Re: [SVG 2] bearing path command and simple drawing of objects with discrete rotation symmetry

On Thu, Feb 13, 2014 at 12:14 AM, Cameron McCormack <cam@mcc.id.au> wrote:

> Hi Olaf,
>
>
> Dr. Olaf Hoffmann wrote:
>
>> In detail: Alternatively to a number representing an angle in degree, it
>> would be useful to be able to note number1/number2.
>> This expression represents a fraction of a full turn.
>> In case number2 is accidently noted as 0, one can define 0 degree as
>> rotation.
>>
>> Advantages:
>> a) Authors do not have to calculate the approximate angle
>> in degrees and do not have to bother about residuals from rounding this
>> number.
>> b) This gives more accurate (semantical) information about the intended
>> shape than rounded numbers, therefore it is simpler to identify the
>> intented
>> meaning or purpose of a shape.
>>
>
> You're right there would be an advantage to allowing fractions in here for
> values like 1/7.  On the other hand we don't allow numbers to be expressed
> like this anywhere else in SVG.
>
> For stars, pie charts, etc., which are the kinds of things that I'm
> thinking the bearing commands will be used for, fractions of the form 1/n
> would be appropriate.  I wonder though whether people would want to have
> more complex expressions, like "0.5 + 1/7".  (Of course they can just
> compute that to "8/14".)
>
> People have previously asked to be able to use CSS length values in the
> middle of path data strings, and <polygon> points attributes.  Although we
> hadn't planned on doing that right now, as it's quite a change, it would
> let you do fractions using calc().
>

This makes the most sense to me, as it re-uses existing spec and is more
powerful than randomly enabling fractions for one particular attribute.


> I think if we allowed fraction values, implementations wouldn't
> necessarily perform their path/bearing calculations using fraction values
> but instead still work with floating point.
>
>