Can I enable scrolling with middle-button-drag in OS X?

Question

I have a mouse with three buttons but no wheel.

In OS X, is there any way (perhaps with addon software) that would allow me to use my third button for scrolling by holding it and moving the mouse?

Answer 1

Smart Scroll does what you are looking for, with its 'Grab Scroll' feature. Assign it to 'Button 3 (Middle)' and dragging on both axes will work in apps such as browsers (Chrome), Terminal, Adobe Photoshop, and Finder - no app I've tried hasn't worked with it (using the 4.0 betas up and up). It has a free trial.

Answer 2

I did it with Hammerspoon with the following configuration script inspired by this thread: https://github.com/tekezo/Karabiner/issues/814#issuecomment-337643019

Steps:

• Install Hammerspoon
• Click its menu icon and select Open Config

• Paste the following lua script into the configuration:

  -- HANDLE SCROLLING WITH MOUSE BUTTON PRESSED
  local scrollMouseButton = 2
  local deferred = false
  
  overrideOtherMouseDown = hs.eventtap.new({ hs.eventtap.event.types.otherMouseDown }, function(e)
      -- print("down")
      local pressedMouseButton = e:getProperty(hs.eventtap.event.properties['mouseEventButtonNumber'])
      if scrollMouseButton == pressedMouseButton 
          then 
              deferred = true
              return true
          end
  end)
  
  overrideOtherMouseUp = hs.eventtap.new({ hs.eventtap.event.types.otherMouseUp }, function(e)
      -- print("up")
      local pressedMouseButton = e:getProperty(hs.eventtap.event.properties['mouseEventButtonNumber'])
      if scrollMouseButton == pressedMouseButton 
          then 
              if (deferred) then
                  overrideOtherMouseDown:stop()
                  overrideOtherMouseUp:stop()
                  hs.eventtap.otherClick(e:location(), pressedMouseButton)
                  overrideOtherMouseDown:start()
                  overrideOtherMouseUp:start()
                  return true
              end
              return false
          end
          return false
  end)
  
  local oldmousepos = {}
  local scrollmult = -4   -- negative multiplier makes mouse work like traditional scrollwheel
  
  dragOtherToScroll = hs.eventtap.new({ hs.eventtap.event.types.otherMouseDragged }, function(e)
      local pressedMouseButton = e:getProperty(hs.eventtap.event.properties['mouseEventButtonNumber'])
      -- print ("pressed mouse " .. pressedMouseButton)
      if scrollMouseButton == pressedMouseButton 
          then 
              -- print("scroll");
              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}
          else 
              return false, {}
          end 
  end)
  
  overrideOtherMouseDown:start()
  overrideOtherMouseUp:start()
  dragOtherToScroll:start()
  

Answer 3

There's a very nice open source app called Karabiner which will do this and a whole lot more (Keyboard and mouse remapping etc). See this question for some examples. Also for certain manufacturers they supply custom control software which may allow for improved/modified functionality (e.g. Logitech Control Center).

As mentioned in the comments below that whilst a new version of 'Karabiner Elements' has been released for MacOS Sierra (10.12) onwards it only provides for keyboard based remapping so far - so currently mouse remapping can't be done with it.

However Hammerspoon is another free open source tool that may be used, amongst many other things, to remap the keys on the mouse (and/or keyboard) to different functions. You'll need to install the tool and supply it with some appropriate config - see examples here for mouse remapping.

To check which event types and mouseEventButtonNumbers are being generated by your device you can run this (just copy/paste the 4 lines into the console) in the Hammerspoon console (Use reload config to stop it):

hs.eventtap.new({"all"},function(e)
print(e,"mouseEventButtonNumber:",
e:getProperty(hs.eventtap.event.properties['mouseEventButtonNumber']))
end):start()

Note: If you've installed the Logitech Control Centre (LCC) tools - it grabs the events directly from the Logitech devices using their installed kernel module so Hammerspoon can't see them. You'll need to uninstall LCC if you want to remap the mouse buttons using Hammerspoon.

Answer 4

Smooze does that, among other things. (I'm the developer)

What differentiate it from other suggestions is the ability to use it in every mac app while still identify links, for example. (in case you use your middle button drag to grab and throw but still want that a middle button click will act as a middle button)

With Smooze is more like grab-drag-throw than grab-drag. The release effects the momentum and animation of the scroll, similar to the iPhone scroll.

Answer 5

+1 for Hammerspoon and a script, a normal mouse/trackball drives me mad on a Mac.

I wrote one to scroll while middle mouse button is pressed down - the further you move the mouse the faster it will scroll.

Click still works like a normal click with a 5 pixel dead-zone so you don't have to keep the mouse perfectly still between pressing and releasing the wheel.

------------------------------------------------------------------------------------------
-- AUTOSCROLL WITH MOUSE WHEEL BUTTON
-- timginter @ GitHub
------------------------------------------------------------------------------------------

-- id of mouse wheel button
local mouseScrollButtonId = 2

-- scroll speed and direction config
local scrollSpeedMultiplier = 0.1
local scrollSpeedSquareAcceleration = true
local reverseVerticalScrollDirection = false
local mouseScrollTimerDelay = 0.01

-- circle config
local mouseScrollCircleRad = 10
local mouseScrollCircleDeadZone = 5

------------------------------------------------------------------------------------------

local mouseScrollCircle = nil
local mouseScrollTimer = nil
local mouseScrollStartPos = 0
local mouseScrollDragPosX = nil
local mouseScrollDragPosY = nil

overrideScrollMouseDown = hs.eventtap.new({ hs.eventtap.event.types.otherMouseDown }, function(e)
    -- uncomment line below to see the ID of pressed button
    --print(e:getProperty(hs.eventtap.event.properties['mouseEventButtonNumber']))

    if e:getProperty(hs.eventtap.event.properties['mouseEventButtonNumber']) == mouseScrollButtonId then
        -- remove circle if exists
        if mouseScrollCircle then
            mouseScrollCircle:delete()
            mouseScrollCircle = nil
        end

        -- stop timer if running
        if mouseScrollTimer then
            mouseScrollTimer:stop()
            mouseScrollTimer = nil
        end

        -- save mouse coordinates
        mouseScrollStartPos = hs.mouse.getAbsolutePosition()
        mouseScrollDragPosX = mouseScrollStartPos.x
        mouseScrollDragPosY = mouseScrollStartPos.y

        -- start scroll timer
        mouseScrollTimer = hs.timer.doAfter(mouseScrollTimerDelay, mouseScrollTimerFunction)

        -- don't send scroll button down event
        return true
    end
end)

overrideScrollMouseUp = hs.eventtap.new({ hs.eventtap.event.types.otherMouseUp }, function(e)
    if e:getProperty(hs.eventtap.event.properties['mouseEventButtonNumber']) == mouseScrollButtonId then
        -- send original button up event if released within 'mouseScrollCircleDeadZone' pixels of original position and scroll circle doesn't exist
        mouseScrollPos = hs.mouse.getAbsolutePosition()
        xDiff = math.abs(mouseScrollPos.x - mouseScrollStartPos.x)
        yDiff = math.abs(mouseScrollPos.y - mouseScrollStartPos.y)
        if (xDiff < mouseScrollCircleDeadZone and yDiff < mouseScrollCircleDeadZone) and not mouseScrollCircle then
            -- disable scroll mouse override
            overrideScrollMouseDown:stop()
            overrideScrollMouseUp:stop()

            -- send scroll mouse click
            hs.eventtap.otherClick(e:location(), mouseScrollButtonId)

            -- re-enable scroll mouse override
            overrideScrollMouseDown:start()
            overrideScrollMouseUp:start()
        end

        -- remove circle if exists
        if mouseScrollCircle then
            mouseScrollCircle:delete()
            mouseScrollCircle = nil
        end

        -- stop timer if running
        if mouseScrollTimer then
            mouseScrollTimer:stop()
            mouseScrollTimer = nil
        end

        -- don't send scroll button up event
        return true
    end
end)

overrideScrollMouseDrag = hs.eventtap.new({ hs.eventtap.event.types.otherMouseDragged }, function(e)
    -- sanity check
    if mouseScrollDragPosX == nil or mouseScrollDragPosY == nil then
        return true
    end

    -- update mouse coordinates
    mouseScrollDragPosX = mouseScrollDragPosX + e:getProperty(hs.eventtap.event.properties['mouseEventDeltaX'])
    mouseScrollDragPosY = mouseScrollDragPosY + e:getProperty(hs.eventtap.event.properties['mouseEventDeltaY'])

    -- don't send scroll button drag event
    return true
end)

function mouseScrollTimerFunction()
    -- sanity check
    if mouseScrollDragPosX ~= nil and mouseScrollDragPosY ~= nil then
        -- get cursor position difference from original click
        xDiff = math.abs(mouseScrollDragPosX - mouseScrollStartPos.x)
        yDiff = math.abs(mouseScrollDragPosY - mouseScrollStartPos.y)

        -- draw circle if not yet drawn and cursor moved more than 'mouseScrollCircleDeadZone' pixels
        if mouseScrollCircle == nil and (xDiff > mouseScrollCircleDeadZone or yDiff > mouseScrollCircleDeadZone) then
            mouseScrollCircle = hs.drawing.circle(hs.geometry.rect(mouseScrollStartPos.x - mouseScrollCircleRad, mouseScrollStartPos.y - mouseScrollCircleRad, mouseScrollCircleRad * 2, mouseScrollCircleRad * 2))
            mouseScrollCircle:setStrokeColor({["red"]=0.3, ["green"]=0.3, ["blue"]=0.3, ["alpha"]=1})
            mouseScrollCircle:setFill(false)
            mouseScrollCircle:setStrokeWidth(1)
            mouseScrollCircle:show()
        end

        -- send scroll event if cursor moved more than circle's radius
        if xDiff > mouseScrollCircleRad or yDiff > mouseScrollCircleRad then
            -- get real xDiff and yDiff
            deltaX = mouseScrollDragPosX - mouseScrollStartPos.x
            deltaY = mouseScrollDragPosY - mouseScrollStartPos.y

            -- use 'scrollSpeedMultiplier'
            deltaX = deltaX * scrollSpeedMultiplier
            deltaY = deltaY * scrollSpeedMultiplier

            -- square for better scroll acceleration
            if scrollSpeedSquareAcceleration then
                -- mod to keep negative values
                deltaXDirMod = 1
                deltaYDirMod = 1

                if deltaX < 0 then
                    deltaXDirMod = -1
                end
                if deltaY < 0 then
                    deltaYDirMod = -1
                end

                deltaX = deltaX * deltaX * deltaXDirMod
                deltaY = deltaY * deltaY * deltaYDirMod
            end

            -- math.floor - scroll event accepts only integers
            deltaX = math.floor(deltaX)
            deltaY = math.floor(deltaY)

            -- reverse Y scroll if 'reverseVerticalScrollDirection' set to true
            if reverseVerticalScrollDirection then
                deltaY = deltaY * -1
            end

            -- send scroll event
            hs.eventtap.event.newScrollEvent({-deltaX, deltaY}, {}, 'pixel'):post()
        end
    end

    -- restart timer
    mouseScrollTimer = hs.timer.doAfter(mouseScrollTimerDelay, mouseScrollTimerFunction)
end

-- start override functions
overrideScrollMouseDown:start()
overrideScrollMouseUp:start()
overrideScrollMouseDrag:start()

------------------------------------------------------------------------------------------
-- END OF AUTOSCROLL WITH MOUSE WHEEL BUTTON
------------------------------------------------------------------------------------------

Answer 6

It depends on the software - for example, Firefox supports it, while Google Chrome does not.

Currently there is no software to enable such feature system-wide in OS X, sadly.

Answer 7

I used Better Touch Tool to assign Ctrl+middle-click to PgUp, and Option+Middle-click to PgDown. It's free, excellent software, and works well.