Hammerspoon config to use mouse button 3 for scrolling, remap button 4 to middle button

fix-mouse.lua

-- HANDLE SCROLLING WITH MOUSE BUTTON PRESSED
local scrollMouseButton = 3
local deferred = false

overrideOtherMouseDown = hs.eventtap.new({ hs.eventtap.event.types.otherMouseDown }, function(e)
    -- print(hs.eventtap.event.properties['mouseEventButtonNumber'])
    local mouseButton = e:getProperty(hs.eventtap.event.properties['mouseEventButtonNumber'])
    if mouseButton == scrollMouseButton then 
        deferred = true
        return true
    end

    -- Re-map "button 4" to button middle mouse button (for center-click-to-open-in-new-tabs)
    if mouseButton == 4 then
        local point = hs.mouse.getAbsolutePosition()
        hs.eventtap.event.newMouseEvent(hs.eventtap.event.types['middleMouseDown'], point):post()
        return true
    end
end)

overrideOtherMouseUp = hs.eventtap.new({ hs.eventtap.event.types.otherMouseUp }, function(e)
    -- print(hs.eventtap.event.properties['mouseEventButtonNumber'])
    local mouseButton = e:getProperty(hs.eventtap.event.properties['mouseEventButtonNumber'])

    -- Re-map "button 4" to button middle mouse button (for center-click-to-open-in-new-tabs)
    if mouseButton == 4 then
        local point = hs.mouse.getAbsolutePosition()
        hs.eventtap.event.newMouseEvent(hs.eventtap.event.types['middleMouseUp'], point):post()
        return true
    end
end)

local oldmousepos = {}
local scrollmult = -2	-- negative multiplier makes mouse work like traditional scrollwheel

dragOtherToScroll = hs.eventtap.new({ hs.eventtap.event.types.otherMouseDragged }, function(e)
    local mouseButton = e:getProperty(hs.eventtap.event.properties['mouseEventButtonNumber'])
    -- print ("pressed mouse " .. mouseButton)
    if scrollMouseButton == mouseButton 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()