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I have stack traces that are coming either from a process or remote server that have ^M at the end of the lines. I can disable read only mode and remove trailing white space, but it would be nice if I could just hide the unwanted characters automatically. I tried playing with set-buffer-process-coding-system, but it says no process.

This question is not the same as the many others asking about ^M characters because I'm talking about a read only buffer. There is no file being visited, so I can't set the file encoding.

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  • Is the "read only" part relevant? I.e. if you made the buffer writeable, would you want the carriage returns to be made visible again?
    – phils
    Aug 26, 2022 at 0:59
  • No, I don't want to see them; they're distracting. I see your point. The read only part doesn't really matter. The buffers I'm looking at happen to be read only because they are the output of a process. But I would want the ^M gone even if the buffer weren't marked read only.
    – Todd
    Aug 26, 2022 at 12:53

2 Answers 2

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You can use Display Tables to achieve what you’re after. Arrange for the following code to be run in those buffers:

(setq buffer-display-table (make-display-table))
(aset buffer-display-table ?\^M [])

(Also posted on comp.emacs many moons ago.)

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The accepted answer mostly does what I want, but it needs a little more work. I want to limit this to buffers that aren't files because, as it happens, I have at least one script with a legitimate ^M character. Also sometimes a buffer opens in a window without actually switching to it, so I think I need two hooks here.

(defun tg/hide-carriage-return ()
    (when (and (not buffer-file-name) (not buffer-display-table))
      (setq buffer-display-table (make-display-table))
      (aset buffer-display-table ?\^M [])))
(add-hook 'after-change-major-mode-hook 'tg/hide-carriage-return)
(add-hook 'buffer-list-update-hook 'tg/hide-carriage-return)

I'm not sure if this is exactly correct, but it seems to get the job done.

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