W3C home > Mailing lists > Public > www-svg@w3.org > June 2018

Re: Rectangle height and width

From: Steven Pemberton <steven.pemberton@cwi.nl>
Date: Sun, 10 Jun 2018 12:26:23 +0200
To: "David Dailey" <ddailey@zoominternet.net>, "Amelia Bellamy-Royds" <amelia.bellamy.royds@gmail.com>
Cc: www-svg <www-svg@w3.org>
Message-ID: <op.zkd1x9lysmjzpq@steven-xps>
On Sat, 09 Jun 2018 18:42:24 +0200, Amelia Bellamy-Royds  
<amelia.bellamy.royds@gmail.com> wrote:

> While I agree with you both that it would be a mathematical convenience  
> to >define negative width/height as an inversion of the rectangle, but I  
> think it >is far too late to change this now. The restriction on  
> negative numbers has >been there since the beginning and is supported  
> universally.
But it's a restriction, not a feature. You don't support a restriction,  
but adhere to it. By lifting the restriction you don't introduce any  
incompatibilities: old SVG files still render properly; however, by  
lifting it you do add new possibilities, and make life easier for SVG  
authors.

> Furthermore, with SVG 2 conversion of width and height to presentation  
> >attributes with matching CSS properties means that we need to match the  
> >syntax used for the CSS properties, which have the same restriction.
Matching the syntax doesn't require matching the semantics surely.

Best wishes,

Steven Pemberton

>
> In contrast, the startOffset restriction was changed much earlier on,  
> and >didn't affect any other specifications.
>
> ~Amelia
>
> On 9 June 2018 at 08:20, David Dailey <ddailey@zoominternet.net> wrote:
>> Fwiw, I kinda like the use case. It makes sense to me. (which sometimes  
>> >>proves to be a mark of doom for suggestions SVG, so apologies if my  
>> >>weighing in jinxes the idea.)
>>
>> I would concur that "there are probably other places in the spec where  
>> >>negative values are unnecessarily restricted."
>>
>> I remember back around 2008 strolling through Nuremberg with Eric  
>> Dahlstrom >>and complaining that this example:
>> http://srufaculty.sru.edu/david.dailey/svg/newstuff/textpath1.svg  
>> didn't >>work as I thought it should, because the value of startoffset  
>> on a textPath >>was confined to being non-negative. He replied that no  
>> one had quite >>imagined doing that particular thing, but that it made  
>> sense. Within a few >>years this example ran in all browsers (this was  
>> pre-IE-SVG, so one used >>the Adobe plugin).
>> Cheers
>> David
>>
>> -----Original Message-----
>> From: Steven Pemberton [mailto:steven.pemberton@cwi.nl]Sent: Saturday,  
>> June 09, 2018 7:43 AM
>> To: www-svg@w3.org
>> Subject: Rectangle height and width
>>
>> https://svgwg.org/svg2-draft/shapes.html#RectElement
>>
>> "The width and height properties define the overall width and height of  
>> the rectangle. A negative value for either property is illegal and must  
>> be ignored as a parsing error."
>>
>> Please please please fix this! There is absolutely no abstract  
>> justification for saying a rectangle cannot have a negative height (or  
>> width). It's just the same dimension in the other direction!
>>
>> If you're interested in a very natural use case, please see
>> https://homepages.cwi.nl/~steven/xforms/histogram.html
>>
>> (There are probably other places in the spec where negative values are  
>> unnecessarily restricted, but this is the one that I ran into in the  
>> above example).
>>
>> Best wishes,
>>
>> Steven Pemberton
>> CWI, Amsterdam
Received on Sunday, 10 June 2018 10:27:02 UTC

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