The capitalization axis of CanvasRenderingContext2D.fontVariant.
This is the CSS longhand and fontVariant the shorthand, so writing here
replaces only the caps token and leaves the other axes -- figures,
ligatures, alternates -- as they were. An unrecognised value is ignored,
as the standard requires of an attribute setter.
How text is selected and positioned: the font, its variable axes, alignment and wrapping.