[BUG] Empty string as display property

[BUG] Empty string as display property

[Lars Hansen]

An empty string as display property has the advantage over the invisible
property that it can be made conditional. However, an empty string as
display property does not work. Try this:

(defun test ()
  (interactive)
  (select-window (display-buffer (get-buffer-create "*test*")))
  (erase-buffer)
  (insert "line 1\naaa"
          (propertize "bbb" 'display "")
          "ccc\nline 3"))

Maybe someone who knows the redisplay code would like to look at this bug.

Re: [BUG] Empty string as display property

[Luc Teirlinck]

Lars Hansen wrote:

   An empty string as display property has the advantage over the invisible
   property that it can be made conditional.

That is not what the display property is for.  If you want to make
text invisible, use the invisibility property.  The display property
is already abused enough as is.   There are things like
buffer-invisibility-spec for conditional invisibility.

Sincerely,

Luc.

Re: [BUG] Empty string as display property

[David Kastrup]

Luc Teirlinck <teirllm@dms.auburn.edu> writes:

> Lars Hansen wrote:
>
>    An empty string as display property has the advantage over the invisible
>    property that it can be made conditional.
>
> That is not what the display property is for.  If you want to make
> text invisible, use the invisibility property.  The display property
> is already abused enough as is.

Whatever.  But this is not an additional use of the display property,
but merely a special case of existing functionality.  As such, it
should not fail, regardless whether or not other means to achieve
similar effects exist.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum

Re: [BUG] Empty string as display property

[Lars Hansen]

>That is not what the display property is for.
>
You may argue so, but it is a bug anyway.
If empty strings are not allowed, it should be stated in the manual and
an error should be signaled. Now emacs just silently malfunctions.

Re: [BUG] Empty string as display property

[Kim F. Storm]

Lars Hansen <larsh@math.ku.dk> writes:

> An empty string as display property has the advantage over the invisible
> property that it can be made conditional. However, an empty string as
> display property does not work. Try this:
>
> (defun test ()
>   (interactive)
>   (select-window (display-buffer (get-buffer-create "*test*")))
>   (erase-buffer)
>   (insert "line 1\naaa"
>           (propertize "bbb" 'display "")
>           "ccc\nline 3"))
>
> Maybe someone who knows the redisplay code would like to look at this bug.

Thank you for the report.
I just installed a fix.

-- 
Kim F. Storm <storm@cua.dk> http://www.cua.dk