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Re: Again with the getIntersectionList()

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Fri, 13 Nov 2009 11:26:45 -0500
Message-ID: <4AFD88C5.2050705@mit.edu>
To: Doug Schepers <schepers@w3.org>
CC: www-svg <www-svg@w3.org>, Jeff Schiller <codedread@gmail.com>
On 11/13/09 3:49 AM, Doug Schepers wrote:
> A) SVGRect1 {x:20, y:20, width:0, height:0}
> getIntersectionList( SVGRect1 );
>
> This is essentially a point that will return everything that intersects
> that point, regardless of document order

I would have actually expected this to return nothing, since all 
intersections are empty (zero area)...

If that's not what's intended, the spec needs to be _very_ clear on 
this, and then all sorts of interesting issues are raised.  For example, 
does a rectangle with x=0,y=0,width=5,height=5 intersect a rectangle 
with x=5,y=5,width=5,height=5?  I posit the intuitive answer that most 
people would want is "no".  How is this different from the case above?

For what it's worth, in Gecko rectangles in the css renderer are 
effectively considered closed on top and left and open on bottom and 
right; so a rectangle with x=0,y=0,width=5,height=5 is described by the 
inequalities: 0 <= x < 5, 0 <= y < 5.  Hence the two rectangles I 
describe above do not in fact intersect, and any rectangle with width=0 
or height=0 is the empty set.

I'm not sure what Gecko's svg implementation does in this regard, though 
I suspect it's similar.

-Boris
Received on Friday, 13 November 2009 16:27:33 GMT

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