CoreText does not synthesize font styles (italic and bold).
This means that if you pick a font that has neither a Bolded
or Italicized versions available, CoreText will not create a
dynamic font that is merely a slanted version of the font for
italic, or a boldened version from the original font. In
those cases, if you want to synthesize the font, you could
apply a Matrix transformation to slant the font (it will still
be wrong, but will look slanted). For bolding, you could
stroke the font twice, or manually extend the glyph path.