THPDFHeadlessAppearanceFailure

THPDFHeadlessAppearanceFailure = (haInvalidOptions, haInvalidFont,
  haEmbeddingDenied, haInvalidUnicode, haMissingGlyph, haLimitExceeded,
  haUnsupportedText);

Classifies invalid dimensions or budgets, malformed font metadata or Unicode cmap, denied outline embedding, malformed Unicode or control characters, absent glyphs, exhausted byte or glyph limits and text outside the direct horizontal layout profile

EHPDFHeadlessAppearanceError.Failure exposes this code, whilst its message supplies the specific refusal