23.0.50; display property and continuation arrows

[Stephen Berman]

GNU Emacs 23.0.50.1 (i686-pc-linux-gnu, GTK+ Version 2.12.0) of
2007-12-09 on escher

1. emacs -Q

2. Type a line of text that extends beyond (window-width) with auto-fill
mode is disabled so that continuation arrows are displayed in the
fringes.

3. Put the cursor on the second column after the left continuation arrow
and evaluate this sexp: (put-text-property (1- (point)) (point) 'display
" \n").

4. Now the rest of the text, from point to the end, appears to have
moved down by one line, i.e., the continuation arrows remain but after
the left continuation arrow it looks like there is an empty line before
the rest of the text.

Compare this with the following step instead of 3:

3'. Put the cursor on the first column after the left continuation arrow
and evaluate this sexp: (put-text-property (1- (point)) (point) 'display
" \n").

5. Now the rest of the text, from point to the end, appears in the same
position as before step 3' but the continuation arrows have vanished,
i.e., it looks like there are two lines of text, not one continued line.

Is the difference between 4 and 5, resulting from the different
positions of the display property, expected?  If so, is it conceivable
to change the display code so that doing step 3 (not step 3') would
result in the appearance in 5 instead of that in 4?

Steve Berman