D3 Differentiate between click and drag for an element which has a drag behavior

Question

I am unable to successfully distinguish between the click event and the drag event on an element that is bound to both using D3.js v3. The circle in the code below is assigned a drag behaviour and also a click listener. Demo here

var dragGroup = d3.behavior.drag()
    .on('dragstart', function () {
    console.log('Start Dragging Group');
})
    .on('drag', function (d, i) {
    d.x += d3.event.dx;
    d.y += d3.event.dy;
    d3.select(this).attr("transform", "translate(" + d.x + "," + d.y + ")");
});

var dragCircle = d3.behavior.drag()
    .on('dragstart', function () {
    d3.event.sourceEvent.stopPropagation();
    d3.event.sourceEvent.preventDefault();
    console.log('Start Dragging Circle');
})
    .on('drag', function (d, i) {
    d.cx += d3.event.dx;
    d.cy += d3.event.dy;
    d3.select(this).attr('cx', d.cx).attr('cy', d.cy);
});

var svg = d3.select('body').append('svg').attr('viewBox', '-50 -50 300 300');
var g = svg.selectAll('g').data([{
    x: 10,
    y: 10
}])
    .enter().append('g').call(dragGroup);

g.append('rect').attr('width', 100).attr('height', 100);

g.selectAll('circle').data([{
    cx: 90,
    cy: 80
}]).enter()
    .append('circle')
    .attr('cx', function (d) {
    return d.cx;
})
    .attr('cy', function (d) {
    return d.cy;
})
    .attr('r', 30)
    .call(dragCircle)
    .on('click', function () {
    console.log('clicked circle');
});

Whenever I click the circle in the example I get the console logging the drag event aswell as the click event. I also get the same behavior when dragging, first the drag event is logged and on mouseup the click event gets logged.

What is the correct way to handle these events separately?
The use case is an attempt to handle a node-click and a node-drag/drop in a tree layout.

Answer 1

The key bit that's missing is the check whether the default behaviour of an event has been prevented. That is, there's a matching sibling to d3.event.preventDefault() -- d3.event.defaultPrevented. You need to check this in your click handler to see whether any dragging action is going on.

See also the answer to this question.