distance_sq = function(x1,y1, x2,y2)
	return (x2-x1)^2+(y2-y1)^2
end

x_at_y = function(startx,starty, endx,endy, y)
	-- x at a given y on a line
	-- Could be nil when the line is parallel to the x axis.
	if starty == endy then
		return
	end
	return (endx-startx)/(endy-starty)*(y-starty) + startx
end

y_at_x = function(startx,starty, endx,endy, x)
	-- y at a given x on a line
	-- Could be nil when the line is parallel to the y axis.
	if startx == endx then
		return
	end
	return (endy-starty)/(endx-startx)*(x-startx) + starty
end

intersect_with_centroid = function(node, sx,sy)
	local h = node_height(Edge.source)
	local c = {
		sx=Edge.source.x + Edge.source.w/2,
		sy=Edge.source.y + h/2
	}
	if c.sx == sx then
		if sy > c.sy then
			return {sx=sx, sy=Edge.source.y + h + 10}
		else
			return {sx=sx, sy=Edge.source.y - 10}
		end
	end
	-- collect nearest intersection with all 4 boundaries
	local candidates = {}
	local y = y_at_x(sx,sy, c.sx,c.sy, Edge.source.x-10)
	if y and y >= Edge.source.y-10 and y < Edge.source.x+h+10 then
		table.insert(candidates, {sx=Edge.source.x-10, sy=y})
	end
	y = y_at_x(sx,sy, c.sx,c.sy, Edge.source.x + Edge.source.w + 10)
	if y and y >= Edge.source.y-10 and y < Edge.source.x+h+10 then
		table.insert(candidates, {sx=Edge.source.x+Edge.source.w+10, sy=y})
	end
	local x = x_at_y(sx,sy, c.sx,c.sy, Edge.source.y-10)
	if x and x >= Edge.source.x-10 and x < Edge.source.x + Edge.source.w + 10 then
		table.insert(candidates, {sx=x, sy=Edge.source.y-10})
	end
	x = x_at_y(sx,sy, c.sx,c.sy, Edge.source.y+h+10)
	if x and x >= Edge.source.x-10 and x < Edge.source.x + Edge.source.w + 10 then
		table.insert(candidates, {sx=x, sy=Edge.source.y+h+10})
	end
	if #candidates == 0 then
		-- no intersection; just return the same point
		return {sx=sx, sy=sy}
	end
	if #candidates == 1 then
		return candidates[1]
	end
	assert(#candidates == 2)
	if distance_sq(sx,sy, candidates[1].sx, candidates[1].sy) < distance_sq(sx,sy, candidates[2].sx, candidates[2].sy) then
		return candidates[1]
	else
		return candidates[2]
	end
end

node_height = function(node)
	-- we store the node's height internally, but it can be too small
	return math.max(node.h, 3*node.editor.line_height)
end

table.length = function(h)
	-- length of a table (not just the array side)
	local result = 0
	for _ in pairs(h) do
		result = result+1
	end
	return result
end

			local h = math.max(node.h, 3*node.editor.line_height)

			local h = node_height(node)

					return true

					return node

					return true

					return node

				local buffer_height = math.max(node.h, 3*node.editor.line_height)
				if sy >= node.y and sy < node.y + buffer_height then

				if sy >= node.y and sy < node.y + node_height(node) then

			local buffer_height = math.max(node.h, 3*node.editor.line_height)
			if sy >= node.y and sy < node.y+buffer_height then

			if sy >= node.y and sy < node.y+node_height(node) then

end

end

	a={type='text', x=0,y=0, margin=0, width=120},

	a={type='text', x=0,y=0, margin=0, width=120, outgoing_edges={}, incoming_edges={}},

	if Border then
		App.color{r=0,g=1,b=1}
		love.graphics.circle('fill', vx(Border.sx),vy(Border.sy), 5)

	if Edge then
		App.color{r=0,g=0,b=1}
		if Edge.s.debug_info then
			for _,p in ipairs(Edge.s.debug_info) do
				love.graphics.circle('line', vx(p.sx), vy(p.sy), 5)
			end
		end
		App.color{r=0,g=0,b=0}
		love.graphics.line(vx(Edge.s.sx),vy(Edge.s.sy), vx(Edge.e.sx),vy(Edge.e.sy))
		love.graphics.circle('fill', vx(Edge.s.sx),vy(Edge.s.sy), 5)
		love.graphics.circle('fill', vx(Edge.e.sx),vy(Edge.e.sy), 5)

		local buffer_height = math.max(node.h, 3*node.editor.line_height)

		local buffer_height = node_height(node)

	if Move_node then

	if Edge then
		Edge.s = intersect_with_centroid(Edge.source, sx,sy)
		Edge.e = {sx=sx, sy=sy}
	elseif Move_node then

	elseif Border then
		Border = nil

	elseif Edge then
		local src = Edge.source
		local line_height = Edge.source.editor.line_height
		local dest = {id=next_key(), type='text', x=sx(x)-60,y=sy(y)-1.5*line_height, margin=0, width=120, outgoing_edges={}, incoming_edges={src.id}}
		Nodes[dest.id] = dest
		table.insert(Nodes[src.id].outgoing_edges, dest.id)
		Edge = nil
		A()

		Border = {sx=sx, sy=sy}

		Edge = {source=node, s={sx=sx, sy=sy}, e={sx=sx, sy=sy}}

end

end