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RE: Balanced lines

From: Glenn A. Adams <glenn@xfsi.com>
Date: Thu, 14 Aug 2003 10:55:22 -0400
Message-ID: <7249D02C4D2DFD4D80F2E040E8CAF37C03BD16@longxuyen.xfsi.com>
To: <Johnb@screen.subtitling.com>
Cc: <public-tt@w3.org>
The list of visual style properties enumerated in TT-AF-1-0-REQ requirement R306 is not intended to be exhaustive, at least in the sense that other properties would be precluded. So I'm not sure how you derive "effectively preclude" in the following.
I expect that during the process of defining the TT-AF specification, we will discover derived requirements that cause us to add additional features not indicated in the requirements document. Beyond that, we will most certainly provide extensibility mechanisms that permit use of non-standardized style properties.
I can see us adding a line-breaking-strategy property if we need to do so. I would note that XSL, whose property set we have given preference to, uses an implied mechanism for determining the line breaking algorithm, e.g., in Section 7.29.24: "In general, linguistic services (line-justification strategy, line-breaking and hyphenation) may depend on a combination of the "language", "script", and "country" properties.".
I find Al Gilman's follow-on email on the subject of time as the scarcest resource to be quite interesting and bears further consideration.


	From: Johnb@screen.subtitling.com [mailto:Johnb@screen.subtitling.com] 
	Sent: Thursday, August 14, 2003 4:50 AM
	To: Glenn A. Adams
	Cc: public-tt@w3.org
	[GA>]  and I would not expect any AF to DF (distribution format) transcoder to implement such a feature simply on the basis of cost to benefit ratio.
	Yet the present set of CSS properties [JB> ] effectively  preclude the use of 'river control' even if an AF to DF transcoder implements it as a matter of customer requirement. I notice that the line-break property in CSS3 Candidate Release is commented as follows:
	"This property selects the set of line breaking rules to be used for text. The values described below are especially useful to CJK authors, but the property itself is open to other, not yet specified settings for non-CJK authors as well. (This is an area for future expansion.)"
	bold is my emphasis.
	I wonder if there isn't a window of opportunity to suggest that a 'auto' value be included for this property - such that the UA can make it's own choice of line-break strategy? The 'normal' value has no specified behaviour for non CJK text - but I personally feel that a UA which implemented river-control for non CJK text for line-break="normal" would be contrary to most users expectations.
	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 Thursday, 14 August 2003 10:55:26 UTC

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