Function dragstart

d3-3.2.8/d3.js:1115–1148

(id, position, move, end)

      })[0];
    }
    function dragstart(id, position, move, end) {
      return function() {
        var target = this, parent = target.parentNode, event_ = event.of(target, arguments), eventTarget = d3.event.target, eventId = id(), drag = eventId == null ? "drag" : "drag-" + eventId, origin_ = position(parent, eventId), dragged = 0, offset, w = d3.select(d3_window).on(move + "." + drag, moved).on(end + "." + drag, ended), dragRestore = d3_event_dragSuppress();
        if (origin) {
          offset = origin.apply(target, arguments);
          offset = [ offset.x - origin_[0], offset.y - origin_[1] ];
        } else {
          offset = [ 0, 0 ];
        }
        event_({
          type: "dragstart"
        });
        function moved() {
          if (!parent) return ended();
          var p = position(parent, eventId), dx = p[0] - origin_[0], dy = p[1] - origin_[1];
          dragged |= dx | dy;
          origin_ = p;
          event_({
            type: "drag",
            x: p[0] + offset[0],
            y: p[1] + offset[1],
            dx: dx,
            dy: dy
          });
        }
        function ended() {
          w.on(move + "." + drag, null).on(end + "." + drag, null);
          dragRestore(dragged && d3.event.target === eventTarget);
          event_({
            type: "dragend"
          });
        }
      };
    }
    drag.origin = function(x) {
      if (!arguments.length) return origin;
      origin = x;