Implement simple search in playlist

src/Application.vala

@@ -9,12 +9,14 @@ public class Music.Application : Gtk.Application {
     public const string ACTION_PLAY_PAUSE = "action-play-pause";
     public const string ACTION_PREVIOUS = "action-previous";
     public const string ACTION_SHUFFLE = "action-shuffle";
+    public const string ACTION_FIND = "action-find";
 
     private const ActionEntry[] ACTION_ENTRIES = {
         { ACTION_PLAY_PAUSE, action_play_pause, null, "false" },
         { ACTION_NEXT, action_next },
         { ACTION_PREVIOUS, action_previous },
-        { ACTION_SHUFFLE, action_shuffle }
+        { ACTION_SHUFFLE, action_shuffle },
+        { ACTION_FIND, action_find }
     };
 
     private PlaybackManager? playback_manager = null;
@@ -40,6 +42,8 @@ public class Music.Application : Gtk.Application {
 
         add_action_entries (ACTION_ENTRIES, this);
 
+        set_accels_for_action (ACTION_PREFIX + ACTION_FIND, {"<Ctrl>F"});
+
         ((SimpleAction) lookup_action (ACTION_PLAY_PAUSE)).set_enabled (false);
         ((SimpleAction) lookup_action (ACTION_PLAY_PAUSE)).set_state (false);
         ((SimpleAction) lookup_action (ACTION_NEXT)).set_enabled (false);
@@ -179,6 +183,10 @@ public class Music.Application : Gtk.Application {
         playback_manager.shuffle ();
     }
 
+    private void action_find () {
+        ((MainWindow)active_window).start_search ();
+    }
+
     private void on_bus_acquired (DBusConnection connection, string name) {
         try {
             connection.register_object ("/org/mpris/MediaPlayer2", new MprisRoot ());

src/MainWindow.vala

@@ -7,6 +7,8 @@ public class Music.MainWindow : Gtk.ApplicationWindow {
     private Gtk.Button repeat_button;
     private Gtk.Button shuffle_button;
     private Settings settings;
+    private Gtk.SearchEntry search_entry;
+    private Gtk.Revealer search_revealer;
 
     construct {
         var playback_manager = PlaybackManager.get_default ();
@@ -20,9 +22,20 @@ public class Music.MainWindow : Gtk.ApplicationWindow {
 
         repeat_button = new Gtk.Button ();
 
+        search_entry = new Gtk.SearchEntry () {
+            placeholder_text = _("Search titles in playlist")
+        };
+
+        search_revealer = new Gtk.Revealer () {
+            child = search_entry
+        };
+
+        playback_manager.bind_property (
+            "has-items", search_revealer, "reveal-child", DEFAULT | SYNC_CREATE
+        );
         var queue_header = new Gtk.HeaderBar () {
             show_title_buttons = false,
-            title_widget = new Gtk.Label ("")
+            title_widget = search_revealer
         };
         queue_header.add_css_class (Granite.STYLE_CLASS_DEFAULT_DECORATION);
         queue_header.pack_start (start_window_controls);
@@ -171,6 +184,30 @@ public class Music.MainWindow : Gtk.ApplicationWindow {
         queue_listbox.row_activated.connect ((row) => {
             playback_manager.current_audio = ((TrackRow) row).audio_object;
         });
+
+        search_entry.search_changed.connect (() => {
+            int pos = playback_manager.find_title (search_entry.text);
+            if (pos >= 0) {
+                queue_listbox.select_row (queue_listbox.get_row_at_index (pos));
+                var adj = scrolled.vadjustment;
+                // Search entry is hidden if n_items is zero so no need to check
+                var ratio = (double)pos / (double)playback_manager.n_items;
+                adj.@value = adj.upper * ratio;
+            }
+        });
+
+        search_entry.activate.connect (() => {
+            var selected = queue_listbox.get_selected_row ();
+            if (selected != null) {
+                selected.activate ();
+            }
+        });
+    }
+
+    public void start_search () {
+        if (search_revealer.child_revealed) {
+            search_entry.grab_focus ();
+        }
     }
 
     private void action_open () {

src/PlaybackManager.vala

@@ -6,6 +6,12 @@
 public class Music.PlaybackManager : Object {
     public AudioObject? current_audio { get; set; default = null; }
     public ListStore queue_liststore { get; private set; }
+    public bool has_items { get; private set; }
+    public uint n_items {
+        get {
+            return queue_liststore != null ? queue_liststore.get_n_items () : 0;
+        }
+    }
     public int64 playback_position { get; private set; }
     public signal void invalids_found (int count);
 
@@ -50,8 +56,8 @@ public class Music.PlaybackManager : Object {
 
         queue_liststore.items_changed.connect (() => {
             var shuffle_action_action = (SimpleAction) GLib.Application.get_default ().lookup_action (Application.ACTION_SHUFFLE);
+            has_items = queue_liststore.get_n_items () > 0;
             shuffle_action_action.set_enabled (queue_liststore.get_n_items () > 1);
-
             update_next_previous_sensitivity ();
         });
 
@@ -348,6 +354,28 @@ public class Music.PlaybackManager : Object {
         }
     }
 
+    public int find_title (string term) {
+        var search_object = new AudioObject ("") {
+            title = term
+        };
+
+        int found_at = -1;
+        uint position;
+        if (queue_liststore.find_with_equal_func (
+            search_object,
+            (a, b) => {
+                var term_a = ((AudioObject)a).title.down ();
+                var term_b = ((AudioObject)b).title.down ();
+                return term_a.contains (term_b);
+            },
+            out position
+        )) {
+            found_at = (int)position;
+        }
+
+        return found_at;
+    }
+
     private void update_next_previous_sensitivity () {
         var next_sensitive = false;
         var previous_sensitive = false;