Elisp: Text Properties

By Xah Lee. Date: . Last updated: .

Text in a buffer can have “text properties”.

Text properties is used to color text, or add keybinding to that text (for example, pressing Enter on a link in HTML opens the link instead of insert return.), and other purposes.

Here's a command that makes a region red, by adding a text property of 'font-lock-face to it.

(defun x-make-word-red (begin end)
  "make current region colored red, using text properties"
  (interactive "r")
  (put-text-property begin end 'font-lock-face '(:foreground "red")))

Select a region, then Alt+x x-make-word-red

Here's example of adding a keymap to text, so that when Enter is pressed, it tries to open the file, taking current line as file name/path.

(defun x-open-me ()
  "open a file, using current line as file name/path"
  (interactive)
  (find-file
   (buffer-substring-no-properties (line-beginning-position) (line-end-position))))

(defvar x-keymap nil "sample keymap")
(setq x-keymap (make-sparse-keymap))
(define-key x-keymap (kbd "RET") 'x-open-me)

(defun x-add-prop (begin end)
  "add text properties to a region."
  (interactive "r")
    (put-text-property begin end 'font-lock-face '(:foreground "blue"))
    (put-text-property begin end 'keymap x-keymap))

To try the above code:

  1. Open a new file, with some lines being file path.
  2. Go to a line that's a file path, select it, then Alt+x x-add-prop. The region will be colored blue, and pressing Enter key on it will call x-open-me

What's Text Property

Text Property is a property list attached to text.

A property list is a list but interpreted as key and value pairs. Like this:

'(key1 val1 key2 val2 …)

[see Elisp: Property List]

When a property list is attached to text, some keys have special meaning that are predefined by emacs.

Here are some of the most useful property keys for writing a major/minor mode:

For a complete list, see (info "(elisp) Special Properties")

Functions for Working with Text Property

There are many functions to get values of text properties, add/change/delete them, or find out where a property begins, etc. See

(info "(elisp) Text Properties")

Elisp, Writing Major Mode

  1. Syntax Coloring
  2. Font Lock Mode
  3. Define Face
  4. Color Comment
  5. Comment Command
  6. Your Own Comment Command
  7. Keyword Completion Command
  8. Create Keymap
  9. Abbrev/Template
  10. Text Properties
  11. Overlay Highlighting
  12. Lookup Doc
  13. Syntax Table

  1. How to Name Your Major Mode
  2. provide, require, features
  3. load, load-file, autoload

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