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RE: 'knife and fork' model

From: Glenn A. Adams <glenn@xfsi.com>
Date: Wed, 13 Aug 2003 10:20:47 -0400
Message-ID: <7249D02C4D2DFD4D80F2E040E8CAF37C0199F8@longxuyen.xfsi.com>
To: <Johnb@screen.subtitling.com>
Cc: <public-tt@w3.org>

	-----Original Message-----
	From: Johnb@screen.subtitling.com [mailto:Johnb@screen.subtitling.com] 
	Sent: Wednesday, August 13, 2003 10:21 AM
	To: Glenn A. Adams
	Cc: public-tt@w3.org
	Subject: RE: 'knife and fork' model
	comments below in green

		-----Original Message-----
		From: Glenn A. Adams [mailto:glenn@xfsi.com]
		Sent: 12 August 2003 16:48
		To: Johnb@screen.subtitling.com
		Cc: public-tt@w3.org
		Subject: RE: 'knife and fork' model
		I guess what you are describing is essentially:

		1.	authoring time line layout (hard layout) 
		2.	presentation time line layout (soft layout)

		We have already included the style property wrap-option, defined at [1] to support authoring time determination of which of these models apply. 
		[JB> ] CSS wrap-option property does not have a value that produces balanced lines. Justification properties do not appear to help either. 

			GA: What do you mean by "balanced lines"? If you mean left and right block justified, then the text-align property would be used to specify justify. Whether to perform soft layout, i.e., UA line wrapping, is independent of the alignment of line areas in the containing block area.

		In order to express authoring time line separators, we have included force line break as a presentation flow vocabulary item and break-after and break-before as style properties that induce the same effect.
		[JB> ] Might I suggest also a requirement for prefix-before in order to support the inclusion of symbols such as # (for music) and - or >> for speaker change? Or can this be handled in another way? - can't be in content if supporting soft layout! 

			GA: This model is supported by the Generated Content mechanisms of CSS2, e.g., using the :before and :after pseudo-element selectors in combination with the content property. However, there are some possible problems with using such a facility for anything more than very simiple content generation, e.g., one can't specify marked up content in the style sheet in order to correctly support generic internationalized text.
			Thus far, we have not entertained a requirement to support stylesheet based generated content. Would you propose we do so?

		What we haven't yet defined in the requirements document is an ability for the author to express timing or style semantics to be applied to line areas that are produced by the second of the above modes (soft layout). This is why I suggested the idea of a pseudo selector that allows expressing authorial intent about objects that are produced by an implied presentation process, i.e., line and glyph areas.
		[JB> ]  The pseudo selector may allow the imposition of style on soft layout - though I have questions - see other post. However, I don't see how it works for timing. Given soft timing of text into a given sized region - there is nothing that hints to the UA how to control the flow of text into that region. The display property gives boolean control (visible | hidden) but not a pop on , off, on mode. There is no property to control the mark space ratio between visible and hidden during the soft timed period. If you are intending to use the region as a snaked or line by line region you would set the overflow properties to scroll - but there is insufficient subtlety in the related properties to achieve the desired effect.

		[JB> ] I will try and enumerate all the possible combinations that might be wanted, as a sequence of diagrams of how the region would change over time. I know you asked for this originally - but I was hoping I might avoid it :-)

	John Birch 

	The views and opinions expressed are the author's own and do not necessarily 
	reflect the views and opinions of Screen Subtitling Systems Limited. 
Received on Wednesday, 13 August 2003 10:20:48 UTC

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