File: vendors/jquery-sparkline/src/simpledraw.js

    // Provide a cross-browser interface to a few simple drawing primitives
    $.fn.simpledraw = function (width, height, useExisting, interact) {
        var target, mhandler;
        if (useExisting && (target = this.data('_jqs_vcanvas'))) {
            return target;
        }

        if ($.fn.sparkline.canvas === false) {
            // We've already determined that neither Canvas nor VML are available
            return false;

        } else if ($.fn.sparkline.canvas === undefined) {
            // No function defined yet -- need to see if we support Canvas or VML
            var el = document.createElement('canvas');
            if (!!(el.getContext && el.getContext('2d'))) {
                // Canvas is available
                $.fn.sparkline.canvas = function(width, height, target, interact) {
                    return new VCanvas_canvas(width, height, target, interact);
                };
            } else if (document.namespaces && !document.namespaces.v) {
                // VML is available
                document.namespaces.add('v', 'urn:schemas-microsoft-com:vml', '#default#VML');
                $.fn.sparkline.canvas = function(width, height, target, interact) {
                    return new VCanvas_vml(width, height, target);
                };
            } else {
                // Neither Canvas nor VML are available
                $.fn.sparkline.canvas = false;
                return false;
            }
        }

        if (width === undefined) {
            width = $(this).innerWidth();
        }
        if (height === undefined) {
            height = $(this).innerHeight();
        }

        target = $.fn.sparkline.canvas(width, height, this, interact);

        mhandler = $(this).data('_jqs_mhandler');
        if (mhandler) {
            mhandler.registerCanvas(target);
        }
        return target;
    };

    $.fn.cleardraw = function () {
        var target = this.data('_jqs_vcanvas');
        if (target) {
            target.reset();
        }
    };