bug#11484: 23.4; Scrolling leaves traces of old text behind

[Kenichi Handa]

In article <jwva9ve9e93.fsf-monnier+emacs@gnu.org>, Stefan Monnier 
<monnier@iro.umontreal.ca> writes:

> > Now Emacs should be able to use those PCF fonts via XFT.

> It actually crashed with an assertion violation because a font `spec'
> was nil where a vector was expected.

It means font_spec_from_name failed, which means
font_parse_name failed.  But, I didn't get that crach.
Please find what font name is given to font_parse_name, and
why it fails with that name.

> I used the quick-fix below which
> appeared to work, but without knowing what it implies.  Can you take
> a look and help me figure out what the right fix should be?

I think the better way is to do something like this:

  if (NILP (spec))
    signal_error ("Invalid font name", ascii_font);

---
Kenichi Handa
handa@gnu.org