RE: [cgmo-webcgm] What to do with WebCGMMatrix

["Weidenbrueck, Dieter" <dweidenbrueck@ptc.com>]

inverse is certainly needed in a lot of situations.

And it is cumbersome to have it done in JScript for an average script writer

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From: Lofton Henderson [mailto:lofton@rockynet.com]
Sent: Dienstag, 10. Juni 2008 10:53
To: Bezaire, Benoit; cgmo-webcgm@lists.oasis-open.org
Subject: RE: [cgmo-webcgm] What to do with WebCGMMatrix

Benoit's repackaging of the transform functionality in 
original message of this thread is tidy -- all of the individual transform forms 
(scale, etc) become convenience methods on the WebCGMMatrix interface, to 
convert to canonical matrix form, and only matrix goes in and out of 
WebCGMAppStructure.  

Although I'm a little leery of this 
repackaging at this stage, on the other hand it seems harmless if we decide and 
do it now, before heavy implementation investment.

So what do the users 
want?  

1.) rotate(degrees,replace) directly into DOM?  or, 
2.) setTransform(rotate(degrees),replace)?

#1 is closest to what we 
have now, and closest to Benoit's modified proposal (just below).   My 
own preference is towards Benoit's modified proposal, but then again I'm not an 
application programmer for this stuff.

Thoughts?

Also ... do we 
have a strong use case for inverse?  Matrix inversion is one 
computationally expensive operation (although there are probably quick shortcuts 
for these special 3x3 homogeneous transforms).

-Lofton.


At 
10:33 AM 6/10/2008 -0400, Bezaire, Benoit wrote:

I guess another alternative could be:
- keep translate, rotate, scale on the WebCGMAppStructure
- replace the matrix API with the setTransform()
- remove createWebCGMMatrix.
 
So users could call translate, rotate, scale for the basic operations. And if they want to go for more complex, they could do a getTransform() which returns a WebCGMMatrix; and then modify the values as desired before calling setTransform.
 
Benoit.

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From: Galt, Stuart A [mailto:stuart.a.galt@boeing.com]
Sent: Tuesday, June 10, 2008 10:20 AM
To: Bezaire, Benoit; cgmo-webcgm@lists.oasis-open.org
Subject: RE: [cgmo-webcgm] What to do with WebCGMMatrix

I suspect that most of the transforms will be simple translate, rotate or scale.  If I needed to do more complicated stuff I would probably do my calculations ahead of time (as much as possible) and the output would inlude the javascript to do the transforms.  So I guess my answer for 1,2 is either the attribute should be writeable or we need a method to set the matrix to the value I specify.
 
As far as removing scale, rotate and translate from WebCGMAppStructure I guess the only question I have is does this have an negative impact on performance because two (or more) methods are needed or is that faster than the overhead of allocating a new data structure behind the scenes?
 

--
Stuart Galt
SGML Resource Group
stuart.a.galt@boeing.com
(206) 544-3656

 

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From: Bezaire, Benoit [mailto:bbezaire@ptc.com]

Sent: Tuesday, June 10, 2008 5:58 AM

To: cgmo-webcgm@lists.oasis-open.org

Subject: RE: [cgmo-webcgm] What to do with WebCGMMatrix

I wasn't proposing to remove getTransform() All I'm saying is that I do not believe many script writers will venture in that area. Regardless, here is the WebCGMMatrix proposal

interface WebCGMMatrix {

    attribute float a;

    attribute float b;

    attribute float c;

    attribute float d;

    attribute float e;

    attribute float f;

WebCGMMatrix multiply (in WebCGMMatrix m);

WebCGMMatrix inverse(); // raises exception

WebCGMMatrix translate( in float x, in float y );

WebCGMMatrix scale( in float sx, in float sy );

WebCGMMatrix rotate( in float angle, in float rx, in float ry );

};

I would then replace WebCGMAppStructure::translate(), rotate(), scale() and matrix() for a new API WebCGMAppStructure::setTransform ( in WebCGMMatrix, in WebCGMString replace );

getTransform() would return a WebCGMMatrix.

And we need a new API either on the Picture or Metafile interface ::createWebCGMMatrix (it returns a new WebCGMMatrix initialize to the identity matrix).

Questions:

1) Should attributes a..f be read only (i.e., the idea is to prevent the user from messing up matrix)?

2) Do we need other methods on the WebCGMMatrix interface?

3) WebCGMAppStructure methods, translate, scale, rotate and matrix are gone, what do people think of that?

Regards,

Benoit

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From: Lofton Henderson [mailto:lofton@rockynet.com]

Sent: Monday, June 09, 2008 5:34 PM

To: Bezaire, Benoit; cgmo-webcgm@lists.oasis-open.org

Subject: RE: [cgmo-webcgm] What to do with WebCGMMatrix

I tend to agree with Dieter, although I am not an experienced practitioner in DOM programming.

However, I also have a procedural/timing concern.  I'm thinking that this is not best timing to discuss removing getTransform() -- unless everyone were enthusiastically unanimous to do so -- as we are trying to prepare CD02 text.  (Recall that there are small windows for technical adjustment in the WG; and then the TC approves any substantive changes when the work comes back from the W3C.)

If we don't remove the getTransform() now, then we need to have a parameterization of the return value.  Which means either array matrix[6] or interface WebCGMMatrix.  (Rob has concerns about whether such return type as matrix[6] is supported by IE, regardless of whether it is valid in IDL and ECMAScript.)

Let's discuss further (on Wednesday, if not here).

-Lofton.

At 02:39 PM 6/9/2008 -0400, Weidenbrueck, Dieter wrote:

Benoit,

I think it is needed. If you request the current transform of an object you have no idea what it might be, and very easily it may be a complex matrix resulting from multiple transforms (in fact, this should be the default case for even a simple rotation).

So if you want to concatenate transforms (e.g. a rotation) and be able to restore the result before the concatenation, you can only use a matrix IMO.

Regards,

Dieter

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From: Bezaire, Benoit [mailto:bbezaire@ptc.com]

Sent: Montag, 9. Juni 2008 13:58

To: cgmo-webcgm@lists.oasis-open.org

Subject: [cgmo-webcgm] What to do with WebCGMMatrix

Hi All,

I honestly don't know if we need WebCGMMatrix. The methods (translate, rotate, scale, matrix) may not the "prettiest" from a coding stand-point, but I think they get the job done.

Personally, I think very few users will use matrix() and getTransform(), so I don't know if it justifies a new WebCGMMatrix interface.

I think it makes more sense to add a WebCGMRect interface than a WebCGMMatrix interface.

Thoughts on this?

If many of you want WebCGMMatrix in, I can add it; but I get the impression I'm alone on this one.

Benoit.

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