Somewhat OT, line routing for diagramming tool

[pherthyl]

Hi everyone,

Sorry, this is a little off topic. I have a "boxes and lines" type program using QGraphicsView, where people can drag boxes and connect them with "smart" connectors. Just like Visio, openoffice draw, Dia, etc. A connector line can be attached from any side of one box to any side of another box, and be routed so that it won't cross the start or end box. (I've attached a pic of some example routings it would do)

I've got a simple implementation, but it's not smart at all, just does a sort of ok job most of the time. What I want is something that can connect two boxes with a line and respect some basic rules of symmetry (like putting the corners halfway between two points)...

It seems like such a simple problem, but I can't for the life of me figure out a good way to do it. I thought about just special casing all the different scenarios, but that just seems like it'll be a mess. In the past I've also implemented an A* pathfinding algorithm, but it seems way overkill for something as simple as this, and I don't know how I would divide up the space into a coarser grid if the start and end points can be at any pixel coordinates...

So, anyone done this before? I must not be searching for the right terms because my google searching is bringing up nothing and I'm getting really discouraged... Any help greatly appreciated.