Subject: Re: bug#66167: 29.1; wrap-prefix text property with :align-to space keyword broken

From: Eli Zaretskii <[email-masked]>
Date: Sat, 23 Sep 2023 11:41:29 +0300

tags 66167 notabug wontfix
thanks

> Date: Sat, 23 Sep 2023 18:04:27 +1000
> From:  "Paul W. Rankin" via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <[email-masked]>
> 
> Description:
> 
> The wrap-prefix text property with :align-to space keyword has been 
> broken. (Regression).
> 
> To reproduce:
> 
> 1. emacs -Q
> 2. in *scratch*, ensure visual-line-mode is enabled
> 3. insert enough text to wrap lines
> 4. M-: (put-text-property (point-min) (point-max) 'wrap-prefix '(space 
> :align-to 10))
> 
> Expected results:
> 
> Wrapped text should align to column 10.
> 
> Actual result:
> 
> Wrapped text does not align. (No effect.)

This is not a bug.  The argument of :align-to specifies a column
number, and the column number does not get reset when the line wraps
or the window is hscrolled.  IOW, the column number is measured from
the beginning of the physical line, not from the beginning of the
screen line.

The previous code handled this incorrectly and inconsistently, and was
fixed in Emacs 29 (or was it 28?).