Refactor and extract SearchPlaylist's playlist item sync code.

And use it for DynamicPlaylist now as well.

dynamicplaylist.cpp

@@ -151,7 +151,11 @@ void DynamicPlaylist::updateItems()
 
     if(m_siblings != siblings) {
         m_siblings = siblings;
-        slotUpdateItems();
+        this->synchronizeItemsTo(siblings);
+
+        if(m_synchronizePlaying) {
+            synchronizePlayingItems(m_playlists, true);
+        }
     }
 }
 
@@ -174,19 +178,4 @@ void DynamicPlaylist::checkUpdateItems()
     m_dirty = false;
 }
 
-////////////////////////////////////////////////////////////////////////////////
-// private slots
-////////////////////////////////////////////////////////////////////////////////
-
-void DynamicPlaylist::slotUpdateItems()
-{
-    // This should be optimized to check to see which items are already in the
-    // list and just adding those and removing the ones that aren't.
-
-    clear();
-    createItems(m_siblings);
-    if(m_synchronizePlaying)
-        synchronizePlayingItems(m_playlists, true);
-}
-
 // vim: set et sw=4 tw=0 sta:

dynamicplaylist.h

@@ -99,9 +99,6 @@ private:
      */
     void checkUpdateItems();
 
-private slots:
-    void slotUpdateItems();
-
 private:
     QList<PlaylistObserver *> m_observers;
     PlaylistItemList m_siblings;

playlist.cpp

@@ -35,6 +35,7 @@
 #include <QCursor>
 #include <QDir>
 #include <QDirIterator>
+#include <QHash>
 #include <QToolTip>
 #include <QFile>
 #include <QFileDialog>
@@ -51,6 +52,7 @@
 #include <QPixmap>
 #include <QStackedWidget>
 #include <QScrollBar>
+
 #include <id3v1genres.h>
 
 #include <time.h>
@@ -937,6 +939,39 @@ void Playlist::removeFromDisk(const PlaylistItemList &items)
     }
 }
 
+void Playlist::synchronizeItemsTo(const PlaylistItemList &itemList)
+{
+    const auto &existingItems = items();
+    if(qAbs(itemList.count() - existingItems.count()) >
+        qMax(itemList.count(), existingItems.count()) / 2)
+    {
+        // Large imbalance in list sizes, just clear all and add without
+        // figuring out the diff also
+        clearItems(existingItems);
+        createItems(itemList);
+        return;
+    }
+
+    // Determine differences between existing playlist items and patch up
+    QHash<CollectionListItem *, PlaylistItem *> oldItems;
+    oldItems.reserve(qMax(existingItems.count(), itemList.count()));
+
+    for(const auto &item : existingItems) {
+        oldItems.insert(item->collectionItem(), item);
+    }
+
+    PlaylistItemList newItems;
+
+    for(const auto &item : itemList) {
+        if(oldItems.remove(item->collectionItem()) == 0) {
+            newItems.append(item->collectionItem());
+        }
+    }
+
+    clearItems(PlaylistItemList(oldItems.values()));
+    createItems(newItems);
+}
+
 void Playlist::dragEnterEvent(QDragEnterEvent *e)
 {
     if(CoverDrag::isCover(e->mimeData())) {

playlist.h

@@ -414,6 +414,15 @@ protected:
      */
     void removeFromDisk(const PlaylistItemList &items);
 
+    /**
+     * Adds and removes items from this Playlist as necessary to ensure that
+     * the same items are present in this Playlist as in @p itemList.
+     *
+     * No ordering guarantees are imposed, just that the playlist will have the
+     * same items as in the given list afterwards.
+     */
+    void synchronizeItemsTo(const PlaylistItemList &itemList);
+
     // the following are all reimplemented from base classes
 
     virtual bool eventFilter(QObject *watched, QEvent *e);
@@ -437,7 +446,7 @@ protected:
     virtual void addColumn(const QString &label, int width = -1);
 
     /**
-     * Do some finial initialization of created items.  Notably ensure that they
+     * Do some final initialization of created items.  Notably ensure that they
      * are shown or hidden based on the contents of the current PlaylistSearch.
      *
      * This is called by the PlaylistItem constructor.

searchplaylist.cpp

@@ -55,25 +55,8 @@ void SearchPlaylist::updateItems()
     // Here we don't simply use "clear" since that would involve a call to
     // items() which would in turn call this method...
 
-    PlaylistItemList l = Playlist::items();
-
-    QHash<CollectionListItem *, PlaylistItem *> oldItems;
-    oldItems.reserve(503);
-
-    foreach(PlaylistItem *item, l)
-        oldItems.insert(item->collectionItem(), item);
-
     m_search.search();
-    PlaylistItemList matched = m_search.matchedItems();
-    PlaylistItemList newItems;
-
-    foreach(PlaylistItem *item, matched) {
-        if(oldItems.remove(item->collectionItem()) == 0)
-            newItems.append(item->collectionItem());
-    }
-
-    clearItems(PlaylistItemList(oldItems.values()));
-    createItems(newItems);
+    synchronizeItemsTo(m_search.matchedItems());
 
     if(synchronizePlaying()) {
         qCDebug(JUK_LOG) << "synchronizing playing";