[calamares] Progress"tree" is a list

- No need for a TreeView when it's just a one-dimensional
  list of items.

src/calamares/progresstree/ProgressTreeView.cpp

@@ -24,26 +24,17 @@
 #include "ViewManager.h"
 
 ProgressTreeView::ProgressTreeView( QWidget* parent )
-    : QTreeView( parent )
+    : QListView( parent )
 {
     this->setObjectName( "sidebarMenuApp" );
     setFrameShape( QFrame::NoFrame );
     setContentsMargins( 0, 0, 0, 0 );
 
-    setHeaderHidden( true );
-    setRootIsDecorated( true );
-    setExpandsOnDoubleClick( true );
-
     setSelectionMode( QAbstractItemView::NoSelection );
     setDragDropMode( QAbstractItemView::NoDragDrop );
     setAcceptDrops( false );
-    setUniformRowHeights( false );
-
-    setIndentation( 0 );
-    setSortingEnabled( false );
 
-    m_delegate = new ProgressTreeDelegate( this );
-    setItemDelegate( m_delegate );
+    setItemDelegate( new ProgressTreeDelegate( this ) );
 
     QPalette plt = palette();
     plt.setColor( QPalette::Base,
@@ -63,8 +54,7 @@ ProgressTreeView::setModel( QAbstractItemModel* model )
         return;
     }
 
-    QTreeView::setModel( model );
-    expandAll();
+    QListView::setModel( model );
 
     connect(
         Calamares::ViewManager::instance(),

src/calamares/progresstree/ProgressTreeView.h

@@ -20,15 +20,13 @@
 #ifndef PROGRESSTREEVIEW_H
 #define PROGRESSTREEVIEW_H
 
-#include <QTreeView>
-
-class ProgressTreeDelegate;
+#include <QListView>
 
 /**
  * @brief The ProgressTreeView class is a modified QTreeView which displays the
  * available view steps and the user's progress through them.
  */
-class ProgressTreeView : public QTreeView
+class ProgressTreeView : public QListView
 {
     Q_OBJECT
 public:
@@ -39,9 +37,6 @@ public:
      * @brief setModel assigns a model to this view.
      */
     void setModel( QAbstractItemModel* model ) override;
-
-private:
-    ProgressTreeDelegate* m_delegate;
 };
 
 #endif  // PROGRESSTREEVIEW_H