Re: truncate-lines as newline property

[Eli Zaretskii <eliz@gnu.org>]

> From: Evgeny Zajcev <lg.zevlg@gmail.com>
> Date: Sun, 10 Mar 2024 21:53:19 +0300
> 
> (setq truncate-lines nil)
> (insert "<very long line>"
>           (propertize "\n" 'truncate-lines t))   ; this line will be truncated
> (insert "<another very long line>" "\n")    ; this line will be wrapped

Btw, this specification would mean that redisplay needs to go all the
way to the newline to know what to do when a screen line exceeds the
window width, which could happen long before the newline is rendered.
This is completely against the current design of the display engine,
which tries very hard not to examine any characters except those it
needs to display.  So a better design would be to have the special
text property on the first character of a line, the one that _follows_
the newline, so as to make sure the display code knows whether or not
to truncate as soon as it needs to make that decision.