-- context menu to manually fix rotation
function onLoad()
  self.addContextMenuItem("rotate alt preview", reverse)
end

-- rotates the alt_view_angle
function reverse()
  local angle = self.alt_view_angle
  if angle.y == 0 then
    angle.y = 180
  else
    angle.y = 0
  end
  self.alt_view_angle = angle
end