Create a font from its family, style, point size and weight.
Fonts are reusable: constructing a font with the same
family/style/points/weight returns the existing instance from
@fonts (see font<-lookup).
Resolution against Pango is lazy â the underlying Pango font is only
built when xpce first needs metrics or wants to render text.
The new font is auto-bound to the global reference
@<family>_<style>_<points> for
convenience.
New code is normally clearer when it picks fonts by alias name (the
type-checker calls font<-convert)
than by spelling out the constructor.
