local touches = {}

local function monitor(event)
	if event.phase == 'began' or event.phase == 'moved' then
		touches[event.id] = event.target
	else
		touches[event.id] = nil
	end
end

function touchesInRegion(r)
	local n = 0
	for touch, target in pairs(touches) do
		if target == r then
			n = n + 1
		end
	end
	return n
end

function trackRegion(r)
	r:addEventListener('touch', monitor)
end

function ignoreRegion(r)
	r:removeEventListener('touch', monitor)
end