QmlProfiler: Guard against the temporary trace file going away

If we cannot open a temporary file to cache a trace or retrieve a
previously cached trace, the QML profiler won't work correctly. Show
an error in this case.

Change-Id: I468d74d9c33033b9ad19501bccbd69a9fe164fed
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/qmlprofiler/qmlprofilerdatamodel.cpp

@@ -101,7 +101,9 @@ QmlProfilerDataModel::QmlProfilerDataModel(QObject *parent) :
             this, &QmlProfilerDataModel::detailsChanged);
     connect(d->detailsRewriter, &QmlProfilerDetailsRewriter::eventDetailsChanged,
             this, &QmlProfilerDataModel::allTypesLoaded);
-    d->file.open();
+    if (!d->file.open())
+        emit traceFileError();
+    else
         d->eventStream.setDevice(&d->file);
 }
 
@@ -170,7 +172,10 @@ void QmlProfilerDataModel::clear()
 {
     Q_D(QmlProfilerDataModel);
     d->file.remove();
-    d->file.open();
+    d->eventStream.unsetDevice();
+    if (!d->file.open())
+        emit traceFileError();
+    else
         d->eventStream.setDevice(&d->file);
     d->eventTypes.clear();
     d->detailsRewriter->clearRequests();
@@ -207,14 +212,16 @@ static bool isStateful(const QmlEventType &type)
     return message == PixmapCacheEvent || message == MemoryAllocation;
 }
 
-void QmlProfilerDataModel::replayEvents(qint64 rangeStart, qint64 rangeEnd,
+bool QmlProfilerDataModel::replayEvents(qint64 rangeStart, qint64 rangeEnd,
                                         QmlProfilerModelManager::EventLoader loader) const
 {
     Q_D(const QmlProfilerDataModel);
     QStack<QmlEvent> stack;
     QmlEvent event;
     QFile file(d->file.fileName());
-    file.open(QIODevice::ReadOnly);
+    if (!file.open(QIODevice::ReadOnly))
+        return false;
+
     QDataStream stream(&file);
     bool crossedRangeStart = false;
     while (!stream.atEnd()) {
@@ -271,6 +278,7 @@ void QmlProfilerDataModel::replayEvents(qint64 rangeStart, qint64 rangeEnd,
 
         loader(event, type);
     }
+    return true;
 }
 
 void QmlProfilerDataModel::finalize()

src/plugins/qmlprofiler/qmlprofilerdatamodel.h

@@ -55,12 +55,13 @@ public:
     bool isEmpty() const;
     void addEvent(const QmlEvent &event);
     void addEvents(const QVector<QmlEvent> &events);
-    void replayEvents(qint64 startTime, qint64 endTime,
+    bool replayEvents(qint64 startTime, qint64 endTime,
                       QmlProfilerModelManager::EventLoader loader) const;
     void finalize();
 
 signals:
     void allTypesLoaded();
+    void traceFileError();
 
 protected slots:
     void detailsChanged(int typeId, const QString &newString);

src/plugins/qmlprofiler/qmlprofilermodelmanager.cpp

@@ -176,6 +176,10 @@ QmlProfilerModelManager::QmlProfilerModelManager(QObject *parent) :
     d->textMarkModel = new QmlProfilerTextMarkModel(this);
     connect(d->model, &QmlProfilerDataModel::allTypesLoaded,
             this, &QmlProfilerModelManager::processingDone);
+    connect(d->model, &QmlProfilerDataModel::traceFileError,
+            this, [this]() {
+        emit error(tr("Could not open a temporary file for storing QML traces."));
+    });
 }
 
 QmlProfilerModelManager::~QmlProfilerModelManager()
@@ -543,12 +547,17 @@ void QmlProfilerModelManager::restrictToRange(qint64 startTime, qint64 endTime)
     setVisibleFeatures(0);
 
     startAcquiring();
-    d->model->replayEvents(startTime, endTime,
+    if (!d->model->replayEvents(startTime, endTime,
                                 std::bind(&QmlProfilerModelManagerPrivate::dispatch, d,
-                                     std::placeholders::_1, std::placeholders::_2));
+                                          std::placeholders::_1, std::placeholders::_2))) {
+        emit error(tr("Could not re-read events from temporary trace file. "
+                      "The trace data is lost."));
+        clear();
+    } else {
         d->notesModel->setNotes(notes);
         d->traceTime->restrictToRange(startTime, endTime);
         acquiringDone();
+    }
 }
 
 bool QmlProfilerModelManager::isRestrictedToRange() const

src/plugins/qmlprofiler/qmlprofilerstatisticsmodel.cpp

@@ -120,13 +120,17 @@ void QmlProfilerStatisticsModel::restrictToFeatures(qint64 features)
         return;
 
     clear();
-    d->modelManager->qmlModel()->replayEvents(d->modelManager->traceTime()->startTime(),
+    if (!d->modelManager->qmlModel()->replayEvents(d->modelManager->traceTime()->startTime(),
                                                    d->modelManager->traceTime()->endTime(),
                                                    std::bind(&QmlProfilerStatisticsModel::loadEvent,
                                                              this, std::placeholders::_1,
-                                                        std::placeholders::_2));
+                                                             std::placeholders::_2))) {
+        emit d->modelManager->error(tr("Could not re-read events from temporary trace file."));
+        clear();
+    } else {
         finalize();
         notesChanged(-1); // Reload notes
+    }
 }
 
 const QHash<int, QmlProfilerStatisticsModel::QmlEventStats> &QmlProfilerStatisticsModel::getData() const

src/plugins/qmlprofiler/qmlprofilertracefile.cpp

@@ -668,7 +668,8 @@ void QmlProfilerFileWriter::saveQtd(QIODevice *device)
         stream.writeStartElement(_("profilerDataModel"));
 
         QStack<QmlEvent> stack;
-        m_model->replayEvents(-1, -1, [this, &stack, &stream](const QmlEvent &event,
+        const bool success = m_model->replayEvents(
+                    -1, -1, [this, &stack, &stream](const QmlEvent &event,
                     const QmlEventType &type) {
             if (isCanceled())
                 return;
@@ -741,6 +742,10 @@ void QmlProfilerFileWriter::saveQtd(QIODevice *device)
             if ((event.timestamp() & 0xfff) == 0)
                 updateProgress(event.timestamp());
         });
+        if (!success) {
+            emit error(tr("Could not re-read events from temporary trace file. Saving failed."));
+            return;
+        }
 
         stream.writeEndElement(); // profilerDataModel
     }
@@ -807,8 +812,9 @@ void QmlProfilerFileWriter::saveQzt(QFile *file)
 
     if (!isCanceled()) {
         buffer.open(QIODevice::WriteOnly);
-        m_model->replayEvents(-1, -1, [this, &stream, &buffer, &bufferStream](
-                              const QmlEvent &event, const QmlEventType &type) {
+        const bool success = m_model->replayEvents(
+                    -1, -1, [this, &stream, &buffer, &bufferStream](const QmlEvent &event,
+                                                                    const QmlEventType &type) {
             Q_UNUSED(type);
             bufferStream << event;
             // 32MB buffer should be plenty for efficient compression
@@ -822,6 +828,10 @@ void QmlProfilerFileWriter::saveQzt(QFile *file)
                 updateProgress(event.timestamp());
             }
         });
+        if (!success) {
+            emit error(tr("Could not re-read events from temporary trace file. Saving failed."));
+            return;
+        }
     }
 
     if (isCanceled()) {