How To Use And Setup Emacs's whitespace-mode

Emacs 23 has this whitespace-mode feature. It renders spaces, tabs, newlines characters with a visible glyph.

This feature is useful for working with “tab separated values” (CSV) that's a common format for importing/exporting address books or spreadsheets. It's also important in whitespace-significant langs such as Python.

Type “Alt+x whitespace-mode” to toggle it on and off. Type “Alt+x global-whitespace-mode” to toggle it globally. There is also whitespace-newline-mode and global-whitespace-newline-mode. They only show newline chars.

The default rendering of whitespace-mode, pretty unreadable. Different placement and mix of whitespaces are rendered with different colors. Also, long lines are colored dark purple. (download whitespace_sample_file.txt)

Select a region then type “Alt+x whitespace-cleanup”, which will delete spaces or tabs in a smart way. (call describe-function to see detail.)

You can also use delete-trailing-whitespace, delete-whitespace-rectangle. Both works on a region.

For more fine control of deleting whitespaces, you can use use query-replace, query-replace-regexp, to replace whitespaces.

The following methods works everywhere, including when you are in minibuffer.

To insert a literal tab char, press “Ctrl+q Tab”.

To type a newline char, type “Ctrl+q Ctrl+j”.

You need to use the above sometimes because for example in minibuffer, pressing Tab does name completion and pressing Return finishes the prompt. In most programing language modes, pressing Return or Tab also does some auto indenting and formatting.

Note: doesn't matter if your file uses Unix or Windows or classic Mac's Newline convention, emacs always uses Line Feed (ascii 10) to represent them in the buffer.

Put the following in your emacs init file:

; make whitespace-mode use just basic coloring
(setq whitespace-style (quote
  ( spaces tabs newline space-mark tab-mark newline-mark)))

How to make whitespace-mode use the pilcrow sign “¶” for newline instead of the dollar sign?

Put the following in your emacs init file:

;; make whitespace-mode use “¶” for newline and “▷” for tab.
;; together with the rest of its defaults
(setq whitespace-display-mappings
 '(
   (space-mark 32 [183] [46]) ; normal space
   (space-mark 160 [164] [95])
   (space-mark 2208 [2212] [95])
   (space-mark 2336 [2340] [95])
   (space-mark 3616 [3620] [95])
   (space-mark 3872 [3876] [95])
   (newline-mark 10 [182 10]) ; newlne
   (tab-mark 9 [9655 9] [92 9]) ; tab
))

In the above, the numbers are unicode char code in decimal. Depending on your choice of font, some glyphs may not show up with your font. If so, you can try the following unicode chars.

Glyph	Number	Name
·	183	MIDDLE DOT
¶	182	PILCROW SIGN
↵	8629	DOWNWARDS ARROW WITH CORNER LEFTWARDS
▷	9655	WHITE RIGHT POINTING TRIANGLE
▶	9654	BLACK RIGHT-POINTING TRIANGLE
→	8594	RIGHTWARDS ARROW
↦	8614	RIGHTWARDS ARROW FROM BAR
⇥	8677	RIGHTWARDS ARROW TO BAR