hostGlyphOutline

The outline of text in the host face this canvas draws a font without embedded outlines in, chosen from fontSpec as drawGlyphs chooses it. The outline is in glyph space: 1000 units per em, y up, and the pen at the origin on the baseline. A document handler strokes and clips such text with it, since a missing font program does not excuse the stroke (ISO 32000-1, 9.3.6).

The default is null: this canvas has no outlines for its host faces, and a stroked run then paints filled in the stroke colour.