[libcalamaresui] Tell the manager explicitly when loading is done

- Add some extra checks for validity of m_currentStep (an index)
- Start off with explicitly invalid index, and keep it so until
  loading is complete; this prevents the situation where quit-at-end
  gets triggered after loading the very first module.

src/calamares/CalamaresApplication.cpp

@@ -339,14 +339,8 @@ CalamaresApplication::initViewSteps()
     }
 
     cDebug() << "STARTUP: Window now visible and ProgressTreeView populated";
-
-    const auto& steps = Calamares::ViewManager::instance()->viewSteps();
-    cDebug() << Logger::SubEntry << steps.count() << "view steps loaded.";
-    // Tell the first view that it's been shown.
-    if ( steps.count() > 0 )
-    {
-        steps.first()->onActivate();
-    }
+    cDebug() << Logger::SubEntry << Calamares::ViewManager::instance()->viewSteps().count() << "view steps loaded.";
+    Calamares::ViewManager::instance()->onInitComplete();
 }
 
 void

src/libcalamaresui/ViewManager.cpp

@@ -65,7 +65,7 @@ ViewManager::instance( QObject* parent )
 
 ViewManager::ViewManager( QObject* parent )
     : QAbstractListModel( parent )
-    , m_currentStep( 0 )
+    , m_currentStep( -1 )
     , m_widget( new QWidget() )
 {
     Q_ASSERT( !s_instance );
@@ -122,7 +122,7 @@ ViewManager::insertViewStep( int before, ViewStep* step )
     // TODO: this can be a regular slot
     connect( step, &ViewStep::nextStatusChanged, this, [this]( bool status ) {
         ViewStep* vs = qobject_cast< ViewStep* >( sender() );
-        if ( vs )
+        if ( vs && currentStepValid() )
         {
             if ( vs == m_steps.at( m_currentStep ) )
             {
@@ -238,6 +238,18 @@ ViewManager::onInitFailed( const QStringList& modules )
     insertViewStep( 0, new BlankViewStep( title, description.arg( *Calamares::Branding::ProductName ), detailString ) );
 }
 
+void
+ViewManager::onInitComplete()
+{
+    m_currentStep = 0;
+
+    // Tell the first view that it's been shown.
+    if ( m_steps.count() > 0 )
+    {
+        m_steps.first()->onActivate();
+    }
+}
+
 ViewStepList
 ViewManager::viewSteps() const
 {
@@ -248,7 +260,7 @@ ViewManager::viewSteps() const
 ViewStep*
 ViewManager::currentStep() const
 {
-    return m_steps.value( m_currentStep );
+    return currentStepValid() ? m_steps.value( m_currentStep ) : nullptr;
 }
 
 
@@ -279,12 +291,22 @@ isAtVeryEnd( const ViewStepList& steps, int index )
     {
         return false;
     }
+    // .. and if the index is invalid, ignore it too
+    if ( !( ( 0 <= index ) && ( index < steps.count() ) ) )
+    {
+        return false;
+    }
     return ( index >= steps.count() ) || ( index == steps.count() - 1 && steps.last()->isAtEnd() );
 }
 
 void
 ViewManager::next()
 {
+    if ( !currentStepValid() )
+    {
+        return;
+    }
+
     ViewStep* step = m_steps.at( m_currentStep );
     bool executing = false;
     if ( step->isAtEnd() )
@@ -416,6 +438,11 @@ ViewManager::updateButtonLabels()
 void
 ViewManager::back()
 {
+    if ( !currentStepValid() )
+    {
+        return;
+    }
+
     ViewStep* step = m_steps.at( m_currentStep );
     if ( step->isAtBeginning() && m_currentStep > 0 )
     {

src/libcalamaresui/ViewManager.h

@@ -184,6 +184,12 @@ public Q_SLOTS:
      */
     void onInitFailed( const QStringList& modules );
 
+    /** @brief Tell the manager that initialization / loading is complete.
+     *
+     * Call this at least once, to tell the manager to activate the first page.
+     */
+    void onInitComplete();
+
 signals:
     void currentStepChanged();
     void enlarge( QSize enlarge ) const;  // See ViewStep::enlarge()
@@ -211,6 +217,8 @@ private:
     void updateButtonLabels();
     void updateCancelEnabled( bool enabled );
 
+    inline bool currentStepValid() const { return ( 0 <= m_currentStep ) && ( m_currentStep < m_steps.length() ); }
+
     static ViewManager* s_instance;
 
     ViewStepList m_steps;