在Spacemacs中配置Fira Code并启用ligatures特性

Fira是Mozilla主推的字体系列。Fira Code是其中的一员，专为写程序而生。出来具有等宽等基本属性外，还加入了编程连字特性（ligatures）。编程连字特性，其实就是利用这个特性对编程中的常用符号进行优化，比如把输入的「!=」直接显示成「≠」或者把「>=」变成「≥ 」等等，以此来提高代码的可读性。

作为传说中的程序员，Fira Code也早已称为我的各大常用编辑器标配字体。Fira Code在其他编辑器和终端上配置较为简单，选中字体过后，启用Ligatures Feature即可。Spacemacs和Emacs的配置稍微复杂一些，这里分享一下Fira Code在Spacemacs下的配置。

第一步

第二步

获取并安装 Fira Code Symbol Font。对于Linux系统，可以直接把字体解压并放到 /usr/share/fonts 目录，并重载字体的cache，使其生效。

第三步

在Spacemacs中，使用<SPC> f e d 编辑 ~/.spacemacs配置文件。对于Emacs用户来说，可以编辑 ~/.emacs.d/init.el。

在配置文件中，加入如下设置：

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dotspacemacs-default-font '(("FuraCode Nerd Font Mono"
                               :size 16
                               :weight medium
                               :width normal
                               :powerline-scale 1.1)
                               ("Fira Code Symbol"
                               :size 16
                               :weight normal
                               :width normal
                               :powerline-scale 1.1))

第四步

同样是编辑配置文件，在Spacemacs的配置项dotspacemacs-user-config中加入如下配置：

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(defun dotspacemacs/user-config()
 "Configuration function for user code."
;; Font Ligatures
  (defun my-correct-symbol-bounds (pretty-alist)
      "Prepend a TAB character to each symbol in this alist,
  this way compose-region called by prettify-symbols-mode
  will use the correct width of the symbols
  instead of the width measured by char-width."
      (mapcar (lambda (el)
                (setcdr el (string ?\t (cdr el)))
                el)
              pretty-alist))
  (defun my-ligature-list (ligatures codepoint-start)
      "Create an alist of strings to replace with
  codepoints starting from codepoint-start."
      (let ((codepoints (-iterate '1+ codepoint-start (length ligatures))))
        (-zip-pair ligatures codepoints)))
  (setq my-fira-code-ligatures
      (let* ((ligs '("www" "**" "***" "**/" "*>" "*/" "\\\\" "\\\\\\"
                    "{-" "[]" "::" ":::" ":=" "!!" "!=" "!==" "-}"
                    "--" "---" "-->" "->" "->>" "-<" "-<<" "-~"
                    "#{" "#[" "##" "###" "####" "#(" "#?" "#_" "#_("
                    ".-" ".=" ".." "..<" "..." "?=" "??" ";;" "/*"
                    "/**" "/=" "/==" "/>" "//" "///" "&&" "||" "||="
                    "|=" "|>" "^=" "$>" "++" "+++" "+>" "=:=" "=="
                    "===" "==>" "=>" "=>>" "<=" "=<<" "=/=" ">-" ">="
                    ">=>" ">>" ">>-" ">>=" ">>>" "<*" "<*>" "<|" "<|>"
                    "<$" "<$>" "<!--" "<-" "<--" "<->" "<+" "<+>" "<="
                    "<==" "<=>" "<=<" "<>" "<<" "<<-" "<<=" "<<<" "<~"
                    "<~~" "</" "</>" "~@" "~-" "~=" "~>" "~~" "~~>" "%%"
                    "x" ":" "+" "+" "*")))
        (my-correct-symbol-bounds (my-ligature-list ligs #Xe100))))
  (defun my-set-fira-code-ligatures ()
      "Add fira code ligatures for use with prettify-symbols-mode."
      (setq prettify-symbols-alist
            (append my-fira-code-ligatures prettify-symbols-alist))
      (prettify-symbols-mode))
  (add-hook 'prog-mode-hook 'my-set-fira-code-ligatures))

第五步

最后，重载Spacemacs/Emacs的配置文件，使配置生效，即可启用Fira Code字体的Ligatures连字特性。