ISSUE-106: XSL linebreaking not specified

Linebreaking

XSL linebreaking not specified

State:
CLOSED
Product:
TTML 1.0
Raised by:
Sean Hayes
Opened on:
2009-05-19
Description:
XSL:FO Section 4.7.2 is somewhat vague as to what constitutes a legal line breaking algorithm.

"The partitioning occurs at legal line-breaks. Specifically, if A is the last area of Si and B is the first area of Si+1, then the rules of the language, script and hyphenation constraints (7.10 Common Hyphenation Properties, 7.16.1 hyphenation-keep, and 7.16.2 hyphenation-ladder-count) in effect must permit a line-break between A and B, within the context of all areas in Si and Si+1"

As we refer to this via Section 9.4 this means timed text is also similarly vague. While we would not want to constrain implementations to any specific line breaking algorithm (this would likely be impossible anyway), we should clarify this situation by defining that any such an algorithm respect Unicode line breaking opportunities, and refer to Unicode for those opportunities (e.g. UAX #14 : http://www.unicode.org/unicode/reports/tr14/tr14-17.html)

Note however that Unicode line breaking opportunities are not compatible with the so called 'snake mode' for multiline dynamic flow, and so to support that mode we would need to provide authorial override.
Related Actions Items:
No related actions
Related emails:
  1. Agenda for meeting 22-05-09 (from Sean.Hayes@microsoft.com on 2009-05-22)
  2. ISSUE-106 (Linebreaking): XSL linebreaking not specified [DFXP 1.0] (from sysbot+tracker@w3.org on 2009-05-19)

Related notes:

resolved in TTAF1-DFXP WD Editor's Copy Update - 20090529

Glenn Adams, 29 May 2009, 04:36:02

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David Singer <singer@apple.com>, Nigel Megitt <nigel.megitt@bbc.co.uk>, Chairs, Thierry Michel <tmichel@w3.org>, Philippe Le H├ęgaret <plh@w3.org>, Staff Contacts
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