hover events for labels/legends

I would like to be able to know when the user hovers or clicks on my label or legend items. Specifically, I would like to be able to highlight a given pie slice or bar trace when a particular label or legend item is hovered over. d3pie does this, and an example can be seen here: http://d3pie.org/#generator-start

As a starting point, it would be useful to have this click handler fire an event after it calls Plotly.restyle or Plotly.relayout: https://github.com/plotly/plotly.js/blob/47b13b0c2ecffae3ecb0b37d957978f3004a7ac7/src/components/legend/index.js#L484

A hover handler for the same traces would help a lot as well.

[bruggsy]

For anybody looking to add hover events to the the Plotly legend, here’s are some simple events I added to the traceToggle item that highlights the hovered legend item using opacity:

`

traceToggle.on('mouseenter', function() {
var legendItem = g.data()[0][0],
    fullData = gd._fullData,
    trace = legendItem.trace,
    legendgroup = trace.legendgroup,
    tracei,
    allTraces = [],
    i,
    traceOpacity = [];

if(trace.visible === true){	    
        for(i = 0; i < fullData.length; i++) {
	allTraces.push(i);
	traceOpacity.push(
	    Registry.traceIs(fullData[i], 'notLegendIsolatable') ? 1.0: 0.1
	);
        }

    if(legendgroup === ''){
	traceOpacity[trace.index] = 1.0;
    } else{
	for(i = 0; i < fullData.length; i++) {
	    tracei = fullData[i];
	    if(tracei.legendgroup === legendgroup) {
		traceOpacity[allTraces.indexOf(i)] = 1.0;
	    }
	}
    }

    var update = {
	opacity: traceOpacity
    };
    Plotly.restyle(gd,update,allTraces);
}
});
traceToggle.on('mouseleave',function() {

var legendItem = g.data()[0][0],
    fullData = gd._fullData,
    trace = legendItem.trace,
    allTraces = [],
    i;
if(trace.visible === true){	    

    var update = {
	opacity: 1.0
    };
    for(i = 0; i < fullData.length; i++){
	allTraces.push(i);
    }

    Plotly.restyle(gd,update,allTraces);
}

});

`

[mauritzvdworm]

Another vote here.

Another use for this would be if you have a plot with a collection of line graphs corresponding to different groups. The user could then hover over the legend to highlight the particular plot similar to the d3pie example above.