Idle Highlight Mode

Simple symbol highlighting package for Emacs.

Available via melpa.

Motivation

The aim for this package is to be fast and light.

While there are many similar packages (see Other Packages) that have the same basic functionality these they tend towards being heavier by supporting advanced functionality.

For example running operation on every key-stroke or marking symbols over the entire buffer which can cause poor performance editing large files.

The following guarantees ensure good performance:

• Only update when idle.
• Only operate on visible regions.
• The idle timer is only enabled as needed (it's turned off when the active buffer isn't using ``idle-highlight-mode``).

Usage

Commands

idle-highlight-mode

Enable idle highlight mode for this buffer.

idle-highlight-global-mode

Enable idle highlight mode for all buffers.

Customization

Global Settings

idle-highlight

Face used for highlighting the symbol.

idle-highlight-exceptions: nil

A list of words to exclude from highlighting.

This may also be set to a function that takes the word as an argument, returning non-nil to exclude the word.

idle-highlight-exceptions-face: '(font-lock-keyword-face font-lock-string-face)

Faces to exclude from highlighting (defaults to ignore keywords & strings).

This may also be set to a function that takes a list of faces, returning non-nil to exclude the word.

idle-highlight-exceptions-syntax: ^w_

Syntax table to ignore.

see documentation for skip-syntax-forward, use nil to skip this check.

idle-highlight-exclude-point: nil

When non-nil, don't highlight the symbol under the cursor.

idle-highlight-before-point

When non-nil, also highlight words directly before the cursor.

idle-highlight-visible-buffers: nil

Apply the current highlighting to all visible buffers.

idle-highlight-idle-time: 0.35

Delay before highlighting (in seconds).

idle-highlight-global-ignore-modes: nil

A list of modes that won't enable idle-highlight from idle-highlight-global-mode.

Buffer Local Settings

idle-highlight-global-ignore-buffer

When not nil, the buffer won't enable idle-highlight from idle-highlight-global-mode.

This may also be a function that takes a single buffer argument, where returning nil will enable idle-highlight, anything else will not.

This example shows idle-highlight being disabled for ORG mode and for read-only buffers.

(setq idle-highlight-ignore-modes (list 'org-mode))
(setq idle-highlight-global-ignore-buffer (lambda (buf) (buffer-local-value 'buffer-read-only buf)))

(idle-highlight-global-mode)

Installation

(use-package idle-highlight-mode
  :config (setq idle-highlight-idle-time 0.2)

  :hook ((prog-mode text-mode) . idle-highlight-mode))

Hints

You may wish to set this to a different value for each mode, e.g:

(add-hook 'after-change-major-mode-hook
  (lambda ()
    (when (derived-mode-p 'c-mode)
      (setq-local idle-highlight-exceptions '("unsigned" "signed" "long" "int" "shot" "char")))
    (when (derived-mode-p 'python-mode)
      (setq-local idle-highlight-exceptions '("list" "tuple" "int" "float" "str" "bool")))))

Other Packages

• auto-highlight-symbol.
• highlight-symbol.
• symbol-overlay.