[libcalamaresui] Manual QML loading trickery

- The slideshow item needs a parent to be visible,
 - QML gets size 0,0 unless explicitly sized to the surrounding widget.

src/libcalamaresui/ExecutionViewStep.cpp

@@ -38,6 +38,7 @@
 #include <QProgressBar>
 #include <QQmlComponent>
 #include <QQmlEngine>
+#include <QQuickItem>
 #include <QQuickWidget>
 #include <QVBoxLayout>
 
@@ -150,9 +151,18 @@ ExecutionViewStep::onActivate()
     loadQml();
     if ( m_qmlComponent )
     {
-        m_qmlObject = m_qmlComponent->create();
-        cDebug() << "Created QML object" << (void *)m_qmlObject << m_qmlObject->objectName();
-        cDebug() << "Show root" << m_qmlShow->rootObject() << "context" << m_qmlShow->rootContext();
+        auto* rootItem = m_qmlShow->quickWindow()->contentItem();
+        rootItem->setSize( m_qmlShow->size() );
+
+        QObject* o = m_qmlComponent->create();
+        m_qmlObject = qobject_cast< QQuickItem* >( o );
+        if ( !m_qmlObject )
+            delete o;
+        else
+        {
+            m_qmlObject->setParentItem( rootItem );
+            m_qmlObject->setSize( m_qmlShow->size() );
+        }
     }
 
     JobQueue* queue = JobQueue::instance();

src/libcalamaresui/ExecutionViewStep.h

@@ -27,8 +27,9 @@
 class QLabel;
 class QObject;
 class QProgressBar;
-class QQuickWidget;
 class QQmlComponent;
+class QQuickItem;
+class QQuickWidget;
 
 namespace Calamares
 {
@@ -65,7 +66,7 @@ private:
     QLabel* m_label;
     QQuickWidget* m_qmlShow;
     QQmlComponent* m_qmlComponent;
-    QObject* m_qmlObject;  //< The actual show
+    QQuickItem* m_qmlObject;  //< The actual show
 
     QStringList m_jobInstanceKeys;