Re: Debugging printing to stderr prior glyph row values ....

[Eli Zaretskii <eliz@gnu.org>]

> Date:  Thu, 23 May 2019 10:23:03 -0700
> From:  Keith David Bershatsky <esq@lawlist.com>
> Cc:  emacs-devel@gnu.org
> 
> I will add a test for the `used` row member to ensure that it is positive.  The crashing reported in the initial post only happens somtimes, so I'll need to do some further testing.

Did you look at the problematic row with the GDB command "pgrowx"?
It's important to understand what kind of glyphs are in that row and
how many of them do you have there.

> I am looking to programmatically distinguish between the following three types of consecutive rows:  (1) the penultimate row _not_ ending in ZV that immediately precedes a row with _only_ ZV; (2) the last row that contains _only_ ZV; and, (3) rows that follow a row with _only_ ZV.

There's a 4th case: when a row ends at ZV, but does have glyphs.  This
happens, for example, when visiting a file that doesn't end in a
newline.

> A better method of determining row_at_zv_p (without consulting ROW - 1) would be appreciated, if such a test exists.

I don't understand why you don't just look at the ends_at_zv_p flag,
that's what it's for.