简单撸了一个，还请各位坛友多多指教：
(require 'treesit)
(require 'posframe)
(defgroup treesit-context nil
"Show the context of the currently visible buffer contents."
:group 'treesit)
(defvar treesit-context--buffer (generate-new-buffer "*treesit-context-posframe-buffer*")
"Buffer used to display the context.")
(defvar treesit-context--list nil
"List used to store the context needs showing.")
(defvar treesit-context--timer nil
"Timer for updating the context.")
(defcustom treesit-context--background "#454545"
"Background color for the context."
:group 'treesit-context)
(defun treesit-context ()
"Show code context."
(interactive)
(unless (not (treesit-available-p))
(local-unset-key (kbd "C-g"))
(local-set-key (kbd "C-g") 'treesit-context-abort)
;; (add-hook 'post-command-hook #'treesit-context--update nil 'local)
(setq treesit-context--timer (run-with-idle-timer 0.1 t 'treesit-context--update))
(treesit-context--update)))
(defun treesit-context-abort ()
"Abort showing code context."
(interactive)
(posframe-hide treesit-context--buffer)
(local-set-key (kbd "C-g") 'keyboard-quit)
;; (kill-buffer treesit-context--buffer)
;; (remove-hook 'post-command-hook #'treesit-context--update 'local)
(when treesit-context--timer
(cancel-timer treesit-context--timer)))
(defun treesit-context--add-to-list (node)
"Add the text of the node into `treesit-context--list'."
(if (or (string= (treesit-node-type node) "if_statement")
(string= (treesit-node-type node) "for_statement")
(string= (treesit-node-type node) "struct_specifier")
(string= (treesit-node-type node) "while_statement")
(string= (treesit-node-type node) "function_definition"))
(progn
(let* ((text (treesit-node-text node))
(buf (generate-new-buffer "*treesit-context-temp-buffer*"))
(text-showed nil))
(with-current-buffer buf
(goto-char (point-min)) (insert text)
(goto-char (point-min))
(setq text-showed (buffer-substring
(point-min) (line-end-position))))
(push text-showed treesit-context--list)
(kill-buffer buf)))))
(defun treesit-context--get-context-from-list ()
"Get the context of `treesit-context--list'"
(let ((context ""))
(dolist (text treesit-context--list)
(setq context (concat context text "\n")))
context))
(defun treesit-context--update ()
"Update `treesit-context--ov'."
(unless (or (minibufferp) (not (buffer-live-p treesit-context--buffer)))
(setq treesit-context--list nil)
(ignore-errors
(let* ((node (treesit-node-at (point))))
(cl-loop while node
do (treesit-context--add-to-list node)
do (setq node (treesit-node-parent node)))))
(if treesit-context--list
(progn
(with-current-buffer treesit-context--buffer
(erase-buffer)
(insert (treesit-context--get-context-from-list)))
(when (posframe-workable-p)
(posframe-show treesit-context--buffer
:poshandler #'posframe-poshandler-window-top-right-corner
:background-color "#454545"
:border-width 5
:border-color "#454545")))
(posframe-hide treesit-context--buffer))))
(provide 'treesit-context)
依赖:
- Emacs 29 or above, bulit with tree-sitter support
- posframe
使用
M-x treesit-context
ps: 其实这个东西昨天晚上就写好了，但是是用overlay实现的，经过 @milan-glacier 大佬的指点，在权衡利弊后改用了 posframe 实现（原来想用 child-frame 手搓的，结果太复杂了没太看懂 
）
当初说要用异步实现的，结果食言了 
，觉得有点杀鸡用牛刀，改成了 (run-with-idle-timer) 实现，幸好这个update函数并不慢，直接绑在post-command-hook上也几乎没有卡顿，所以整体体验应该还是可以的，不会出现卡手的情况。