keep edges short

This had some dead ends. I spent some time trying to use the
parametric equation of a line. But the parameter is not comparable
across two lines.

0006-on.mouse_press

@@ -24,9 +24,9 @@ on.mouse_press = function(x,y, mouse_button)
 	end
 	node = on_border(sx,sy)
 	if node then
-		Border = {sx=sx, sy=sy}
+		Edge = {source=node, s={sx=sx, sy=sy}, e={sx=sx, sy=sy}}
 		return
 	end
 	-- default
 	Pan = {sx=sx,sy=sy}
-end
+end

0017-on.mouse_release

@@ -1,8 +1,14 @@
 on.mouse_release = function(x,y, mouse_button)
 	if Pan then
 		Pan = nil
-	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()
 	elseif Resize_node then
 		Resize_node = nil
 		Resize = nil

0018-on.update

@@ -7,7 +7,10 @@ on.update = function(dt)
 	end
 	local sx = sx(App.mouse_x())
 	local sy = sy(App.mouse_y())
-	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
 		Move_node.x = sx - Move.sx
 		Move_node.y = sy - Move.sy
 		A1(Move_node.id)

0021-compute_layout

@@ -31,7 +31,7 @@ compute_layout = function(node, x,y, nodes_to_render, preserve_screen_top_of_cur
 		table.insert(nodes_to_render, node)
 		move_bar.w = node.w/2
 		bounding_box.w = node.w+20
-		local buffer_height = math.max(node.h, 3*node.editor.line_height)
+		local buffer_height = node_height(node)
 		bounding_box.h = buffer_height+20
 		-- resize affordance
 		table.insert(nodes_to_render, {type='line', r=0.7,g=0.7,b=0.7, data={node.x+node.w+20,node.y, node.x+node.w+20,node.y+buffer_height}, id=node.id})

0026-on.draw

@@ -22,8 +22,16 @@ on.draw = function()
 			end
 		end
 	end
-	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)
 	end
 end

0031-Nodes

@@ -1,3 +1,3 @@
 Nodes = {
-	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={}},
 }

0037-on_resize

@@ -1,10 +1,9 @@
 on_resize = function(sx,sy)
 	for _,node in pairs(Nodes) do
 		if sx >= node.x+node.w+20 and sx < node.x+node.w+24 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
 				return node
 			end
 		end
 	end
-end
+end

0039-on_node

@@ -2,8 +2,7 @@ on_node = function(sx,sy)
 	for _,node in ipairs(Surface) do
 		if node.type == 'text' then
 			if sx >= node.x and sx < node.x + node.w 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
 					return node
 				end
 			end

0041-on_border

@@ -5,15 +5,15 @@ on_border = function(sx,sy)
 	end
 	for _,node in ipairs(Surface) do
 		if node.type == 'text' then
-			local h = math.max(node.h, 3*node.editor.line_height)
+			local h = node_height(node)
 			if sx >= node.x-10-corner_radius and sx < node.x + node.w+10+corner_radius then
 				if near(sy, node.y-10) or near(sy, node.y+h+10) then
-					return true
+					return node
 				end
 			end
 			if sy >= node.y-10-corner_radius and sy < node.y + h+10+corner_radius then
 				if near(sx, node.x-10) or near(sx, node.x+node.w+10) then
-					return true
+					return node
 				end
 			end
 		end

0049-table.length

@@ -0,0 +1,8 @@
+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

0050-node_height

@@ -0,0 +1,4 @@
+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

0051-intersect_with_centroid

@@ -0,0 +1,45 @@
+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

0055-y_at_x

@@ -0,0 +1,8 @@
+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

0056-x_at_y

@@ -0,0 +1,8 @@
+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

0057-distance_sq

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