Implemented d3.svg.arc.cornerRadius

[bm-w]

See #1131. This implementation uses approach C for the case of large corner radius relative to arc length—i.e. using Bézier curve approximations to both align the corner start points with those of neighbouring slices and also touch the inner and outer radius, at the expense of the corners no longer being circular.

This features adds about 1.3kB to the minified library (comparing the results of make).

NB. I went ahead and implemented this approach, though I'm still open to switching to the other approaches if so desired.

[lgrkvst]

Hi,

I've tested your cornerRadius implementation and it works really good - sleek corners! Thank you for doing this.

The oddest little caveat though - I can't seem to do this:
var d3hull = d3.geom.hull();

This throws the following:
Uncaught TypeError: Cannot read property 'length' of undefined d3.min.bm-w.cornerradius.js:4
zi.geom.hull d3.min.bm-w.cornerradius.js:4
(anonymous function) force_with_labels.js:18

I'm not entiry sure, but it points towards d3.min.bm-w.cornerradius.js as it all works when I change to the "normal" d3.v3.min.js.

It should be easy to reproduce, otherwise, I'm doing something wrong on my end.

Keep up the good work!

Best regards,
Christian

[ruphin]

Hi,

This pull request adds a useful feature to D3 Arcs. We are currently using the latest version of D3 with these changes added on top, and haven't encountered any issues. Perhaps someone can take a look at this pull request, it would be nice to have it merged so we can use the main release of D3 again.

With kind regards,
Goffert

[lgrkvst]

Seconded! :>

[chrisvfritz]

This has been very useful in my projects as well and I also have not encountered any issues.

[terite]

👍

[mbostock]

Can I ask you to sign the CLA, per D3’s CONTRIBUTING guidelines?

[bm-w]

@mbostock Signed. Note that this PR is fairly old. I currently haven't got the time to update, but I'm sure the signature leaves anyone else who is interested free to do so (@o-o-, @ruphin, @chrisvfritz, @terite?).

[mbostock]

Finally looking at this now for 3.5. I love the diagram you made illustrating the different approaches. I think I’m inclined to approach B — truncating the radius if the arc is too thin — based on it being similar to how SVG treats rx and ry for rounded rects (per @deanmalmgren’s comment).

Also for backwards-compatibility (and based on expected usage), I think it makes sense to have the cornerRadius default to zero rather than default to an accessor like the other properties.

I plan on working on integrating this in the next few days.

[chrisvfritz]

🎉 !

[mbostock]

Fixed in #2118 for 3.5.