Isle 1.7.1

With more than one display, the brightness shows in the island instead of a flickering popup. To update:
click Update on the new-version alert (or Settings → About → Update), then log out and back in.

Fixed

• With more than one display, changing the brightness while the pointer was on another display showed GNOME's own
  brightness popup on the island's display, flickering as GNOME showed and took it back display after display. The
  brightness of the island's own display (a laptop's screen) shows in the island, wherever the pointer is;
  another display's brightness shows in GNOME's popup on that display. The volume is as before: with
  the pointer on another display, GNOME's popup shows on every display. (#51) Thanks to @Hazem-Samir.