[plasmalnf] Give the themes a selected-state

- This kind of runs around the selection model on the view,
  but we're drawing radio buttons ourselves **anyway**
  and the list of themes knows which is selected / current
  independent of the view.

src/modules/plasmalnf/Config.cpp

@@ -98,6 +98,8 @@ Config::setConfigurationMap( const QVariantMap& configurationMap )
             m_themeModel->showOnlyThemes( listedThemes );
         }
     }
+
+    m_themeModel->select( m_preselectThemeId );
 }
 
 Calamares::JobList
@@ -157,5 +159,6 @@ Config::setTheme( const QString& id )
             cDebug() << "Plasma look-and-feel applied" << id;
         }
     }
+    m_themeModel->select( id );
     emit themeChanged( id );
 }

src/modules/plasmalnf/PlasmaLnfPage.cpp

@@ -43,6 +43,7 @@ ThemeDelegate::paint( QPainter* painter, const QStyleOptionViewItem& option, con
 {
     auto label = index.data( ThemesModel::LabelRole ).toString();
     auto description = index.data( ThemesModel::DescriptionRole ).toString();
+    auto selected = index.data( ThemesModel::SelectedRole ).toBool() ? QStyle::State_On : QStyle::State_Off;
     auto image_v = index.data( ThemesModel::ImageRole );
     QPixmap image = image_v.canConvert< QPixmap >() ? qvariant_cast< QPixmap >( image_v ) : QPixmap();
 
@@ -52,7 +53,7 @@ ThemeDelegate::paint( QPainter* painter, const QStyleOptionViewItem& option, con
     labelRect.setWidth( labelRect.width() / 3 );
 
     QStyleOptionButton rbOption;
-    rbOption.state |= QStyle::State_Enabled | QStyle::State_On;
+    rbOption.state |= QStyle::State_Enabled | selected;
     rbOption.rect = labelRect;
     rbOption.text = label;
     option.widget->style()->drawControl( QStyle::CE_RadioButton, &rbOption, painter, option.widget );

src/modules/plasmalnf/ThemeInfo.cpp

@@ -34,6 +34,7 @@ struct ThemeInfo
     QString imagePath;
     mutable QPixmap pixmap;
     bool show = true;
+    bool selected = false;
 
     ThemeInfo() {}
 
@@ -138,6 +139,8 @@ ThemesModel::data( const QModelIndex& index, int role ) const
         return item.id;
     case ShownRole:
         return item.show;
+    case SelectedRole:
+        return item.selected;
     case DescriptionRole:
         return item.description;
     case ImageRole:
@@ -151,7 +154,11 @@ ThemesModel::data( const QModelIndex& index, int role ) const
 QHash< int, QByteArray >
 ThemesModel::roleNames() const
 {
-    return { { LabelRole, "label" }, { KeyRole, "key" }, { ShownRole, "show" }, { ImageRole, "image" } };
+    return { { LabelRole, "label" },
+             { KeyRole, "key" },
+             { SelectedRole, "selected" },
+             { ShownRole, "show" },
+             { ImageRole, "image" } };
 }
 
 void
@@ -219,6 +226,26 @@ ThemesModel::imageSize()
              qMax( 8 * CalamaresUtils::defaultFontHeight(), 80 ) };
 }
 
+void
+ThemesModel::select( const QString& themeId )
+{
+    int i = 0;
+    for ( auto& t : *m_themes )
+    {
+        if ( t.selected && t.id != themeId )
+        {
+            t.selected = false;
+            emit dataChanged( index( i, 0 ), index( i, 0 ), { SelectedRole } );
+        }
+        if ( !t.selected && t.id == themeId )
+        {
+            t.selected = true;
+            emit dataChanged( index( i, 0 ), index( i, 0 ), { SelectedRole } );
+        }
+        ++i;
+    }
+}
+
 
 /**
  * Massage the given @p path to the most-likely

src/modules/plasmalnf/ThemeInfo.h

@@ -25,7 +25,8 @@ public:
     {
         LabelRole = Qt::DisplayRole,
         KeyRole = Qt::UserRole,
-        ShownRole,
+        ShownRole,  // Should theme be displayed
+        SelectedRole,  // Is theme selected
         DescriptionRole,
         ImageRole
     };
@@ -49,6 +50,15 @@ public:
     /// @brief Shows the keys in the @p onlyThese map, and hides the rest
     void showOnlyThemes( const QMap< QString, QString >& onlyThese );
 
+    /** @brief Mark the @p themeId as current / selected
+     *
+     * One theme can be selected at a time; this will emit data
+     * changed signals for any (one) theme already selected, and
+     * the newly-selected theme. If @p themeId does not name any
+     * theme, none are selected.
+     */
+    void select( const QString& themeId );
+
     /** @brief The size of theme Images
      *
      * The size is dependent on the font size used by Calamares,