hostTextParts

glyphs as the parts a canvas without a layout of its own draws them in (#588): the pieces of spacedPieces, each cut into the drawOrderParts. A part of more than one glyph is shaped when a character of it changes shape or place with its neighbours, as Arabic letters join and an Indic vowel sign moves, so that the text engine sees them together. Advances move the pen by advanceScale each, and the spacing a glyph adds after it by adjustScale.