W3C home > Mailing lists > Public > www-svg@w3.org > August 2001

Re: Multiple inheritance used in the SVG DOM interfaces.

From: Johnny Stenback <jst@netscape.com>
Date: Sun, 12 Aug 2001 17:42:21 -0700
Message-ID: <3B77226D.4040603@netscape.com>
To: Alex Fritze <alex.fritze@crocodile-clips.com>
CC: www-svg@w3.org, Chris Lilley <chris@w3.org>, Jon Ferraiolo <jferraio@adobe.com>
Alex Fritze wrote:

> In Mozilla's SVG implementation we have implemented the SVG DOM by keeping
> one single principal inheritance thread for the interfaces & 'promising' to
> implement all the other interfaces that would otherwise be mixed into the
> interface tree. E.g. we inherit the SVGCircleElement interface directly from
> SVGElement (which in turn inherits from Element and Node) and 'promise' that
> every object implementing SVGCircleElement also implements the interfaces
> SVGStylable, SVGTransformable etc.

This is exactly what the SVG WG should've done, just like the DOM WG has 
done in all the DOM specs.

> IMO flattening interfaces is ok for untyped languages like js, but doesn't
> do COM/C++ justice. If there is one flat interface per SVG entity, you lose
> all polymorphic capabilities. How are you going to implement functions like
> Translate(SVGTransformable*)? With flattened interfaces you'd need
> Translate(IUnknown*) (or XPCOM: Translate(nsISupports*) ) and then QI for
> every possible interface that supports SVGTransformable functionality.
> Alex
> --------------------------------------------------------------
>  alex fritze
>  crocodile clips ltd      [w] www.croczilla.com/svg
>  11 randolph place        [e] alex.fritze@crocodile-clips.com
>  edinburgh                [t] +44 (0) 131 226 3263
>  eh3 7ta                  [f] +44 (0) 131 226 1522
>  scotland
> --------------------------------------------------------------
>>-----Original Message-----
>>From: www-svg-request@w3.org [mailto:www-svg-request@w3.org]On
>>Behalf Of Jon
>>Sent: 11 August 2001 19:04
>>To: Johnny Stenback
>>Cc: Chris Lilley; www-svg@w3.org
>>Subject: Re: Multiple inheritance used in the SVG DOM interfaces.
>>Adobe takes the SVG IDL and runs a flattening process to expand all base
>>classes before sending it through the MS COM tools, such as midl. This is
>>really a very simple process. If the W3C were to provide COM bindings for
>>its various DOMs, this is the approach that would be used in the COM
>>Note that W3C documented ECMAScript bindings in effect do the same sort of
>>flattening because ECMAScript doesn't even support single inheritance. For
>>example, here is an excerpt from the ECMAScript language binding for DOM
>>level 2 core for the Element interface:
>>Object Element
>>Element has the all the properties and methods of the Node object
>>as well as
>>the properties and methods defined below. ....
>>There is indeed a viable approach to implementing the SVG DOM in COM
>>environments and at least one implementation has successfully implemented
>>this approach. The flattening approach used to implement COM interfaces
>>matches the approach used to implement ECMAScript interfaces.
>>Jon Ferraiolo
>>SVG 1.0 Editor
>>At 03:23 PM 8/10/01 -0700, Johnny Stenback wrote:
>>Chris Lilley wrote:
>>Johnny Stenback wrote:
>>Does silence mean that nobody cares if the SVG DOM interfaces are
>>un-implementable in COM like environments?
>>No, it means that there was some discussion recently between Philippe, Jon
>>and myself and that it turns out that Adobe has in fact
>>implemented SVG DOM
>>in a COM environment. I have asked them for some more details of
>>Any resolution to this yet? I see the SVG spec moving forward, but I don't
>>see how that can happen w/o resolving this issue?

Received on Sunday, 12 August 2001 20:41:01 UTC

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