Hi Michael.
Bishop, Michael W. CTR USJFCOM JFL:
> I think I've seen something like this before, but I haven't been able
> to find it in the archives. Here's what's going on. I have some SVG
> defined in <defs>. Elsewhere in the document, I have a <g> with the
> attribute "pointer-events" set to visible. Within this <g>, I have
> <use> elements that reference the SVG found in <defs>. The <use>
> elements have further attributes on them.
>
> I'm registering a DOM "mouse-down" listener on the <g> tag. Pointer
> events are being generated, but the event "target" is the SVG defined
> in <defs> and I can't access the unique attributes found on my <use>
> element. Is there anyway to discover information about the <use>
> element instead of the SVG it "uses"?
>
> <defs>
> <circle id="circle" ... />
> </defs>
>
> <g pointer-events="visible">
> <use xlink:href="#circle" id="12345"/>
> </g>
>
> I want to discover the "id" attribute on the <use> element, but I'm
> getting the <circle> as the event target.
So according to the spec, event flow should go like this:
SVGGElement CAPTURING
SVGUseElement CAPTURING
SVGElementInstance corresponding to the <circle> AT_TARGET
SVGUseElement BUBBLING
SVGGElement BUBBLING
Batik doesn’t implement the SVGElementInstance stuff; what it actually
does is actually close the <use>d content into a hidden tree and
dispatches events to those. So the <circle> that the event is
dispatched to in the AT_TARGET phase is actually a copy of the <circle>
element from your document.
Per spec, if you wanted to find out which <use> element you’re in, you’d
do:
event.target.correspondingUseElement
since event.target would be the SVGElementInstance object. But that
won’t work at the moment. Batik creates a fake DOM node to be the root
of the cloned shadow tree, and it has a pointer to the <use> element
that it’s the root of the shadow tree for. So you can do this:
var n = event.target;
while (n.parentNode) {
n = n.parentNode;
}
// here, n will be an org.apache.batik.dom.svg.SVGOMUseShadowRoot
n = n.getCSSParentNode();
// now n will be the <use> element
This is non-standard of course, but it should suffice until the proper
element instance tree is implemented.
--
Cameron McCormack ≝ http://mcc.id.au/
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