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Explain after-change-functions and chars vs bytes.

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Richard M. Stallman 1997-08-22 05:58:17 +00:00
parent 839dd8341f
commit 584b810416
1 changed files with 10 additions and 3 deletions
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13
lispref/text.texi
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@ -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