[gnome-music/wip/jfelder/empty-playlist-v2: 2/2] playlistswidget: Display a special view for an empty playlist

[Jean Felder <jfelder src gnome org>]

commit 267ed391e56ab203b2f78eef155b28f1f75b9fd3
Author: Jean Felder <jfelder src gnome org>
Date:   Wed Nov 11 21:18:50 2020 +0100

    playlistswidget: Display a special view for an empty playlist
    
    When a playlist does not contain any song, the view seems broken: the
    big empty space makes the feature appear ambiguous and the line at the
    top also looks out of place (see #424).
    
    This issue is fixed by replacing the default state by a new empty view
    when a playlist is empty. This view contains the icon introduced in
    the previous commit.
    
    closes: #424

 data/ui/PlaylistsWidget.ui            | 27 +++++++++++++++-
 gnomemusic/widgets/playlistswidget.py | 60 ++++++++++++++++++++++++++++++++++-
 po/POTFILES.in                        |  1 +
 3 files changed, 86 insertions(+), 2 deletions(-)
---
diff --git a/data/ui/PlaylistsWidget.ui b/data/ui/PlaylistsWidget.ui
index fbc7882b4..74f72e401 100644
--- a/data/ui/PlaylistsWidget.ui
+++ b/data/ui/PlaylistsWidget.ui
@@ -9,7 +9,7 @@
       </object>
     </child>
     <child>
-      <object class="GtkScrolledWindow" id="playlist-container">
+      <object class="GtkScrolledWindow" id="_playlist_container">
         <property name="vexpand">True</property>
         <property name="visible">True</property>
         <child>
@@ -27,6 +27,31 @@
         </child>
       </object>
     </child>
+    <child>
+      <object class="GtkBox" id="_empty_playlist">
+        <property name="hexpand">True</property>
+        <property name="orientation">vertical</property>
+        <property name="valign">center</property>
+        <property name="vexpand">True</property>
+        <property name="visible">False</property>
+        <child>
+          <object class="GtkImage" id="_empty_playlist_icon">
+            <property name="visible">True</property>
+            <property name="icon_size">0</property>
+            <property name="pixel_size">128</property>
+            <property name="margin_bottom">18</property>
+          </object>
+        </child>
+        <child>
+          <object class="GtkLabel" id="_empty_playlist_label">
+            <property name="visible">True</property>
+            <style>
+              <class name="no-music-found-label"/>
+            </style>
+          </object>
+        </child>
+      </object>
+    </child>
   </template>
   <object class="GtkGestureMultiPress" id="_songs_list_ctrlr">
     <property name="widget">_songs_list</property>
diff --git a/gnomemusic/widgets/playlistswidget.py b/gnomemusic/widgets/playlistswidget.py
index 00f9fbcd2..a12f36abf 100644
--- a/gnomemusic/widgets/playlistswidget.py
+++ b/gnomemusic/widgets/playlistswidget.py
@@ -22,13 +22,21 @@
 # code, but you are not obligated to do so.  If you do not wish to do so,
 # delete this exception statement from your version.
 
-from gi.repository import Gdk, GObject, Gtk
+from __future__ import annotations
+
+from gettext import gettext as _
+from typing import Optional
+import typing
+
+from gi.repository import Gdk, GLib, GObject, Gtk
 
 from gnomemusic.widgets.notificationspopup import PlaylistNotification
 from gnomemusic.widgets.playlistcontextmenu import PlaylistContextMenu
 from gnomemusic.widgets.playlistcontrols import PlaylistControls  # noqa: F401
 from gnomemusic.widgets.playlistdialog import PlaylistDialog
 from gnomemusic.widgets.songwidget import SongWidget
+if typing.TYPE_CHECKING:
+    from gnomemusic.grilowrappers.grltrackerplaylists import Playlist
 
 
 @Gtk.Template(resource_path="/org/gnome/Music/ui/PlaylistsWidget.ui")
@@ -37,7 +45,11 @@ class PlaylistsWidget(Gtk.Box):
 
     __gtype_name__ = "PlaylistsWidget"
 
+    _empty_playlist = Gtk.Template.Child()
+    _empty_playlist_icon = Gtk.Template.Child()
+    _empty_playlist_label = Gtk.Template.Child()
     _pl_ctrls = Gtk.Template.Child()
+    _playlist_container = Gtk.Template.Child()
     _songs_list = Gtk.Template.Child()
     _songs_list_ctrlr = Gtk.Template.Child()
 
@@ -60,6 +72,10 @@ class PlaylistsWidget(Gtk.Box):
 
         self._pl_ctrls.props.application = application
 
+        self._previous_playlist: Optional[Playlist] = None
+        self._count_id = 0
+        self._count_timeout = 0
+
         self._song_popover = PlaylistContextMenu(application, self._songs_list)
 
         play_song = self._window.lookup_action("play_song")
@@ -84,6 +100,22 @@ class PlaylistsWidget(Gtk.Box):
 
         self._songs_list.bind_model(
             playlist.props.model, self._create_song_widget, playlist)
+
+        if self._count_id > 0:
+            self._previous_playlist.disconnect(self._count_id)
+            self._count_id = 0
+
+        self._previous_playlist = playlist
+        self._count_id = playlist.connect(
+            "notify::count", self._on_count_changed)
+        if playlist.props.count == 0:
+            self._pl_ctrls.props.visible = False
+            self._playlist_container.props.visible = False
+            self._count_timeout = GLib.timeout_add(
+                500, self._on_count_changed, playlist)
+        else:
+            self._on_count_changed(playlist)
+
         if playlist.props.is_smart:
             playlist.update()
 
@@ -91,6 +123,32 @@ class PlaylistsWidget(Gtk.Box):
 
         self._remove_song_action.set_enabled(not playlist.props.is_smart)
 
+    def _on_count_changed(
+            self, playlist: Playlist,
+            value: GObject.GParamSpec = None) -> None:
+        if self._count_timeout > 0:
+            GLib.source_remove(self._count_timeout)
+            self._count_timeout = 0
+
+        if playlist.props.count == 0:
+            self._pl_ctrls.props.visible = False
+            self._playlist_container.props.visible = False
+            self._empty_playlist.props.visible = True
+            pl_icon = playlist.props.icon_name
+            self._empty_playlist_icon.props.icon_name = pl_icon
+
+            if playlist.props.is_smart:
+                label_suffix = _("Will Appear Here")
+            else:
+                label_suffix = _("Is Empty")
+
+            empty_label = "{} {}".format(playlist.props.title, label_suffix)
+            self._empty_playlist_label.props.label = empty_label
+        else:
+            self._empty_playlist.props.visible = False
+            self._pl_ctrls.props.visible = True
+            self._playlist_container.props.visible = True
+
     def _create_song_widget(self, coresong, playlist):
         can_dnd = not playlist.props.is_smart
         song_widget = SongWidget(coresong, can_dnd, True)
diff --git a/po/POTFILES.in b/po/POTFILES.in
index c88c5b2cc..e947a235a 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -40,6 +40,7 @@ gnomemusic/widgets/lastfmdialog.py
 gnomemusic/widgets/notificationspopup.py
 gnomemusic/widgets/playertoolbar.py
 gnomemusic/widgets/playlistcontrols.py
+gnomemusic/widgets/playlistswidget.py
 gnomemusic/widgets/playlistdialog.py
 gnomemusic/widgets/starhandlerwidget.py
 gnomemusic/window.py