About Emacs Spell Check Support

General

Emacs ‑ at least up to v27.2 ‑ does not include spell check software
The documentation says: "Usually one of Hunspell, Aspell, Ispell or Enchant are installed on a GNU/Linux system"

My approach for Emacs 27.2 under Windows 10

Under Windows, normally none of these are installed. Hence:

I downloaded hunspell-1.3.2-3-w32-bin.zip from https://sourceforge.net/projects/ezwinports/files/
- Unpack in a user directory. I chose C:/Users/username/OneDrive/myPrograms/hunspell-1.3.2-3-w32
Only dictionaries for en_GB and en_US are part of the ZIP file.
- There are directories named hu and it but without dictionary files
- The files default.dic and default.aff in share/hunspell are copies of en_US.dic and en_US.aff
- The en_GB and en_US dictionaries in the Hunspell ZIP might not be the most recent and/or "best" ones
You might want to add more languages
- Per language, you need a pair of .dic and .aff files

Various Sources for Hunspell Language Dictionaries

Thunderbird (under Windows 10)
- I could not find a hunspell.exe executable within the Thunderbird installed directory structure
- You download dictionaries within Thunderbird (no admin rights needed)
  - They get stored in C:\Users\username\AppData\Roaming\Thunderbird\Profiles\xxxxxxxx.default-release\extensions
  - Stored as e.g. de-DE@dictionaries.addons.mozilla.org.xpi
  - .xpi file is a .zip, which contains the .dic and .aff file in directory dictionaries
I had to rename de_DE_frami.dic and de_DE_frami.aff to de_DE.dic and de_DE.aff and copy to C:/Users/username/OneDrive/myPrograms/hunspell-1.3.2-3-w32/share/hunspell for Hunspell to find the files
- Under Debian Linux, this is achieved by using symlinks
Emacs M-x ispell-change-dictionary <RET> DICT <RET> or "Tools → Change Dictionary…" (TAB completion works) has its own system, how the languages are named
- To be clarified how those language names are mapped onto the .dic- and .aff-files
LibreOffice is said to also use Hunspell
- To be clarified how Hunspell is implemented there
- I do not have LibreOffice installed (would be under Windows in my case)
Softmaker ‑ a Nürnberg based software provider of multi platform office software ‑ also uses Hunspell in their products
- They offer dictionaries for download from their web-site

Various Emacs Settings in `init.el`

I need to tell Emacs where to find the spell check executable:

'(ispell-program-name "C:/Users/username/OneDrive/myPrograms/hunspell-1.3.2-3-w32/bin/hunspell.exe")

Optionally set default spelling language to British English:
```
'(ispell-dictionary "en_GB")
```

For org-mode, you might want to exclude several artefacts from spell checking

(add-to-list 'ispell-skip-region-alist '(":\\(PROPERTIES\\|LOGBOOK\\):" . ":END:"))
(add-to-list 'ispell-skip-region-alist '("#\\+BEGIN_SRC" . "#\\+END_SRC"))
(add-to-list 'ispell-skip-region-alist '("#\\+BEGIN_EXAMPLE" . "#\\+END_EXAMPLE"))

You might want to specify where your personal dictionary shall be stored
```
'(ispell-personal-dictionary "~/myspelldict")
```
But this did not work in my case. Specifying an absolute path did not help.
- ~/.hunspell-default is documented as personal dictionary on the Hunspell man page. When run from the cmd.exe, indeed ~/hunspell-default (without a leading ".") gets used as personal dictionary file. But that does not seem to be used when Hunspell is used from within Emacs

Approach under Debian 12 "Bookworm"

For Debian and likely other Linux distributions, spelling support seems to be system wide (you need admin rights to install)
Under Debian Linux, both Hunspell and the dict files are available as normal installation packages. Hence you would do
```
apt install hunspell
```
which includes an en_US dictionary and e.g. further
```
apt install hunspell-de-de-frami
apt install hunspell-en-gb
apt install hunspell-fr-classical
```
- The executable gets stored as /usr/bin/hunspell (See dpkg -L hunspell)
- Dictionaries get stored under /usr/share/hunspell
- How do these files get re-used when using other tools like LibreOffice and Thunderbird?

Also under Debian you need to tell Emacs in init.el to use Hunspell:

'(ispell-program-name "hunspell")

The reason is that ispell had been installed automatically in my case and aspell was installed as a dependency of Inkscape. The effect was that Emacs used aspell.

Usage

Start spell checking in current buffer: M-$ and then type ? for help
Resume spell checking: C-u M-$

Documentation about Hunspell

Man pages in Hunspell ZIP file
Online e.g. https://manpages.debian.org/bullseye/hunspell/hunspell.1.en.html
About the .dic and .aff files e.g. https://manpages.ubuntu.com/manpages/bionic/man5/hunspell.5.html