Re: info invisible changes

[storm@cua.dk (Kim F. Storm)]

"Stefan Monnier" <monnier+gnu/emacs/pretest@rum.cs.yale.edu> writes:

> > 1) it doesn't test for 'invisible properties, so it happily processes
> >    invisible text when deciding the (visible) width of the lines,
> 
> Are you sure ?  It uses current-column which does pay attention
> to `invisible' properties.

It works in relation to fill, yes.

But in general, the behaviour of current-column is "questionable" when
the buffer contains invisible newlines.  Consider the following code:

(let ((b (get-buffer-create "current-column test")))
   (set-buffer b)
   (erase-buffer)
   (insert "abc\ndef\nghi")
   (add-text-properties 4 5 '(invisible t))
   (add-text-properties 8 9 '(invisible t))
   ;; buffer now displays as one line: abcdefghi
   ;; position on the `h'
   (goto-char 10)
   (current-column))

It creates a buffer with the following data line (where # indicates an
invisible newline):

        abc#
        def#
        ghi

I.e. the visible result is:

        abcdefghi

Here, current-column claims that `h' is in column 1.

This is because current_column_1 uses scan_newline to find the
line start, but scan_newline doesn't skip over invisible newlines...


> 
> > 3) when the fill code inserts a newline to wrap the text, it may
> >    insert that newline in an invisible part of the buffer, so it has
> >    no visible effect (i.e. displaying one very long line rather than
> >    two normal width lines).
> 
> You can fix this easily.  See fill-nobreak-predicate.

Thanks.  I learn something new every day.

++kfs