Gets the glyph's origin in device space, the space the CTM maps to: text space's origin mapped by TextMatrix and then Ctm. For a page run, whose initial CTM is the identity, this is default user space (device-independent).
public PathPoint DeviceOrigin { get; }
ISO 32000-2 §9.4.4 and §8.3.2.3: (0, 0) × T_rm × CTM. For vertical writing the text matrix already places the glyph at
the current point minus its position vector (§9.7.4.3).