Re: Padding on tt:p and tt:span elements

On Tue, Jul 16, 2013 at 12:31 PM, Andreas Tai <tai@irt.de> wrote:

>  As a couple of TTML.next issues are discussed at the moment I want to
> bring up the padding issue again. This is filed as Issue 168.
>
> Currently it is hard to solve following requirement for background colour
> fill that is defined in the Youview TTML profile[1]:
>
> > Where text with tts:backgroundColor is applied at the span level, the
> filled area shall extend the width of a space character to the left of the
> first rendered character on each line and to the right of the last rendered
> character on each line.
>

One way to achieve this as a work around (in the near term) is to use NBSP,
EM SPACE, EN SPACE, THIN SPACE and so on, using tts:wrapOption as needed to
prevent line breaks.


>
> If in TTML.next padding could be applied to a span: to what a percentage
> value would relate to?  In XSL 1.1 and CSS 2.1 it relates to the width of
> the containing block [2]. So assumed this will be the same definition in
> TTML, a span would be the child of a p element and a padding value would be
> specified in percentage for that span than it would be the width of that p
> element?
>

Actually, the XSL-FO definition is based on the nearest ancestor reference
area, which is the block-container generated by tt:region. So a percentage
would be resolved according to the contain region size. When we do map to
CSS we will need to translate to non-percentage values in order to avoid
the distinct CSS definition.


> This would be very similar to the current definition. In TTML the
> percentage value for padding is defined as relative to the width and height
> of the region. As the extent of a p is the same as the extent of the region
> where it is contained the width of the containing block is effectively the
> with of the region.
>
> As the width of the region could vary this seems not a good solution for
> the requirement defined by the Youview spec.
>
> The only possible solution to establish a relation between the chosen font
> and the padding value seems to be the cell metric. To emulate the width of
> a space the padding value of the start edge for the first span in a line
> and the padding value for the end edge of the last span in line could be
> set to 1c (assumed that the font-size is 1c). Is there any more intuitive
> solution?
>

Use NBSP. Any any case, 1c doesn't mean 1 EM unless fontSize is defined as
1c.


>
> Best regards,
>
> Andreas
>
> [1]
> https://industry.youview.com/resources/YouView_Core_Technical_Specification_1.0.pdf,
> page 120, Section 4.4.4.4
> [2] http://www.w3.org/TR/xsl/#padding-before
>
>
>
>
> Am 24.05.2012 08:33, schrieb Andreas Tai:
>
> For the EBU subset of TTML we have to include a change of the padding
> attribute in the version 1.0 to meet requirements of our target group. As
> understood a change that adresses Issue 168 (
> http://www.w3.org/AudioVideo/TT/tracker/issues/168) will be adopted in
> TTML earliest in 2013. Nevertheless it would be good that the wording in
> the EBU-TT spec is aligned with an expected change in TTML 1.1.
>
> The application of padding to p and span will be specified in the EBU-TT
> spec as follows:
>
> "Padding (or inset) space on all sides of a block area generated by a tt:p
> element or an inline area generated by a tt:span element.
>
> The padding property shall not be inherited."
>
> It would be great to hear your opinion.
>
> Best regards,
>
> Andreas
>
>
> Am 08.05.2012 22:27, schrieb Sean Hayes:
>
> Hmm. I was sure I'd created an issue for this, but apparently not.
>
>  ISSUE-168 <https://www.w3.org/AudioVideo/TT/tracker/issues/168> added to
> database
>
>
>   ------------------------------
> *From:* Andreas Tai [tai@irt.de]
> *Sent:* 08 May 2012 6:26 PM
> *To:* Sean Hayes
> *Cc:* Glenn Adams; John Birch; public-tt@w3.org
> *Subject:* Re: Padding on tt:p and tt:span elements
>
>  Will there be an entry in the tracker for this?
>
> In addition I attach an html-example that shows the wished behaviour and a
> CSS definition that is similiar to the needed TTML styles.
>
> Best regards,
>
> Andreas
>
> Am 25.04.2012 21:56, schrieb Sean Hayes:
>
>  While what you say is true it is very inconvenient from an authoring
> perspective, and if the user can set the font (which is a requirement of
> the FCC rules), then you need the region to be able to adapt. Better to use
> the <p> background which does adapt naturally. You can artificially
> introduce the padding using spans with preserved space, however this is a
> pretty ugly hack. I think it makes sense to allow padding on these elements.
>
>
>
> *From:* Glenn Adams [mailto:glenn@skynav.com <glenn@skynav.com>]
> *Sent:* 25 April 2012 17:04
> *To:* John Birch
> *Cc:* tai@irt.de; public-tt@w3.org
> *Subject:* Re: Padding on tt:p and tt:span elements
>
>
>
>
>
> On Wed, Apr 25, 2012 at 9:33 AM, John Birch <John.Birch@screensystems.tv>
> wrote:
>
> You hit the nail on the head. Font size at authoring time is only true if
> font exists at browser... Otherwise substitution means all bets are off.
>
>
>
> not quite; you can always overestimate the size which permits containment
> without overflow
>
>
>
>  Best regards,
> John
>
>
>
> *From*: Glenn Adams [mailto:glenn@skynav.com]
> *Sent*: Wednesday, April 25, 2012 04:00 PM
> *To*: John Birch
> *Cc*: Andreas Tai <tai@irt.de>; public-tt <public-tt@w3.org>
> *Subject*: Re: Padding on tt:p and tt:span elements
>
>
>
>
> On Wed, Apr 25, 2012 at 5:22 AM, John Birch <John.Birch@screensystems.tv>
> wrote:
>
> In TTML as I understand it(as a result of derivation from xsl:fo?), there
> is no possible mechanism that can *set* the region size as a result of a
> calculation of the *rendered* text size on the display. In contrast to
> broadcast practises, in TTML the text is fitted inside a predefined region
> (or overflows / clips), rather than the region (growing) fitting the text.
>
>
>
> it can, if the size can be determined at authoring time; but that will
> depend on font usage; so you are correct that if the font size is unknown,
> then you may have to overestimate the size, e.g., by using em or c length
> units
>
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> --
> ------------------------------------------------
> Andreas Tai
> Production Systems Television IRT - Institut fuer Rundfunktechnik GmbH
> R&D Institute of ARD, ZDF, DRadio, ORF and SRG/SSR
> Floriansmuehlstrasse 60, D-80939 Munich, Germany
>
> Phone: +49 89 32399-389 | Fax: +49 89 32399-200
> http: www.irt.de | Email: tai@irt.de
> ------------------------------------------------
>
> registration court&  managing director:
> Munich Commercial, RegNo. B 5191
> Dr. Klaus Illgner-Fehns
> ------------------------------------------------
>
>
>
> --
> ------------------------------------------------
> Andreas Tai
> Production Systems Television IRT - Institut fuer Rundfunktechnik GmbH
> R&D Institute of ARD, ZDF, DRadio, ORF and SRG/SSR
> Floriansmuehlstrasse 60, D-80939 Munich, Germany
>
> Phone: +49 89 32399-389 | Fax: +49 89 32399-200
> http: www.irt.de | Email: tai@irt.de
> ------------------------------------------------
>
> registration court&  managing director:
> Munich Commercial, RegNo. B 5191
> Dr. Klaus Illgner-Fehns
> ------------------------------------------------
>
>
>
> --
> ------------------------------------------------
> Andreas Tai
> Production Systems Television IRT - Institut fuer Rundfunktechnik GmbH
> R&D Institute of ARD, ZDF, DRadio, ORF and SRG/SSR
> Floriansmuehlstrasse 60, D-80939 Munich, Germany
>
> Phone: +49 89 32399-389 | Fax: +49 89 32399-200
> http: www.irt.de | Email: tai@irt.de
> ------------------------------------------------
>
> registration court&  managing director:
> Munich Commercial, RegNo. B 5191
> Dr. Klaus Illgner-Fehns
> ------------------------------------------------
>
>