bug#10304: 24.0.92: display bug

[Eli Zaretskii]

> From: Lars Magne Ingebrigtsen <larsi@gnus.org>
> Cc: 10304@debbugs.gnu.org
> Date: Sat, 05 Jan 2013 12:38:07 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > According to this, the window had 70 lines, of which 43 displayed
> > text; that text was comprised of empty lines, except for the 2nd line
> > which displayed the text "Link "; and point was on that 2nd line.
> > Does that sound reasonable?
> 
> Yes, the only text in the buffer was the Link thing, and that was
> probably on the second line.  However, the window was (let's see) 43
> lines tall.

OK, that's my misreading of the dump: the "(0)" part means the line is
disabled in the glyph matrix, i.e. not displayed.

> The image was (faultily) displayed right below the Link.

So the bug seems to be that we don't clear those empty lines which
occupied the screen estate of the image.  Hmm...

> > Btw, next time please use (dump-glyph-matrix 2), to get more
> > information about the glyphs on display.
> 
> Will do.

Also, I just installed a few changes on the emacs-24 branch that make
the matrix dump better, please resync if you can.