Use #map.node() for drag surface instead of svg #surface

This is because #surface can be transformed during a partial redraw
and d3.mouse() returns transformed point, not the real screen point.
a2cf4f32ec/src/point.js (L4-L9)

modules/behavior/drag.js

@@ -60,7 +60,7 @@ export function behaviorDrag() {
             };
 
 
-    function mousedown() {
+    function dragstart() {
         target = this;
         event_ = eventOf(target, arguments);
 
@@ -84,8 +84,9 @@ export function behaviorDrag() {
 
         if (touchId === null) d3.event.stopPropagation();
 
+
         function point() {
-            var p = target.parentNode || surface;
+            var p = surface || target.parentNode;
             return touchId !== null ? d3.touches(p).filter(function(p) {
                 return p.identifier === touchId;
             })[0] : d3.mouse(p);
@@ -143,7 +144,7 @@ export function behaviorDrag() {
 
     function drag(selection) {
         var matchesSelector = utilPrefixDOMProperty('matchesSelector'),
-            delegate = mousedown;
+            delegate = dragstart;
 
         if (selector) {
             delegate = function() {
@@ -152,7 +153,7 @@ export function behaviorDrag() {
                 for (; target && target !== root; target = target.parentNode) {
                     if (target[matchesSelector](selector) &&
                             (!filter || filter(target.__data__))) {
-                        return mousedown.call(target, target.__data__);
+                        return dragstart.call(target, target.__data__);
                     }
                 }
             };

modules/modes/drag_node.js

@@ -152,11 +152,6 @@ export function modeDragNode(context) {
             loc = context.projection.invert(currMouse),
             d = datum();
 
-console.log('event.point = ' + (d3.event && d3.event.point) +
-    ', currMouse = ' + currMouse +
-    ', context.mouse = ' + context.mouse()
-);
-
         if (d.type === 'node' && d.id !== entity.id) {
             loc = d.loc;
         } else if (d.type === 'way' && !d3.select(d3.event.sourceEvent.target).classed('fill')) {
@@ -241,7 +236,7 @@ console.log('event.point = ' + (d3.event && d3.event.point) +
 
     var behavior = behaviorDrag()
         .delegate('g.node, g.point, g.midpoint')
-        .surface(context.surface().node())
+        .surface(d3.select('#map').node())
         .origin(origin)
         .on('start', start)
         .on('move', move)