The max width parameter is optional. I am not sure what are you trying to do with the graphs though. This library is not for graphs or trees. It's for points on single axis.
This is not reingold-tilford. The algorithm has two parts. The first part is a heuristic to distribute nodes into multiple layers when it won't fit in one. Then for each layer, it is a physics simulation with the labels. Each label has attraction force to the desired position, but they also push each other.
The intention of this work was to find ways to put labels on any axis (1D). So if you want to use this to label peaks of area chart you can run labella to get the x position and then figure out y position by yourself.
But it won't support placing label on a zigzag path.
http://twitter.github.io/labella.js/with_text.html
The max width parameter is optional. I am not sure what are you trying to do with the graphs though. This library is not for graphs or trees. It's for points on single axis.