todo/public/vendor/jquery-sparkline/src/vcanvas-canvas.js

    VCanvas_canvas = createClass(VCanvas_base, {
        init: function (width, height, target, interact) {
            VCanvas_canvas._super.init.call(this, width, height, target);
            this.canvas = document.createElement('canvas');
            if (target[0]) {
                target = target[0];
            }
            $.data(target, '_jqs_vcanvas', this);
            $(this.canvas).css({ display: 'inline-block', width: width, height: height, verticalAlign: 'top' });
            this._insert(this.canvas, target);
            this._calculatePixelDims(width, height, this.canvas);
            this.canvas.width = this.pixelWidth;
            this.canvas.height = this.pixelHeight;
            this.interact = interact;
            this.shapes = {};
            this.shapeseq = [];
            this.currentTargetShapeId = undefined;
            $(this.canvas).css({width: this.pixelWidth, height: this.pixelHeight});
        },

        _getContext: function (lineColor, fillColor, lineWidth) {
            var context = this.canvas.getContext('2d');
            if (lineColor !== undefined) {
                context.strokeStyle = lineColor;
            }
            context.lineWidth = lineWidth === undefined ? 1 : lineWidth;
            if (fillColor !== undefined) {
                context.fillStyle = fillColor;
            }
            return context;
        },

        reset: function () {
            var context = this._getContext();
            context.clearRect(0, 0, this.pixelWidth, this.pixelHeight);
            this.shapes = {};
            this.shapeseq = [];
            this.currentTargetShapeId = undefined;
        },

        _drawShape: function (shapeid, path, lineColor, fillColor, lineWidth) {
            var context = this._getContext(lineColor, fillColor, lineWidth),
                i, plen;
            context.beginPath();
            context.moveTo(path[0][0] + 0.5, path[0][1] + 0.5);
            for (i = 1, plen = path.length; i < plen; i++) {
                context.lineTo(path[i][0] + 0.5, path[i][1] + 0.5); // the 0.5 offset gives us crisp pixel-width lines
            }
            if (lineColor !== undefined) {
                context.stroke();
            }
            if (fillColor !== undefined) {
                context.fill();
            }
            if (this.targetX !== undefined && this.targetY !== undefined &&
                context.isPointInPath(this.targetX, this.targetY)) {
                this.currentTargetShapeId = shapeid;
            }
        },

        _drawCircle: function (shapeid, x, y, radius, lineColor, fillColor, lineWidth) {
            var context = this._getContext(lineColor, fillColor, lineWidth);
            context.beginPath();
            context.arc(x, y, radius, 0, 2 * Math.PI, false);
            if (this.targetX !== undefined && this.targetY !== undefined &&
                context.isPointInPath(this.targetX, this.targetY)) {
                this.currentTargetShapeId = shapeid;
            }
            if (lineColor !== undefined) {
                context.stroke();
            }
            if (fillColor !== undefined) {
                context.fill();
            }
        },

        _drawPieSlice: function (shapeid, x, y, radius, startAngle, endAngle, lineColor, fillColor) {
            var context = this._getContext(lineColor, fillColor);
            context.beginPath();
            context.moveTo(x, y);
            context.arc(x, y, radius, startAngle, endAngle, false);
            context.lineTo(x, y);
            context.closePath();
            if (lineColor !== undefined) {
                context.stroke();
            }
            if (fillColor) {
                context.fill();
            }
            if (this.targetX !== undefined && this.targetY !== undefined &&
                context.isPointInPath(this.targetX, this.targetY)) {
                this.currentTargetShapeId = shapeid;
            }
        },

        _drawRect: function (shapeid, x, y, width, height, lineColor, fillColor) {
            return this._drawShape(shapeid, [[x, y], [x + width, y], [x + width, y + height], [x, y + height], [x, y]], lineColor, fillColor);
        },

        appendShape: function (shape) {
            this.shapes[shape.id] = shape;
            this.shapeseq.push(shape.id);
            this.lastShapeId = shape.id;
            return shape.id;
        },

        replaceWithShape: function (shapeid, shape) {
            var shapeseq = this.shapeseq,
                i;
            this.shapes[shape.id] = shape;
            for (i = shapeseq.length; i--;) {
                if (shapeseq[i] == shapeid) {
                    shapeseq[i] = shape.id;
                }
            }
            delete this.shapes[shapeid];
        },

        replaceWithShapes: function (shapeids, shapes) {
            var shapeseq = this.shapeseq,
                shapemap = {},
                sid, i, first;

            for (i = shapeids.length; i--;) {
                shapemap[shapeids[i]] = true;
            }
            for (i = shapeseq.length; i--;) {
                sid = shapeseq[i];
                if (shapemap[sid]) {
                    shapeseq.splice(i, 1);
                    delete this.shapes[sid];
                    first = i;
                }
            }
            for (i = shapes.length; i--;) {
                shapeseq.splice(first, 0, shapes[i].id);
                this.shapes[shapes[i].id] = shapes[i];
            }

        },

        insertAfterShape: function (shapeid, shape) {
            var shapeseq = this.shapeseq,
                i;
            for (i = shapeseq.length; i--;) {
                if (shapeseq[i] === shapeid) {
                    shapeseq.splice(i + 1, 0, shape.id);
                    this.shapes[shape.id] = shape;
                    return;
                }
            }
        },

        removeShapeId: function (shapeid) {
            var shapeseq = this.shapeseq,
                i;
            for (i = shapeseq.length; i--;) {
                if (shapeseq[i] === shapeid) {
                    shapeseq.splice(i, 1);
                    break;
                }
            }
            delete this.shapes[shapeid];
        },

        getShapeAt: function (el, x, y) {
            this.targetX = x;
            this.targetY = y;
            this.render();
            return this.currentTargetShapeId;
        },

        render: function () {
            var shapeseq = this.shapeseq,
                shapes = this.shapes,
                shapeCount = shapeseq.length,
                context = this._getContext(),
                shapeid, shape, i;
            context.clearRect(0, 0, this.pixelWidth, this.pixelHeight);
            for (i = 0; i < shapeCount; i++) {
                shapeid = shapeseq[i];
                shape = shapes[shapeid];
                this['_draw' + shape.type].apply(this, shape.args);
            }
            if (!this.interact) {
                // not interactive so no need to keep the shapes array
                this.shapes = {};
                this.shapeseq = [];
            }
        }

    });