Have emacs highlight characters over 80? [duplicate]

Question

I have seen some solutions on here which will highlight an entire line if it goes beyond 80 characters, and also to do a line-wrap once the line becomes greater than 80. What I would like to do is to edit my .emacs file so that any character beyond 80 takes on a different background. So the first 80 characters will have my current emacs background, then characters > 80 would have a black background say. Can someone point me in the right directions? Thanks!

Answer 1

I recently wrote an extensive article on the subject. Here's the gist of it:

(require 'whitespace)
(setq whitespace-line-column 80) ;; limit line length
(setq whitespace-style '(face lines-tail))

(add-hook 'prog-mode-hook 'whitespace-mode)

Answer 2

Here are some other solutions that people use, in addition to the one that @BozhidarBatsov mentions:

• Library column-marker.el -- highlight any column(s)
• Library fill-column-indicator.el -- highlight the fill column
• Library mode-line-posn.el -- highlight column number in mode line when greater than limit
• Library wide-column.el -- highlight cursor when column passes limit

See also:

• FindLongLines
• HighlightLongLines
• EightyColumnRule
• MarginMode

(FWIW, my personal preference is mode-line-posn.el --- less intrusive, just the right amount of indication.)