Eric Seidel <[email protected]> skreiv Tue, 02 Feb 2010 21:04:33 +0100
Definitely a bug.
Some of these are on file, some are not:
http://webkit.org/quality/reporting.html
Thanks, Eric and Dean, for your feedback. I have reported bug 34521 [1].
Hopefully I will be able to host the test case soon. Best of luck on
implementation! Feel free to ask me if you have questions or concerns.
-Leif Arne
[1] https://bugs.webkit.org/show_bug.cgi?id=34521
On Tue, Feb 2, 2010 at 8:17 AM, Leif Arne Storset <[email protected]>
wrote:
Hello,
While doing some SVG-related work over here I discovered that WebKit's
rendering of SVG in <img> tags differs from Opera's. Since WebKit and
Opera to my knowledge are the only engines that currently support SVG in
<img> we thought it would be worthwhile to make sure we are compatible.
As far as I can tell from the latest nightly builds (and the latest
Chrome
release on Linux), WebKit will render an SVG in <img> much like a
bitmap:
it will resolve the width and height of the image and stretch it to fill
the content box. It will respect any viewbox (presumably synthesizing
one
if it is missing), but preserveAspectRatio [1] seems not to be applied
to
an SVG in <img>, and the default rendering (whether there is a viewbox
or
not) is as if preserveAspectRatio="none".
Opera (Presto engine) will also resolve image dimensions and synthesize
missing viewboxes, and will synthesize a viewBox if it can, as outlined
in SVG WG ISSUE-2258 [2], and applies preserveAspectRatio as specified
in
SVG 1.1 (note that pAR has a default value 'xMidYMid meet'). The viewBox
(whether specified or synthetic) are used together with pAR when
rendering
the SVG into the viewport established by the <img> element.
The attached images and test case illustrate the two renderings.
A quick Google search of webkit.org revealed little on
preserveAspectRatio
except a reference to a 2008 bug in SVGImageElement. However, for
<svg:image> (that is: <image> elements inside of an <svg>), pAR seems to
be applied as per the spec.
We believe that not applying the pAR on svg in <img> means that WebKit
has invalid rendering behaviour according to the SVG 1.1 specification.
To enhance cross-browser compatibility it would be good if WebKit also
considered synthesizing viewBoxes as outlined in [2], as this makes it
easier to reuse existing svg content created by svg editors such as
Inkscape (such content most often has a width and height, but lacks a
viewBox).
I hope you find these recommendations useful. Please let me know if I
can
be of further assistance. If desired I can file a bug in your issue
tracker.
--
Leif Arne Storset
Layout developer, Opera Software
[1] http://www.w3.org/TR/SVG11/coords.html#PreserveAspectRatioAttribute
[2] http://www.w3.org/Graphics/SVG/WG/track/issues/2258
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Leif Arne
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