make playbin authoritative on the current play queue position

src/meson.build

@@ -4,6 +4,7 @@ audrey_sources = [
   'globalconf.vala',
   'main.vala',
   'mpris.vala',
+  'play_queue.vala',
   'playbin.vala',
   'ui/play_queue.vala',
   'ui/setup.vala',

src/play_queue.vala

@@ -0,0 +1,136 @@
+// this is a custom SelectionModel that lets us only signal the
+// selection has changed on user interaction
+internal class Audrey.PlayQueue : GLib.Object, GLib.ListModel, Gtk.SelectionModel {
+    public GLib.ListStore inner { get; private set; }
+    // if current_position == inner.get_n_items (), play queue is stopped
+    public uint current_position { get; private set; }
+
+    // emitted when a track is purposefully selected
+    public signal void user_selected (uint position);
+
+    public PlayQueue () {
+        this.inner = new GLib.ListStore (typeof (Song));
+        this.current_position = this.inner.get_n_items ();
+
+        this.inner.items_changed.connect (this.on_inner_items_changed);
+    }
+
+    // only called by playbin
+    // does not emit user_selected
+    internal void playbin_select (uint new_position) {
+        var previous_position = this.current_position;
+        this.current_position = new_position;
+
+        if (previous_position < this.inner.get_n_items ()) {
+            if (new_position < this.inner.get_n_items ()) {
+                if (previous_position < new_position) {
+                    this.selection_changed (previous_position, new_position-previous_position+1);
+                } else {
+                    this.selection_changed (new_position, previous_position-new_position+1);
+                }
+            } else {
+                this.selection_changed (previous_position, 1);
+            }
+        } else {
+            if (new_position < this.inner.get_n_items ()) {
+                this.selection_changed (new_position, 1);
+            }
+        }
+    }
+
+    // called by anything else that wishes to switch tracks
+    // emits user_selected
+    public void user_select (uint position)
+            requires (position < this.get_n_items ())
+    {
+        this.user_selected (position);
+    }
+
+    private void on_inner_items_changed (GLib.ListModel inner, uint position, uint removed, uint added) {
+        // FIXME: potentially try to see if the current item was reordered
+        // see what Gtk.SingleSelection does
+
+        bool emit_signal = false;
+
+        if (this.current_position >= position) {
+            if (this.current_position < position+removed && added == 0) {
+                emit_signal = true;
+                this.current_position = position;
+            } else {
+                this.current_position += added;
+                this.current_position -= removed;
+            }
+        }
+
+        this.items_changed (position, removed, added);
+        if (emit_signal) this.selection_changed (position, 1);
+        // user_select doesnt need to be signalled, since the playqueue
+        // handles this on its own
+    }
+
+    // Gtk.SelectionModel methods
+
+    Gtk.Bitset get_selection_in_range (uint position, uint n_items)
+            requires (position+n_items <= this.inner.get_n_items ())
+    {
+        var bitset = new Gtk.Bitset.empty ();
+        bitset.add (this.current_position);
+        return bitset;
+    }
+
+    bool is_selected (uint position)
+            requires (position < this.inner.get_n_items ())
+    {
+        return position == this.current_position;
+    }
+
+    bool select_all () {
+        return false;
+    }
+
+    bool select_item (uint position, bool unselect_rest)
+        requires (position < this.inner.get_n_items ())
+    {
+        if (!unselect_rest) {
+            return false;
+        }
+      
+        this.user_select (position);
+
+        return true;
+    }
+
+    bool select_range (uint position, uint n_items, bool unselect_rest) {
+        return false;
+    }
+
+    bool set_selection (Gtk.Bitset selected, Gtk.Bitset mask) {
+        return false;
+    }
+
+    bool unselect_all () {
+        return false;
+    }
+
+    bool unselect_item (uint position) {
+        return false;
+    }
+
+    bool unselect_range (uint position, uint n_items) {
+        return false;
+    }
+
+    // GLib.ListView methods
+
+    Object? get_item (uint position) {
+        return this.inner.get_item (position);
+    }
+
+    Type get_item_type () {
+        return this.inner.get_item_type ();
+    }
+
+    uint get_n_items () {
+        return this.inner.get_n_items ();
+    }
+}

src/playbin.vala

@@ -25,18 +25,21 @@ class Playbin : GLib.Object {
 
     public PlaybinState state { get; private set; default = PlaybinState.STOPPED; }
 
-    // true if a timer should update the postion property
+    // true if a timer should update the position property
     private bool update_position = false;
     public int64 position { get; private set; default = 0; }
 
     public Subsonic api { get; set; default = null; }
 
     // sent when a new song starts playing
-    public signal void now_playing (uint index, Song song, int64 duration);
+    // continues: whether the track is a gapless continuation
+    public signal void now_playing (bool continues, uint index, Song song, int64 duration);
 
-    // FIXME this should be synced with the selection model, right??
-    public uint playing_index { get; private set; }
+    // the index of the track in the play queue that is currently playing
+    // must equal play queue len iff state is STOPPED
+    public uint current_position { get; private set; }
 
+    // whether we are expecting a gapless continuation next
     private bool next_gapless;
 
     private void source_setup (Gst.Element playbin, dynamic Gst.Element source) {
@@ -45,7 +48,7 @@ class Playbin : GLib.Object {
 
     // ASSUMPTION: about-to-finish will be signalled exactly once per track
     // even if seeking backwards after
-    GLib.AsyncQueue<string> next_uri = new GLib.AsyncQueue<string> ();
+    private GLib.AsyncQueue<string> next_uri = new GLib.AsyncQueue<string> ();
 
     private ListModel _play_queue = null;
     private ulong _play_queue_items_changed;
@@ -79,27 +82,30 @@ class Playbin : GLib.Object {
             return;
         }
 
-        if (this.playing_index >= position) {
-            if (this.playing_index < position+removed) {
+        if (this.current_position >= position) {
+            if (this.current_position < position+removed) {
                 // current track was removed, start playing something else
                 // TODO check if it was actually reordered
 
-                this.begin_playback (position);
+                if (position == play_queue.get_n_items ()) {
+                    this.stop ();
+                } else {
+                    this.select_track (position);
+                }
             } else {
                 // unaffected
                 // fix up playing index though
-                this.playing_index += added;
-                this.playing_index -= removed;
+                this.current_position = this.current_position + added - removed;
             }
-        } else if (this.playing_index+1 == position) {
+        } else if (this.current_position+1 == position) {
             // next track was changed
             // try to fix up gapless transition
             string? next_uri = this.next_uri.try_pop ();
             if (next_uri != null) {
                 // we're in luck, about-to-finish hasn't been triggered yet
                 // we can get away with replacing it
-                if (this.playing_index+1 < play_queue.get_n_items ()) {
-                    Song song = (Song) play_queue.get_item (this.playing_index+1);
+                if (this.current_position+1 < play_queue.get_n_items ()) {
+                    Song song = (Song) play_queue.get_item (this.current_position+1);
                     this.next_uri.push (this.api.stream_uri (song.id));
                 } else {
                     this.next_uri.push ("");
@@ -162,19 +168,20 @@ class Playbin : GLib.Object {
 
             this.position = 0;
 
+            bool continues = this.next_gapless;
             if (this.next_gapless) {
                 // advance position in play queue
-                this.playing_index += 1;
+                this.current_position += 1;
             } else {
                 this.next_gapless = true;
             }
 
-            var now_playing = (Song) play_queue.get_item (this.playing_index);
+            var now_playing = (Song) play_queue.get_item (this.current_position);
             if (this.api.stream_uri (now_playing.id) == (string) this.playbin.current_uri) {
-                this.now_playing (this.playing_index, now_playing, duration);
+                this.now_playing (continues, this.current_position, now_playing, duration);
 
-                if (this.playing_index+1 < play_queue.get_n_items ()) {
-                    Song song = (Song) play_queue.get_item (this.playing_index+1);
+                if (this.current_position+1 < play_queue.get_n_items ()) {
+                    Song song = (Song) play_queue.get_item (this.current_position+1);
                     this.next_uri.push (this.api.stream_uri (song.id));
                 } else {
                     this.next_uri.push ("");
@@ -182,7 +189,7 @@ class Playbin : GLib.Object {
             } else {
                 // edge case
                 // just flush everything and pray next stream-start is fine
-                this.begin_playback (this.playing_index);
+                this.select_track (this.current_position);
             }
         });
 
@@ -206,10 +213,13 @@ class Playbin : GLib.Object {
         }
     }
 
-    public void begin_playback (uint position) {
+    // manually changes which track in the play queue to play
+    public void select_track (uint position)
+            requires (position < this.play_queue.get_n_items ())
+    {
         this.state = PlaybinState.PLAYING;
 
-        this.playing_index = position;
+        this.current_position = position;
         this.playbin.set_state (Gst.State.READY);
         this.playbin.uri = this.api.stream_uri (((Song) this.play_queue.get_item (position)).id);
         this.playbin.set_state (Gst.State.PLAYING);
@@ -233,4 +243,10 @@ class Playbin : GLib.Object {
         this.playbin.set_state (Gst.State.PLAYING);
         this.state = PlaybinState.PLAYING;
     }
+
+    public void stop () {
+        this.playbin.set_state (Gst.State.READY);
+        this.state = PlaybinState.STOPPED;
+        this.current_position = this.play_queue.get_n_items ();
+    }
 }

src/ui/play_queue.vala

@@ -1,108 +1,3 @@
-// this is a custom SelectionModel that lets us only signal the
-// selection has changed on user interaction
-class PlayQueueSelection : GLib.Object, GLib.ListModel, Gtk.SelectionModel {
-    public ListStore inner { get; private set; }
-    
-    private uint _selected_position;
-    public uint selected_position {
-        get { return _selected_position; }
-        set {
-            var previous = _selected_position;
-            _selected_position = value;
-
-            if (previous < inner.get_n_items ()) {
-                this.selection_changed (previous, 1);
-            }
-            if (value < inner.get_n_items ()) {
-                this.selection_changed (value, 1);
-            }
-        }
-    }
-
-    public signal void user_selected (uint position);
-
-    internal PlayQueueSelection () {
-        this.inner = new GLib.ListStore (typeof (Song));
-        this._selected_position = inner.get_n_items ();
-
-        this.inner.items_changed.connect ((position, removed, added) => {
-            bool emit_signal = false;
-
-            if (this.selected_position >= position) {
-                if (this.selected_position < position+removed && added == 0) {
-                    emit_signal = true;
-                    this._selected_position = position;
-                } else {
-                    this._selected_position += added;
-                    this._selected_position -= removed;
-                }
-            }
-
-            this.items_changed (position, removed, added);
-            if (emit_signal) this.selection_changed (position, 1);
-        });
-    }
-
-    Gtk.Bitset get_selection_in_range (uint position, uint n_items) {
-        var bitset = new Gtk.Bitset.empty ();
-        if (this.selected_position < this.inner.get_n_items ()) {
-            bitset.add (selected_position);
-        }
-        return bitset;
-    }
-
-    bool is_selected (uint position) {
-        return position == this.selected_position;
-    }
-
-    bool select_all () {
-        return false;
-    }
-
-    bool select_item (uint position, bool unselect_rest) {
-        if (!unselect_rest) {
-            return false;
-        }
-      
-        this.selected_position = position;
-        this.user_selected (position);
-
-        return true;
-    }
-
-    bool select_range (uint position, uint n_items, bool unselect_rest) {
-        return false;
-    }
-
-    bool set_selection (Gtk.Bitset selected, Gtk.Bitset mask) {
-        return false;
-    }
-
-    bool unselect_all () {
-        return false;
-    }
-
-    bool unselect_item (uint position) {
-        return false;
-    }
-
-    bool unselect_range (uint position, uint n_items) {
-        return false;
-    }
-
-    Object? get_item (uint position) {
-        return this.inner.get_item (position);
-    }
-
-    Type get_item_type () {
-        return this.inner.get_item_type ();
-    }
-
-    uint get_n_items () {
-        return this.inner.get_n_items ();
-    }
-}
-
 [GtkTemplate (ui = "/eu/callcc/audrey/ui/play_queue.ui")]
 public class Ui.PlayQueue : Adw.NavigationPage {
     [GtkChild] private unowned Gtk.ColumnView view;

src/ui/window.vala

@@ -28,7 +28,7 @@ class Ui.Window : Adw.ApplicationWindow {
     public Gdk.Paintable playing_cover_art { get; set; }
 
     public Playbin playbin { get; private set; default = new Playbin (); }
-    public PlayQueueSelection play_queue_model { get; private set; default = new PlayQueueSelection (); }
+    public Audrey.PlayQueue play_queue_model { get; private set; default = new Audrey.PlayQueue (); }
 
     public Window (Gtk.Application app) {
         Object (application: app);
@@ -61,15 +61,15 @@ class Ui.Window : Adw.ApplicationWindow {
         this.setup.connected.connect ((api) => {
             this.playbin.api = api;
 
-            this.playbin.now_playing.connect ((position, song, duration) => {
+            this.playbin.now_playing.connect ((continues, position, song, duration) => {
                 this.song = song;
                 this.duration = duration;
                 api.scrobble.begin (song.id);
-                this.play_queue_model.selected_position = position;
+                this.play_queue_model.playbin_select (position);
             });
 
             this.play_queue_model.user_selected.connect ((position) => {
-                this.playbin.begin_playback (position);
+                this.playbin.select_track (position);
             });
 
             public_api = api;
@@ -189,12 +189,14 @@ class Ui.Window : Adw.ApplicationWindow {
     }
 
     [GtkCallback] private void on_skip_forward_clicked () {
-        this.play_queue_model.select_item (this.playbin.playing_index+1, true);
+        if (this.playbin.current_position+1 < this.playbin.play_queue.get_n_items ()) {
+            this.playbin.select_track (this.playbin.current_position+1);
+        }
     }
 
     [GtkCallback] private void on_skip_backward_clicked () {
-        if (this.playbin.playing_index > 0) {
-            this.play_queue_model.select_item (this.playbin.playing_index-1, true);
+        if (this.playbin.current_position > 0) {
+            this.play_queue_model.user_select (this.playbin.current_position-1);
         }
     }