better experience of moving a node around

After noodling about it for a few days, this seems like an improvement:
* When I "pick up" a node it's above the surface and doesn't disturb
  other nodes until I "put it down".

* There's a shadow around the node as I move it around, showing what is
  likely to be disturbed when I put it down.

* If I put down really close to where I picked up, it's considered an
  undo and no collisions are resolved.

* There's a hint around the original location to help me put it back
  there.

0006-on.mouse_press

@@ -26,9 +26,9 @@ on.mouse_press = function(x,y, mouse_button)
 	if node then
 		-- move node
 		prepare_to_move(node)
-		Move = {xoff=App.mouse_x()-vx(node.x), yoff=App.mouse_y()-vy(node.y), node=node}
+		Move = {xoff=App.mouse_x()-vx(node.x), yoff=App.mouse_y()-vy(node.y), node=node, oldx=node.x, oldy=node.y}
 		return
 	end
 	-- pan surface
 	Pan = {x=Viewport.x+x/Viewport.zoom, y=Viewport.y+y/Viewport.zoom}
-end
+end

0017-on.mouse_release

@@ -7,6 +7,12 @@ on.mouse_release = function(x,y, mouse_button)
 		Pan = nil
 		A()
 	elseif Move then
+		-- resolve collisions unless I'm trying to put it back carefully where I started.
+		if dist(vx(Move.node.x), vy(Move.node.y), vx(Move.oldx), vy(Move.oldy)) > 10 then
+			Move.node.pos.x = Move.node.x+Move.node.hs.x
+			Move.node.pos.y = Move.node.y+Move.node.hs.y
+			move_others(Move.node)
+		end
 		Move = nil
 		A()
 	elseif Cursor_node then

0018-on.update

@@ -23,9 +23,8 @@ on.update = function(dt)
 		-- quantize the x axis to discrete columns
 		Move.node.x = round(Move.node.x/100)*100
 		A1(Move.node.key)
-		Move.node.pos.x = Move.node.x+Move.node.hs.x
-		Move.node.pos.y = Move.node.y+Move.node.hs.y
-		move_others(Move.node)
+		Move.node.pos.x = Move.node.x+Move.node.w/2
+		Move.node.pos.y = Move.node.y+Move.node.h/2+30
 		return
 	end
 end

0026-on.draw

@@ -5,6 +5,14 @@ on.draw = function()
 		love.graphics.draw(Canvas, q, 0,0)
 		return
 	end
+	-- some hacky stuff outside of LuaML
+	if Move then
+		-- a hint for original location of node, to help put it back
+		App.color{r=0.8, g=0.8, b=0.8}
+		love.graphics.rectangle('fill', vx(Move.oldx), vy(Move.oldy), scale(Move.node.w), scale(Move.node.h))
+		-- a hint about the amount of padding we're going to clear when we set the node down
+		draw_move_node_shadow()
+	end
 	for _,obj in ipairs(Surface) do
 		love.graphics.setColor(obj.r or 0, obj.g or 0, obj.b or 0)
 		if obj.type == 'rectangle' then

0129-prepare_to_move

@@ -8,11 +8,11 @@ prepare_to_move = function(target)
 		if def.hs == nil then def.hs = {} end
 		def.hs.x = def.w/2
 		def.hs.y = def.h/2 + 30
+		def.pos.x = def.x + def.hs.x
+		def.pos.y = def.y + def.hs.y
 		if def == target then
 			def.hs.x = def.hs.x + 50
 			def.hs.y = def.hs.y + math.max(30, math.min(def.h/3, 200))
 		end
-		def.pos.x = def.x + def.hs.x
-		def.pos.y = def.y + def.hs.y
 	end
 end

0133-dist

@@ -0,0 +1,3 @@
+dist = function(x1,y1, x2,y2)
+	return ((x2-x1)^2+(y2-y1)^2)^0.5
+end

0134-draw_move_node_shadow

@@ -0,0 +1,7 @@
+draw_move_node_shadow = function()
+	love.graphics.rectangle('fill',
+		vx(Move.node.pos.x-Move.node.hs.x),
+		vy(Move.node.pos.y-Move.node.hs.y),
+		scale(Move.node.hs.x*2),
+		scale(Move.node.hs.y*2))
+end