Using the quadtree structure to search closest point (pointing in protovis)

[Ricardo]

I'm doing a scatter chart for which I would like to show point labels
as the mouse moves close to those points (same behavior as in
protovis). I could search for the minimum distance from the mouse to
all the points but that seems like a very intensive operation for
"mousemove". I'm assuming a quadtree will help here. Divide and
conquer.

After looking at the quadtree class https://github.com/mbostock/d3/blob/master/src/geom/quadtree.js
I can't find a very nice method such as quadtree.closest(x,y) that
returns a list of the closest nodes (a list because if there are
various nodes at the same location I would like to have them all).
Before embarking in doing this I would like to know if there is
already such function somewhere?

[Danny Korenblum]

this example should help:

http://bl.ocks.org/mbostock/4343214

see the 

function search(quadtree, x0, y0, x3, y3) {
  quadtree.visit(function(node, x1, y1, x2, y2)

part of the code, the visit() function gets called recursively as described in

https://github.com/mbostock/d3/wiki/Quadtree-Geom