Merge branch 'tapDistance-180' into two

README.md

@@ -69,7 +69,7 @@ The propagation of all consumed events is [immediately stopped](https://dom.spec
 <br>³ Only applies immediately after some mouse-based gestures; see [*zoom*.clickDistance](#zoom_clickDistance).
 <br>⁴ Necessary to allow [click emulation](https://developer.apple.com/library/ios/documentation/AppleApplications/Reference/SafariWebContent/HandlingEvents/HandlingEvents.html#//apple_ref/doc/uid/TP40006511-SW7) on touch input; see [d3-drag#9](https://github.com/d3/d3-drag/issues/9).
 <br>⁵ Ignored if within 500ms of a touch gesture ending; assumes [click emulation](https://developer.apple.com/library/ios/documentation/AppleApplications/Reference/SafariWebContent/HandlingEvents/HandlingEvents.html#//apple_ref/doc/uid/TP40006511-SW7).
-<br>⁶ Double-click and double-tap initiate a transition that emits start, zoom and end events.
+<br>⁶ Double-click and double-tap initiate a transition that emits start, zoom and end events; see [*zoom*.tapDistance](#zoom_tapDistance)..
 <br>⁷ The first wheel event emits a start event; an end event is emitted when no wheel events are received for 150ms.
 <br>⁸ Ignored if already at the corresponding limit of the [scale extent](#zoom_scaleExtent).
 
@@ -220,6 +220,10 @@ If *extent* is specified, sets the translate extent to the specified array of po
 
 If *distance* is specified, sets the maximum distance that the mouse can move between mousedown and mouseup that will trigger a subsequent click event. If at any point between mousedown and mouseup the mouse is greater than or equal to *distance* from its position on mousedown, the click event following mouseup will be suppressed. If *distance* is not specified, returns the current distance threshold, which defaults to zero. The distance threshold is measured in client coordinates ([*event*.clientX](https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/clientX) and [*event*.clientY](https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/clientY)).
 
+<a href="#zoom_tapDistance" name="zoom_tapDistance">#</a> <i>zoom</i>.<b>tapDistance</b>([<i>distance</i>]) · [Source](https://github.com/d3/d3-zoom/blob/master/src/zoom.js)
+
+If *distance* is specified, sets the maximum distance that a double-tap gesture can move between first touchstart and second touchend that will trigger a subsequent double-click event. If *distance* is not specified, returns the current distance threshold, which defaults to 10. The distance threshold is measured in client coordinates ([*event*.clientX](https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/clientX) and [*event*.clientY](https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/clientY)).
+
 <a href="#zoom_duration" name="zoom_duration">#</a> <i>zoom</i>.<b>duration</b>([<i>duration</i>]) · [Source](https://github.com/d3/d3-zoom/blob/master/src/zoom.js)
 
 If *duration* is specified, sets the duration for zoom transitions on double-click and double-tap to the specified number of milliseconds and returns the zoom behavior. If *duration* is not specified, returns the current duration, which defaults to 250 milliseconds. If the duration is not greater than zero, double-click and -tap trigger instantaneous changes to the zoom transform rather than initiating smooth transitions.

src/zoom.js

@@ -61,10 +61,12 @@ export default function() {
       interpolate = interpolateZoom,
       listeners = dispatch("start", "zoom", "end"),
       touchstarting,
+      touchfirst,
       touchending,
       touchDelay = 500,
       wheelDelay = 150,
-      clickDistance2 = 0;
+      clickDistance2 = 0,
+      tapDistance = 10;
 
   function zoom(selection) {
     selection
@@ -328,7 +330,7 @@ export default function() {
     if (touchstarting) touchstarting = clearTimeout(touchstarting);
 
     if (started) {
-      if (g.taps < 2) touchstarting = setTimeout(function() { touchstarting = null; }, touchDelay);
+      if (g.taps < 2) touchfirst = p[0], touchstarting = setTimeout(function() { touchstarting = null; }, touchDelay);
       interrupt(this);
       g.start();
     }
@@ -341,8 +343,6 @@ export default function() {
         n = touches.length, i, t, p, l;
 
     noevent(event);
-    if (touchstarting) touchstarting = clearTimeout(touchstarting);
-    g.taps = 0;
     for (i = 0; i < n; ++i) {
       t = touches[i], p = pointer(t, this);
       if (g.touch0 && g.touch0[2] === t.identifier) g.touch0[0] = p;
@@ -360,6 +360,7 @@ export default function() {
     }
     else if (g.touch0) p = g.touch0[0], l = g.touch0[1];
     else return;
+
     g.zoom("touch", constrain(translate(t, p, l), g.extent, translateExtent));
   }
 
@@ -383,8 +384,11 @@ export default function() {
       g.end();
       // If this was a dbltap, reroute to the (optional) dblclick.zoom handler.
       if (g.taps === 2) {
-        var p = select(this).on("dblclick.zoom");
-        if (p) p.apply(this, arguments);
+        t = pointer(t, this);
+        if (Math.hypot(touchfirst[0] - t[0], touchfirst[1] - t[1]) < tapDistance) {
+          var p = select(this).on("dblclick.zoom");
+          if (p) p.apply(this, arguments);
+        }
       }
     }
   }
@@ -434,5 +438,9 @@ export default function() {
     return arguments.length ? (clickDistance2 = (_ = +_) * _, zoom) : Math.sqrt(clickDistance2);
   };
 
+  zoom.tapDistance = function(_) {
+    return arguments.length ? (tapDistance = +_, zoom) : tapDistance;
+  };
+
   return zoom;
 }