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Use composite to call harfbuzz for ligatures

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This is based on code from microsoft -> cascadia-code repository
(issue #153), which sets a
proper composition-function-table according to specific ligature regexp.

Using variables also allows to disable the ligatures for org-mode, where
org-bullets might be incompatible

It has a fallback to old pretty-code behaviour.
This commit is contained in:
Gerry Agbobada 2020-01-09 10:24:41 +01:00
parent d4acd9721e
commit 810baea2ea
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85
modules/ui/pretty-code/config.el
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@ -98,10 +98,95 @@ Otherwise it builds `prettify-code-symbols-alist' according to
(add-hook 'after-change-major-mode-hook #'+pretty-code-init-pretty-symbols-h)
(defvar +prog-ligatures-alist
'((?! . ".\\(?:\\(==\\|[!=]\\)[!=]?\\)")
(?# . ".\\(?:\\(###?\\|_(\\|[(:=?[_{]\\)[#(:=?[_{]?\\)")
(?$ . ".\\(?:\\(>\\)>?\\)")
(?% . ".\\(?:\\(%\\)%?\\)")
(?& . ".\\(?:\\(&\\)&?\\)")
(?* . ".\\(?:\\(\\*\\*\\|[*>]\\)[*>]?\\)")
;; (?* . ".\\(?:\\(\\*\\*\\|[*/>]\\).?\\)")
(?+ . ".\\(?:\\([>]\\)>?\\)")
;; (?+ . ".\\(?:\\(\\+\\+\\|[+>]\\).?\\)")
(?- . ".\\(?:\\(-[->]\\|<<\\|>>\\|[-<>|~]\\)[-<>|~]?\\)")
;; (?. . ".\\(?:\\(\\.[.<]\\|[-.=]\\)[-.<=]?\\)")
(?. . ".\\(?:\\(\\.<\\|[-=]\\)[-<=]?\\)")
(?/ . ".\\(?:\\(//\\|==\\|[=>]\\)[/=>]?\\)")
;; (?/ . ".\\(?:\\(//\\|==\\|[*/=>]\\).?\\)")
(?0 . ".\\(?:\\(x[a-fA-F0-9]\\).?\\)")
(?: . ".\\(?:\\(::\\|[:<=>]\\)[:<=>]?\\)")
(59 . ".\\(?:\\(;\\);?\\)") ;; 59 is ;
(?< . ".\\(?:\\(!--\\|\\$>\\|\\*>\\|\\+>\\|-[-<>|]\\|/>\\|<[-<=]\\|=[<>|]\\|==>?\\||>\\||||?\\|~[>~]\\|[$*+/:<=>|~-]\\)[$*+/:<=>|~-]?\\)")
(?= . ".\\(?:\\(!=\\|/=\\|:=\\|<<\\|=[=>]\\|>>\\|[=>]\\)[=<>]?\\)")
(?> . ".\\(?:\\(->\\|=>\\|>[-=>]\\|[-:=>]\\)[-:=>]?\\)")
(?? . ".\\(?:\\([.:=?]\\)[.:=?]?\\)")
(91 . ".\\(?:\\(|\\)[]|]?\\)") ;; 91 is [
;; (?\ . ".\\(?:\\([\\n]\\)[\\]?\\)")
(?^ . ".\\(?:\\(=\\)=?\\)")
(?_ . ".\\(?:\\(|_\\|[_]\\)_?\\)")
(?w . ".\\(?:\\(ww\\)w?\\)")
(?{ . ".\\(?:\\(|\\)[|}]?\\)")
(?| . ".\\(?:\\(->\\|=>\\||[-=>]\\||||*>\\|[]=>|}-]\\).?\\)")
(?~ . ".\\(?:\\(~>\\|[-=>@~]\\)[-=>@~]?\\)"))
"An alist containing all the ligatures used when in a `+prog-ligatures-modes' mode.
The car is the character ASCII number, cdr is a regex which will call `font-shape-gstring'
when matched.
Because of the underlying code in :ui pretty-code module, the regex should match a string
starting with the character contained in car."
)
;; Defaults to not org-mode because org-bullets might be incompatible
;; with the ?*-based replacements in the default value of +prg-ligatures-alist
(defvar +prog-ligatures-modes '(not org-mode)
"List of major modes in which ligatures should be enabled.
If t, enable it everywhere.
If the first element is 'not, enable it in any mode besides what is listed.
If nil, fallback to the prettify-symbols based replacement (add +font features to pretty-code)."
)
(defun +pretty-code-init-ligatures-h ()
"Enable ligatures.
If in fundamental-mode, or a mode derived from special, comint, eshell or term
modes, this function does nothing.
Otherwise it sets the buffer-local composition table to a composition table enhanced with
`+prog-ligatures-alist' ligatures regexes."
(unless (or (eq major-mode 'fundamental-mode)
(eq (get major-mode 'mode-class) 'special)
(derived-mode-p 'comint-mode 'eshell-mode 'term-mode))
(when (or (eq +prog-ligatures-modes t)
(if (eq (car +prog-ligatures-modes) 'not)
(not (memq major-mode (cdr +prog-ligatures-modes)))
(memq major-mode +prog-ligatures-modes)))
(setq-local composition-function-table composition-ligature-table))))
(add-hook 'after-change-major-mode-hook #'+pretty-code-init-ligatures-h)
(use-package! composite
:when (and (version<= "27.0" emacs-version) (string-match-p "HARFBUZZ" system-configuration-features))
:init
(defvar composition-ligature-table (make-char-table nil))
:config
(dolist (char-regexp +prog-ligatures-alist)
(set-char-table-range composition-ligature-table (car char-regexp)
`([,(cdr char-regexp) 0 font-shape-gstring])))
(set-char-table-parent composition-ligature-table composition-function-table))
;; The emacs-mac build of Emacs appear to have built-in support for ligatures,
;; so use that instead if this module is enabled.
(cond ((and IS-MAC (fboundp 'mac-auto-operator-composition-mode))
(mac-auto-operator-composition-mode))
;; Harfbuzz builds do not need font-specific ligature support
((and (version<= "27.0" emacs-version)
(string-match-p "HARFBUZZ" system-configuration-features)
(not (null +prog-ligatures-modes)))
nil)
;; Font-specific ligature support
((featurep! +fira)
(load! "+fira"))