How to make your line clickable (isPointInStroke)

Summary: A guide for making the whole line clickable with the new isPointInStroke() function - not just the points along that line.

Currently you can use the drawing API Poly object to draw a shape around your line and then use the Poly objects tooltip or events to add interactivity. Now though, since the addition of the isPointInStroke() function, the process is made much easier as the example below shows. It involves:

• Draw your Line chart as normal
• Add a draw event listener that draws a transparent line using of the Line chart coordinates
• Since this transparent line is the last path drawn on the canvas we can add a click event and test using the isPointInStroke() function.
• If the test is positive - the line has been clicked.

1. The original Line chart

Here is the original Line chart before the new path is created.

[No canvas support]

<script>
    line = new RGraph.Line({
        id: 'cvs',
        data: [4,8,6,3,5,2,4],
        options: {
            marginInner: 15,
            linewidth: 5,
            xaxisLabels: ['Mon','Tue','Wed','Thu','Fri','Sat','Sun'],
            backgroundGridVlinesCount: 6,
            textSize: 14
        }
    }).draw();
</script>

2. The Line chart with the draw event listener

Now a draw event listener is added that draws a line. Since this is drawn after the line chart it will be the last path that is drawn on the canvas. Normally you would make this a transparent color - but so that you can see it, it's been drawn in semi-opaque black.

[No canvas support]

<script>
    line = new RGraph.Line({
        id: 'cvs',
        data: [4,8,6,3,5,2,4],
        options: {
            marginInner: 15,
            linewidth: 5,
            xaxisLabels: ['Mon','Tue','Wed','Thu','Fri','Sat','Sun'],
            backgroundGridVlinesCount: 6,
            textSize: 14
        }
    }).on('draw', function (obj)
    {
        var co     = obj.context;
        var coords = obj.coords

        co.beginPath();
            co.lineWidth = 7;
            co.strokeStyle = 'rgba(0,0,0,0.25)';
            
            co.moveTo(coords[0][0], coords[0][1]);
            
            
            for (var i=1; i<coords.length; i+=1) {
                co.lineTo(coords[i][0], coords[i][1]);
            }
        co.stroke();
    }).draw();
</script>

3. The Line chart with the draw event listener and the click event listener

Now the click event is added to the canvas. Since the line that we drew using the Line chart coordinates was the last path added to the canvas the isPointInStroke() function can be used to see if the path (ie the line) was clicked.

[No canvas support]

<script>
    line = new RGraph.Line({
        id: 'cvs',
        data: [4,8,6,3,5,2,4],
        options: {
            marginInner: 15,
            linewidth: 5,
            xaxisLabels: ['Mon','Tue','Wed','Thu','Fri','Sat','Sun'],
            backgroundGridVlinesCount: 6,
            textSize: 14
        }
    }).on('draw', function (obj)
    {
        var co     = obj.context;
        var coords = obj.coords

        co.beginPath();
            co.lineWidth = 7;
            co.strokeStyle = 'rgba(0,0,0,0.25)';
            
            co.moveTo(coords[0][0], coords[0][1]);
            
            
            for (var i=1; i<coords.length; i+=1) {
                co.lineTo(coords[i][0], coords[i][1]);
            }
        co.stroke();
    }).on('mousemove', function (e)
    {
        var mouseXY = RGraph.getMouseXY(e);

        if (line.context.isPointInStroke(mouseXY[0], mouseXY[1])) {
            e.target.style.cursor = 'pointer';
        } else {
            e.target.style.cursor = 'default';
        }
    }).on('click', function (e)
    {
        var mouseXY = RGraph.getMouseXY(e);

        if (line.context.isPointInStroke(mouseXY[0], mouseXY[1])) {
            alert('The line was clicked');
        }
    }).draw();
</script>