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Re: Comments on rotationAngle

From: Brendan Kenny <bckenny@gmail.com>
Date: Fri, 1 Apr 2011 13:34:39 -0700
Message-ID: <AANLkTi=ww_ZTA+HJnNHZTfGRA0mn67YWWsU10k3zGRGs@mail.gmail.com>
To: Cathy.Chan@nokia.com
Cc: mbrubeck@mozilla.com, public-webevents@w3.org
unfortunately the CSS/SVG rotation convention tends to be *more*
confusing to math majors, who assume a designer somewhere just picked
a direction :)

I assumed that, and it took me much longer than I'll admit to realize
what's going on: the positive-y axis points down in the browser, so
there's an implicit reflection applied to everything. Anticlockwise
becomes clockwise.

It tends to confuse a lot of people, but going the other way would
have as well (especially when dealing with the transformation matrix
directly), so I agree that the strongest argument now is just
following the established convention.

Brendan

On Fri, Apr 1, 2011 at 12:31 PM,  <Cathy.Chan@nokia.com> wrote:
> I agree with following the CSS/SVG convention for the exact reasons that you stated.
> - Cathy.
>
> -----Original Message-----
> From: public-webevents-request@w3.org [mailto:public-webevents-request@w3.org] On Behalf Of ext Matt Brubeck
> Sent: Friday, April 01, 2011 1:11 PM
> To: public-webevents@w3.org
> Subject: Re: Comments on rotationAngle
>
> On 04/01/2011 09:56 AM, Matt Brubeck wrote:
>> Oops! I was a math major, and assumed that *everybody* knew that
>> positive angles are counter-clockwise:
>> http://en.wikipedia.org/wiki/Angle#Positive_and_negative_angles
>>
>> But I see that other W3C specs are "backward," so I will change the
>> Touch Events spec to match them. :)
>
> To complicate matters, the InkML Candidate Recommendation defines pen rotation in counter-clockwise degrees around the origin.  So now I'm not sure.
>
> InkML is more closely related, as it is defining the shape of a pen tip (including ellipses like the ones in the Touch Events spec). On the other hand, CSS 2D Transforms and SVG are more widespread, and are certain to be used alongside Touch Events.
>
> I'm leaning toward the CSS/SVG convention, so authors won't need to flip angles around when translating touch areas into CSS or SVG rotations to draw them on the screen.  Any comments?
>
>
>
>
Received on Friday, 1 April 2011 20:35:12 GMT

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