Gnuplot canvas terminal mouse coordinates

Hello,

I'm using the gnuplot canvas terminal, starting with some of Ethan
Merritt's demo page stuff to show some plots where the x axis goes
from, say, 3590.01 to 3590.42. (infrared spectra with wavenumber)

The returned coordinates on the canvas and in the HTML table (mb0 and
mb1) have very poor resolution, so that it only shows 3590 wherever I
move or click the mouse.

I tried hacking the gnuplot_mouse.js file by changing the
x.toPrecision( ) call, but that didn't help.
How can I increase the resolution of the returned coordinates to
something like %9.4f

Any help is greatly appreciated!

I'm using Perl 5.10.0, Gnuplot 4.4, Apache 2.2.21, Firefox 12.0 all
running on MacOS 10.6.8
.