Make runtime initialization optionally not block QML

Runtime initialization made non-blocking by offloading it to a worker
thread. This causes various object thread affinities in runtime
to be incorrect. This is relevant at least for the singaling,
where having affinity to non-existing initialization thread would
cause signals to not be delivered.
To work around this issue, signal proxy thread affinitions and
signal connections are set after initialization has completed.
Similarly, behavior script QML engine initialization is deferred
so that it can be done in correct thread.

Task-number: QT3DS-3805
Change-Id: Ie8b64f4ecd93e4c422e369e625080652d67bde27
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>

1 files changed, 41 insertions, 16 deletions

diff --git a/src/runtime/Qt3DSQmlEngine.cpp b/src/runtime/Qt3DSQmlEngine.cpp
index b9b2067..a945f14 100644
--- a/src/runtime/Qt3DSQmlEngine.cpp
+++ b/src/runtime/Qt3DSQmlEngine.cpp
@@ -385,12 +385,13 @@ private:
 
     CScriptCallbacks m_ScriptCallbacks;
 
-    QQmlEngine m_engine;
+    QScopedPointer<QQmlEngine> m_engine;
     QMap<QString, QQmlComponent *> m_components;
     QVector<Q3DSQmlScript *> m_scripts;
 
     QSet<int> m_availableIds;
     QHash<TElement *, int> m_elementIdMap;
+    QVector<QPair<TElement *, QString>> m_deferredScriptLoads;
 
 public:
     CQmlEngineImpl(NVFoundationBase &fnd, ITimeProvider &inTimeProvider);
@@ -406,7 +407,10 @@ public:
     qt3ds::runtime::IApplication *GetApplication() override;
     void Initialize() override;
 
-    void LoadScript(IPresentation *presentation, TElement *element, const CHAR *path) override;
+    void loadScript(TElement *element, const QString &sourcePath);
+    void LoadScript(IPresentation *presentation, TElement *element, const CHAR *path,
+                    bool initInRenderThread) override;
+    void loadDeferredScripts() override;
     Q3DStudio::INT32 InitializeApplicationBehavior(const char *) override
     {
         return -1;
@@ -667,20 +671,15 @@ bool CQmlEngineImpl::GetAttribute(const char *element, const char *attName, char
     return false;
 }
 
-void CQmlEngineImpl::LoadScript(IPresentation *presentation, TElement *element, const CHAR *path)
+void CQmlEngineImpl::loadScript(TElement *element, const QString &sourcePath)
 {
-    QString presPath = QFileInfo(presentation->GetFilePath()).absolutePath();
-
-    QString sourcePath(presPath + QLatin1Char('/') + path);
-    sourcePath.replace(QLatin1Char('\\'), QLatin1Char('/'));
-
-    TElement *parent = element->GetParent();
-    if (!parent)
-        return;
+    if (m_engine.isNull())
+        m_engine.reset(new QQmlEngine);
 
     if (!m_components.contains(sourcePath)) {
-        m_components[sourcePath] = new QQmlComponent(&m_engine, QUrl::fromLocalFile(sourcePath),
-                                                     &m_engine);
+        m_components[sourcePath] = new QQmlComponent(m_engine.data(),
+                                                     QUrl::fromLocalFile(sourcePath),
+                                                     m_engine.data());
     }
 
     QQmlComponent *component = m_components[sourcePath];
@@ -705,6 +704,32 @@ void CQmlEngineImpl::LoadScript(IPresentation *presentation, TElement *element,
     }
 }
 
+void CQmlEngineImpl::LoadScript(IPresentation *presentation, TElement *element, const CHAR *path,
+                                bool initInRenderThread)
+{
+    QString presPath = QFileInfo(presentation->GetFilePath()).absolutePath();
+
+    QString sourcePath(presPath + QLatin1Char('/') + path);
+    sourcePath.replace(QLatin1Char('\\'), QLatin1Char('/'));
+
+    TElement *parent = element->GetParent();
+    if (!parent)
+        return;
+
+    // Defer engine initialization until we are in render thread
+    if (initInRenderThread)
+        loadScript(element, sourcePath);
+    else
+        m_deferredScriptLoads.append({element, sourcePath});
+}
+
+void CQmlEngineImpl::loadDeferredScripts()
+{
+    for (const auto &data : qAsConst(m_deferredScriptLoads))
+        loadScript(data.first, data.second);
+    m_deferredScriptLoads.clear();
+}
+
 void CQmlEngineImpl::FireEvent(const char *element, const char *evtName)
 {
     TElement *theElement = getTarget(element);
@@ -2001,7 +2026,7 @@ void CQmlEngineImpl::createComponent(QQmlComponent *component, TElement *element
     if (!parent)
         return;
 
-    QQmlContext *context = new QQmlContext(&m_engine, &m_engine);
+    QQmlContext *context = new QQmlContext(m_engine.data(), m_engine.data());
     QObject *obj = component->beginCreate(context);
     if (!obj) {
         context->deleteLater();
@@ -2439,7 +2464,7 @@ bool CQmlEngineImpl::getAttributeVector2(QVector<QByteArray> &outAttVec,
 
 QJSValue CQmlEngineImpl::buildJSFunc(const QString &userFunc)
 {
-    auto res = this->m_engine.evaluate(userFunc);
+    auto res = this->m_engine->evaluate(userFunc);
     if (res.isError()) {
         qWarning() << __FUNCTION__
             << "Uncaught exception during datainput evaluation. Evaluator function" << userFunc;
@@ -2457,7 +2482,7 @@ QVariant CQmlEngineImpl::callJSFunc(const QString &controllerName,
 
     // get the most recent set values for datainput sources (arguments) in the expression
     for (auto diVal : sourceDIs)
-        args << this->m_engine.toScriptValue(diMap[diVal].value);
+        args << this->m_engine->toScriptValue(diMap[diVal].value);
 
     if (diDef.evalFunc.isCallable()) {
         QJSValue res = diDef.evalFunc.call(args);