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List:       whatwg
Subject:    [whatwg]  canvas 2d's ellipse
From:       Rik Cabanier <cabanier () gmail ! com>
Date:       2013-04-30 21:20:09
Message-ID: CAGN7qDBxhL-zyfNHx_bxO_L9S1x3EbUCiYhpBhFdwQQdfrBLPQ () mail ! gmail ! com
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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 2=F0, or, if the anticlockwise argument is true
andstartAngle-endAngle is equal to or greater than 2=F0, then the arc is th=
e
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 2=F0 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-elem=
ent.html#dom-context-2d-ellipse
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