Gets the glyph id that a character code selects in the font's program; 0, the missing glyph (.notdef), when none.
public int GetGlyphId(byte code)
The character code.
f_i, has no single glyph id and gives 0 while the display list draws its
components); 0 for every code when the font has neither.
ISO 32000-2 §9.6.5.2: the code's glyph name from the font's encoding (GetGlyphName(Byte), whose base is
the program's built-in encoding for an embedded font) is looked up among the program's glyph names; a name the program does not
have selects .notdef.