From: Rik Cabanier <cabanier@gmail.com>

Date: Tue, 30 Apr 2013 21:12:34 -0700

Message-ID: <CAGN7qDC_wj8VYN0sfx+HfYj4ix_jsFXeyP6YnaKVViAB9Y2FOA@mail.gmail.com>

To: whatwg@whatwg.org

Date: Tue, 30 Apr 2013 21:12:34 -0700

Message-ID: <CAGN7qDC_wj8VYN0sfx+HfYj4ix_jsFXeyP6YnaKVViAB9Y2FOA@mail.gmail.com>

To: whatwg@whatwg.org

I think the API should look like this: void ellipse(unrestricted double x, optional unrestricted double y, unrestricted double radiusX, optional unrestricted double radiusY, optional unrestricted double rotation, optional unrestricted double startAngle, optional unrestricted double endAngle, optional boolean anticlockwise); with the following behavior: - if radiusY is omitted, it's the same as radiusX - if rotation is omitted, it's equal to 0 - if startAngle is omitted, it's equal to 0 - if endAngle is omitted, it's equal to 0 - if anticlockwise is omitted, it's equal to false startAngle and endAngle always refer to points on the circle. If they coincide, the end result is a full circle (with a closepath). On Tue, Apr 30, 2013 at 2:20 PM, Rik Cabanier <cabanier@gmail.com> wrote: > People on the blink team are starting to implement 'ellipse' [1]. > Looking at this API, I have a couple of questions: > > 1. Why are most of the parameters not optional? > Currently, none of the parameter to ellipse are optional. > So, if you want to draw a simple circle, you have to supply 8 parameters, > even though only 3 are needed. > All other calls have anticlockwise optional, why not ellipse? > > 2. when is an ellipse closed? > It's not clear from the prose if there is ever a 'closepath'. So, if you > have square end caps, you will see a discontinuity unless you call > 'closepath'. > > 3. the following lines are somewhat confusing: > > If the anticlockwise argument false and endAngle-startAngle is equal to or > greater than 2ð, or, if the anticlockwise argument is true > andstartAngle-endAngle is equal to or greater than 2ð, then the arc is the > whole circumference of this ellipse. > > and: > > Since the points are on the ellipse, as opposed to being simply angles > from zero, the arc can never cover an angle greater than 2ð radians. > > Why not simply say that the angles define the points on the ellips and > draw the arc between them? That seems more clear. > > 1: > http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#dom-context-2d-ellipse >Received on Wednesday, 1 May 2013 04:13:00 UTC

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