一个简单的hack，还原了类似 IntelliJ IDE 那种通过 Ctrl 加鼠标点击跳转到函数定义位置或选择该函数被哪些地方使用了。适合用来阅读大型项目的 elisp 源码，这和我平时工作中体验一致，还是比较舒服的。需要的小伙伴自取：
(bind-key (kbd "C-<down-mouse-1>") 'xref-find-definitions-or-usages-at-mouse 'emacs-lisp-mode-map)
(bind-key (kbd "C-<down-mouse-1>") 'xref-find-definitions-or-usages-at-mouse 'c-mode-map)
(bind-key (kbd "<mouse-4>") 'xref-go-back 'emacs-lisp-mode-map)
(bind-key (kbd "<mouse-4>") 'xref-go-back 'c-mode-map)
(bind-key (kbd "<mouse-5>") 'xref-go-forward 'emacs-lisp-mode-map)
(bind-key (kbd "<mouse-5>") 'xref-go-forward 'c-mode-map)
(defun xref-in-definition-p ()
"判断当前点是否在函数定义的名称位置。"
(when-let ((sym (symbol-at-point)))
(save-excursion
(beginning-of-thing 'symbol)
(and ;; 向前搜索最近的左括号
(condition-case nil
(progn (up-list -1) t)
(error nil))
(or
;; 检查左括号后面的单词是否是定义形式
(looking-at "(def\\(un\\|macro\\|generic\\|method\\|subst\\)\\s-+")
(looking-at "(cl-def\\(un\\|macro\\|generic\\|method\\)\\s-+")
(looking-at "(defalias\\s-+")
(looking-at "(lambda\\s-+")
(looking-at "(def\\(var\\|var-local\\)\\s-+")
(looking-at "\\(?:setq\\|seq-local\\|setf\\)\\s-+.*#'?"))))))
(defun xref-find-definitions-or-usages ()
(interactive)
(if (xref-in-definition-p)
(counsel-git-grep (format "%s" (symbol-at-point)))
(xref-find-definitions (xref-backend-identifier-at-point
(xref-find-backend)))))
(defun xref-find-definitions-or-usages-at-mouse (event)
(interactive "e")
(if (xref-in-definition-p)
(counsel-git-grep (format "%s" (symbol-at-point)))
(xref-find-definitions-at-mouse event)))