Emacs Shift-Tab 左移代码块

Question

我该如何让Emacs使用ShiftTab将选中的文本向左移动4个空格？

- user90150

Answer 1

为了实现这一目的，我使用命令indent-rigidly，将其绑定到C-x TAB。给它参数-4，将选定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

- Sean

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根据同一手册条目，您可能更喜欢使用indent-code-rigidly，因为它不会影响注释和多行字符串。 - user23987

Answer 2

这将从当前行的开头删除4个空格（如果存在空格）。

(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恰好为4（并且您想要“撤消”它），则可以将(looking-at "^ ")替换为更通用的内容，例如(concat "^" (make-string tab-width ?\ ))。

此外，该代码将使用untabify将行首的制表符转换为空格。

- Trey Jackson

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很好！但我会使用WHEN而不是IF，因为没有else子句。 - Ken

对我而言，它在选择区域时无效。只有在第一行时才有效 :-/ - Ismael

@Mauricio A. Cinelli -- 对 (kbd "<S-tab>") 进行绑定没有生效，但是对 (kbd "<backtab>") 进行绑定可以解决问题。 - modulitos

Answer 3

我编写了一些函数，用于通过按tab或shift+tab将区域向左或向右缩进四个空格：

我编写了一些函数，用于通过按Tab键或Shift+Tab键将文本区域向左或向右缩进四个空格：

(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代码，以检查是否处于minibuffer中，以及在特定缓冲区（例如shell）进行选项卡补全。

- Stanley Bak

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不错，被采纳的答案只适用于一行，而不是区域。 - Hello_world

完美。适用于区域和行。复制其他常见编辑器的功能。 - mythicalcoder

Answer 4

我对Stanley Bak的答案进行了改进。 对我来说，这个全局键绑定会干扰minibuffer完成。 因此，我也包括了minibuffer的情况。

编辑：将indent-region重命名为indent-region-custom。 indent-region与现有命令冲突，在保存时出现缩进错误（钩子为保存之前）和其他一些按键组合。

(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)

- mythicalcoder