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readme.rst

########
Spell Fu
########

Fast highlighting of misspelled words.

This is a light weight spell checker for Emacs,
that runs from the syntax highlighter without starting external processes.

Available on `Melpa <https://melpa.org/#/spell-fu>`__.


Motivation
==========

There are two main areas this package focuses on.

- Fast on-screen highlighting.

*Currently most alternative solutions run an external processes and don't always update on-screen results.*

- Hack-able spell-checking.

*Easily to customize for users, for different major-modes.*


Usage
=====

You may enable this globally which has the following defaults.

.. code-block:: elisp

(use-package spell-fu)
(global-spell-fu-mode)

Or you may wish to configure this per-mode, e.g:

.. code-block:: elisp

(use-package spell-fu)

(add-hook 'org-mode-hook
(lambda ()
(setq spell-fu-faces-exclude
'(org-block-begin-line
org-block-end-line
org-code
org-date
org-drawer org-document-info-keyword
org-ellipsis
org-link
org-meta-line
org-properties
org-properties-value
org-special-keyword
org-src
org-tag
org-verbatim))
(spell-fu-mode)))

(add-hook 'emacs-lisp-mode-hook
(lambda ()
(spell-fu-mode)))

Multiple languages can be used in the same buffer by configuring multiple dictionaries:

.. code-block:: elisp

(add-hook 'spell-fu-mode-hook
(lambda ()
(spell-fu-dictionary-add (spell-fu-get-ispell-dictionary "de"))
(spell-fu-dictionary-add (spell-fu-get-ispell-dictionary "fr"))
(spell-fu-dictionary-add
(spell-fu-get-personal-dictionary "de-personal" "/home/user/.aspell.de.pws"))
(spell-fu-dictionary-add
(spell-fu-get-personal-dictionary "fr-personal" "/home/user/.aspell.fr.pws"))))


Customization
-------------


Global Settings
^^^^^^^^^^^^^^^

``spell-fu-directory``
The directory used for storing the dictionary cached.

``spell-fu-idle-delay`` (0.25 seconds)
The idle time before marking words as misspelled.

This can be set to zero, in this case an idle timer won't be used,
and spelling will be checked as part of syntax highlighting.

``spell-fu-incorrect-face`` (red, underline)
The font to use for the spell checking overlay.

``global-spell-fu-ignore-modes`` nil
A list of modes that won't enable spell-checking from ``global-spell-fu-mode``.

``spell-fu-debug`` nil
Enable to see additional messages which may help to debug failure to initialize dictionaries.

After enabling you may want to call the command ``spell-fu-reset``.


Buffer Local Settings
^^^^^^^^^^^^^^^^^^^^^

You may wish to set these values differently based on the current major-mode.

``spell-fu-syntax-table``
The syntax table used for spell-checking.

Useful when the current syntax-table for a major-mode is set for a programming language
which doesn't make sense to use for natural language.

``spell-fu-word-regexp``
The regular expression to use for scanning words.

``spell-fu-faces-include``
When not ``nil``, only faces in this list will be checked.

``spell-fu-faces-exclude``
When not ``nil``, text with faces in this list won't be checked.

Note that you may wish to add faces to this list if keywords or commands are marked as being spelled incorrectly.
In this case, the face used by these commands may be added to this list so as to skip them.

``global-spell-fu-ignore-buffer``
When not ``nil``, the buffer won't enable spell-checking from ``global-spell-fu-mode``.

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

This example shows spell-fu being disabled for ORG mode and for read-only buffers.

.. code-block:: elisp

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

(global-spell-fu-mode)


Buffer Local Words
^^^^^^^^^^^^^^^^^^

You may optionally define a buffer-local word list.

``spell-fu-buffer-session-localwords``
A list of strings to accept as correctly spelled words.
These may be set by file or directory locals.

Changing this while spell-fu is already active requires calling:
``spell-fu-buffer-session-localwords-update``.
Calling outside of ``spell-fu-mode`` has no effect.


Advanced Buffer Local Settings
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

These options allow for applying your own rules to how the spell checker runs,
they aren't necessary for typical usage.

``spell-fu-check-range``
This is the main function which checks words,
in most cases this can be left at it's default.

In some cases you may wish to scan the text in the given range using more sophisticated checks,
skipping text based on your own rules.

This function takes ``(point-start point-end)`` arguments,
which are guaranteed to be on line boundaries.

``(spell-fu-check-word point-start point-end word-string)`` should be called for each word you wish to check.

Note that setting this function causes the following settings to be ignored:

- ``spell-fu-faces-include``
- ``spell-fu-faces-exclude``
- ``spell-fu-word-regexp``
- ``spell-fu-syntax-table``


Other Settings
--------------

In most cases there is no need to change these settings,
however they will be used when set:

``ispell-program-name``
Used to call aspell (when this points to ``aspell``, otherwise ``aspell`` is called).

``ispell-dictionary``
When generating the word-list, this variable is used when present,
otherwise aspell's default dictionary is used.

``ispell-local-dictionary``
Setting this allows you to have different languages set per-buffer.

``ispell-personal-dictionary``
When generating the word-list, this file is included when present.


Commands
--------

While this package is intended to be used with minimal interaction,
there are some commands provided which may come in handy.

``spell-fu-goto-next-error``
Moves the point to the next error.

``spell-fu-goto-previous-error``
Moves the point to the previous error.

``spell-fu-buffer``
Checks spelling for the entire buffer, reporting the number of misspelled words found.

``spell-fu-word-add``
Add the word under the cursor to a personal dictionary.

``spell-fu-word-remove``
Remove the word under the cursor from a personal dictionary.

``spell-fu-reset``
Toggle ``spell-fu`` mode for all buffers and resets cache,
use this if you suspect errors relating to invalid cache.

This can be useful if you use the ``default`` dictionary, then change the systems locale.


Multiple dictionaries
---------------------

Multiple dictionaries can be enabled and used alongside each other.

``spell-fu-dictionaries``
Variable which lists the currently enabled dictionaries.

``spell-fu-dictionary-add``
Enable a dictionary in the current buffer.

``spell-fu-dictionary-remove``
Disable a dictionary in the current buffer.

``spell-fu-get-ispell-dictionary``
Get the ispell / aspell dictionary with the given name.

``spell-fu-get-personal-dictionary``
Get a writable personal dictionary for saving user words.


Details
=======

- All programming modes only check comments and strings.
- All other major modes check all words.
- Currently this package requires ``aspell`` to generate the word-list.


Other Packages
==============

`FlySpell <https://www.emacswiki.org/emacs/FlySpell>`__
As of Emacs 28, this doesn't provide a way to automatically check all on-screen text,
and running this on an entire buffer can be slow.

`WCheck Mode <https://github.com/tlikonen/wcheck-mode>`__
This is a close match to Spell-fu, the main differences is that it's calling a sub-process
on each word which gives slower results.
I also found its configuration rather difficult to manage.

Spell-fu in contrast takes a different approach,
instead of exposing many advanced options,
you can set your own function to extract words from a region of text.


TODO
====

- Support alternates to ``aspell`` for generating word lists.
- Support a custom command for generating a word list.
- Support refreshing the word list at run-time when ispell updates the personal dictionary
*(currently updates require re-enabling the mode).*