How to let Emacs display a different character from that actually stored?

elisp, emacs

Solution

One way to do this is to add font lock keywords for the relevant modes, and to use `compose-region` to display the new glyph in place of the old string:

(font-lock-add-keywords
 'latex-mode `(("\\(\\\\alpha\\)"
                (0 (progn (compose-region (match-beginning 1)
                                          (match-end 1) "α")
                          nil)))))

Please also note that `org-mode` has a feature of this kind already built-in, not only for links as you mentioned, but also for LaTeX-like entities:

(setq org-pretty-entities t)

Problem

I want to implement dynamical text replacement (only the display is replaced, the actual stored file is not replaced) for Emacs, using Elisp. For example, in LaTeX documents, I want to type `\alpha`, and let Emacs display it just as `α`, so it is easier to read. But in the result `.tex` file, I still want `\alpha`, instead of `α` to be saved. (Remark: I could use XeTeX or LuaTeX myself to support UTF-8 directly. But for the reason of collaboration and journal requirements, I don't want the UTF-8 characters to be directly saved in the `.tex` files. Alternatively I could use preview in AUCTeX. But that doesn't help when I am editing the formula) An existing example is in org-mode, when we type `[[link][name]]`, right after typing the last `]`, the displayed text is replaced by just the name, with hyperlink. On the other hand, when saving this file, the saved content is the original `[[link][name]]`, different from the displayed one. Any ideas how this could be implemented? PS: The Display Specs That Replace The Text section of Emacs manual goes close. However, I need to specify the start and end points, instead of the desired string for the replacements. This means I need to do search after every user input to decide the start and end points. This looks unrealistic due to performance and complexity of algorithm.

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