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Re: elliptical canvas.arc?

From: Ian Hickson <ian@hixie.ch>
Date: Wed, 11 May 2011 03:30:06 +0000 (UTC)
To: "Mike \\\"Pomax\\\" Kamermans" <pomax@nihongoresources.com>
cc: public-canvas-api@w3.org
Message-ID: <Pine.LNX.4.64.1105110316220.25791@ps20323.dreamhostps.com>
On Mon, 9 May 2011, Mike \"Pomax\" Kamermans wrote:
>
> Much more severe is that there is no corresponding elliptical arc 
> command. This means that people cannot draw ellitical arcs, nor 
> ellipses.

You can just approximate it using bezier curves. See, for instance:

   http://canvaspaint.org/blog/2006/12/ellipse/


> This omission should not remain the case for the final API.

There's never a "final" API, the Web platform is continuously evolving and 
we're always adding new features, based on what people need and what 
browser vendors are willing to implement.


> That said, while it is possible that some believe the API is already too 
> far in its draft process to change something like this, I would like to 
> remind everyone that the whole point of a draft is to make sure 
> everything makes sense before making it as final - now is the only time 
> oddities like these can still be caught.

That's not really how specs are developed in reality. We can always add 
new features, if there's a need and browsers are willing to ship them. 
Similarly, once browsers have shipped a feature, it's essentially locked, 
even if it is not well-designed. (So for instance, we can't move the spec 
to using a Path primitive instead of just having a single active path, 
though we may add a separate Path primitive later.)

What would prevent adding an ellipse feature to the API is lack of 
implementation desire. What drives implementation desire is usually author 
need, which is usually expressed as use cases.

What is the use case for a dedicated ellipse API rather than using 
beziers?


> Browser makers can change their browsers and push an update as long as 
> the API is in draft, but once it hits final, that's it. Any oddity left 
> in is there essentially forever.

Sadly, the "that's it" moment actually happens when pages start using the 
API. Whether that happens before or after we would like is sadly mostly 
out of our control.


> To explain a bit more why this command is necessary: every graphics 
> package in existence lets users define ellipses. From Illustrator to 
> Sketchup to Processing to Maya, people expect to be able to draw 
> ellipses, and canvas currently simply can't.

Sure you can:

   http://canvaspaint.org/
   http://canvaspaint.org/9d3c6.png

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Wednesday, 11 May 2011 03:30:31 UTC

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