ISSUE-163: Clarify use of cell units in certain properties

Cell units

Clarify use of cell units in certain properties

State:
PENDING REVIEW
Product:
TTML 1.0
Raised by:
Sean Hayes
Opened on:
2012-03-12
Description:
Some properties that take a length as a value, e.g. border, textOutline, and padding (one value supplied) do not forbid a cell unit. It is not clear to me what pixel value one would assign to these lengths if the cell in not a square. We should either prohibit cell in these contexts, or define which length is intended.

Let’s say the root is tts:extent="852px 480px" ttp:cellResolution="30 20" Then in pixels the horizontal cell size is : 852/30 = 28.4 pixels, in the vertical 480/20 = 24 pixels

If you state tts:textOutline=”black 0.25c” the outline thickness could be either 7.1 or 6 pixels. For border if I state tts:border="0.1c” is the border 2.84 pixels uniformly; 2.4 pixels uniformly; or 2.84 left and right, and 2.4 top and bottom?
Related Actions Items:
Related emails:
  1. TTWG Agenda March 7, 2013 (from momartin@microsoft.com on 2013-03-07)
  2. Re: TTML Agenda for 28/2/13 (from glenn@skynav.com on 2013-02-28)
  3. RE: TTML Agenda for 28/2/13 (from mdolan@newtbt.com on 2013-02-28)
  4. TTML Agenda for 28/2/13 (from momartin@microsoft.com on 2013-02-28)
  5. TTWG Meeting Minutes Feb 28 (from momartin@microsoft.com on 2013-02-28)
  6. TTWG Meeting Minutes Feb 7, 2013 (from momartin@microsoft.com on 2013-02-14)
  7. TTWG Meeting Minutes Feb 7, 2013 (from momartin@microsoft.com on 2013-02-07)
  8. TTML Agenda for 07/02/13 (from Sean.Hayes@microsoft.com on 2013-02-07)
  9. Minutes TTWG Aug 16, 2012 (from momartin@microsoft.com on 2012-08-17)
  10. RE: TTML Agenda for 15/8/12 (from momartin@microsoft.com on 2012-08-16)
  11. Fwd: TTML Agenda for 15/8/12 (from geoff_freed@wgbh.org on 2012-08-16)
  12. Re: TTML Agenda for 15/8/12 (from geoff_freed@wgbh.org on 2012-08-16)
  13. TTML Agenda for 15/8/12 (from Sean.Hayes@microsoft.com on 2012-08-16)
  14. Re: {minutes} TTML Agenda for 15/3/12 (from geoff_freed@wgbh.org on 2012-03-15)
  15. {minutes} TTML Agenda for 15/3/12 (from glenn@skynav.com on 2012-03-15)
  16. RE: Cell Grid Safe Area [was Re: ISSUE-163 (Cell units): Clarify use of cell units in certain properties [DFXP 1.0]] (from Sean.Hayes@microsoft.com on 2012-03-13)
  17. Cell Grid Safe Area [was Re: ISSUE-163 (Cell units): Clarify use of cell units in certain properties [DFXP 1.0]] (from glenn@skynav.com on 2012-03-13)
  18. RE: ISSUE-163 (Cell units): Clarify use of cell units in certain properties [DFXP 1.0] (from John.Birch@screensystems.tv on 2012-03-13)
  19. Re: ISSUE-163 (Cell units): Clarify use of cell units in certain properties [DFXP 1.0] (from glenn@skynav.com on 2012-03-13)
  20. RE: ISSUE-163 (Cell units): Clarify use of cell units in certain properties [DFXP 1.0] (from John.Birch@screensystems.tv on 2012-03-13)
  21. ISSUE-163 (Cell units): Clarify use of cell units in certain properties [DFXP 1.0] (from sysbot+tracker@w3.org on 2012-03-12)

Related notes:

See Sean Hayes suggested text in TTWG minutes Feb 21: http://www.w3.org/2013/02/21-tt-minutes.html.
Style properties that operate in both the horizontal and vertical direction, such as border, outline thickness etc. may be specified using a single value which is based on the cell unit. When the cell is non-square, the computed value is calculated based on the height of the cell. For example: Given a root extent of 852px 480px and a ttp:cellResolution="30 20"; then in pixels the horizontal cell size is : 852/30 = 28.4 pixels, in the vertical 480/20 = 24 pixels. The relative unit to be used is 28.4px.

Monica Martin, 21 Feb 2013, 16:45:22

added clarifying note at end of 6.2.1 ttp:cellResolution (in 1.0SE)

Glenn Adams, 2 May 2013, 04:32:38

Changelog:

Created issue 'Clarify use of cell units in certain properties' nickname Cell units owned by Sean Hayes on product DFXP 1.0, description 'Some properties that take a length as a value, e.g. border, textOutline, and padding (one value supplied) do not forbid a cell unit. It is not clear to me what pixel value one would assign to these lengths if the cell in not a square. We should either prohibit cell in these contexts, or define which length is intended.
' non-public

Sean Hayes, 12 Mar 2012, 13:45:38

Description changed to 'Some properties that take a length as a value, e.g. border, textOutline, and padding (one value supplied) do not forbid a cell unit. It is not clear to me what pixel value one would assign to these lengths if the cell in not a square. We should either prohibit cell in these contexts, or define which length is intended.

Let’s say the root is tts:extent="852px 480px" ttp:cellResolution="30 20" Then in pixels the horizontal cell size is : 852/30 = 28.4 pixels, in the vertical 480/20 = 24 pixels

If you state tts:textOutline=”black 0.25c” the outline thickness could be either 7.1 or 6 pixels. For border if I state tts:extent="0.1c” is the border 2.84 pixels uniformly; 2.4 pixels uniformly; or 2.84 left and right, and 2.4 top and bottom?
'

Sean Hayes, 12 Mar 2012, 14:42:02

Description changed to 'Some properties that take a length as a value, e.g. border, textOutline, and padding (one value supplied) do not forbid a cell unit. It is not clear to me what pixel value one would assign to these lengths if the cell in not a square. We should either prohibit cell in these contexts, or define which length is intended.

Let’s say the root is tts:extent="852px 480px" ttp:cellResolution="30 20" Then in pixels the horizontal cell size is : 852/30 = 28.4 pixels, in the vertical 480/20 = 24 pixels

If you state tts:textOutline=”black 0.25c” the outline thickness could be either 7.1 or 6 pixels. For border if I state tts:border="0.1c” is the border 2.84 pixels uniformly; 2.4 pixels uniformly; or 2.84 left and right, and 2.4 top and bottom?
'

Sean Hayes, 12 Mar 2012, 14:43:34

Status changed to 'pending review'

Glenn Adams, 2 May 2013, 04:32:38

Sean Hayes <sean.hayes@microsoft.com>, Chair, Philippe Le Hégaret <plh@w3.org>, Staff Contact
Tracker: documentation, (configuration for this group), originally developed by Dean Jackson, is developed and maintained by the Systems Team <w3t-sys@w3.org>.
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