Re: How to determine if a font is a fallback font?

[Urs Liska]

Am 28.04.2015 um 18:14 schrieb Urs Liska:
> Am 28.04.2015 um 17:53 schrieb Urs Liska:
> > I think I have found something.
> >
> > After some experimenting with a copy of font-config-get-font-file and 
> > trying different approaches I could guess from the documentations 
> > available I found that replacing an item in the FcPatternGetString 
> > call this function returns the font name and not the Postscript name 
> > or the font file.
> >
> > The following preliminary function (if added to 
> > font-config-scheme.cc) returns either the Font Name (if the font 
> > exists) or "Emmentaler-11" (on my system) if it doesn't exist. I 
> > assume it would return other names on other systems:
> >
> > LY_DEFINE (ly_font_config_font_exists, "ly:font-config-font-exists", 
> > 1, 0, 0,
> >
> > ...
> >
> > Best
> > Urs
>
> Wrapping this Scheme function around that:
>
> fontExists =
> #(define-scheme-function (parser location font-name)(string?)
>    (string=? font-name (ly:font-config-font-exists font-name)))
>
> shows that my idea is right: The C++ function returns the family name 
> of either the given font or the (system-dependent) fallback font. Now 
> all there would be to it is moving the comparison of the latter Scheme 
> function to the C++ function .
>
> Urs


Last one for this working session: The following function 
ly:font-config-font-exists will return true or false depending on 
whether the given font is available. The only drawback (yet) is that now 
the comparison is case sensitive. But *that* should be easy now?

Urs

LY_DEFINE (ly_font_config_font_exists, "ly:font-config-font-exists", 1, 
0, 0,
           (SCM name),
           "Determine if font @var{name} exists.")
{
  LY_ASSERT_TYPE (scm_is_string, name, 1);

  string in_name = ly_scm2string (name).c_str ();

  FcPattern *pat = FcPatternCreate ();
  FcValue val;

  val.type = FcTypeString;
  val.u.s = (const FcChar8 *)ly_scm2string (name).c_str (); // 
FC_SLANT_ITALIC;
  FcPatternAdd (pat, FC_FAMILY, val, FcFalse);

  FcResult result;
  SCM scm_result = SCM_BOOL_F;

  FcConfigSubstitute (NULL, pat, FcMatchFont);
  FcDefaultSubstitute (pat);

  pat = FcFontMatch (NULL, pat, &result);
  FcChar8 *str = 0;
  if ((FcPatternGetString (pat, FC_FAMILY, 0, &str) == FcResultMatch) &&
      (in_name.compare((char const *)str) == 0))
      scm_result = SCM_BOOL_T;

  FcPatternDestroy (pat);
  return scm_result;
}