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Re: [CSSWG] Minutes and Resolutions 2010-02-24

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Wed, 3 Mar 2010 13:07:56 -0600
Message-ID: <dd0fbad1003031107l7b85a43au4a3e44bc6d6694f5@mail.gmail.com>
To: Erik Dahlstrom <ed@opera.com>
Cc: "www-style@w3.org" <www-style@w3.org>
On Wed, Mar 3, 2010 at 12:48 PM, Erik Dahlstrom <ed@opera.com> wrote:
>>   <fantasai>
>> http://lists.w3.org/Archives/Public/www-style/2010Feb/0164.html
>>   fantasai: The "none' value is asserted as necessary for SVG. I am not
>> sure
>>             that this is so.
>>   fantasai: If CSS decides on the view box size and SVG decides how to
>> fill
>>             it then there is no need for a 'none' value because SVG
>> setting
>>             will be used anyway
>>   ACTION (all) read Elika's answer above
>
> The 'none' property value could be used as a way of telling SVG to respect
> the 'preserveAspectRatio' attribute (basically rendering as if
> image-fit/image-position were not implemented). Is there any other way of
> doing that?

The intention expressed today in the conf call was that SVG should
*always* respect preserveAspectRatio, *unless* image-fit is specified
*on the <svg> element*.  <img src=foo.svg style=image-fit:fill;> would
just hand a fill-sized box to SVG and ask it to scale itself however
it wants.  Being able to tell SVG how to scale itself in this
situation is something we want to do, but with a general method for
specifying that CSS should cascade through to linked content, not
something SVG or element-specific.

>>   wrt Don't inherit
>>   Daniel: It is suggested to not inherit image-postition and image-fit
>>   fantasai: the use case for inheritance is "nested object elements" but
>> it's
>>             more important to match SVG's preserveAspectRatio
>>   Simon: I am fine with no inheritance
>>   Bert: me too
>>   RESOLVED: Do what is best for SVG
>>   N. B. if what is best for SVG involves no inheritance, then there will
>> be
>>         no inheritance
>>   ACTION (Elika): Find out what is best for SVG
>
> Inheriting would be problematic for SVG because an SVG author probably
> wouldn't expect all elements that establish new viewports to suddenly look
> different. Take for example the case of nested svg elements.

That makes sense to me.

>>   wrt A new 'auto' behavior
>>   Bert: I do not like it; I think we can do without it
>>   Peter: how do we get the default behaviors without it
>>   fantasai: We can say that we assign the box and the content "filler"
>> does
>>             what ever it thinks is right
>>   fantasai: using the model above, the content filler is given the size of
>>             the area to fill and it makes the decision on how to fill it
>>   Sylvain: Would 'auto' be the default behavior then?
>>   Answer: yes
>>   dbaron: Because "object" is so hard to implement, perhpas we should not
>>           force that on every other kind of element
>>   Sylvain and dbaron: auto should not be the default just because it is
>> good
>>                       for "object"
>>   Daniel: do you agree that a new "auto" value is needed?
>>   <dbaron> I think <object> behavior might be a bunch of quirks... and
>>            object isn't used very much for any of this.
>>   <dbaron> I think the right behavior for <object> might be to switch
>>            implementations to doing 'fill'.
>>   Sylvain and dbaron: no, we do not agree there is a need
>>   RESOLVED: the proposal for a new "auto" value is not accepted
>
> There is general agreement in the SVG WG to allow image-fit/image-position
> to override 'preserveAspectRatio', and to use it for the elements where it
> makes sense, e.g <svg> and <image>.

Yeah, that's a good idea.

> In doing so we would naturally like to
> avoid breaking existing content. If the image-* properties in any way
> changes the rendering when not explicitly specified then that's not good.
> The initial values should be chosen such that they describe current
> behaviour. An 'auto' value is one way of dealing with this complexity. There
> might be other ways too. In any case introducing the
> image-fit/image-position feature while at the same time breaking existing
> content (e.g svg content referenced by <object>) is not acceptable.

Does SVG need a different default value for image-fit than 'fill' for
the case when preserveAspectRatio isn't specified at all?  If so, can
this be specified by SVG itself, similar to how browsers would specify
"video{image-fit:contain;}" in their UA stylesheets?  When
preserveAspectRatio *is* specified, it can still work as expected.

~TJ
Received on Wednesday, 3 March 2010 19:08:48 GMT

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