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RE: re[2]: invalid/extreme rectangles in setView()

From: Galt, Stuart A <stuart.a.galt@boeing.com>
Date: Fri, 12 Dec 2008 08:23:27 -0800
Message-ID: <C8D2620C74DE75488C5FDFBDB9475D6F0CF07D5B@XCH-NW-7V1.nw.nos.boeing.com>
To: "Lofton Henderson" <lofton@rockynet.com>, "WebCGM WG" <public-webcgm-wg@w3.org>

My sense of what was said in the telecon was slightly different

TRUE gets returned if the viewer changed the view and FALSE gets
returned if
the viewer did not set the view.  In theory the viewer could return
FALSE even
though you passed it a valid rectangle but it was feeling ornery that
day and didn't want to change the view...

--
Stuart Galt

 

> -----Original Message-----
> From: Lofton Henderson [mailto:lofton@rockynet.com] 
> Sent: Friday, December 12, 2008 8:04 AM
> To: WebCGM WG
> Subject: RE: re[2]: invalid/extreme rectangles in setView()
> 
> 
> In the telecon and email, we agreed with Benoit's proposal 
> for Option 1; his proposed wording on this part of the 
> setView() issue was:
> 
> "i) boolean: TRUE if new view was set; FALSE if rectangle was 
> invalid."
> 
> Is that the wording that we should use?  (Benoit, as the 
> proposer, is this the wording thatyou want?)
> 
> [We had some discussion in the telecon about it:  some sense 
> the TRUE and FALSE do not apply to the same condition/test.]
> 
> Per the telecon, I am putting the above into the DoC unless 
> there is some quick substitute wording.  (It may be reopened 
> later, in the next cycle.)
> 
> -Lofton.
> 
> At 03:57 PM 12/4/2008 -0500, Bezaire, Benoit wrote:
> 
> >Let's try an make is easy for script writers, ok? Else these new DOM 
> >calls will never get used.
> >
> >Two opposite corner points just complicates the code for script 
> >writers, they have to add 'checks' to determine which point 
> is which. I 
> >didn't oppose the decision for viewcontext back in WebCGM 2.0 since 
> >script writers were unlikely to change the viewcontext. I think it's 
> >different for WebCGMRect() though.
> >
> >Benoit.
> >
> >-----Original Message-----
> >From: public-webcgm-wg-request@w3.org
> >[mailto:public-webcgm-wg-request@w3.org] On Behalf Of Don
> >Sent: Thursday, December 04, 2008 3:30 PM
> >To: Lofton Henderson; WebCGM WG
> >Subject: re[2]: invalid/extreme rectangles in setView()
> >
> >
> >Lofton,
> >
> >  >  At 01:12 PM 12/4/2008 -0600, Don wrote:
> >
> >  >  >Lofton,
> >  >  >
> >  >  >  >  All --
> >  >  >
> >  >  >  >  This is a dangling open piece of Benoit's 
> setView() questions.
> >We closed  >  >  >  the other piece (about different aspect 
> ratios).  I 
> >can't find any thread  >  >  >  discussion about this piece, after 
> >Benoit's message below (top), and  >  >  >  it apparently 
> remains open.
> >  >  >
> >  >  >  >  Discussion?
> >  >  >
> >  >  >I believe we should have very basic checking for Invalid 
> >rectangle and  >  >return boolean as Benoit suggested. A minimal 
> >invalidity check would be  >  >if ymax < ymin or xmax < ymin.
> >
> >  >  Side question:  I just looked at WebCGMRect.  Does 
> anyone recall 
> >why we  >  parameterized it in terms of "lower left corner" 
> and "upper 
> >right
> > >  corner"?  Why not just "two diagonally opposite corner points P1 
> > > and
> >P2  >  [(x1,y1) and (x2,y2)]"?
> >
> >I not sure why but I think it would be nice to be consistent with 
> >viewcontext where we define viewcontext as "defining two 
> corner points 
> >of a rectangle".
> >
> >http://www.w3.org/TR/2008/WD-webcgm21-20080917/WebCGM21-IC.ht
ml#webcgm_
> >3
> >_2_2_2
> >
> >  >  For the former, it sets up an error condition (or is 
> "error prone").
> >Do we  >  need that error condition?  For the latter, the only error 
> >condition is a  >  degenerate rectangle, i.e., zero area, i.e., 
> >xmin=xmax and/or ymin=ymax.
> >
> >I don't think we need any error checking at all on WebCGMRect. A 
> >programmer may want to set a WebCGMRect = 0,0,0,0 for 
> example as some 
> >kind of indication.
> >
> >Don.
> >  >  There may be a reason we did it this way (more error prone, or 
> >allows  >  setting an error), but I don't recall it.  I do 
> recall the 
> >stuff about  >  getObjExt() on an APS with no primitives, but we now 
> >return 'null' for  >  that, so we don't need the somewhat hokey 
> >mirrored rectangle.
> >
> >  >
> >http://www.w3.org/TR/2008/WD-webcgm21-20080917/WebCGM21-DOM.h
tml#webcgm
> >r
> >ect
> >
> >  >  -Lofton.
> >
> >
> >  >  >  >  -Lofton.
> >  >  >
> >  >  >  >  At 09:44 AM 11/19/2008 -0500, Bezaire, Benoit wrote:
> >  >  >  >  I remember this thread. I don't want to reopen old issues.
> >  >  >  >
> >  >  >  >  However, for this particular API, a script writer 
> can easily 
> >loose the  >  >  >  display (zooming on a very small rectangle or 
> >zooming our far enough that  >  >  >  nothing is displayed). I think 
> >the API should at least return a more  >  >  >  meaningful  value.
> >  >  >  >
> >  >  >  >  Some options:
> >  >  >  >  i) boolean: TRUE if new view was set; FALSE is 
> rectangle was 
> >invalid.
> >  >  >  >  ii) float: returns the scale factor between the 
> old view and 
> >the new view.
> >  >  >  >  > 0 is successful, failed otherwise.
> >  >  >  >  iii) WebCGMRect: a rectangle defining the old view.
> >  >  >  >
> >  >  >  >  Any of those would help the script writer understand what 
> >went wrong,  >  >  >  instead of getting in touch with 
> technical support.
> >  >  >  >
> >  >  >  >  Benoit.
> >  >  >
> >  >  >  >  From: Lofton Henderson 
> [mailto:lofton@rockynet.com]  >  >  >
> >Sent: Tuesday, November 18, 2008 7:08 PM  >  >  >  To: 
> Bezaire, Benoit; 
> >WebCGM WG  >  >  >  Subject: Re: Question about setView()  > 
>  >  >  >  
> >>
> > >  At 08:57 AM 11/18/2008 -0500, Bezaire, Benoit wrote:
> >  >  >  >  I'm wondering if the wording of setView() is not 
> a bit short?
> >The draft  >  >  >  doesn't say anything about invalid 
> rectangles being 
> >passed in for example.
> >  >  >  >
> >  >  >  >  Should more feedback be sent to the user? Currently, the 
> >function  >  >  >  prototype has a void return type. Should 
> we change 
> >that to a boolean or  >  >  >  something else? or throw an exception 
> >perhaps.
> >  >  >  >  Dieter raised and we discussed a similar question a few 
> >months back.
> >As a
> >  >  >  >  general rule, CGM and WebCGM say what happens with valid 
> >input but have  >  >  >  been relatively silent about error 
> fallbacks, 
> >viewer error reactions, etc.
> >  >  >  >  What we have done most recently is say something like 
> >"...has no effect".
> >  >  >  >  We generally have not gone to more extensive 
> error reactions.
> >See for  >  >  >  example the 'grnode' stuff that we added to the 
> >interfaces.
> >  >  >
> >  >  >  >  My view is that, if we start opening the door to 
> saying what 
> >viewers do  >  >  >  for this and that bad input, where do we stop?
> >Should we go back and  >  >  >  define mandatory error responses for 
> >all bad input?
> >  >  >
> >  >  >  >  Note that the profile (Ch.6) *does* talk a lot about 
> >"degeneracies".
> >It
> >  >  >  >  says what is the graphical effect of a degenerate 
> primitive, 
> >etc., and  >  >  >  this is what is *suggested* in CGM:1999 
> itself -- 
> >WebCGM just makes  >  it  >  >  >  normative.  (But saysnothing more 
> >about what the viewer should do  >  when  >  >  >  encountering 
> >degeneracies. Silent?  Warning?  Task-bar "abnormality"
> >  >  >  >  icon?)
> >  >  >
> >  >  >  >  I guess I favor "...invalid input has no effect, neither 
> >graphical nor to  >  >  >  the DOM tree."  Then leave it to the 
> >implementor, what else the viewer  >  >  >  might do in the way of 
> >error response to the user.
> >  >  >  >
> >  >  >  >  I also question the possibility of a major scale 
> change, ex:
> >scaling  >  > in by  >  >  >  a factor of 100 (and loosing 
> sight of the 
> >overall picture). Should the  >  >  >  user be told that 
> such a change 
> >occurred?
> >  >  >  >  I guess I view this as another choice for implementors.
> >  >  >
> >  >  >  >  I could also live with putting some valid limits on it.
> >"Valid rectangles  >  >  >  shall not change the scale by more than 
> >...blah..."
> >  >  >
> >  >  >  >  -Lofton.
> 
> 
> 
Received on Friday, 12 December 2008 16:24:18 GMT

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