Add append_playlist function

src/appBase.js

@@ -17,6 +17,7 @@ class ClapperAppBase extends Gtk.Application
         });
 
         this.doneFirstActivate = false;
+        this.isFileAppend = false;
     }
 
     vfunc_startup()
@@ -79,11 +80,15 @@ class ClapperAppBase extends Gtk.Application
 
         const [playlist, subs] = Misc.parsePlaylistFiles(urisArr);
         const { player } = this.active_window.get_child();
+        const action = (this.isFileAppend) ? 'append' : 'set';
 
         if(playlist && playlist.length)
-            player.set_playlist(playlist);
+            player[`${action}_playlist`](playlist);
         if(subs)
             player.set_subtitles(subs);
+
+        /* Restore default behavior */
+        this.isFileAppend = false;
     }
 
     _onFirstActivate()

src/player.js

@@ -221,19 +221,33 @@ class ClapperPlayer extends GstClapper.Clapper
         if(this.state !== GstClapper.ClapperState.STOPPED)
             this.stop();
 
+        debug('new playlist');
+
         this.playlistWidget.removeAll();
         this.canAutoFullscreen = true;
 
-        for(let source of playlist) {
-            const uri = this._getSourceUri(source);
-            this.playlistWidget.addItem(uri);
-        }
+        this._addPlaylistItems(playlist);
 
         /* If not mapped yet, first track will play after map */
         if(this.windowMapped)
             this._playFirstTrack();
     }
 
+    append_playlist(playlist)
+    {
+        debug('appending playlist');
+        this._addPlaylistItems(playlist);
+
+        if(
+            !this.windowMapped
+            || this.state !== GstClapper.ClapperState.STOPPED
+        )
+            return;
+
+        if(!this.playlistWidget.nextTrack())
+            debug('playlist append failed');
+    }
+
     set_subtitles(source)
     {
         const uri = this._getSourceUri(source);
@@ -370,6 +384,7 @@ class ClapperPlayer extends GstClapper.Clapper
             case 'play':
             case 'pause':
             case 'set_playlist':
+            case 'append_playlist':
             case 'set_subtitles':
                 this[action](value);
                 break;
@@ -394,6 +409,16 @@ class ClapperPlayer extends GstClapper.Clapper
         }
     }
 
+    _addPlaylistItems(playlist)
+    {
+        for(let source of playlist) {
+            const uri = this._getSourceUri(source);
+
+            debug(`added uri: ${uri}`);
+            this.playlistWidget.addItem(uri);
+        }
+    }
+
     _getSourceUri(source)
     {
         return (source.get_uri != null)