How can I create a frame and open two files split vertically in it?

Question

I am trying to write an Elisp function that will create a new frame and in that new frame open two files split vertically.

I have been unable to find anything about this in the Elisp manual, node Creating Frames

How can I do this?

Answer 1

You can try this function:

(defun my/open-files-vert-in-new-frame (file1 file2)
  (interactive "f\nf")
  (select-frame-set-input-focus (make-frame))
  (find-file file1)
  (split-window-below)
  (find-file file2))

The key is select-frame-set-input-focus which makes subsequent functions operating on windows of the new frame and set input focus on it.