ISSUE-178: initial values and style set calculations are unclear, especially for transformable attributes

Inital values

initial values and style set calculations are unclear, especially for transformable attributes

State:
CLOSED
Product:
TTML2
Raised by:
Mike Dolan
Opened on:
2012-08-23
Description:
The style set calculation of section 8.4 is unclear in relation to initial values, and especially for attributes that are defined to be transforms of the parent value.

For example, in a document that otherwise does not define tts:fontSize, the occurrence of tts:fontSize=”200%” (as I understand the text, and at least for the % metric) is a transformation of the attribute's initial value (1c) resulting in effective fontSize of 2c.

And, it is unclear that it is at all possible to set a different initial value (e.g. on <tt>).

Also, these transformable attribute definitions do not clearly distinguish that the behavior is apparently metric-dependent. For example, the fontSize text says: "...font size is interpreted as a scaling transform to the font's design EM square". Although % works as I describe above, px, c and em really cannot (or if they do, how?).

In addition to clarifying the definitions of these attributes, to help illustrate the effect of initial values it would be useful to explicitly set various attributes in some example document and define the resulting attribute value, perhaps in the example intermediate synchronic documents of 9.3.4, which might include an explicit setting of all initial values.
Related Actions Items:
No related actions
Related emails:
  1. TTML Agenda for 03/10/13 (from Sean.Hayes@microsoft.com on 2013-10-03)
  2. Re: TTML Minutes for 25/09/13 (from tmichel@w3.org on 2013-09-27)
  3. RE: TTML Minutes for 25/09/13 (from silviapfeiffer1@gmail.com on 2013-09-27)
  4. RE: TTML Minutes for 25/09/13 (from nigel.megitt@bbc.co.uk on 2013-09-26)
  5. TTML Agenda for 25/09/13 (from Sean.Hayes@microsoft.com on 2013-09-25)
  6. TTML Agenda for 19/09/13 (from Sean.Hayes@microsoft.com on 2013-09-19)
  7. No Meeting today 12-09-13 (from Sean.Hayes@microsoft.com on 2013-09-12)
  8. Minutes for 05/09/13 (from nigel.megitt@bbc.co.uk on 2013-09-05)
  9. Agenda for 05/09/13 (from glenn@skynav.com on 2013-09-04)
  10. RE: TTML Agenda for 29/08/13 (from mdolan@newtbt.com on 2013-08-28)
  11. TTML Agenda for 29/08/13 (from glenn@skynav.com on 2013-08-28)
  12. TTWG Meeting Minutes Feb 7, 2013 (from momartin@microsoft.com on 2013-02-14)
  13. TTWG Meeting Minutes Feb 7, 2013 (from momartin@microsoft.com on 2013-02-07)
  14. TTML Agenda for 07/02/13 (from Sean.Hayes@microsoft.com on 2013-02-07)
  15. ISSUE-178: initial values and style set calculations are unclear, especially for transformable attributes [DFXP 1.0] (from sysbot+tracker@w3.org on 2012-08-23)

Related notes:

Did you possibly miss that each property that permits percentage values includes a "Percentages:" line it its definition? For example, fontSize says:

Percentages: relative to parent element's font size

Initial values cannot be modified. However, for properties that are marked as Inherited, like fontSize, one can place a fontSize property on any ancestor in order to have it apply to what is below (unless overridden). Section 8.4.2.1 clearly defines this behavior.

In order to understand the semantics of presentation properties, it is necessary to understand the XSL-FO definitions, which in most of the cases in TTML, are based on CSS definitions.

There used to be more linkage to this chain of references, but some over-eager sanitizing of XSL-FO references prior to publishing the 1.0 REC removed some of these, which makes it somewhat more difficult to follow the thread of definitional semantics.

If you want to propose some particular examples be added, I'm open to adding them. But absent a more specific proposal, I'm inclined to close this issue, but will simply change to POSTPONED.

Glenn Adams, 2 May 2013, 03:31:44

Reopening this for v.next

Sean Hayes, 17 Jun 2013, 16:00:08

Suggest closing this due to lack of a specific problem statement and due to recent ML explanations and firming up of specification language. If specific problem with existing text can be identified, then suggest opening a new issue with a focused statement of problem.

Glenn Adams, 25 Aug 2013, 01:11:41

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