Re: 23.0.50; display property and continuation arrows

[Stephen Berman <Stephen.Berman@gmx.net>]

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On Sun, 23 Dec 2007 16:12:01 -0500 Richard Stallman <rms@gnu.org> wrote:

>     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.
>
> When I try this, the continuation arrows do not disappear.

This surprises me.  I continue to see what I reported with current
sources, GNU Emacs 23.0.50.2 (i686-pc-linux-gnu, GTK+ Version 2.12.0) of
2008-01-03 on escher.  Perhaps the steps I gave to reproduce it were not
clear.  I've made screen shots showing what I see.  Here is the buffer
at step 3 of my OP, before evalling the display sexp:


[-- Attachment #2: continuation1 --]
[-- Type: image/png, Size: 3477 bytes --]

[-- Attachment #3: Type: text/plain, Size: 127 bytes --]


Note the cursor is over the "e" of the last occurrence of "testing".
And here is the buffer after evalling the display sexp:


[-- Attachment #4: continuation2 --]
[-- Type: image/png, Size: 4847 bytes --]

[-- Attachment #5: Type: text/plain, Size: 150 bytes --]


Note the continuation arrows and the appearance of an "empty" line.
Next, here is the buffer at step 3' of my OP, before evalling the
display sexp:


[-- Attachment #6: continuation3 --]
[-- Type: image/png, Size: 4756 bytes --]

[-- Attachment #7: Type: text/plain, Size: 164 bytes --]


Note the cursor is over the first "t" of the last occurrence of
"testing", immediately after the fringe.  And here is the buffer after
evalling the display sexp:


[-- Attachment #8: continuation4 --]
[-- Type: image/png, Size: 5981 bytes --]

[-- Attachment #9: Type: text/plain, Size: 712 bytes --]


Note the absence of the continuation arrows and of the "empty" line.
Are you unable to reproduce this?

> I am not sure that there is a bug here.

I don't know if it is a bug, because the results seen above may be
consistent with the code (I cannot tell).  My OP was a request for a
explanation of the difference seen in the second and fourth images, as
well as (if it is not a bug) a feature request: I would like *not* to
have continuation arrows and an "empty" line in the second image.  In
other words, I would like the appearance in the second image to be like
that in the last image (modulo the cursor position and the position of
the display property).  Is this possible?  If not, why not?

Steve Berman

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