THPDFHeadlessShapedGlyph
A glyph from HPDFHeadlessShaping contains GlyphID, Advance, XOffset and YOffset in the 1000-unit font coordinate system
UnicodeText retains its complete logical UTF-16 cluster, ligatures and combining sequences included; SourceOffset is the zero-based UTF-16 offset in the paragraph input after any requested wrapping
LineBreak marks a paragraph boundary rather than a drawable glyph; its geometry fields are zero