QmlProfiler: Use EngineControl to hold engines until we're done

Holding the engines with EngineControl makes sure we always receive the
full trace before the connection drops.

Change-Id: I32e7d17886cdbc4749e3e54719e198d45169cbfe
Task-number: QTBUG-66269
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

src/plugins/qmlprofiler/qmlprofilertraceclient.cpp

@@ -77,6 +77,8 @@ public:
     QStack<QmlTypedEvent> rangesInProgress;
     QQueue<QmlEvent> pendingMessages;
     QQueue<QmlEvent> pendingDebugMessages;
+
+    QList<int> trackedEngines;
 };
 
 int QmlProfilerTraceClientPrivate::resolveType(const QmlTypedEvent &event)
@@ -216,6 +218,22 @@ QmlProfilerTraceClient::QmlProfilerTraceClient(QmlDebug::QmlDebugConnection *cli
     setRequestedFeatures(features);
     connect(&d->engineControl, &QmlDebug::QmlEngineControlClient::engineAboutToBeAdded,
             this, &QmlProfilerTraceClient::sendRecordingStatus);
+    connect(&d->engineControl, &QmlDebug::QmlEngineControlClient::engineAboutToBeRemoved,
+            this, [this](int engineId) {
+        // We may already be done with that engine. Then we don't need to block it.
+        if (d->trackedEngines.contains(engineId))
+            d->engineControl.blockEngine(engineId);
+    });
+    connect(this, &QmlProfilerTraceClient::traceFinished,
+            &d->engineControl, [this](qint64 timestamp, const QList<int> &engineIds) {
+        Q_UNUSED(timestamp);
+        // The engines might not be blocked because the trace can get finished before engine control
+        // sees them.
+        for (int blocked : d->engineControl.blockedEngines()) {
+            if (engineIds.contains(blocked))
+                d->engineControl.releaseEngine(blocked);
+        }
+    });
 }
 
 QmlProfilerTraceClient::~QmlProfilerTraceClient()
@@ -243,6 +261,7 @@ void QmlProfilerTraceClient::clear()
 {
     d->eventTypeIds.clear();
     d->serverTypeIds.clear();
+    d->trackedEngines.clear();
     clearEvents();
 }
 
@@ -334,12 +353,15 @@ void QmlProfilerTraceClient::messageReceived(const QByteArray &data)
         emit complete(d->maximumTime);
     } else if (d->currentEvent.type.message() == Event
                && d->currentEvent.type.detailType() == StartTrace) {
-        emit traceStarted(d->currentEvent.event.timestamp(),
+        const QList<int> engineIds = d->currentEvent.event.numbers<QList<int>, qint32>();
-                          d->currentEvent.event.numbers<QList<int>, qint32>());
+        d->trackedEngines.append(engineIds);
+        emit traceStarted(d->currentEvent.event.timestamp(), engineIds);
     } else if (d->currentEvent.type.message() == Event
                && d->currentEvent.type.detailType() == EndTrace) {
-        emit traceFinished(d->currentEvent.event.timestamp(),
+        const QList<int> engineIds = d->currentEvent.event.numbers<QList<int>, qint32>();
-                           d->currentEvent.event.numbers<QList<int>, qint32>());
+        for (int engineId : engineIds)
+            d->trackedEngines.removeAll(engineId);
+        emit traceFinished(d->currentEvent.event.timestamp(), engineIds);
     } else if (d->updateFeatures(d->currentEvent.type.feature())) {
         d->processCurrentEvent();
     }