How to generate well-aligned Equal Signs?

Question

There are many project description files using a quite neat structure like this:

Introduction
============

......bla..bla.....


Details
=======

......bla..bla.....

My question is: Is there any convenient ways to generate automatically the title using such structure as:

Title
=====

, where the number of Equal Sign(=) is well aligned to the that of characters of the title just preceding it.

Answer 1

The documentation for yasnippet gives almost exactly this workflow as an example of its "field mirroring" capabilities. That's for entering titles; it might be possible to adapt it to edit existing well-structured text too.

For example, with the following snippet, press C-c u and start typing. When you're done, press TAB.

# -*- mode: snippet -*-
# name: underline
# binding : C-c u
# --
${1:}
${1:$(make-string (string-width yas-text) ?\=)}

$0

Answer 2

You can use the following command to underline the line at point.

(defun underline ()
  (interactive)
  (let* ((line (string-trim (thing-at-point 'line t)))
         (underline (make-string (string-width line) ?\=))
         (padding (save-excursion
                    (forward-line 0)
                    (when (re-search-forward "[^ ]" (point-at-eol) t)
                      (make-string (1- (current-column)) ?\s)))))
    (unless (string-empty-p underline)    
      (insert (format "\n%s%s\n\n" padding underline)))))