Introduce functions to set properties during creation

Change-Id: Idd4c8ab9e34b9bc3e00f21d7cf1e4f1a70586e7f
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

9 files changed, 109 insertions, 11 deletions

diff --git a/src/qml/qml/qqmlapplicationengine.cpp b/src/qml/qml/qqmlapplicationengine.cpp
index e93cfcadb9..d04a89b514 100644
--- a/src/qml/qml/qqmlapplicationengine.cpp
+++ b/src/qml/qml/qqmlapplicationengine.cpp
@@ -131,7 +131,7 @@ void QQmlApplicationEnginePrivate::finishLoad(QQmlComponent *c)
         q->objectCreated(nullptr, c->url());
         break;
     case QQmlComponent::Ready: {
-        auto newObj = c->create();
+        auto newObj = initialProperties.empty() ? c->create() : c->createWithInitialProperties(initialProperties);
         objects << newObj;
         QObject::connect(newObj, &QObject::destroyed, q, [&](QObject *obj) { objects.removeAll(obj); });
         q->objectCreated(objects.constLast(), c->url());
@@ -279,6 +279,22 @@ void QQmlApplicationEngine::load(const QString &filePath)
 }
 
 /*!
+   Sets the initial properties with which the QML component gets initialized after
+   it gets loaded.
+
+
+   \sa QQmlComponent::setInitialProperties
+   \sa QQmlApplicationEngine::load
+   \sa QQmlApplicationEngine::loadData
+   \since 5.14
+*/
+void QQmlApplicationEngine::setInitialProperties(const QVariantMap &initialProperties)
+{
+    Q_D(QQmlApplicationEngine);
+    d->initialProperties = initialProperties;
+}
+
+/*!
   Loads the QML given in \a data. The object tree defined by \a data is
   instantiated immediately.
 
diff --git a/src/qml/qml/qqmlapplicationengine.h b/src/qml/qml/qqmlapplicationengine.h
index bb5d6b5d68..2b4de91154 100644
--- a/src/qml/qml/qqmlapplicationengine.h
+++ b/src/qml/qml/qqmlapplicationengine.h
@@ -66,6 +66,7 @@ public:
 public Q_SLOTS:
     void load(const QUrl &url);
     void load(const QString &filePath);
+    void setInitialProperties(const QVariantMap &initialProperties);
     void loadData(const QByteArray &data, const QUrl &url = QUrl());
 
 Q_SIGNALS:
diff --git a/src/qml/qml/qqmlapplicationengine_p.h b/src/qml/qml/qqmlapplicationengine_p.h
index 7a341847bd..1279e400e8 100644
--- a/src/qml/qml/qqmlapplicationengine_p.h
+++ b/src/qml/qml/qqmlapplicationengine_p.h
@@ -73,6 +73,7 @@ public:
     void loadTranslations(const QUrl &rootFile);
     void finishLoad(QQmlComponent *component);
     QList<QObject *> objects;
+    QVariantMap initialProperties;
 };
 
 QT_END_NAMESPACE
diff --git a/src/qml/qml/qqmlcomponent.cpp b/src/qml/qml/qqmlcomponent.cpp
index fefe2bc685..ed8c41a582 100644
--- a/src/qml/qml/qqmlcomponent.cpp
+++ b/src/qml/qml/qqmlcomponent.cpp
@@ -350,6 +350,32 @@ void QQmlComponentPrivate::clear()
     compilationUnit = nullptr;
 }
 
+QObject *QQmlComponentPrivate::doBeginCreate(QQmlComponent *q, QQmlContext *context)
+{
+    if (!engine) {
+        // ###Qt6: In Qt 6, it should be impossible for users to create a QQmlComponent without an engine, and we can remove this check
+        qWarning("QQmlComponent: Must provide an engine before calling create");
+        return nullptr;
+    }
+    if (!context)
+        context = engine->rootContext();
+    return q->beginCreate(context);
+}
+
+bool QQmlComponentPrivate::setInitialProperty(QObject *component, const QString& name, const QVariant &value)
+{
+    QQmlProperty prop(component, name);
+    auto privProp = QQmlPropertyPrivate::get(prop);
+    if (!prop.isValid() || !privProp->writeValueProperty(value, nullptr)) {
+        QQmlError error{};
+        error.setUrl(url);
+        error.setDescription(QLatin1String("Could not set property %1").arg(name));
+        state.errors.push_back(error);
+        return false;
+    } else
+        return true;
+}
+
 /*!
     \internal
 */
@@ -780,18 +806,28 @@ QObject *QQmlComponent::create(QQmlContext *context)
 {
     Q_D(QQmlComponent);
 
-    if (!d->engine) {
-        // ###Qt6: In Qt 6, it should be impossible for users to create a QQmlComponent without an engine, and we can remove this check
-        qWarning("QQmlComponent: Must provide an engine before calling create");
-        return nullptr;
-    }
+    QObject *rv = d->doBeginCreate(this, context);
+    if (rv)
+        completeCreate();
+    return rv;
+}
 
-    if (!context)
-        context = d->engine->rootContext();
+/*!
+    Create an object instance of this component, and initialize its toplevel properties according to initalPropertyValues.
 
-    QObject *rv = beginCreate(context);
-    if (rv)
+
+    \sa QQmlComponent::create
+    \since 5.14
+*/
+QObject *QQmlComponent::createWithInitialProperties(const QVariantMap& initialProperties, QQmlContext *context)
+{
+    Q_D(QQmlComponent);
+
+    QObject *rv = d->doBeginCreate(this, context);
+    if (rv) {
+        setInitialProperties(rv, initialProperties);
         completeCreate();
+    }
     return rv;
 }
 
@@ -1067,6 +1103,26 @@ void QQmlComponent::create(QQmlIncubator &incubator, QQmlContext *context,
     enginePriv->incubate(incubator, forContextData);
 }
 
+/*!
+   Set toplevel properties of the component.
+
+
+   This method provides advanced control over component instance creation.
+   In general, programmers should use
+   \l QQmlComponent::createWithInitialProperties to create a component.
+
+   Use this method after beginCreate and before completeCreate has been called.
+   If a provided property does not exist, a warning is issued.
+
+   \since 5.14
+*/
+void QQmlComponent::setInitialProperties(QObject *component, const QVariantMap &properties)
+{
+    Q_D(QQmlComponent);
+    for (auto it = properties.constBegin(); it != properties.constEnd(); ++it)
+        d->setInitialProperty(component, it.key(), it.value());
+}
+
 /*
     This is essentially a copy of QQmlComponent::create(); except it takes the QQmlContextData
     arguments instead of QQmlContext which means we don't have to construct the rather weighty
diff --git a/src/qml/qml/qqmlcomponent.h b/src/qml/qml/qqmlcomponent.h
index 39b6d4526f..f259c99b08 100644
--- a/src/qml/qml/qqmlcomponent.h
+++ b/src/qml/qml/qqmlcomponent.h
@@ -100,6 +100,8 @@ public:
     QUrl url() const;
 
     virtual QObject *create(QQmlContext *context = nullptr);
+    QObject *createWithInitialProperties(const QVariantMap& initialProperties, QQmlContext *context = nullptr);
+    void setInitialProperties(QObject *component, const QVariantMap &properties);
     virtual QObject *beginCreate(QQmlContext *);
     virtual void completeCreate();
 
diff --git a/src/qml/qml/qqmlcomponent_p.h b/src/qml/qml/qqmlcomponent_p.h
index 9a967501c9..2170646b89 100644
--- a/src/qml/qml/qqmlcomponent_p.h
+++ b/src/qml/qml/qqmlcomponent_p.h
@@ -143,6 +143,9 @@ public:
     static QQmlComponentPrivate *get(QQmlComponent *c) {
         return static_cast<QQmlComponentPrivate *>(QObjectPrivate::get(c));
     }
+
+    QObject *doBeginCreate(QQmlComponent *q, QQmlContext *context);
+    bool setInitialProperty(QObject *component, const QString &name, const QVariant& value);
 };
 
 QT_END_NAMESPACE
diff --git a/src/quick/items/qquickview.cpp b/src/quick/items/qquickview.cpp
index 61477360bf..17fc16d44b 100644
--- a/src/quick/items/qquickview.cpp
+++ b/src/quick/items/qquickview.cpp
@@ -240,6 +240,22 @@ void QQuickView::setSource(const QUrl& url)
 }
 
 /*!
+   Sets the initial properties with which the QML component gets initialized after
+   calling \l QQuickView::setSource.
+
+
+   Note that you can only use this function to initialize toplevel properties.
+
+   \sa QQmlComponent::createWithInitialProperties
+   \since 5.14
+*/
+void QQuickView::setInitialProperties(const QVariantMap &initialProperties)
+{
+    Q_D(QQuickView);
+    d->initialProperties = initialProperties;
+}
+
+/*!
     \internal
 
     Set the source \a url, \a component and content \a item (root of the QML object hierarchy) directly.
@@ -471,7 +487,7 @@ void QQuickView::continueExecute()
         return;
     }
 
-    QObject *obj = d->component->create();
+    QObject *obj = d->initialProperties.empty() ? d->component->create() : d->component->createWithInitialProperties(d->initialProperties);
 
     if (d->component->isError()) {
         const QList<QQmlError> errorList = d->component->errors();
diff --git a/src/quick/items/qquickview.h b/src/quick/items/qquickview.h
index ecae25e90b..4122fcac79 100644
--- a/src/quick/items/qquickview.h
+++ b/src/quick/items/qquickview.h
@@ -88,6 +88,7 @@ public:
 
 public Q_SLOTS:
     void setSource(const QUrl&);
+    void setInitialProperties(const QVariantMap &initialProperties);
     void setContent(const QUrl& url, QQmlComponent *component, QObject *item);
 
 Q_SIGNALS:
diff --git a/src/quick/items/qquickview_p.h b/src/quick/items/qquickview_p.h
index 3f284c0519..b1ab8d8e8c 100644
--- a/src/quick/items/qquickview_p.h
+++ b/src/quick/items/qquickview_p.h
@@ -108,6 +108,8 @@ public:
     QQuickView::ResizeMode resizeMode;
     QSize initialSize;
     QElapsedTimer frameTimer;
+
+    QVariantMap initialProperties;
 };
 
 QT_END_NAMESPACE