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

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Mon Aug 2 03:38:12 PDT 2021


Sergio Villar Senin <svillar at igalia.com> changed:

           What    |Removed                     |Added
                 CC|                            |svillar at igalia.com

--- Comment #2 from Sergio Villar Senin <svillar at igalia.com> ---
(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.

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