marble.lua

-- Source:https://github.com/tekezo/Karabiner/issues/814#issuecomment-415388742

-- HANDLE SCROLLING WITH MOUSE BUTTON PRESSED
local backMouseButton = 3
local forwardMouseButton = 4
local deferred = false

function setOverrides(e)
    overrideOtherMouseDown:stop()
    overrideOtherMouseUp:stop()
    hs.eventtap.otherClick(e:location(), 0, pressedMouseButton)
    overrideOtherMouseDown:start()
    overrideOtherMouseUp:start()	
end

overrideOtherMouseDown = hs.eventtap.new({ hs.eventtap.event.types.otherMouseDown }, function(e)
    -- print("down")    
    local pressedMouseButton = e:getProperty(hs.eventtap.event.properties['mouseEventButtonNumber'])
    if backMouseButton == pressedMouseButton or forwardMouseButton == 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 backMouseButton == pressedMouseButton 
        then 
            if (deferred) then
                setOverrides(e)
                hs.eventtap.keyStroke({"cmd"}, "[")
                return true
            end
            return false
        end
        
        if forwardMouseButton == pressedMouseButton 
            then 
                if (deferred) then
                    setOverrides(e)
                    hs.eventtap.keyStroke({"cmd"}, "]")
                    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 backMouseButton == pressedMouseButton or forwardMouseButton == pressedMouseButton 
        then 
            -- print("scroll");
            deferred = false
            oldmousepos = hs.mouse.absolutePosition()    
            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.absolutePosition(oldmousepos)
            return true, {scroll}
        else 
            return false, {}
        end 
end)

overrideOtherMouseDown:start()
overrideOtherMouseUp:start()
dragOtherToScroll:start()