bug#49695: 27.2; wrap-prefix text property doesn't work with display property

[Eli Zaretskii]

> Date: Thu, 22 Jul 2021 21:51:23 +0900
> From: Shingo Tanaka <shingo.fg8@gmail.com>
> 
> wrap-prefix text property doesn't work properly when a character with display
> property is in the beginning of a line.  Here is how to reproduce.
> 
> 1. Goto *scratch* buffer
> 2. Evaluate below preconditioning function.
> 
> (defun preconditioning ()
>   (interactive)
>   (goto-char (point-min))
>   (insert "This is a sample text.\n")
>   (forward-line -1)
>   (put-text-property (line-beginning-position) (line-end-position)
>                      'wrap-prefix "    ")
>   (search-forward "This is a ")
>   (put-text-property (point) (1+ (point)) 'display "X")
>   (goto-char (point-min)))
> 
> 3. Execute it with M-x preconditioning
> 4. Confirm the text "This is a sample text." is inserted in the beginning of
>    the buffer and your cursor is as well.  Note that this text has wrap-prefix
>    property and "X" is the character which has display property.
> 5. Start typing spaces (or any character) and observe how the text is wrapped.
> 6. You will see wrap-prefix works correctly until wrapped point gets "X" like:
> 
>                                                               This is a Xample
>     text.
> 
> 7. However, you will see it doesn't work when "X" gets in the beginning of the
>    line like:
> 
>                                                                      This is a
> Xample text.

Thanks, should be fixed now on the master branch.