Should tts:direction apply only to <span>?

[palemieux]

TTML1 specifies that tts:direction follows the semantics of XSL Section 7.29.1, which states that:

The "writing-mode" property establishes both the block-progression-direction and the inline-progression-direction. The "direction" property only changes the inline-progression-direction and is used primarily for formatting objects that generate inline-areas that are not also reference areas. Use of the "direction" property for other formatting objects is deprecated in this specification.

So shouldn't tts:direction only apply to span (which generates inline-areas) and not to p (which generates block-areas)?

[skynavga]

On Mon, Jan 9, 2017 at 11:11 PM, Pierre-Anthony Lemieux < ***@***.***> wrote: TTML1 specifies that tts:direction follows the semantics of XSL Section 7.29.1, which states that: *The "writing-mode" property establishes both the block-progression-direction and the inline-progression-direction. The "direction" property only changes the inline-progression-direction and is used primarily for formatting objects that generate inline-areas that are not also reference areas. Use of the "direction" property for other formatting objects is deprecated in this specification.* So shouldn't tts:direction only apply to span (which generates inline-areas) and not to p (which generates block-areas)?

No. See w3c/ttml2#142.

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[andreastai]

As tts:direction is inheritable...does it make any difference if is applied to p? Each character/anonymous span descendant of a p would have the inherited value of tts:direction`.

[skynavga]

Semantically, they are different. When applied to p, it only sets the default paragraph direction (which is already set by the writing mode, but can be overridden by direction). When applied to span, it works in conjunction with tts:unicodeBidi to wrap the content of the span in a {RLE,LRE} or {RLO,LRO} and a {PDF}.

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On Tue, Jan 10, 2017 at 11:24 AM, Andreas Tai ***@***.***> wrote: As tts:direction is inheritable...does it make any difference if is applied to p? Each character/anonymous span descendant of a p would have the inherited value oftts:direction`. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#227 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAXCb6kYyKXiISgBV_S8XJ09wlq9eyGoks5rQ8zMgaJpZM4LfEEX> .

[skynavga]

Need clarification of meaning of 'ltr' and 'rtl' on tts:direction in the context of writing mode.

[nigelmegitt]

[Meeting 2017-01-12] Decided that tts:direction applies to p, but that it would be useful to open a new editorial issue to add a comment on how to compute direction in vertical writing modes (added as #228).

[dae-kim]

See http://unicode.org/reports/tr9/#Vertical_Text:

"In the case of vertical line orientation, the Bidirectional Algorithm is still used to determine the levels of the text. However, these levels are not used to reorder the text, because the characters are usually ordered uniformly from top to bottom. Instead, the levels are used to determine the rotation of the text."