Insert space but don't move point

Question

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I'd like to insert a single space (just like when you hit SPC) but without changing point. I come up with an example (let | be the cursor). Say you have foobar in a buffer and you placed the cursor in-between.

foo|bar

Then I'd like to hit a key sequence that inserts a space character at point, but leaves point where it is, instead of moving it past the inserted char. Like so:

foo| bar

Perhaps something like insert-space-right. I could easily write some Elisp code that does this for me, but I'd like to find out whether such a thing is indeed already built-in and I'm just unable to find it.

Answer 1

There's no built-in command to insert a character before the point, presumably because any key binding for it would have to include at least one key stroke in addition to the character, and if you're going to type two keystrokes then the feature already exists: SPC Left or SPC Ctrl+B.

There is a built-in command open-line to insert a newline before the point. It exists because it does a few more things than simply inserting a newline, including adding a fill prefix or a margin if inserting a newline would normally add one.

The simplest way to write a command that inserts a character before the point is to insert a character, then move the point back.

(defun insert-space-before-point ()
  (interactive)
  (insert " ")
  (backward-char))

This works, but there's a clearer way to express that the point isn't moving, which is to call save-excursion around the part that moves the point. Among other advantages, this makes it straightforward to support a numeric repeat count like you can use when inserting a character.

(defun insert-space-before-point (&optional n)
  (interactive "p")
  (save-excursion
    (insert-char ?\  n)))

Depending on what you're doing, you may be better off using Emacs's support for right-to-left text, or in a very different vein Picture mode.