diff options
Diffstat (limited to 'lisp/emacs-lisp')
| -rw-r--r-- | lisp/emacs-lisp/subr-x.el | 21 |
1 files changed, 14 insertions, 7 deletions
diff --git a/lisp/emacs-lisp/subr-x.el b/lisp/emacs-lisp/subr-x.el index 298d370cb25..9339acc9096 100644 --- a/lisp/emacs-lisp/subr-x.el +++ b/lisp/emacs-lisp/subr-x.el @@ -417,16 +417,23 @@ this defaults to the current buffer." process))) (defmacro with-buffer-unmodified-if-unchanged (&rest body) - "Like `progn', but change buffer modification status only if buffer is changed. -That is, if the buffer is marked as unmodified before BODY, and -BODY does modifications that, in total, means that the buffer is -identical to the buffer before BODY, mark the buffer as -unmodified again. In other words, this won't change buffer -modification status: + "Like `progn', but change buffer-modified status only if buffer text changes. +If the buffer was unmodified before execution of BODY, and +buffer text after execution of BODY is identical to what it was +before, ensure that buffer is still marked unmodified afterwards. +For example, the following won't change the buffer's modification +status: (with-buffer-unmodified-if-unchanged (insert \"a\") - (delete-char -1))." + (delete-char -1)) + +Note that only changes in the raw byte sequence of the buffer text, +as stored in the internal representation, are monitored for the +purpose of detecting the lack of changes in buffer text. Any other +changes that are normally perceived as \"buffer modifications\", such +as changes in text properties, `buffer-file-coding-system', buffer +multibytenes, etc. -- will still cause the buffer to become modified." (declare (debug t) (indent 0)) (let ((hash (gensym)) (buffer (gensym))) |