[libcalamaresui] Qml loading

- this is mostly copied from ExecutionViewStep (only the V2 QML
   loading), which does the same kind of thing.
 - loading from QRC does not work yet

src/libcalamaresui/viewpages/QmlViewStep.cpp

@@ -18,8 +18,14 @@
 
 #include "QmlViewStep.h"
 
+#include "utils/Dirs.h"
+#include "utils/Logger.h"
 #include "widgets/WaitingWidget.h"
 
+#include <QQmlComponent>
+#include <QQmlEngine>
+#include <QQuickItem>
+#include <QQuickWidget>
 #include <QVBoxLayout>
 #include <QWidget>
 
@@ -31,9 +37,24 @@ QmlViewStep::QmlViewStep( const QString& name, QObject* parent )
     , m_name( name )
     , m_widget( new QWidget )
     , m_spinner( new WaitingWidget( tr( "Loading ..." ) ) )
+    , m_qmlWidget( new QQuickWidget )
 {
     QVBoxLayout* layout = new QVBoxLayout( m_widget );
     layout->addWidget( m_spinner );
+
+    m_qmlWidget->setSizePolicy( QSizePolicy::Expanding, QSizePolicy::Expanding );
+    m_qmlWidget->setResizeMode( QQuickWidget::SizeRootObjectToView );
+    m_qmlWidget->engine()->addImportPath( CalamaresUtils::qmlModulesDir().absolutePath() );
+
+    // TODO: search for suitable file
+    QString qrcName = QStringLiteral( ":/%1.qml" ).arg( m_name );
+    m_qmlFileName = qrcName;
+
+    cDebug() << "QmlViewStep loading" << m_qmlFileName;
+    m_qmlComponent = new QQmlComponent(
+        m_qmlWidget->engine(), QUrl( m_qmlFileName ), QQmlComponent::CompilationMode::Asynchronous );
+    connect( m_qmlComponent, &QQmlComponent::statusChanged, this, &QmlViewStep::loadComplete );
+    cDebug() << Logger::SubEntry << "Status" << m_qmlComponent->status();
 }
 
 QmlViewStep::~QmlViewStep() {}
@@ -94,3 +115,53 @@ Calamares::QmlViewStep::widget()
 {
     return m_widget;
 }
+
+void
+Calamares::QmlViewStep::loadComplete()
+{
+    cDebug() << "QML component" << m_qmlFileName << m_qmlComponent->status();
+    if ( m_qmlComponent->isReady() && !m_qmlObject )
+    {
+        cDebug() << "QML component complete" << m_qmlFileName;
+        // Don't do this again
+        disconnect( m_qmlComponent, &QQmlComponent::statusChanged, this, &QmlViewStep::loadComplete );
+
+        QObject* o = m_qmlComponent->create();
+        m_qmlObject = qobject_cast< QQuickItem* >( o );
+        if ( !m_qmlObject )
+        {
+            cError() << Logger::SubEntry << "Could not create QML from" << m_qmlFileName;
+            delete o;
+        }
+        else
+        {
+            // setContent() is public API, but not documented publicly.
+            // It is marked \internal in the Qt sources, but does exactly
+            // what is needed: sets up visual parent by replacing the root
+            // item, and handling resizes.
+            m_qmlWidget->setContent( QUrl( m_qmlFileName ), m_qmlComponent, m_qmlObject );
+            showQml();
+        }
+    }
+}
+
+void
+Calamares::QmlViewStep::showQml()
+{
+    if ( !m_qmlWidget || !m_qmlObject )
+    {
+        cDebug() << "showQml() called but no QML object";
+        return;
+    }
+    if ( m_spinner )
+    {
+        m_widget->layout()->removeWidget( m_spinner );
+        m_widget->layout()->addWidget( m_qmlWidget );
+        delete m_spinner;
+        m_spinner = nullptr;
+    }
+    else
+    {
+        cDebug() << "showQml() called twice";
+    }
+}

src/libcalamaresui/viewpages/QmlViewStep.h

@@ -58,12 +58,19 @@ public:
 
     virtual JobList jobs() const override;
 
+private Q_SLOTS:
+    void loadComplete();
+
 private:
+    /// @brief Swap out the spinner for the QQuickWidget
+    void showQml();
+
     QString m_name;
+    QString m_qmlFileName;
 
     QWidget* m_widget = nullptr;
     WaitingWidget* m_spinner = nullptr;
-    QQuickWidget* m_qmlShow = nullptr;
+    QQuickWidget* m_qmlWidget = nullptr;
     QQmlComponent* m_qmlComponent = nullptr;
     QQuickItem* m_qmlObject = nullptr;
 };