Rather than producing separate files for each module, the default build now
produces a single file. This should encourage better page-load performance as
the files were relatively small. Also, it's easier to deal with only one file
rather than many, especially if you're not quite sure what the dependencies are.
You may still create minimized builds, if you don't want every feature.
This commit also demotes the chart components to the examples directory, rather
than keeping them as part of the core library. As always, D3 is not a charting
library, and these were ever only intended to serve as examples.
There's an edge condition which is not discussed in the original algorithm
("Visualization of Large Hierarchical Data by Circle Packing", Wang et. al):
what happens if the first intersecting circle C_j is equidistant from C_m and
C_n? In other words, it is both after C_n on the front-chain, and before C_m.
The correct answer is that you should splice the smaller of the two circles. If
C_m is smaller than C_n, then splice from C_j to C_n and set C_m to C_j;
otherwise, splice from C_m to C_j, and set C_n to C_j.
This test makes sure NaN doesn't creep in due to Math.acos being called
on numbers like +/- 1.000000000004, so it's more descriptive to check
isNaN rather than the exact numerical results.
Mike Bostock
Jon Seymour
Jason Davies