[svgwg] Issue: <svg:use> shadow tree shouldn't be open. (#875) marked as Agenda+

karlcow has just labeled an issue for https://github.com/w3c/svgwg as "Agenda+":

== <svg:use> shadow tree shouldn't be open. ==
https://www.w3.org/TR/SVG2/struct.html#UseShadowTree"

> The shadow tree is open (inspectable by script), but read-only. Any attempt to directly modify the elements, attributes, and other nodes in the shadow tree must throw a NoModificationAllowedError. 

Reasons why this is bad:

 * Implementations might want to throw-away the tree and recreate it on some kinds of mutations. If it was inspectable by script we couldn't do it because it'd loose node identity.
 * Throwing on modification is error prone and requires very invasive changes to very hot code across the whole engine.
 * In all engines the shadow tree has always been closed.

Most important reason is the second, IMO.

See https://github.com/w3c/svgwg/issues/875


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Received on Tuesday, 18 November 2025 00:59:14 UTC