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Re: SVG12: snapshotTime optional

From: Chris Lilley <chris@w3.org>
Date: Thu, 5 Jan 2006 16:06:51 +0100
Message-ID: <845627850.20060105160651@w3.org>
To: Bjoern Hoehrmann <derhoermi@gmx.net>
Cc: www-svg@w3.org

On Wednesday, January 4, 2006, 1:17:20 AM, Bjoern wrote:

BH> * Chris Lilley wrote:
>>BH>   In
>>BH> http://www.w3.org/TR/2005/WD-SVGMobile12-20050413/struct.html the
>>BH> snapshotTime attribute is defined as
>>BH> [...]
>>BH>   Indicates a moment in time which is most relevant for a still-image of
>>BH>   the animated svg content. This time can be used as a hint to the SVG
>>BH>   User Agent for rendering a still-image of an animated SVG Document,
>>BH>   such as a preview.
>>BH> [...]
>>BH> This language suggests that implementation of this feature is optional.
>>It is thumbnail generation which is optional. SVG says nothing about how
>>big a thumbnail should be, whether it is animated, etc.

BH> Well, it laters also says for the example "UA with snapshot support at
BH> the left, without snapshot support at the right" which clearly suggests
BH> that it may be possible for a user agent to not support "snapshot"
BH> (which should probably be 'snapshotTime').

It only clearly suggests it if you change snapshot to snapshotTime.

The reason it says "snapshot" and not "snapshotTime" is to differentiate
a) software that generates thumbnails b) support for the snapshotTime
attribute. Perhaps this would be clearer if it said "UA which generates
thumbnails based on snapshotTime at the left, thumbnails from static
rendering at the right" ?

BH> The discussion of the example also notes that this is for a "static
BH> view" of the image and in the "WICD Core 1.0" Working Draft I see

BH>   For SVG child objects, the document time used for rendering a
BH>   frozen or static image shall be that given by the SVG 'snapshotTime'
BH>   attribute. If no 'snapshotTime' is present in the animation, a
BH>   document time of zero (0) must be used.

Yes, other specifications can require use of this information of course.

BH> It seems the SVG Tiny 1.2 Working Draft should require this behavior
BH> whenever implementations render a graphic into a static context; that
BH> would make the feature not optional and address my concern.

That would require all static implementations to implement the animation

In WICD Core, the implementations all have animation capability so they
can clearly require this. The timeline is moved to the specified time, a
static rendering is taken, and thus resources (CPU and battery) are
saved when displaying something that is not currently being animated.

 Chris Lilley                    mailto:chris@w3.org
 Chair, W3C SVG Working Group
 W3C Graphics Activity Lead
 Co-Chair, W3C Hypertext CG
Received on Thursday, 5 January 2006 15:06:56 UTC

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