qt4 playlist: don't rebuild on move (finally!) + refresh current item on sort

When using tree playlist mode and moving items within sub-nodes, the nodes
will now stay open.

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

@@ -84,6 +84,25 @@ void PLItem::insertChild( PLItem *item, int i_pos, bool signal )
     children.insert( i_pos, item );
 }
 
+void PLItem::removeChild( PLItem *item )
+{
+    children.removeOne( item );
+    delete item;
+}
+
+void PLItem::removeChildren()
+{
+    qDeleteAll( children );
+    children.clear();
+}
+
+void PLItem::takeChildAt( int index )
+{
+    PLItem *child = children[index];
+    child->parentItem = NULL;
+    children.removeAt( index );
+}
+
 /* This function is used to get one's parent's row number in the model */
 int PLItem::row() const
 {

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

@@ -46,6 +46,9 @@ public:
     {
         children.insert( children.count(), item );
     };
+    void removeChild( PLItem * );
+    void removeChildren();
+    void takeChildAt( int );
 
     PLItem *child( int row ) { return children.value( row ); };
     int childCount() const { return children.count(); };

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

@@ -151,9 +151,12 @@ private:
     void recurseDelete( QList<PLItem*> children, QModelIndexList *fullList );
     void doDeleteItem( PLItem *item, QModelIndexList *fullList );
     void UpdateTreeItem( PLItem *, bool, bool force = false );
+    void dropAppendCopy( QByteArray& data, PLItem *target );
+    void dropMove( QByteArray& data, PLItem *target, int new_pos );
+    void TakeItem( PLItem * );
+    void InsertChildren( PLItem *node, QList<PLItem*>& items, int i_pos );
     /* The following actions will not signal the view! */
     void RemoveItem ( PLItem * );
-    void RemoveChildren( PLItem * );
     void UpdateChildren( PLItem * );
     void UpdateChildren( playlist_item_t *, PLItem * );