Re: "liveness" of SVGMatrix

On Tue, Jul 1, 2008 at 12:54 AM, Erik Dahlström <ed@opera.com> wrote:

> What are the use-cases of having SVGTransform::setMatrix adopt the
> passed-in matrix?
>
> IMHO it seems a bit weird to let it be live in this scenario, especially
> given that there are methods for setting translation, rotation etc on the
> SVGTransform interface. These would then affect the passed-in matrix too.
>
> Another way to get the liveness:
> tfm.setMatrix(mtx); // setting values of the tfm.matrix from mtx
> mtx = tfm.matrix; // mtx is now live


Yeah, that's fine. Just say in setMatrix that the passed-in matrix is
copied, not adopted.

Another question then is if the createSVGTransformFromMatrix method (on
> SVGSVGElement and SVGTransformList) also behaves the same. My testing for
> createSVGTransformFromMatrix so far concludes that all viewers treat the
> passed-in matrix as disconnected from the created SVGTransform (i.e. it's
> not live).


Fine. Just make the spec state that.


>
>
>  Also, I don't understand the entry for "consolidate":
>>
>>> The returned item is the item itself and not a copy. Any changes made to
>>>
>> the item are immediately reflected in the list.
>> I don't think this is right. For lists with more than one matrix, this
>> doesn't seem to make any sense.
>>
>
> Agreed. How about:
> "If the list contains more than one item, then the consolidated matrix is
> written to the first item in the list while the other items are removed from
> the list. The returned item is the first item in the list, and is the item
> itself and not a copy. Any changes made to the item are immediately
> reflected in the list."


You mean accessing the "consolidate" attribute has the side-effect of
reducing the list to one element? That doesn't sound like a good idea to me.
I think "consolidate" should just return a new matrix object every time
which is a copy of the multiplied-together matrices.

Thanks,
Rob
-- 
"He was pierced for our transgressions, he was crushed for our iniquities;
the punishment that brought us peace was upon him, and by his wounds we are
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own way; and the LORD has laid on him the iniquity of us all." [Isaiah
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