Easier programmatic zooming.

Setting the translate and scale now propagates the changes to the scale domains
in the same manner as user interaction. Likewise, setting new scales resets the
translate and scale back to their default values ([0, 0] and 1 respectively).

d3.js

@@ -5245,13 +5245,16 @@
       translate[0] += p[0] - l[0];
       translate[1] += p[1] - l[1];
     }
-    function dispatch(event) {
+    function rescale() {
       if (x1) x1.domain(x0.range().map(function(x) {
         return (x - translate[0]) / scale;
       }).map(x0.invert));
       if (y1) y1.domain(y0.range().map(function(y) {
         return (y - translate[1]) / scale;
       }).map(y0.invert));
+    }
+    function dispatch(event) {
+      rescale();
       d3.event.preventDefault();
       event({
         type: "zoom",
@@ -5327,11 +5330,13 @@
     zoom.translate = function(x) {
       if (!arguments.length) return translate;
       translate = x.map(Number);
+      rescale();
       return zoom;
     };
     zoom.scale = function(x) {
       if (!arguments.length) return scale;
       scale = +x;
+      rescale();
       return zoom;
     };
     zoom.scaleExtent = function(x) {
@@ -5343,12 +5348,16 @@
       if (!arguments.length) return x1;
       x1 = z;
       x0 = z.copy();
+      translate = [ 0, 0 ];
+      scale = 1;
       return zoom;
     };
     zoom.y = function(z) {
       if (!arguments.length) return y1;
       y1 = z;
       y0 = z.copy();
+      translate = [ 0, 0 ];
+      scale = 1;
       return zoom;
     };
     return d3.rebind(zoom, event, "on");