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Re: comments on Matrix

From: Dirk Schulze <dschulze@adobe.com>
Date: Thu, 21 Mar 2013 14:31:35 -0700
To: Rik Cabanier <cabanier@gmail.com>
CC: Brandon Jones <bajones@google.com>, "Tab Atkins Jr." <jackalmage@gmail.com>, James Robinson <jamesr@google.com>, Benoit Jacob <jacob.benoit.1@gmail.com>, "public-fx@w3.org" <public-fx@w3.org>
Message-ID: <39B731C8-E61C-4891-B3E3-C05EC29738DD@adobe.com>

On Mar 21, 2013, at 2:24 PM, Rik Cabanier <cabanier@gmail.com> wrote:

> On Thu, Mar 21, 2013 at 12:52 PM, Brandon Jones <bajones@google.com> wrote:
> I'd like to throw another voice in against throwing exceptions. The faulty assumption here being that if a matrix fails to invert this is worth stopping the entire app for. 
> Realistically most authors will blindly invert and never give a second glance to the result. If invert throws this will result in many apps simply halting, with the only way to get it back being a refresh. If invert returns NaNs or similar most apps will have a bit of graphical data flicker, become lit incorrectly, or possibly disappear. Depending on the structure of the app this may naturally resolve itself within a frame or two. While you can argue that a throw will make invert issues easier to debug I feel that most authors would rather have a suboptimal user experience than no user experience.
> If you absolutely MUST retain compatibility with this aspect of SVGMatrix then so be it, but I would highly favor including a non-throwing variant and promoting that one as the preferred call.
> I think that's fine. We'll add another invert call that returns a boolean and takes a matrix.

Before we do that, we certainly should investigate in Tab's complain that applications may not even check for the exception or do not care. Tab, do you know how we could do that?


> Rik
> On Thu, Mar 21, 2013 at 11:59 AM, Dirk Schulze <dschulze@adobe.com> wrote:
> On Mar 21, 2013, at 11:52 AM, "Tab Atkins Jr." <jackalmage@gmail.com> wrote:
> > On Thu, Mar 21, 2013 at 11:47 AM, Rik Cabanier <cabanier@gmail.com> wrote:
> >> On Thu, Mar 21, 2013 at 11:36 AM, James Robinson <jamesr@google.com> wrote:
> >>> On Thu, Mar 21, 2013 at 11:33 AM, Rik Cabanier <cabanier@gmail.com> wrote:
> >>>> I'll formally object to an exception being thrown here.
> >>>>
> >>>> SVG matrix throws an exception and since this is a drop-in replacement,
> >>>> Matrix needs to throw one too :-(
> >>>
> >>> This is a clear example of SVG making a (bad) mistake that we should not
> >>> inflict on the rest of the web platform.
> >>
> >> Are you objecting to any exceptions being thrown?
> >> There are exceptions in all authors facing APIs.
> >
> > No, he objects for the same reason I am - a matrix being singular is
> > not a particularly exceptional situation
> A singular matrix does not mean the same as NaN and Inf values in the matrix.
> However, you need to take a look when you use inverse() for transformation matrices (again, that is the focus here). They are used to transform between coordinate spaces. And then a returning singular matrix does not make sense.
> Dirk
> > , and whether an
> > implementation considers a matrix singular will depend in some cases
> > on the exact algorithm and FP implementation being used.  This is,
> > thus, a *terrible* example of a place to throw an exception, as
> > authors won't expect it, and it'll vary between platforms for no
> > important reason.
> >
> > ~TJ
> >
Received on Thursday, 21 March 2013 21:32:09 UTC

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