Fwd: "pick" answer for SVG

[Lofton Henderson <lofton@rockynet.com>]

CGM Open members --

Here is some useful background information relating to the open "pick" 
issue -- on hollow/empty filled objects with visible boundary/edge.  I 
looked to see what SVG said.

The answer for SVG is found in:  "16.6 The 'pointer-events' property".  A 
property on the SVG graphical element determines the behavior.  There are 
10 selectable behaviors, settable on a per-object basis, and the default 
(initial) is:

visiblePainted
The given element can be the target element for pointer events when the 
'visibility' property is set to visible and when the pointer is over a 
"painted" area. The pointer is over a painted area if it is over the 
interior (i.e., fill) of the element and the 'fill' property is set to a 
value other than 'none' or it is over the perimeter (i.e., stroke) of the 
element and the 'stroke' property is set to a value other than 'none'.

So by analogy to the SVG default, a hollow or empty filled area object in 
WebCGM with visible border and/or edge would *not* be picked by a mouse 
click to the interior, but would be picked by a click on the border/edge.

I can't what, if anything, the ISO standards (GKS, PHIGS, CGI) say about 
this case.  I have asked some experts on these standards (Hopgood, Duce, 
Bono) if they know the answer.

-Lofton.


>X-Sender: lofton@terminal.rockynet.com
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>Date: Wed, 06 Jun 2001 12:41:31 -0600
>To: Bob Hopgood <bhopgood@brookes.ac.uk>,David Duce <daduce@brookes.ac.uk>
>From: Lofton Henderson <lofton@rockynet.com>
>Subject: "pick" answer for SVG
>X-RCPT-TO: <lofton@rockynet.com>
>
>Bob, David --
>
>Partial answer...
>
>The answer to my "pick" question for SVG is found in:  "16.6 The 
>'pointer-events' property".  A property on the element determines the 
>behavior.  There are 10 selectable behaviors, settable on a per-object 
>basis, and the default (initial) is:
>
>visiblePainted
>The given element can be the target element for pointer events when the 
>'visibility' property is set to visible and when the pointer is over a 
>"painted" area. The pointer is over a painted area if it is over the 
>interior (i.e., fill) of the element and the 'fill' property is set to a 
>value other than 'none' or it is over the perimeter (i.e., stroke) of the 
>element and the 'stroke' property is set to a value other than 'none'.
>
>So by analogy, if the ISO graphics standards behaved as the default in 
>SVG, a hollow or empty filled area object with visible border and/or edge 
>would *not* be picked by a mouse click to the interior, but would be 
>picked by a click on the border/edge.
>
>I can't recall if there are any such specifications in the ISO standards 
>(GKS, PHIGS, CGI).
>
>-Lofton
>