Use of font selection strategy in line height algorithm.

[nigelmegitt]

Currently the tts:fontSelectionStrategy attribute is not listed in the algorithm for normal in tts:lineHeight but since that algorithm (step 4) is based on actual fonts chosen, it should be.

Algorithm should take include tts:fontSelectionStrategy

The algorithm for computing the used value at https://www.w3.org/TR/ttml2/#style-attribute-lineHeight lists in step 4:

the computed values of the tts:fontStyle, tts:fontWeight, and tts:fontVariant style properties of P.

This should additionally include tts:fontSelectionStrategy.

Consistency of referencing back to the algorithm.

tts:fontFamily and tts:fontWeight and
tts:fontVariant all include text like:

In addition to applying to span, the computed value of this property on a p element is used to resolve the normal value of the style property associated with the tts:lineHeight attribute as specified in 10.2.27 tts:lineHeight.

This should be added to tts:fontSelectionStrategy

[skynavga]

Marking this as editorial since the semantics of font selection strategy already require its (explicit) use (if the property is supported) in the determination of the selected font from a list of fonts specified in tts:fontFamily even though it is not at present explicitly listed in step (4) of the line height algorithm. If someone feels strongly the other way (that this is a substantive change), then I will consider changing to substantive.

[skynavga]

Actually, addressing the second part of this issue will require a substantive change, so I'm changing this back to substantive.