CODEWITHSUNDEEP
javascriptcallbackd3.js
djq
djq

Reputation: 15286

Callbacks with D3

I'm using the D3 javascript library to dynamically change line thicknesses. What I want to achieve is a line that increase in thickness, and decreases in thickness, repeatedly constantly. To draw a line, I used the following code:

<!DOCTYPE html>
<html>
<head>  
      <script type="text/javascript" src="http://mbostock.github.com/d3/d3.js"></script>
</head>
<body>  
    <div id="D3line"></div>
            <script type="text/javascript">

            var lineSVG = d3.select("#D3line")  
                .append("svg:svg")
                .attr("width", 500)  
                .attr("height", 200);               

            var myLine = lineSVG.append("svg:line")
                .attr("x1", 60)
                .attr("y1", 60)
                .attr("x2", 450)
                .attr("y2", 150)
                .style("stroke", "rgb(6,120,155)")
                .style("stroke-opacity", 2);                


            </script>
</body>
</html>

Then, to change the line stroke thickness, I used the following code:

var lines = lineSVG.selectAll("line")   // select all lines 

function makeLinesThick()
{
    lines.transition().duration(500)
    .style("stroke-width", "5")
    .each("end", makeLinesThin);
}

function makeLinesThin(){
    lines.transition().duration(500)
    .style("stroke-width", "2")
    .each("end", makeLinesThick);
}

// call function to change lines
makeLinesThick()

However, I end up with this not running properly and getting an 'Unresponsive script' message in my browser. I'm not sure if I am structuring the callbacks properly in this case.

Edit: I changed my incorrect callback handling by removing the () in the .each() line.

Upvotes: 3

Views: 6527

Answers (3)

bailey
bailey

Reputation: 363

use .each("start") and .each("end") to set your transitions

Upvotes: 1

evanlikesstuff
evanlikesstuff

Reputation: 46

var mutateLine =
    function(line, t, width, altWidth) {
        d3.select(line).transition().duration(t).style("stroke-width", width)
        .each("end", function() {
            if ( mutateLine ) mutateLine(line, t, altWidth, width);
        });
    }

// assumes lines is obtained from d3.selectAll()
var mutateLines =
    function(lines, t, width, altWidth) {
        if ( !mutateLine)
            return;
        lines[0].forEach(function(line) {
            mutateLine(line, t, width, altWidth);
        }
    };

// start mutating
mutateLines(lines, 500, 5, 2);

// stop mutating
mutateLine = null;

Upvotes: 0

Lars Kotthoff
Lars Kotthoff

Reputation: 109232

The problem is that .each("end", ...) is called for every element that you're selecting. That is, makeLinesThin is called once for each line in makeLinesThick. This is what causes your browser to hang.

There are several ways you could make it work. You could change your code to do the transitions for each line individually (see the documentation for transition.each()) or you could schedule the transitions on all lines separately using settimeout(). Note in particular the documentation for transition.transition() -- you can schedule another transition before the current one is complete.

You might also want to have a look at d3.timer(), example here.

Upvotes: 6

Related Questions