1 d3.behavior.drag = function() {

     2   var event = d3.dispatch("drag", "dragstart", "dragend");

     3 

     4   function drag() {

     5     this

     6         .on("mousedown.drag", mousedown)

     7         .on("touchstart.drag", mousedown);

     8 

     9     d3.select(window)

    10         .on("mousemove.drag", d3_behavior_dragMove)

    11         .on("touchmove.drag", d3_behavior_dragMove)

    12         .on("mouseup.drag", d3_behavior_dragUp, true)

    13         .on("touchend.drag", d3_behavior_dragUp, true)

    14         .on("click.drag", d3_behavior_dragClick, true);

    15   }

    16 

    17   // snapshot the local context for subsequent dispatch

    18   function start() {

    19     d3_behavior_dragEvent = event;

    20     d3_behavior_dragEventTarget = d3.event.target;

    21     d3_behavior_dragOffset = d3_behavior_dragPoint((d3_behavior_dragTarget = this).parentNode);

    22     d3_behavior_dragMoved = 0;

    23     d3_behavior_dragArguments = arguments;

    24   }

    25 

    26   function mousedown() {

    27     start.apply(this, arguments);

    28     d3_behavior_dragDispatch("dragstart");

    29   }

    30 

    31   drag.on = function(type, listener) {

    32     event.on(type, listener);

    33     return drag;

    34   };

    35 

    36   return drag;

    37 };

    38 

    39 var d3_behavior_dragEvent,

    40     d3_behavior_dragEventTarget,

    41     d3_behavior_dragTarget,

    42     d3_behavior_dragArguments,

    43     d3_behavior_dragOffset,

    44     d3_behavior_dragMoved,

    45     d3_behavior_dragStopClick;

    46 

    47 function d3_behavior_dragDispatch(type) {

    48   var o = d3.event, p = d3_behavior_dragTarget.parentNode, dx = 0, dy = 0;

    49 

    50   if (p) {

    51     p = d3_behavior_dragPoint(p);

    52     dx = p[0] - d3_behavior_dragOffset[0];

    53     dy = p[1] - d3_behavior_dragOffset[1];

    54     d3_behavior_dragOffset = p;

    55     d3_behavior_dragMoved |= dx | dy;

    56   }

    57 

    58   try {

    59     d3.event = {dx: dx, dy: dy};

    60     d3_behavior_dragEvent[type].apply(d3_behavior_dragTarget, d3_behavior_dragArguments);

    61   } finally {

    62     d3.event = o;

    63   }

    64 

    65   o.preventDefault();

    66 }

    67 

    68 function d3_behavior_dragPoint(container, type) {

    69   // TODO Track touch points by identifier.

    70   var t = d3.event.changedTouches;

    71   return t ? d3.svg.touches(container, t)[0] : d3.svg.mouse(container);

    72 }

    73 

    74 function d3_behavior_dragMove() {

    75   if (!d3_behavior_dragTarget) return;

    76   var parent = d3_behavior_dragTarget.parentNode;

    77 

    78   // O NOES! The drag element was removed from the DOM.

    79   if (!parent) return d3_behavior_dragUp();

    80 

    81   d3_behavior_dragDispatch("drag");

    82   d3_eventCancel();

    83 }

    84 

    85 function d3_behavior_dragUp() {

    86   if (!d3_behavior_dragTarget) return;

    87   d3_behavior_dragDispatch("dragend");

    88   d3_behavior_dragTarget = null;

    89 

    90   // If the node was moved, prevent the mouseup from propagating.

    91   // Also prevent the subsequent click from propagating (e.g., for anchors).

    92   if (d3_behavior_dragMoved && d3_behavior_dragEventTarget === d3.event.target) {

    93     d3_behavior_dragStopClick = true;

    94     d3_eventCancel();

    95   }

    96 }

    97 

    98 function d3_behavior_dragClick() {

    99   if (d3_behavior_dragStopClick && d3_behavior_dragEventTarget === d3.event.target) {

   100     d3_eventCancel();

   101     d3_behavior_dragStopClick = false;

   102     d3_behavior_dragEventTarget = null;

   103   }

   104 }