The drawing API Background object API reference

• Usage example
• Properties
• Methods

The background object allows you to add a background to your charts should you need to. An example use might be when you want the background grid to be clickable (ie have a tooltip). In this case, you can use the Background drawing api object (and its own margin settings) to make a grid that spans the whole of the desired area.

The Background object can have its own tooltip and also its own click and mousemove events so if you want to make the whole chart area clickable this is one way that you can do that.

Usage example

<script>
    new RGraph.Drawing.Background({
        id: 'cvs',
        options: {
            title: 'The background object',
            tooltips: ['The drawing API background object'],
            tooltipsCss: {
                fontSize: '16pt'
            },
            textSize: 18,
            textBold: true
        }
    }).draw();
</script>

Properties

• Margin properties
• Background properties
• X-axis properties
• Y-axis properties
• Labels and text properties
• Title properties
• Interactive features properties
• Miscellaneous properties

<div style="margin-left: 50px; display: inline-block">
    <canvas id="cvs" width="650" height="250"></canvas>
</div>

tooltipsFormattedListItems: [
    ['Bill','Jerry','Berty'], // First tooltip
    ['Gill','Carrie','Lucy'], // Second tooltip
    ['Pob','Nobby','Hilda']   // Third tooltip
]

.RGraph_tooltip ul#rgraph_formatted_tooltips_list li {
    text-align: left;
    color: yellow;
}

tooltips: {
    borderLeft: 'gray 2px solid',
    borderBottom: 'gray 2px solid'
}

tooltipsCss: {
    fontFamily: 'Verdana',
    fontSize: '20pt'
}

Methods

<script>
    background.canvas.onclick = function (e)
    {
        RGraph.redraw();
    
        var canvas = e.target,
            obj    = canvas.__object__,
            shape  = obj.getShape(e),
            prop   = obj.properties,
            width  = canvas.width - prop.marginLeft - prop.marginRight,
            height = canvas.height - prop.marginTop - prop.marginBottom;

        if (shape) {            
            // Highlight the main body of the Background object.
            obj.path(
                'lw 10 b r % % % % s black f rgba(255,0,0,0.25)',
                prop.marginLeft, prop.marginTop, width, height
            );
        }
    }
</script>

This method can be used to set an event listener on an object. It operates similarly to the jquery on function. The first argument is the event that you wish to attach to and the second is the handler function. For example:

obj.on('draw', function (obj)
{
    // Put your event code here
});

The function is useful if you use method chaining when creating your charts:

var obj = new RGraph.Drawing.Background({
    id: 'cvs',
}).on('draw', function (obj)
{
    // Put your draw event code here

}).on('click', function (e, shape)
{
    // Handle the click event

}).draw();

The exec function is documented here.