Hammerspoon script to turn cursor moving to scrolling while holding right button on trackball.

init.lua

-- HANDLE SCROLLING

local deferred = false

overrideRightMouseDown = hs.eventtap.new({ hs.eventtap.event.types.rightMouseDown }, function(e)
    --print("down"))
    deferred = true
    return true
end)

overrideRightMouseUp = hs.eventtap.new({ hs.eventtap.event.types.rightMouseUp }, function(e)
    -- print("up"))
    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 scrollmulty = -4	-- negative multiplier makes mouse work like traditional scrollwheel
local scrollmultx = -1
dragRightToScroll = hs.eventtap.new({ hs.eventtap.event.types.rightMouseDragged }, function(e)
    -- 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 * scrollmultx, dy * scrollmulty},{},'pixel')
    
    -- put the mouse back
    hs.mouse.setAbsolutePosition(oldmousepos)

    return true, {scroll}
end)

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