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Re: [SVG Tiny 1.2 CR Comment] spec text of rendering hints is confusing to implementors

From: Chris Lilley <chris@w3.org>
Date: Tue, 17 Oct 2006 22:12:35 +0200
Message-ID: <355227895.20061017221235@w3.org>
To: Jean-Claude Dufourd <jean-claude.dufourd@streamezzo.com>
Cc: www-svg <www-svg@w3.org>

On Tuesday, October 17, 2006, 3:23:34 PM, Jean-Claude wrote:

JCD> The spec text of shape-rendering, text-rendering, image-rendering and 
JCD> color-rendering uses repeatedly the word "shall" in the context of 
JCD> something called "hints".
JCD> This caused our developers to question my statement that although the 
JCD> parsing of these attributes is mandatory, the implementation of these 
JCD> attributes is optional.

Thats an interesting point. The parsing *and implementation* of these attributes is mandatory, hence the shall, but the effect of them on a given renderer depends on how parameterizable its rendering engine is and thus to what extent it can honour requests for geometric precision or speed.

JCD> Please clarify the specification. Suggested action is to replace all 
JCD> instances of "shall" by "should" or "may" in the hints semantics.

That wouldmean (in the case of should) That it should do the required actin unles it has reason not to. That's not really correct.

If, for esxample, a given implementation has a very precise but sow anti-aliasong implementation (like 16x geometric sampling) then clearly if told to prioroitize speed over other things it would swithc off antialiasing.

Another implementation that gets hardware aa for free from the hardware but has to implement non aa rendering in software would respond similarly to a request for'crisp edges' but in the opposite way if told to prioritize speed.

Bassically it comes down to the implementation and how it is done, what the trade-offs are.

 Chris Lilley                    mailto:chris@w3.org
 Interaction Domain Leader
 Co-Chair, W3C SVG Working Group
 W3C Graphics Activity Lead
 Co-Chair, W3C Hypertext CG
Received on Tuesday, 17 October 2006 20:13:07 UTC

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