hammerspoon middle scroll

scroll.lua

-- MacOS middle-click scroll

local deferred = false

overrideRightMouseDown = hs.eventtap.new({ hs.eventtap.event.types.middleMouseDown }, function(e)
  deferred = true
  return true
end)

overrideRightMouseUp = hs.eventtap.new({ hs.eventtap.event.types.middleMouseUp }, function(e)
  if (deferred) then
    overrideRightMouseDown:stop()
    overrideRightMouseUp:stop()
    hs.eventtap.rightClick(e:location())
    overrideRightMouseDown:start()
    overrideRightMouseUp:start()
    return true
  end

  return false
end)

local oldmousepos = {}
local scrollmult = -4	-- negative multiplier makes mouse work like traditional scrollwheel
dragRightToScroll = hs.eventtap.new({ hs.eventtap.event.types.middleMouseDragged }, function(e)
  deferred = false

  oldmousepos = hs.mouse.getAbsolutePosition()    

  local dx = e:getProperty(hs.eventtap.event.properties['mouseEventDeltaX'])
  local dy = e:getProperty(hs.eventtap.event.properties['mouseEventDeltaY'])
  local scroll = hs.eventtap.event.newScrollEvent({-dx * scrollmult, -dy * scrollmult},{},'pixel')

  -- put the mouse back
  hs.mouse.setAbsolutePosition(oldmousepos)

  return true, {scroll}
end)

overrideRightMouseDown:start()
overrideRightMouseUp:start()
dragRightToScroll:start()