Loading many people in a family tree takes a long while. Here are a few things that may improve things.
1. When clicking on a person that is on screen and is a sibling to the currently selected person, there's no need to redraw the entire tree. Just select the person and keep them where they are.
2. When someone gets selected, they don't always appear on screen. Center all selected users on screen.
3. I like the way you shrink anscetors of the currently selected person. Do the same with descendents so that more people will fit on screen.
4. How do you delete the document info (History)? Once the document icon becomes enabled, I see no way of deleting it.
5. It would be nice if all trees were numbered. It would be nice to search for different trees in the same file.