+        if (!runLoop)
+            runLoop = CFRunLoopGetCurrent();
+
+        CFRunLoopAddObserver(runLoop, m_observer, mode);
+    }
+
+private:
+    static void process(CFRunLoopObserverRef, CFRunLoopActivity activity, void *info)
+    {
+        RunLoopObserver *self = static_cast<RunLoopObserver *>(info);
+        ((self->m_delegate)->*(self->m_callback))(activity);
+    }
+
+    T *m_delegate;
+    CallbackFunction m_callback;
+    CFRunLoopObserverRef m_observer;
+};
+
 class QEventDispatcherCoreFoundation : public QAbstractEventDispatcher
 {
     Q_OBJECT
@@ -163,6 +205,8 @@ private:
     RunLoopSource<> m_postedEventsRunLoopSource;
     RunLoopSource<> m_blockingTimerRunLoopSource;
 
+    RunLoopObserver<> m_awakeAndBlockObserver;
+
     QTimerInfoList m_timerInfoList;
     CFRunLoopTimerRef m_runLoopTimerRef;
 
@@ -170,9 +214,12 @@ private:
 
     void processPostedEvents();
     void processTimers();
+
     void maybeStartCFRunLoopTimer();
     void maybeStopCFRunLoopTimer();
 
+    void handleRunLoopActivity(CFRunLoopActivity activity);
+
     static void nonBlockingTimerRunLoopCallback(CFRunLoopTimerRef, void *info);
 };