doomemacs/modules/ui/pretty-code/README.org

#+TITLE:   ui/pretty-code
#+DATE:    June 16, 2018
#+SINCE:   v2.0.9
#+STARTUP: inlineimages nofold

* Table of Contents :TOC_3:noexport:
- [[#description][Description]]
  - [[#maintainers][Maintainers]]
  - [[#module-flags][Module Flags]]
    - [[#font-ligatures-module-flags][Font ligatures module flags]]
  - [[#plugins][Plugins]]
- [[#prerequisites][Prerequisites]]
  - [[#ligatures][Ligatures]]
    - [[#emacs-mac-port-or-emacs-28][Emacs-mac port or Emacs 28+]]
    - [[#not-emacs-mac-and-emacs--27][Not Emacs-mac and Emacs <= 27]]
- [[#features][Features]]
  - [[#mathematical-symbols-replacement][Mathematical symbols replacement]]
  - [[#coding-ligatures][Coding ligatures]]
- [[#configuration][Configuration]]
  - [[#set-pretty-symbols][~set-pretty-symbols!~]]
- [[#troubleshooting][Troubleshooting]]

* Description
This module enables ligatures and/or arbitrary symbol substitutions with
~prettify-symbols-mode~.

** Maintainers
This module has no dedicated maintainers.

** Module Flags
*** Font ligatures module flags
Those flags are ignored on emacs-mac and on other platforms if running emacs 28+
with harfbuzz feature. In those cases, ligatures are handled without needing the
extra configuration provided by those flags.

+ =+fira= Enables =Fira Code= ligatures. This requires Fira Code Symbol and a
  patched version of Fira Code (see below).
+ =+hasklig= Enable =Hasklig= ligatures. This requires a patched version of the
  HaskLig font (see below).
+ =+iosevka= Enable =Iosevka= ligatures. This requires a patched version of the
  Iosevka font (see below).
+ =+pragmata-pro= Enable =Pragmata Pro= ligatures. This requires the [[https://www.fsd.it/shop/fonts/pragmatapro/][Pragmata
  Pro font]].

** Plugins
This module installs no packages.

* Prerequisites
** Ligatures
For ligatures to work, you must either:

- Have a recent enough version of Emacs which will compose ligatures
  automatically, or
- Use one of our font-specific configurations.

*** Emacs-mac port or Emacs 28+
Ligatures are handled without needing additional configuration. If this doesn't
work, report a bug with your current version of emacs and the ligatures which
aren't working.

*** Not Emacs-mac and Emacs <= 27
1. Enable one of the four ligature font flags: =+fira=, =+hasklig=, =+iosevka=
   or =+pragmata-pro=.
2. Install the patched version of the associated font with ~M-x
   +pretty-code/install-patched-font~. Note: Pragmata Pro cannot be installed
   this way because it isn't a non-free font and must be purchased and installed
   manually.

* TODO Features
# An in-depth list of features, how to use them, and their dependencies.
** TODO Mathematical symbols replacement
** Coding ligatures
This module includes configuration to compose combinations like =->= or =::=
into prettier glyphs (called a ligature). Depending on the current version of
emacs, this is implemented in two different ways :

- prettify-symbols-mode method :: this is the "legacy" method. It uses a font
  which haves the ligatures as separate unicode symbols, and using
  prettify-symbols-mode, =->=-like combinations are manually listed and replaced
  with the correct symbol. The mapping between =->=-like sequences and unicode
  values in the font are font-specific ; therefore =+fira=, =+iosevka=... files
  and specific fonts are necessary for it to work.
- composition-function-table method :: regexes are used to match all the usual
  sequences which are composed into ligatures. These regexes are passed to emacs
  directly, which asks Harfbuzz to shape it. Ligatures are obtained
  automatically depending on the capabilities of the font, and no font-specific
  configuration is necessary.

Emacs-mac port implements the /composition-function-table/ method in [[https://bitbucket.org/mituharu/emacs-mac/src/26c8fd9920db9d34ae8f78bceaec714230824dac/lisp/term/mac-win.el?at=master#lines-345:805][its code]],
nothing is necessary on Doom side; otherwise, Doom implements the
/composition-function-table/ for emacs 28+ built with Harfbuzz support, and the
/prettify-symbols-mode/ method otherwise.

Even though harfbuzz has been included in emacs 27, there is currently a [[https://lists.gnu.org/archive/html/bug-gnu-emacs/2020-04/msg01121.html][bug
(#40864)]] which prevents a safe usage of /composition-function-table/ method in
emacs 27.

* TODO Configuration
# How to configure this module, including common problems and how to address them.

** TODO ~set-pretty-symbols!~

* TODO Troubleshooting
# Common issues and their solution, or places to look for help.