pub trait FontExt: 'static {
fn describe(&self) -> Option<FontDescription>;
fn describe_with_absolute_size(&self) -> Option<FontDescription>;
fn coverage(&self, language: &Language) -> Option<Coverage>;
fn face(&self) -> Option<FontFace>;
fn font_map(&self) -> Option<FontMap>;
fn glyph_extents(&self, glyph: Glyph) -> (Rectangle, Rectangle);
fn metrics(&self, language: Option<&Language>) -> Option<FontMetrics>;
fn has_char(&self, wc: char) -> bool;
}