ISSUE: does clipping affect getObjectExtent?

[Lofton Henderson <lofton@rockynet.com>]

ISSUE:  does clipping affect getObjectExtent?

Reference: 
http://lists.w3.org/Archives/Public/public-webcgm-wg/2008Dec/0005.html

Discussion:  The specification is imprecise about what things affect gOE 
[1] and what things do not.  Clipping is one example.  We have previously 
resolved that APS Attributes and non-text Style Properties do not affect 
gOE [1].  This would include the 'visibility' APS attr. -- does not 
affect.  I.e., gOE returns the bounding box (BB) of the loci of the 
primitives in the object, whether 'visible' or not.  By extension, 
visibility in any form would not affect the BB calculation -- Alpha 
transparency (Escape, or "a" of rgba), transparent cell color (TCC), 
occlusion of the object by an opaque object on top of it, etc.  (Is this 
another issue?)

It would be consistent to say that clipping does not affect gOE, i.e., gOE 
should return the bounding box of the loci of the graphical primitives, 
regardless of whether they are clipped or not.  On the other hand, clipping 
is different from the 'visibility' APS attr in that the latter is 
discoverable by getAppStructureAttr().  But it is similar to the other 
sources of visibility (TCC, etc) that are not discoverable via DOM.

The 2.1 Requirements [2] do not answer the question, but hint at a simple 
requirement.  Past related issues have supported simplicity and ease of 
calculation.

[1] 
http://www.w3.org/TR/2009/WD-webcgm21-20090130/WebCGM21-DOM.html#getObjectExtent
[2] 
http://docs.oasis-open.org/webcgm/v2.1/WebCGM_21_Requirements.html#get-extent

Options:
1.) No, clipping does not affect.
2.) Yes, clipping does affect.
3.) add a parameter to gOE to choose behavior.

Recommendation.  Option 1, "No".

### end ###

-Lofton.

p.s. This ultimately has to be resolved by the WG, but I think preliminary 
discussion in the larger audience of the TC is useful.