Force completion of asynchronously loaded components.

[ChangeLog][QtQuick][QQmlComponent] Synchronously complete the loading of a
Asynchronous QQmlComponent, if a PreferSynchronous QQmlComponent is created
for the same url (given that this url does support synchronous loading).

Change-Id: I3291d0569a69bac2aeb4815f1068a426ef2707ef
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

4 files changed, 73 insertions, 0 deletions

diff --git a/src/qml/qml/ftw/qqmlthread.cpp b/src/qml/qml/ftw/qqmlthread.cpp
index 4addcd9e58..62f6f76a7e 100644
--- a/src/qml/qml/ftw/qqmlthread.cpp
+++ b/src/qml/qml/ftw/qqmlthread.cpp
@@ -377,4 +377,31 @@ void QQmlThread::internalPostMethodToMain(Message *message)
     d->unlock();
 }
 
+void QQmlThread::waitForNextMessage()
+{
+    Q_ASSERT(!isThisThread());
+    d->lock();
+    Q_ASSERT(d->m_mainThreadWaiting == false);
+
+    d->m_mainThreadWaiting = true;
+
+    if (d->mainSync || !d->threadList.isEmpty()) {
+        if (d->mainSync) {
+            QQmlThread::Message *message = d->mainSync;
+            unlock();
+            message->call(this);
+            delete message;
+            lock();
+            d->mainSync = 0;
+            wakeOne();
+        } else {
+            d->wait();
+        }
+    }
+
+    d->m_mainThreadWaiting = false;
+    d->unlock();
+}
+
+
 QT_END_NAMESPACE
diff --git a/src/qml/qml/ftw/qqmlthread_p.h b/src/qml/qml/ftw/qqmlthread_p.h
index 86d7d2cf19..73658536ac 100644
--- a/src/qml/qml/ftw/qqmlthread_p.h
+++ b/src/qml/qml/ftw/qqmlthread_p.h
@@ -108,6 +108,8 @@ public:
     template<typename T, typename T2, class V, class V2, class O>
     inline void postMethodToMain(void (O::*Member)(V, V2), const T &, const T2 &);
 
+    void waitForNextMessage();
+
 protected:
     virtual void startupThread();
     virtual void shutdownThread();
diff --git a/src/qml/qml/qqmltypeloader.cpp b/src/qml/qml/qqmltypeloader.cpp
index e860b8e0fa..408f17ffde 100644
--- a/src/qml/qml/qqmltypeloader.cpp
+++ b/src/qml/qml/qqmltypeloader.cpp
@@ -1612,6 +1612,20 @@ QQmlTypeData *QQmlTypeLoader::getType(const QUrl &url, Mode mode)
         } else {
             QQmlTypeLoader::load(typeData, mode);
         }
+    } else if ((mode == PreferSynchronous) && QQmlFile::isSynchronous(url)) {
+        // this was started Asynchronous, but we need to force Synchronous
+        // completion now (if at all possible with this type of URL).
+
+        if (!m_thread->isThisThread()) {
+            // this only works when called directly from the UI thread, but not
+            // when recursively called on the QML thread via resolveTypes()
+
+            while (!typeData->isCompleteOrError()) {
+                unlock();
+                m_thread->waitForNextMessage();
+                lock();
+            }
+        }
     }
 
     typeData->addref();
diff --git a/tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp b/tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp
index bb159d5931..4c1f827915 100644
--- a/tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp
+++ b/tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp
@@ -110,6 +110,7 @@ private slots:
     void qmlCreateParentReference();
     void async();
     void asyncHierarchy();
+    void asyncForceSync();
     void componentUrlCanonicalization();
     void onDestructionLookup();
     void onDestructionCount();
@@ -371,6 +372,35 @@ void tst_qqmlcomponent::asyncHierarchy()
     delete root;
 }
 
+void tst_qqmlcomponent::asyncForceSync()
+{
+    {
+        // 1) make sure that HTTP URLs cannot be completed synchronously
+        TestHTTPServer server;
+        QVERIFY2(server.listen(), qPrintable(server.errorString()));
+        server.serveDirectory(dataDirectory());
+
+        // ensure that the item hierarchy is compiled correctly.
+        QQmlComponent component(&engine);
+        component.loadUrl(server.url("/TestComponent.2.qml"), QQmlComponent::Asynchronous);
+        QCOMPARE(component.status(), QQmlComponent::Loading);
+        QQmlComponent component2(&engine, server.url("/TestComponent.2.qml"), QQmlComponent::PreferSynchronous);
+        QCOMPARE(component2.status(), QQmlComponent::Loading);
+    }
+    {
+        // 2) make sure that file:// URL can be completed synchronously
+
+        // ensure that the item hierarchy is compiled correctly.
+        QQmlComponent component(&engine);
+        component.loadUrl(testFileUrl("/TestComponent.2.qml"), QQmlComponent::Asynchronous);
+        QCOMPARE(component.status(), QQmlComponent::Loading);
+        QQmlComponent component2(&engine, testFileUrl("/TestComponent.2.qml"), QQmlComponent::PreferSynchronous);
+        QCOMPARE(component2.status(), QQmlComponent::Ready);
+        QCOMPARE(component.status(), QQmlComponent::Loading);
+        QTRY_COMPARE_WITH_TIMEOUT(component.status(), QQmlComponent::Ready, 0);
+    }
+}
+
 void tst_qqmlcomponent::componentUrlCanonicalization()
 {
     // ensure that url canonicalization succeeds so that type information