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Re: ISSUE-2129 (definition clarifications): Definition section is too long and needs clarifications (bbox, canvas, etc.) [Last Call: SVG 1.2 Tiny ]

From: Cyril Concolato <cyril.concolato@enst.fr>
Date: Thu, 16 Oct 2008 04:00:32 +0200
Message-ID: <48F6A040.4030300@enst.fr>
To: Doug Schepers <schepers@w3.org>
CC: anthony.grasso@cisra.canon.com.au, SVG Working Group WG <public-svg-wg@w3.org>

Hi,

Doug Schepers a écrit :
> Hi, Guys-
> 
> Nice work on moving the description of bbox to Coords, Anthony.  I have
> one nit, inlin below...
> 
> Anthony Grasso wrote (on 10/15/08 10:34 AM):
>>>>   This definition says:
>>>> "For curved shapes, the bounding box must enclose all portions of the
>>>> shape along the edge, not just end points, but must not include
>>>> control points for curves that are not within the shape itself."
>>>> The 'must not' requirement should be changed to a 'should' because
>>>> depending on the curve and depending on the precision of the
>>>> implementation (fixed point), it may be impossible to make a bounding
>>>> box that does not include the control point. 
>>> There was actually a mistake in my comment. The proposed edit is replace:
>>> "For curved shapes, the bounding box must enclose all portions of the
>>> shape along the edge, not just end points, but must not include
>>> control points for curves that are not within the shape itself."
>>> with
>>> "For curved shapes, the bounding box must enclose all portions of the
>>> shape along the edge, not just end points, but should not include
>>> control points for curves that are not within the shape itself."
>>>
>> As per your suggestion the "must not" was changed to "should not". I
>> added an additional sentence at the end to help clarify the paragraph:
>> "For example, control points of a curve that are at a further distance
>> than the curve edge, from the non-enclosing side of the curve edge, must
>> be excluded from the bounding box."
>>
>> Do you think this sentence helps with clarification of the paragraph?
> 
> The passage was indeed ambiguously worded, previously.  However, I
> thought the new wording was also a bit unclear... the "should not"
> wording could be read to indicate that implementations are permitted to
> include control points in the bbox if there is a good reason for them to
> do so, such as performance.  In fact, the exclusion of control point
> must remain a must, but the passage needed qualifying remarks.  I've
> changed it as below [1], and retained Anthony's f'rinstance:
> 
> [[
> For curved shapes, the bounding box must enclose all portions of the
> shape along the edge, not just end points. Note that control points for
> a curve which are not defined as lying along the line of the resulting
> curve (e.g., the second coordinate pair of a Cubic Bézier command) must
> not contribute to the dimensions of the bounding box (though those
> points may fall within the area of the bounding box, if they lie within
> the shape itself, or along or close to the curve). For example, control
> points of a curve that are at a further distance than the curve edge,
> from the non-enclosing side of the curve edge, must be excluded from the
> bounding box.
> ]]
> 
> [1] http://dev.w3.org/SVG/profiles/1.2T/publish/coords.html#BoundingBox
Reading the new version of the text, I'm fine with it. My only remaining concern is about the bounding box of 'defs' elements.

Cyril
> 
> Regards-
> -Doug


-- 
Cyril Concolato
Maître de Conférences/Associate Professor
Groupe Mutimedia/Multimedia Group
Département Traitement du Signal et Images
/Dept. Signal and Image Processing
Ecole Nationale Supérieure des Télécommunications
46 rue Barrault
75 013 Paris, France
http://tsi.enst.fr/~concolat 
Received on Thursday, 16 October 2008 02:01:14 GMT

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