Abbreviation expansion without spaces

Question

I would like to set up things so that when I type Iuulius, the sequence uu is seamlessly replaced by ū (and a few more such pairs), as soon as I type the second u. I.e. the keystrokes and buffer text would go like this:

• <I> → I∎
• <u> → Iu∎
• <u> → Iū∎
• <l> → Iūl∎

How could I set that up that kind of expansion—without interfering with existing input methods?

Answer 1

I asked the same question recently on emacs-devel and Kenichi Handa told me I could do:

(defvar my-TeX-input-method-tweaked nil)
(defun my-quail-activate-hook ()
  (when (and (not (member (quail-name)
                          my-TeX-input-method-tweaked))
             (member (quail-name) '("TeX" "latin-1-prefix")))
    (quail-defrule "uu" "ū")
    (push (quail-name) my-TeX-input-method-tweaked)))

(add-hook 'quail-activate-hook #'my-quail-activate-hook)

Of course, you'll want to adjust the list of input-methods you want to modify. If you don't want to touch input methods, or if you want the "uu" rewriting to only take place in some specific contexts, you could do something like:

(defun my-uu-rewrite ()
  (when (looking-back "Iuu" (- (point) 3))
    (delete-region (- (point) 2) (point))
    (insert-and-inherit "ū")))
(add-hook 'post-self-insert-hook #'my-uu-rewrite)