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| -rw-r--r-- | lispref/text.texi | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/lispref/text.texi b/lispref/text.texi index 6ba44ecda1a..2780eb56452 100644 --- a/lispref/text.texi +++ b/lispref/text.texi @@ -2973,9 +2973,16 @@ buffer that is about to change is always the current buffer. This variable holds a list of a functions to call after any buffer modification. Each function receives three arguments: the beginning and end of the region just changed, and the length of the text that existed -before the change. (To get the current length, subtract the region -beginning from the region end.) All three arguments are integers. The -buffer that's about to change is always the current buffer. +before the change. All three arguments are integers. The buffer that's +about to change is always the current buffer. + +The length of the old text is measured in bytes; it is the difference +between the buffer positions before and after that text, before the +change. As for the changed text, its length in bytes is simply the +difference between the first two arguments. If you want the length +in @emph{characters} of the text before the change, you should use +a @code{before-change-functions} function that calls @code{chars-in-region} +(@pxref{Chars and Bytes}). @end defvar @defvar before-change-function |