Re: Truncating scroll runs that copy to where we copied to

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 20 Nov 2011 16:13:59 +0900
> From: YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp>
> 
> I think that `scrolling_window' needs to truncate scroll runs that
> copy to where we copied to; otherwise, `assign_row (to, from)' assigns
> a previously disabled bogus row in the desired matrix when we have an
> overlap in the copy destination.  Such truncation can also avoid
> unnecessary copy in the actual graphics operation.
> 
> Could someone double-check the code below?

Could you please elaborate on the rationale?  Like, give a specific
use case with a few rows in the current and desired matrix, and show
why the current code does not DTRT?

I'm not saying you are wrong (I have my doubts about portions of that
function), just that we should at least look into a specific test
case, even if simplified one, to make sure we are fixing a real bug.

TIA