tracklist: Scroll to the requested Track

And wire this up to not only the Now Playing "jump" signal, but also the
next track pickers so we scroll when tracks are changed.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

emmental/__init__.py

@@ -64,12 +64,17 @@ class Application(Adw.Application):
         else:
             track.start()
         self.__set_replaygain(rg_auto=rg_auto)
+        self.__on_jump()
 
     def __pick_next_track(self, *, user: bool, gapless: bool = False) -> None:
         (track, rg_auto, restart) = self.factory.next_track(user=user)
         self.__load_track(track, gapless=gapless,
                           rg_auto=rg_auto, restart=restart)
 
+    def __on_jump(self, nowplay: nowplaying.Card | None = None) -> None:
+        """Handle a jump event."""
+        self.win.tracklist.scroll_to_track(self.db.tracks.current_track)
+
     def __on_seek(self, nowplay: nowplaying.Card, newpos: float) -> None:
         """Handle a seek event."""
         self.player.seek(newpos)
@@ -114,6 +119,7 @@ class Application(Adw.Application):
             self.player.file = track_table.current_track.path
             self.player.pause()
             track_table.current_track.start()
+            self.__on_jump()
 
     def build_header(self) -> header.Header:
         """Build a new header instance."""
@@ -147,6 +153,7 @@ class Application(Adw.Application):
         self.db.settings.bind_setting("now-playing.prefer-artist",
                                       playing, "prefer-artist")
 
+        playing.connect("jump", self.__on_jump)
         playing.connect("play", self.player.play)
         playing.connect("pause", self.player.pause)
         playing.connect("seek", self.__on_seek)

emmental/tracklist/__init__.py

@@ -1,6 +1,7 @@
 # Copyright 2022 (c) Anna Schumaker.
 """A card for displaying a list of tracks."""
 from gi.repository import GObject
+from gi.repository import GLib
 from gi.repository import Gio
 from gi.repository import Gtk
 from .. import db
@@ -39,6 +40,15 @@ class Card(Gtk.Box):
     def __search_changed(self, filter: entry.Filter) -> None:
         self.sql.tracks.filter(filter.get_query())
 
+    def __scroll_idle(self, track: db.tracks.Track) -> bool:
+        self._trackview.scroll_to_track(track)
+        return GLib.SOURCE_REMOVE
+
+    def scroll_to_track(self, track: db.tracks.Track) -> None:
+        """Scroll to the requested Track."""
+        if self.playlist is not None:
+            GLib.idle_add(self.__scroll_idle, track)
+
     @GObject.Property(type=Gio.ListModel)
     def columns(self) -> Gio.ListModel:
         """Get the columns displayed in the Tracklist."""

emmental/tracklist/trackview.py

@@ -77,6 +77,16 @@ class TrackView(Gtk.Frame):
         self.playlist.request_track(self._selection[position])
         self._selection.unselect_all()
 
+    def scroll_to_track(self, track: db.tracks.Track) -> None:
+        """Scroll to the requested Track."""
+        # This is a workaround until the ColumnView has better scrolling
+        # support, which seems to be targeted for Gtk 4.10.
+        adjustment = self._scrollwin.get_vadjustment()
+        for (i, t) in enumerate(self._selection):
+            if t == track:
+                pos = max(i - 3, 0) * adjustment.get_upper()
+                adjustment.set_value(pos / self._selection.get_n_items())
+
     @GObject.Property(type=Gio.ListModel)
     def columns(self) -> Gio.ListModel:
         """Get the ListModel for the columns."""

tests/tracklist/test_tracklist.py

@@ -3,6 +3,7 @@
 import unittest.mock
 import emmental.tracklist
 import tests.util
+from gi.repository import GLib
 from gi.repository import Gtk
 
 
@@ -75,3 +76,20 @@ class TestTracklist(tests.util.TestCase):
         self.tracklist.playlist = self.playlist
         self.assertEqual(self.tracklist.playlist, self.playlist)
         self.assertEqual(self.tracklist._trackview.playlist, self.playlist)
+
+    @unittest.mock.patch("gi.repository.GLib.idle_add")
+    def test_scroll_to_track(self, mock_idle_add: unittest.mock.Mock):
+        """Test the scroll_to_track() function."""
+        self.tracklist.scroll_to_track(None)
+        mock_idle_add.assert_not_called()
+
+        self.tracklist.playlist = self.playlist
+        self.tracklist.scroll_to_track(None)
+        mock_idle_add.assert_called_with(self.tracklist._Card__scroll_idle,
+                                         None)
+
+        with unittest.mock.patch.object(self.tracklist._trackview,
+                                        "scroll_to_track") as mock_scroll:
+            self.assertEqual(self.tracklist._Card__scroll_idle(None),
+                             GLib.SOURCE_REMOVE)
+            mock_scroll.assert_called_with(None)