Emacs Shift-Tab 左移块

Question

如何让 Emacs 以 ShiftTab 将所选文本向左移动 4 个空格？

Answer 1

为此，我使用命令indent-rigidly，绑定到C-x TAB。给它参数 -4 将所选区域向左移动四个空格：C-u -4 C-x TAB。

http://www.gnu.org/s/emacs/manual/html_node/elisp/Region-Indent.html

Answer 2

这会从当前行的前面删除 4 个空格（前提是空格存在）。

(global-set-key (kbd "<S-tab>") 'un-indent-by-removing-4-spaces)
(defun un-indent-by-removing-4-spaces ()
  "remove 4 spaces from beginning of of line"
  (interactive)
  (save-excursion
    (save-match-data
      (beginning-of-line)
      ;; get rid of tabs at beginning of line
      (when (looking-at "^\\s-+")
        (untabify (match-beginning 0) (match-end 0)))
      (when (looking-at "^    ")
        (replace-match "")))))

如果您的变量 tab-width 恰好是 4（这就是您想要“撤消”的内容），那么您可以将 (looking-at "^ ") 替换为更通用的名称，例如 (concat "^" (make-string tab-width ?\ ))。

此外，代码将使用untabify 将行前的制表符转换为空格。

Answer 3

我制作了一些函数，根据您使用的是 tab 还是 shift+tab，将一个区域向左或向右移动四个空格：

(defun indent-region-custom(numSpaces)
    (progn 
        ; default to start and end of current line
        (setq regionStart (line-beginning-position))
        (setq regionEnd (line-end-position))
        
        ; if there's a selection, use that instead of the current line
        (when (use-region-p)
            (setq regionStart (region-beginning))
            (setq regionEnd (region-end))
        )
        
        (save-excursion ; restore the position afterwards            
            (goto-char regionStart) ; go to the start of region
            (setq start (line-beginning-position)) ; save the start of the line
            (goto-char regionEnd) ; go to the end of region
            (setq end (line-end-position)) ; save the end of the line
            
            (indent-rigidly start end numSpaces) ; indent between start and end
            (setq deactivate-mark nil) ; restore the selected region
        )
    )
)

(defun untab-region (N)
    (interactive "p")
    (indent-region-custom -4)
)

(defun tab-region (N)
    (interactive "p")
    (if (active-minibuffer-window)
        (minibuffer-complete)    ; tab is pressed in minibuffer window -> do completion
    ; else
    (if (string= (buffer-name) "*shell*")
        (comint-dynamic-complete) ; in a shell, use tab completion
    ; else
    (if (use-region-p)    ; tab is pressed is any other buffer -> execute with space insertion
        (indent-region-custom 4) ; region was selected, call indent-region-custom
        (insert "    ") ; else insert four spaces as expected
    )))
)

(global-set-key (kbd "<backtab>") 'untab-region)
(global-set-key (kbd "<tab>") 'tab-region)

编辑：添加了 Maven 的代码来检查是否在 minibuffer 中，以及在特定缓冲区（例如 shell）中的 tab 补全。

Answer 4

我改进了 Stanley Bak 的回答。 对我来说，这个全局键绑定破坏了 minibuffer 的完成。

所以我也包含了一个小型缓冲区的案例。

编辑：重命名indent-region -> indent-region-custom。

indent-region 与现有命令冲突，并在保存时缩进（保存前挂钩）和其他一些组合键出现错误。

(defun indent-region-custom(numSpaces)
  (progn
    ;; default to start and end of current line
    (setq regionStart (line-beginning-position))
    (setq regionEnd (line-end-position))
    ;; if there's a selection, use that instead of the current line
    (when (use-region-p)
      (setq regionStart (region-beginning))
      (setq regionEnd (region-end))
      )

    (save-excursion ; restore the position afterwards
      (goto-char regionStart) ; go to the start of region
      (setq start (line-beginning-position)) ; save the start of the line
      (goto-char regionEnd) ; go to the end of region
      (setq end (line-end-position)) ; save the end of the line

      (indent-rigidly start end numSpaces) ; indent between start and end
      (setq deactivate-mark nil) ; restore the selected region
      )
    )
  )

(defun untab-region (N)
  (interactive "p")
  (indent-region-custom -4)
  )

(defun tab-region (N)
  (interactive "p")
  (if (active-minibuffer-window)
      (minibuffer-complete)    ; tab is pressed in minibuffer window -> do completion
    (if (use-region-p)    ; tab is pressed is any other buffer -> execute with space insertion
        (indent-region-custom 4) ; region was selected, call indent-region-custom
      (insert "    ") ; else insert four spaces as expected
      )
    )
  )

(global-set-key (kbd "<backtab>") 'untab-region)
(global-set-key (kbd "<tab>") 'tab-region)