highlight-indent-guides.el

This minor mode highlights indentation levels via font-lock. Indent widths are dynamically discovered, which means this correctly highlights in any mode, regardless of indent width, even in languages with non-uniform indentation such as Haskell. By default, this mode also inspects your theme dynamically, and automatically chooses appropriate colors for highlighting. This mode works properly around hard tabs and mixed indentation, and it behaves well in large buffers.

Screenshots

(setq highlight-indent-guides-method 'fill)

(setq highlight-indent-guides-method 'column)

(setq highlight-indent-guides-method 'character)

Installation

To install from Melpa, use M-x package-install RET highlight-indent-guides RET. Otherwise, download highlight-indent-guides.el and put it in your load path.

Usage

Once the mode is installed, do M-x highlight-indent-guides-mode to enable it. To enable it automatically in most programming modes, use the following:

(add-hook 'prog-mode-hook 'highlight-indent-guides-mode)

Configuration

This mode supports three display methods. To change the display method, customize highlight-indent-guides-method, and set it to one of the following:

• fill: The default method. All whitespace used for indentation is highlighted. The color of each level of indentation alternates between highlight-indent-guides-odd-face and highlight-indent-guides-even-face.
• column: Like fill, but only the first column of each level of indentation is highlighted.
• character: The first column of each level of indentation is drawn using a column of characters. The character to draw with is specified by highlight-indent-guides-character, and it is drawn using the face highlight-indent-guides-character-face.

For example:

(setq highlight-indent-guides-method 'character)

To change the character used for drawing guide lines with the character display method, customize highlight-indent-guides-character.

For example:

(setq highlight-indent-guides-character ?\|)

Highlight Colors

By default, this mode dynamically chooses colors that look acceptable with the loaded theme. It does this by altering the luminosity of the theme's background color by a given percentage. These percentages can be tweaked, to make the colors more intense or subtle.

For example:

(setq highlight-indent-guides-auto-odd-face-perc 15)
(setq highlight-indent-guides-auto-even-face-perc 15)
(setq highlight-indent-guides-auto-character-face-perc 20)

To set the colors manually, disable this feature and customize the faces directly.

For example:

(setq highlight-indent-guides-auto-enabled nil)

(set-face-background 'highlight-indent-guides-odd-face "darkgray")
(set-face-background 'highlight-indent-guides-even-face "dimgray")
(set-face-foreground 'highlight-indent-guides-character-face "dimgray")

Limitations

To display the character method guides, and to highlight tab characters correctly, this mode controls the display text property of some characters via font-lock. Therefore, this mode may or may not play well with other modes that use the display text property. This mode may also interfere with modes that use a display table to modify how whitespace is drawn, e.g., the whitespace minor mode.

Alternatives

Package Name	Widths	Hard Tabs	Other Notes
highlight-indentation.el	Fixed	Unsupported	Very popular
indent-guide.el	Dynamic	Supported	Fairly slow, jittery
hl-indent.el	Dynamic	Unsupported	Slow for large files
visual-indentation-mode.el	Fixed	Unsupported	Fast and slim