- Upstream GTK says that gtk_image_menu_item_new() has been deprecated since
  3.10 [1]. As it recommends using gtk_menu_item_new() instead, there does not
  seem to be official support for icons in menus anymore. We disagree with this
  design choice and shall keep all current instances of GtkImageMenuItem. They
  won't be going away in GTK 3, but should we ever decide to support GTK 4, we
  might need to take action on this somehow.

  [1] https://developer.gnome.org/gtk3/stable/GtkImageMenuItem.html#gtk-image-menu-item-new

- Upstream recommends spawn_async() instead of spawn_sync(), but the bindings
  for it are erroneous.

  See: https://gitlab.gnome.org/GNOME/vala/issues/721
       https://gitlab.gnome.org/GNOME/gobject-introspection/merge_requests/168
       https://gitlab.gnome.org/GNOME/vte/issues/227

- The upstream GTK devel branch has dropped some X11-specific APIs, including
  the interface for urgency hints. Eventually, this feature will have to be
  removed from weltschmerz too.

  See: https://gitlab.gnome.org/GNOME/gtk/merge_requests/766

- Upstream VTE indicates [1] [2] [3] that VteTerminal is incompatible with
  GtkScrolledWindow. weltschmerz has been using the latter since its launch,
  but has yet to run into any problem with it. Depending on how GTK/VTE will
  handle outstanding issues [4] [5], we might have to take action in the
  future. Bug reports or comments regarding this are appreciated.

  Note: A cursory check revealed that at least one other VTE-based emulator,
  terminator, seems to be using GtkScrolledWindow as well. According to [2], an
  implementation for gnome-terminal is planned too, but work seems to have
  stalled.

  [1] https://developer.gnome.org/vte/unstable/VteTerminal.html (see #Description)
  [2] https://gitlab.gnome.org/GNOME/vte/issues/11#note_264921
  [3] https://bugzilla.gnome.org/show_bug.cgi?id=733210#c2
  [4] https://gitlab.gnome.org/GNOME/vte/-/issues/183
  [5] https://gitlab.gnome.org/GNOME/vte/-/issues/234