Permit signals to be emitted in a different thread

The QQmlNotifier approach to connecting to signals did not
support the cross-thread signal/slot model used elsewhere in
Qt.  This change allows one specific case of that - emitting
a signal in a different thread than the one the QObject
lives - to work.

Task-number: QTBUG-25647
Change-Id: Ia8fdaf4c7d7e2ccd7ff7657bb1d8e26277eb60aa
Reviewed-by: Aaron Kennedy <aaron.kennedy@nokia.com>

16 files changed, 131 insertions, 18 deletions

diff --git a/src/qml/qml/qqmlboundsignal.cpp b/src/qml/qml/qqmlboundsignal.cpp
index 358e945d41..8b3a39c12e 100644
--- a/src/qml/qml/qqmlboundsignal.cpp
+++ b/src/qml/qml/qqmlboundsignal.cpp
@@ -221,14 +221,14 @@ void QQmlAbstractBoundSignal::removeFromObject()
 }
 
 QQmlBoundSignal::QQmlBoundSignal(QObject *scope, const QMetaMethod &signal,
-                               QObject *owner)
+                               QObject *owner, QQmlEngine *engine)
 : m_expression(0), m_params(0), m_scope(scope), m_index(signal.methodIndex())
 {
     setParamsValid(false);
     setIsEvaluating(false);
     addToObject(owner);
     callback = &subscriptionCallback;
-    QQmlNotifierEndpoint::connect(scope, m_index);
+    QQmlNotifierEndpoint::connect(scope, m_index, engine);
 }
 
 QQmlBoundSignal::~QQmlBoundSignal()
diff --git a/src/qml/qml/qqmlboundsignal_p.h b/src/qml/qml/qqmlboundsignal_p.h
index 3fb20a1290..c0544251b1 100644
--- a/src/qml/qml/qqmlboundsignal_p.h
+++ b/src/qml/qml/qqmlboundsignal_p.h
@@ -132,7 +132,7 @@ class Q_QML_EXPORT QQmlBoundSignal : public QQmlAbstractBoundSignal,
                                      public QQmlNotifierEndpoint
 {
 public:
-    QQmlBoundSignal(QObject *scope, const QMetaMethod &signal, QObject *owner);
+    QQmlBoundSignal(QObject *scope, const QMetaMethod &signal, QObject *owner, QQmlEngine *engine);
     virtual ~QQmlBoundSignal();
 
     int index() const;
diff --git a/src/qml/qml/qqmlengine.cpp b/src/qml/qml/qqmlengine.cpp
index b6a306085e..f948c31352 100644
--- a/src/qml/qml/qqmlengine.cpp
+++ b/src/qml/qml/qqmlengine.cpp
@@ -80,6 +80,8 @@
 #include <QtCore/qcoreapplication.h>
 #include <QtCore/qdir.h>
 #include <QtCore/qmutex.h>
+#include <QtCore/qthread.h>
+#include <private/qthread_p.h>
 #include <QtNetwork/qnetworkconfigmanager.h>
 
 #include <private/qobject_p.h>
@@ -470,8 +472,51 @@ void QQmlData::signalEmitted(QAbstractDeclarativeData *, QObject *object, int in
     QQmlData *ddata = QQmlData::get(object, false);
     if (!ddata) return; // Probably being deleted
 
-    QQmlNotifierEndpoint *ep = ddata->notify(index);
-    if (ep) QQmlNotifier::emitNotify(ep, a);
+    // In general, QML only supports QObject's that live on the same thread as the QQmlEngine
+    // that they're exposed to.  However, to make writing "worker objects" that calculate data
+    // in a separate thread easier, QML allows a QObject that lives in the same thread as the
+    // QQmlEngine to emit signals from a different thread.  These signals are then automatically
+    // marshalled back onto the QObject's thread and handled by QML from there.  This is tested
+    // by the qqmlecmascript::threadSignal() autotest.
+    if (ddata->notifyList &&
+        QThread::currentThreadId() != QObjectPrivate::get(object)->threadData->threadId) {
+
+        QMetaMethod m = object->metaObject()->method(index);
+        QList<QByteArray> parameterTypes = m.parameterTypes();
+
+        int *types = (int *)malloc((parameterTypes.count() + 1) * sizeof(int));
+        void **args = (void **) malloc((parameterTypes.count() + 1) *sizeof(void *));
+
+        types[0] = 0; // return type
+        args[0] = 0; // return value
+
+        for (int ii = 0; ii < parameterTypes.count(); ++ii) {
+            const QByteArray &typeName = parameterTypes.at(ii);
+            if (typeName.endsWith('*'))
+                types[ii + 1] = QMetaType::VoidStar;
+            else
+                types[ii + 1] = QMetaType::type(typeName);
+
+            if (!types[ii + 1]) {
+                qWarning("QObject::connect: Cannot queue arguments of type '%s'\n"
+                         "(Make sure '%s' is registered using qRegisterMetaType().)",
+                         typeName.constData(), typeName.constData());
+                free(types);
+                free(args);
+                return;
+            }
+
+            args[ii + 1] = QMetaType::create(types[ii + 1], a[ii + 1]);
+        }
+
+        QMetaCallEvent *ev = new QMetaCallEvent(index, 0, 0, object, index,
+                                                parameterTypes.count() + 1, types, args);
+        QCoreApplication::postEvent(object, ev);
+
+    } else {
+        QQmlNotifierEndpoint *ep = ddata->notify(index);
+        if (ep) QQmlNotifier::emitNotify(ep, a);
+    }
 }
 
 int QQmlData::receivers(QAbstractDeclarativeData *d, const QObject *, int index)
diff --git a/src/qml/qml/qqmljavascriptexpression.cpp b/src/qml/qml/qqmljavascriptexpression.cpp
index 569a292a8b..5b1261b1eb 100644
--- a/src/qml/qml/qqmljavascriptexpression.cpp
+++ b/src/qml/qml/qqmljavascriptexpression.cpp
@@ -226,7 +226,7 @@ void QQmlJavaScriptExpression::GuardCapture::captureProperty(QObject *o, int c,
                 Q_ASSERT(g->isConnected(o, n));
             } else {
                 g = Guard::New(expression, engine);
-                g->connect(o, n);
+                g->connect(o, n, engine);
             }
 
             expression->activeGuards.prepend(g);
diff --git a/src/qml/qml/qqmlnotifier.cpp b/src/qml/qml/qqmlnotifier.cpp
index 1ed3a2957d..20b90a7111 100644
--- a/src/qml/qml/qqmlnotifier.cpp
+++ b/src/qml/qml/qqmlnotifier.cpp
@@ -41,6 +41,8 @@
 
 #include "qqmlnotifier_p.h"
 #include "qqmlproperty_p.h"
+#include <QtCore/qdebug.h>
+#include <private/qthread_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -67,10 +69,26 @@ void QQmlNotifier::emitNotify(QQmlNotifierEndpoint *endpoint, void **a)
     else if (endpoint) endpoint->notifying = 0;
 }
 
-void QQmlNotifierEndpoint::connect(QObject *source, int sourceSignal)
+void QQmlNotifierEndpoint::connect(QObject *source, int sourceSignal, QQmlEngine *engine)
 {
     disconnect();
 
+    Q_ASSERT(engine);
+    if (QObjectPrivate::get(source)->threadData->threadId !=
+        QObjectPrivate::get(engine)->threadData->threadId) {
+
+        QString sourceName;
+        QDebug(&sourceName) << source;
+        sourceName = sourceName.left(sourceName.length() - 1);
+        QString engineName;
+        QDebug(&engineName).nospace() << engine;
+        engineName = engineName.left(engineName.length() - 1);
+
+        qFatal("QQmlEngine: Illegal attempt to connect to %s that is in"
+               " a different thread than the QML engine %s.", qPrintable(sourceName),
+               qPrintable(engineName));
+    }
+
     this->source = source;
     this->sourceSignal = sourceSignal;
     QQmlPropertyPrivate::flushSignal(source, sourceSignal);
diff --git a/src/qml/qml/qqmlnotifier_p.h b/src/qml/qml/qqmlnotifier_p.h
index 3192531786..26fa6846e7 100644
--- a/src/qml/qml/qqmlnotifier_p.h
+++ b/src/qml/qml/qqmlnotifier_p.h
@@ -63,6 +63,7 @@ private:
     QQmlNotifierEndpoint *endpoints;
 };
 
+class QQmlEngine;
 class QQmlNotifierEndpoint
 {
 public:
@@ -76,7 +77,7 @@ public:
     inline bool isConnected(QObject *source, int sourceSignal);
     inline bool isConnected(QQmlNotifier *);
 
-    void connect(QObject *source, int sourceSignal);
+    void connect(QObject *source, int sourceSignal, QQmlEngine *engine);
     inline void connect(QQmlNotifier *);
     inline void disconnect();
 
diff --git a/src/qml/qml/qqmlproperty.cpp b/src/qml/qml/qqmlproperty.cpp
index d791d73cbf..111a99bd98 100644
--- a/src/qml/qml/qqmlproperty.cpp
+++ b/src/qml/qml/qqmlproperty.cpp
@@ -987,7 +987,8 @@ QQmlPropertyPrivate::takeSignalExpression(const QQmlProperty &that,
         return signalHandler->takeExpression(expr);
 
     if (expr) {
-        QQmlBoundSignal *signal = new QQmlBoundSignal(that.d->object, that.method(), that.d->object);
+        QQmlBoundSignal *signal = new QQmlBoundSignal(that.d->object, that.method(), that.d->object,
+                                                      expr->context()->engine);
         signal->takeExpression(expr);
     }
     return 0;
diff --git a/src/qml/qml/qqmlvme.cpp b/src/qml/qml/qqmlvme.cpp
index 093b6d1575..852a682630 100644
--- a/src/qml/qml/qqmlvme.cpp
+++ b/src/qml/qml/qqmlvme.cpp
@@ -738,7 +738,7 @@ QObject *QQmlVME::run(QList<QQmlError> *errors,
 
             QMetaMethod signal = target->metaObject()->method(instr.signalIndex);
 
-            QQmlBoundSignal *bs = new QQmlBoundSignal(target, signal, target);
+            QQmlBoundSignal *bs = new QQmlBoundSignal(target, signal, target, engine);
             QQmlBoundSignalExpression *expr =
                 new QQmlBoundSignalExpression(CTXT, context, DATAS.at(instr.value), true, COMP->name, instr.line, instr.column);
             bs->takeExpression(expr);
diff --git a/src/qml/qml/qqmlvmemetaobject.cpp b/src/qml/qml/qqmlvmemetaobject.cpp
index d7e9a28efe..001ed790d3 100644
--- a/src/qml/qml/qqmlvmemetaobject.cpp
+++ b/src/qml/qml/qqmlvmemetaobject.cpp
@@ -473,7 +473,7 @@ void QQmlVMEMetaObjectEndpoint::tryConnect()
 
             QMetaProperty prop = target->metaObject()->property(d->propertyIndex());
             if (prop.hasNotifySignal())
-                connect(target, prop.notifySignalIndex());
+                connect(target, prop.notifySignalIndex(), ctxt->engine);
         }
 
         metaObject.setFlag();
diff --git a/src/qml/qml/v4/qv4bindings.cpp b/src/qml/qml/v4/qv4bindings.cpp
index e19d74370c..896bf21538 100644
--- a/src/qml/qml/v4/qv4bindings.cpp
+++ b/src/qml/qml/v4/qv4bindings.cpp
@@ -443,7 +443,7 @@ void QV4Bindings::subscribeId(QQmlContextData *p, int idIndex, int subIndex)
     }
 }
  
-void QV4Bindings::subscribe(QObject *o, int notifyIndex, int subIndex)
+void QV4Bindings::subscribe(QObject *o, int notifyIndex, int subIndex, QQmlEngine *e)
 {
     Subscription *sub = (subscriptions + subIndex);
     if (sub->isConnected(o, notifyIndex))
@@ -451,7 +451,7 @@ void QV4Bindings::subscribe(QObject *o, int notifyIndex, int subIndex)
     sub->bindings = this;
     sub->method = subIndex; 
     if (o)
-        sub->connect(o, notifyIndex);
+        sub->connect(o, notifyIndex, e);
     else
         sub->disconnect();
 }
@@ -801,7 +801,7 @@ void QV4Bindings::run(int instrIndex, quint32 &executedBlocks,
         QObject *o = 0;
         const Register &object = registers[instr->subscribeop.reg];
         if (!object.isUndefined()) o = object.getQObject();
-        subscribe(o, instr->subscribeop.index, instr->subscribeop.offset);
+        subscribe(o, instr->subscribeop.index, instr->subscribeop.offset, context->engine);
     }
     QML_V4_END_INSTR(Subscribe, subscribeop)
 
@@ -843,7 +843,7 @@ void QV4Bindings::run(int instrIndex, quint32 &executedBlocks,
                 accessors->notifier(object, instr->fetchAndSubscribe.property.accessorData, &notifier);
                 if (notifier) sub->connect(notifier);
             } else if (instr->fetchAndSubscribe.property.notifyIndex != -1) {
-                sub->connect(object, instr->fetchAndSubscribe.property.notifyIndex);
+                sub->connect(object, instr->fetchAndSubscribe.property.notifyIndex, context->engine);
             }
         }
     }
diff --git a/src/qml/qml/v4/qv4bindings_p.h b/src/qml/qml/v4/qv4bindings_p.h
index 8ceccbb731..cb483d1f95 100644
--- a/src/qml/qml/v4/qv4bindings_p.h
+++ b/src/qml/qml/v4/qv4bindings_p.h
@@ -146,7 +146,7 @@ private:
 
     inline void unsubscribe(int subIndex);
     inline void subscribeId(QQmlContextData *p, int idIndex, int subIndex);
-    inline void subscribe(QObject *o, int notifyIndex, int subIndex);
+    inline void subscribe(QObject *o, int notifyIndex, int subIndex, QQmlEngine *);
 
     inline static qint32 toInt32(double n);
     static const double D32;
diff --git a/src/quick/util/qquickconnections.cpp b/src/quick/util/qquickconnections.cpp
index 1740224fad..2257761d29 100644
--- a/src/quick/util/qquickconnections.cpp
+++ b/src/quick/util/qquickconnections.cpp
@@ -279,7 +279,7 @@ void QQuickConnections::connectSignals()
         QQmlProperty prop(target(), propName);
         if (prop.isValid() && (prop.type() & QQmlProperty::SignalProperty)) {
             QQmlBoundSignal *signal =
-                new QQmlBoundSignal(target(), prop.method(), this);
+                new QQmlBoundSignal(target(), prop.method(), this, qmlEngine(this));
 
             QString location;
             QQmlContextData *ctxtdata = 0;
diff --git a/tests/auto/qml/qqmlecmascript/data/threadSignal.qml b/tests/auto/qml/qqmlecmascript/data/threadSignal.qml
new file mode 100644
index 0000000000..8f0e13b735
--- /dev/null
+++ b/tests/auto/qml/qqmlecmascript/data/threadSignal.qml
@@ -0,0 +1,8 @@
+import Qt.test 1.0
+import QtQuick 2.0
+
+MyWorkerObject {
+    property bool passed: false
+    Component.onCompleted: doIt()
+    onDone: passed = (result == 'good')
+}
diff --git a/tests/auto/qml/qqmlecmascript/testtypes.cpp b/tests/auto/qml/qqmlecmascript/testtypes.cpp
index d674fa3eb6..d3eff3b0ad 100644
--- a/tests/auto/qml/qqmlecmascript/testtypes.cpp
+++ b/tests/auto/qml/qqmlecmascript/testtypes.cpp
@@ -43,6 +43,7 @@
 #include <QPlainTextEdit>
 #include <QQmlEngine>
 #include <QJSEngine>
+#include <QThread>
 
 class BaseExtensionObject : public QObject
 {
@@ -154,6 +155,23 @@ static QObject *qobject_api_engine_parent(QQmlEngine *engine, QJSEngine *scriptE
     return o;
 }
 
+class MyWorkerObjectThread : public QThread
+{
+public:
+    MyWorkerObjectThread(MyWorkerObject *o) : QThread(o), o(o) { start(); }
+
+    virtual void run() {
+        emit o->done(QLatin1String("good"));
+    }
+
+    MyWorkerObject *o;
+};
+
+void MyWorkerObject::doIt()
+{
+    new MyWorkerObjectThread(this);
+}
+
 void registerTypes()
 {
     qmlRegisterType<MyQmlObject>("Qt.test", 1,0, "MyQmlObjectAlias");
@@ -170,6 +188,7 @@ void registerTypes()
     qmlRegisterType<MyRevisionedClass>("Qt.test",1,0,"MyRevisionedClass");
     qmlRegisterType<MyDeleteObject>("Qt.test", 1,0, "MyDeleteObject");
     qmlRegisterType<MyRevisionedClass,1>("Qt.test",1,1,"MyRevisionedClass");
+    qmlRegisterType<MyWorkerObject>("Qt.test", 1,0, "MyWorkerObject");
 
     // test scarce resource property binding post-evaluation optimisation
     // and for testing memory usage in property var circular reference test
diff --git a/tests/auto/qml/qqmlecmascript/testtypes.h b/tests/auto/qml/qqmlecmascript/testtypes.h
index e781e7703b..5fb78e81b6 100644
--- a/tests/auto/qml/qqmlecmascript/testtypes.h
+++ b/tests/auto/qml/qqmlecmascript/testtypes.h
@@ -1382,6 +1382,17 @@ private:
     QString m_timespec;
 };
 
+class MyWorkerObject : public QObject
+{
+    Q_OBJECT
+
+public Q_SLOTS:
+    void doIt();
+
+Q_SIGNALS:
+    void done(const QString &result);
+};
+
 void registerTypes();
 
 #endif // TESTTYPES_H
diff --git a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
index a523bea003..40bff34ae2 100644
--- a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
+++ b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
@@ -261,8 +261,8 @@ private slots:
     void deleteRootObjectInCreation();
     void onDestruction();
     void bindingSuppression();
-
     void signalEmitted();
+    void threadSignal();
 
 private:
     static void propertyVarWeakRefCallback(v8::Persistent<v8::Value> object, void* parameter);
@@ -6760,6 +6760,16 @@ void tst_qqmlecmascript::signalEmitted()
     }
 }
 
+// QTBUG-25647
+void tst_qqmlecmascript::threadSignal()
+{
+    QQmlComponent c(&engine, testFileUrl("threadSignal.qml"));
+    QObject *object = c.create();
+    QVERIFY(object != 0);
+    QTRY_VERIFY(object->property("passed").toBool());
+    delete object;
+}
+
 QTEST_MAIN(tst_qqmlecmascript)
 
 #include "tst_qqmlecmascript.moc"