D3 now supports Sizzle, preferring Sizzle to the native Selectors API if Sizzle
is available. Sizzle internally uses the native Selectors API and thus this
should have minimal performance implications; also, it allows you to use Sizzle
proprietary extensions such as ":first".
This commit also restricts the definition of the enter selection so that only
append and insert operations are defined. The other operations were generally
unsupported anyway, and it cleans up the code to have separate implementations
for insert and append. (I might enable additional operations in the future, such
as `filter`, `sort` and `each`, but this seems like a reasonable first pass.)
Includes, as the first behavior, a pan & zoom behavior. The canvas can be panned
by dragging the mouse, and zoomed using the mousewheel (or by double-click). By
listening to redraw events, users can decide whether to implement geometric
zooming (such as by setting the "transform" attribute on an `svg:g` element) or
semantic zooming (by changing the domain of a scale object and repositioning
elements).
This commit also includes two bug fixes. The `d3.format` class now properly
groups thousands of negative numbers, and supports the sign specifier. The
unicode minus symbol \u2212 is used for negative values. The `d3.scale.pow`
class now properly handles negative numbers, as well.
The data join is now specified as a single function of data, as with all other
properties. This allows the key to be computed on the previously-bound data,
rather than requiring the key to be serialized into the DOM (say, as an
attribute). In the case that there is no previously-bound data, it is still
possible to access the associated node as the `this` context.
The `enter` operator no longer performs an append. For symmetry with the `exit`
operator, you must call `append` after obtaining the entering selection. This
requires a tiny bit more code, but should make the code more clear. Also, it
provides an opportunity to use a different instantiation operator, such as the
new `insert` operator. This takes a second argument, which is a selector for the
insert-before reference element. For example, the selector ":first-child" will
prepend nodes.
The `empty` operator allows you to query whether a selection is empty (i.e.,
contains zero matching nodes).
Mike Bostock