THPDFHeadlessRichTextLineHeightKind

THPDFHeadlessRichTextLineHeightKind =
  (hrlhLegacy, hrlhNormal, hrlhNumber, hrlhPoints, hrlhPercent, hrlhEm);

Kind	LineHeight interpretation
hrlhLegacy	Default compatibility layout until an explicit paragraph line-height model is needed
hrlhNormal	The greater of actual face ascent minus descent and FontSize times appearance LineSpacing
hrlhNumber	A non-negative factor multiplied by this run's FontSize
hrlhPoints	A non-negative point length
hrlhPercent	A percentage of this run's FontSize, serialised as a computed point length
hrlhEm	An em multiple of this run's FontSize, serialised as a computed point length

LineHeight must be finite and between zero and 1000000; the computed point height also observes the bounded appearance geometry limit

The XHTML decoder computes percentages and em values before inheritance; a unitless factor remains hrlhNumber