[HarfBuzz] Don't render control characters?

[Richard Wordingham]

On Thu, 6 Mar 2014 22:38:07 +0200
Konstantin Ritt <ritt.ks at gmail.com> wrote:

> Did you meet any single font with glyph for U+0008 (BS)? Honestly, I
> don't imagine what U+0008 glyph representation looks like :)

Back one space!  The underlining in Unix man pages is usually
implemented as overstrike via U+0008.  However, I'd forgotten that
OpenType advance widths can't be negative, so it can't be rendered
under font control.
 
> GC=Cc aren't really a characters but a control codes; some of them are
> historically very common in use, though.

> As for TAB, certain fonts don't have nbsp and/or tab, and most fonts
> don't have line separator, paragraph separator, and many other space
> characters. Since we've touched this topic...in my opinion, HarfBuzz
> should take care of (quite common) issue with missing glyphs for
> characters of property White_Space [1].
> For any of them, a fallback to U+0020 (SPACE) should be enough [2],
> though a more sophisticated mechanism would also take care of glyph
> advances [3], making U+000A..U+000D, U+0085, U+2028..U+2029 occupy no
> space, 

We weren't asked about fallback, but about simply not rendering them.
There are some nice-looking glyphs around for some of them, but perhaps
these belong to the characters U+24xx SYMBOL FOR....

Richard.