W3C home > Mailing lists > Public > www-svg@w3.org > August 2001

Re: Elements that establish viewports

From: Jon Ferraiolo <jferraio@adobe.com>
Date: Tue, 21 Aug 2001 20:06:20 -0700
Message-Id: <4.3.2.7.2.20010821194355.00c7f840@mailsj>
To: "Robert DiBlasi" <r_diblasi@hotmail.com>
Cc: www-svg@w3.org
Robert,

At 07:43 PM 7/19/01 +0000, Robert DiBlasi wrote:
>W3C Working Group and SVG community,
>
>I understand that the following SVG elements establish a new viewport
>
>>svg
>>symbol
>>image
>>marker
>>pattern
>>foreignObject
>
>but as usual... my tedious questioning and literal take on reading the 
>specification leads me to ask another question....

A viewport-creating element does a couple of special things:

1) Define a rectangular region (you might say a viewport) to allow for 
scale-to-fit using attributes 'viewBox' and 'preserveAspectRatio' (some 
non-viewport elements do this also)
2) Redefine the meaning of percentages
3) Define an implicit rectangular clipping path if 'overflow' has the value 
'hidden' (some non-viewport elements do this also)

The SVG working group had a long debate and decided that markers and 
patterns don't establish new viewports. This was mainly due to discussion 
of how to deal with percentages. Markers and patterns satisfy (1) and (3), 
but not (2).

After looking through this email, it looks as if a couple of additional 
sentences in the specification might make this all clearer to the reader.


>is there something different about these elements the also establish new 
>viewports....
>
>g
>def
>use
>switch
>mask
>filter
>feImage
>a
>font
>glyph
>missing-glyph
>
>just trying to get my thoughts straight about how this second group of SVG 
>elements ties into the first group....or do they at all?

These elements don't do the three things which I listed above.

Jon Ferraiolo
SVG 1.0 Editor
jferraio@adobe.com


>please reference:
>www.w3.org/TR/2000/CR-SVG-20001102/coords.html#EstablishingANewViewport
>
>this section seems to ignore the secound group of elements that I have 
>pointed out.
>
>Thank you for your time.....I sorry if I ask such daft question :-)
>
>We all learn by sharing what we know
>Robert A. DiBlasi
>
>
>
>Robert A. DiBlasi
>
>
>_________________________________________________________________
>Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp
Received on Tuesday, 21 August 2001 23:08:08 GMT

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