user3701098 user3701098 - 6 months ago 64
Javascript Question

Drag a Line in d3

I've created a line in d3, which I want to drag around.

var line = d3.select("svg")
.append("line")
.attr("x1",10)
.attr("y1",10)
.attr("x2",200)
.attr("y2",200)
.attr("stroke-width",10)
.attr("stroke","black")
.call(drag);


The problem I have right now, is how to move both Points (x1,y1) (x2,y2) from the line relative to my mouse position, as I probably will need the dragstart mouse position as well.

let drag = d3.behavior.drag()
.on('dragstart', null)
.on('drag', function(){
// move circle
let x1New = d3.select(this).attr('x1')+ ???;
let y1New = d3.select(this).attr('y1')+ ???;
let x2New = d3.select(this).attr('x2')+ ???;
let y2New = d3.select(this).attr('y2')+ ???;
line.attr("x1",x1New)
.attr("y1",y1New)
.attr("x2",x2New)
.attr("y2",y2New);
})
.on('dragend', function(){
});


I hope you can help me with that.

Answer

Do it like this inside your drag function:

.on('drag', function(d){
             // move circle
             var dx = d3.event.dx;//this will give the delta x moved by drag
             var dy = d3.event.dy;//this will give the delta y moved by drag
             var x1New = parseFloat(d3.select(this).attr('x1'))+ dx;
             var y1New = parseFloat(d3.select(this).attr('y1'))+ dy;
             var x2New = parseFloat(d3.select(this).attr('x2'))+ dx;
             var y2New = parseFloat(d3.select(this).attr('y2'))+ dy;
             line.attr("x1",x1New)
                 .attr("y1",y1New)
                 .attr("x2",x2New)
                 .attr("y2",y2New);
             }).on('dragend', function(){
           }); 

working code here

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