Open 'undo-tree-visualize side by side to the buffer, and not "vertically"

Question

Is there any way I can make undo-tree-mode display the visualization in a "horizontal" buffer (ie. C-x 3 vs. C-x 2)?

Answer 1

The undo-tree package uses standard Emacs buffer display functions to show the tree window (as opposed to a specific function). To control how Emacs splits windows, you can customize the variables split-window-preferred-function, split-height-threshold, and split-width-threshold. Also check out the documentation for the function split-window-sensibly.

If you are OK with Emacs in general preferring side-by-side windows over top-and-bottom ones, put this code in your init file:

(setq split-height-threshold 0)

(If you want side-by-side windows only for undo-tree-visualize, the story is a little more complicated.)