Generate thumbnails in the background

lazy_player/main_window.py

@@ -459,6 +459,14 @@ class MainWindow(Gtk.ApplicationWindow, Watcher):
                 texture = Gdk.Texture.new_from_bytes(gbytes)
                 self.thumbnail_picture.set_paintable(texture)
 
+        if self.thumbnailer._work_queue.empty():
+            for i in range(self.list_model.get_n_items()):
+                if item := self.list_model.get_item(i):
+                    assert isinstance(item, FileItem)
+                    if not item.thumbnail.value:
+                        self.thumbnailer.generate_thumbnail(item)
+                        break
+
         return True
 
     def _populate_file_list(self) -> None: