Are there any better alternatives?
Emacs 27 will support a fill column indicator natively by way of the buffer-local minor mode display-fill-column-indicator-mode and its global counterpart global-display-fill-column-indicator-mode.
Here it is in action:
Quoth (emacs) Displaying Boundaries:
14.15 Displaying Boundaries
The built-in line numbering mechanism uses the text-area that is sandwiched between the left/right fringes and/or left/right margins, to the extent that fringes/margins exist. [What happens internally is that the line number glyphs (with a space on each end) are prepended to the glyphs of the display line within the text area.] Thus, setting the fringe or ...
I believe you are looking for the variable disable-point-adjustment. You will want to dead its docstring to better understand how you want to use it (i.e. you'll have to reset it every time point "enters" one of those overlays).
Here's a code snippet that will make all occurrences of " / " appear as " ÷ " in the current buffer:
(add-to-list 'font-lock-extra-managed-props 'display)
'((" \\(/\\) " 1 '(face nil display "÷"))))
The first line makes font-lock manage the display property of text, so that it removes the property when a piece of text no longer ...
Since fill-column-indicator is quite heavy, this solution shows a character to the right of the current line.
So when you're typing you can see the line limit before you exceed it.
This defines the minor-mode hl-line-margin-mode:
;; Global, ensures one active margin for the active buffer.
(defvar hl-line-margin--overlay nil)
I'm not sure about the feasibility of this.
First, I believe this requires a backwards font on the system. I'm no expert on how text is actually rendered but, speaking generally, text is rendered using a "base description", such as a vector mapping. This base information is contained in a font file, such as a .ttf. Without some mapping, Emacs doesn't ...