[Webkit-unassigned] [Bug 228125] [SVG] Attribute change triggers redundant (and out of order) setNeedsLayout call

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=228125

--- Comment #3 from zalan <zalan at apple.com> ---
(In reply to Sergio Villar Senin from comment #2)
> (In reply to zalan from comment #0)
> > <svg id=changeThis></svg>
> > <script>
> >   document.body.offsetHeight;
> >   changeThis.setAttribute("width","100px");
> > </script>
> > 
> > The RenderObject::setNeedsLayout(MarkContainingBlockChain) triggered by the
> > SVGElement::attributeChanged (SVGElement::attributeChanged ->
> > SVGSVGElement::svgAttributeChanged ->
> > RenderSVGResource::markForLayoutAndParentResourceInvalidation()) is
> > incorrect and redundant.
> > Incorrect in the context of how the dirty bits on the render tree should be
> > populated. It is out of order i.e we have to have all the ancestors resolved
> > first when marking descendant renderers dirty.
> > Redundant because this attribute change on the SVG element also triggers
> > style invalidation as part of the "presentational hints" flow (which applies
> > to pretty much all the valid SVG attributes see
> > SVGElement::hasPresentationalHintsForAttribute) and this style invalidation
> > path would properly update the associated renderer's dirty bit through the
> > normal RenderTreeUpdater process (as if it was just yet another non-svg
> > style update e.g. <div dir=ltr <-changing it to rtl).
> 
> Removing the RenderSVGResource::markForLayoutAndParentResourceInvalidation
> call in SVGSVGElement::svgAttributeChanged is not harmless though as it
> makes the test LayoutTests/svg/as-object/embedded-svg-size-changes.html fail.
Yup and that's what someone (preferably with WebKit SVG background) needs to figure out and adjust some other part of the code accordingly.

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