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Re: getBBox() on a <use>

From: Jeff Schiller <codedread@gmail.com>
Date: Wed, 20 Jan 2010 11:04:27 -0600
Message-ID: <da131fde1001200904p13d7cccl248a6dbcaefdbc09@mail.gmail.com>
To: Dirk Schulze <vbs85@gmx.de>
Cc: www-svg <www-svg@w3.org>
Please ignore my 'scaling' comment above.  I re-read
http://www.w3.org/TR/SVG11/struct.html#UseElement and it seems that
the <use>'s width/height attributes are ignored when not referencing a
<symbol> or a <svg> element.  Changing width/height in my test case
had no observable effect.

I also clearly didn't think when I said "huh?" with respect to
WebKit's results, since in looking things over and thinking about what
Dirk said, I would say WebKit's (probably non-compliant)
implementation of getBBox() is more useful than the other
implementations I have been testing.  From WebKit's version, I know
directly that the bounding box of the drawn contents of the <use>
element is (300,300)->(500,400).  This is exactly what has been
painted.

In Firefox/Opera/Batik, I would have to get the bbox, then offset it
by the x,y attributes on the <use> element.  This is what I'll have to
do in SVG-edit, apparently.

Regards,
Jeff

On Wed, Jan 20, 2010 at 6:48 AM, Dirk Schulze <vbs85@gmx.de> wrote:
> Hi,
>
> I don't know the correct behavior of getBbox, but it sound a bit
> strange, that the bbox should be the bbox of the rect? The rect isn't
> placed at 100,100 on applying the <use> coordinates, but why should it
> still have the old coordinates of the rect position?
> That would mean, that the bbox is not very helpful on a use element,
> since it doesn't have any relation to the real position of it or it's
> content?
>
> Greetings,
> Dirk
>
> Am Dienstag, den 19.01.2010, 21:25 -0600 schrieb Jeff Schiller:
>> Is the following test case correct:
>>
>> <svg xmlns="http://www.w3.org/2000/svg"
>> xmlns:xlink="http://www.w3.org/1999/xlink">
>>   <rect id="r" x="100" y="100" width="200" height="100" fill="red" />
>>   <use id="u" x="200" y="200" width="400" height="200" xlink:href="#r"/>
>>
>>   <script><![CDATA[
>>       var u = document.getElementById("u"),
>>               r = document.getElementById("r"),
>>               b = u.getBBox();
>>       if (console && console.log) console.log([b.x,b.y,b.width,b.height]);
>>       if (b.x == 200 && b.y == 200 && b.width == 400 && b.height == 200) ) {
>>               r.setAttribute("fill", "green");
>>       }
>>   ]]></script>
>> </svg>
>>
>> In other words, shouldn't the bbox of a <use> element be defined by
>> its x,y,width,height just like a <rect> or an <image> ?  No browser
>> gives consistent results:
>>
>> Firefox  :  100, 100, 200, 100
>> Opera   :  100, 100, 200, 100
>> WebKit :   300, 300, 200, 100 (huh? clearly a bug!)
>>
>> What's ASV do?
>> What's IE9 do? :)
>>
>> Thanks,
>> Jeff
>
>
>
Received on Wednesday, 20 January 2010 17:05:00 GMT

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