qt4: access visible playlist column selector menu from general playlist popup menu

This fixes the issue that it was not possible to get any column back once all had been hidden

modules/gui/qt4/components/playlist/playlist_model.cpp

@@ -102,11 +102,14 @@ PLModel::PLModel( playlist_t *_p_playlist,  /* THEPL */
     ADD_ICON( NODE, ":/type/node" );
 #undef ADD_ICON
 
+    ContextUpdateMapper = new QSignalMapper(this);
+
     rebuild( p_root );
     CONNECT( THEMIM->getIM(), metaChanged( input_item_t *),
             this, processInputItemUpdate( input_item_t *) );
     CONNECT( THEMIM, inputChanged( input_thread_t * ),
             this, processInputItemUpdate( input_thread_t* ) );
+    CONNECT( ContextUpdateMapper, mapped( int ),  this, toggleColumnShown( int ) );
 }
 
 PLModel::~PLModel()
@@ -1041,9 +1044,27 @@ void PLModel::popup( QModelIndex & index, QPoint &point, QModelIndexList list )
         menu->addSeparator();
         menu->addAction( qtr( I_POP_EXPLORE ), this, SLOT( popupExplore() ) );
     }
+    if( tree || i_popup_item > -1 )
+        menu->addSeparator();
+    QMenu *col_selector = menu->addMenu( qtr( "Visible columns" ) );
+    makeColumnSelectMenu( col_selector );
     menu->popup( point );
 }
 
+void PLModel::makeColumnSelectMenu( QMenu *menu )
+{
+    int i_column = 1;
+    for( i_column = 1; i_column != COLUMN_END; i_column<<=1 )
+    {
+        QAction* option = menu->addAction(
+            qfu( psz_column_title( i_column ) ) );
+        option->setCheckable( true );
+        option->setChecked( shownFlags() & i_column );
+        ContextUpdateMapper->setMapping( option, i_column );
+        CONNECT( option, triggered(), ContextUpdateMapper, map() );
+    }
+}
+
 void PLModel::toggleColumnShown( int meta )
 {
     assert( meta );

modules/gui/qt4/components/playlist/playlist_model.hpp

@@ -128,6 +128,8 @@ public:
     void removeItem( int );
     void rebuild(); void rebuild( playlist_item_t * );
 
+    /* Helpers */
+    void makeColumnSelectMenu( QMenu *menu );
 private:
 
     /* General */

modules/gui/qt4/components/playlist/standardpanel.cpp

@@ -308,22 +308,9 @@ void StandardPLPanel::checkSortingIndicator( int meta )
 
 void StandardPLPanel::popupSelectColumn( QPoint pos )
 {
-    ContextUpdateMapper = new QSignalMapper(this);
-
     QMenu selectColMenu;
 
-    int i_column = 1;
-    for( i_column = 1; i_column != COLUMN_END; i_column<<=1 )
-    {
-        QAction* option = selectColMenu.addAction(
-            qfu( psz_column_title( i_column ) ) );
-        option->setCheckable( true );
-        option->setChecked( model->shownFlags() & i_column );
-        ContextUpdateMapper->setMapping( option, i_column );
-        CONNECT( option, triggered(), ContextUpdateMapper, map() );
-    }
-
-    CONNECT( ContextUpdateMapper, mapped( int ),  model, toggleColumnShown( int ) );
+    model->makeColumnSelectMenu( &selectColMenu );
 
     selectColMenu.exec( QCursor::pos() );
 }