     
    // Class: $.jqplot.CanvasGridRenderer
    // The default jqPlot grid renderer, creating a grid on a canvas element.
    // The renderer has no additional options beyond the <Grid> class.
    $.jqplot.CanvasGridRenderer = function(){
        this.shadowRenderer = new $.jqplot.ShadowRenderer();
    };
    
    // called with context of Grid object
    $.jqplot.CanvasGridRenderer.prototype.init = function(options) {
        this._ctx;
        $.extend(true, this, options);
        // set the shadow renderer options
        var sopts = {lineJoin:'miter', lineCap:'round', fill:false, isarc:false, angle:this.shadowAngle, offset:this.shadowOffset, alpha:this.shadowAlpha, depth:this.shadowDepth, lineWidth:this.shadowWidth, closePath:false, strokeStyle:this.shadowColor};
        this.renderer.shadowRenderer.init(sopts);
    };
    
    // called with context of Grid.
    $.jqplot.CanvasGridRenderer.prototype.createElement = function(plot) {
        var elem;
        // Memory Leaks patch
        if (this._elem) {
          if ($.jqplot.use_excanvas && window.G_vmlCanvasManager.uninitElement !== undefined) {
            elem = this._elem.get(0);
            window.G_vmlCanvasManager.uninitElement(elem);
            elem = null;
          }
          
          this._elem.emptyForce();
          this._elem = null;
        }
      
        elem = plot.canvasManager.getCanvas();

        var w = this._plotDimensions.width;
        var h = this._plotDimensions.height;
        elem.width = w;
        elem.height = h;
        this._elem = $(elem);
        this._elem.addClass('jqplot-grid-canvas');
        this._elem.css({ position: 'absolute', left: 0, top: 0 });
        
        elem = plot.canvasManager.initCanvas(elem);

        this._top = this._offsets.top;
        this._bottom = h - this._offsets.bottom;
        this._left = this._offsets.left;
        this._right = w - this._offsets.right;
        this._width = this._right - this._left;
        this._height = this._bottom - this._top;
        // avoid memory leak
        elem = null;
        return this._elem;
    };
    
    $.jqplot.CanvasGridRenderer.prototype.draw = function() {
        this._ctx = this._elem.get(0).getContext("2d");
        var ctx = this._ctx;
        var axes = this._axes;
        // Add the grid onto the grid canvas.  This is the bottom most layer.
        ctx.save();
        ctx.clearRect(0, 0, this._plotDimensions.width, this._plotDimensions.height);
        ctx.fillStyle = this.backgroundColor || this.background;
        ctx.fillRect(this._left, this._top, this._width, this._height);
        
        ctx.save();
        ctx.lineJoin = 'miter';
        ctx.lineCap = 'butt';
        ctx.lineWidth = this.gridLineWidth;
        ctx.strokeStyle = this.gridLineColor;
        var b, e, s, m;
        var ax = ['xaxis', 'yaxis', 'x2axis', 'y2axis'];
        for (var i=4; i>0; i--) {
            var name = ax[i-1];
            var axis = axes[name];
            var ticks = axis._ticks;
            var numticks = ticks.length;
            if (axis.show) {
                if (axis.drawBaseline) {
                    var bopts = {};
                    if (axis.baselineWidth !== null) {
                        bopts.lineWidth = axis.baselineWidth;
                    }
                    if (axis.baselineColor !== null) {
                        bopts.strokeStyle = axis.baselineColor;
                    }
                    switch (name) {
                        case 'xaxis':
                            drawLine (this._left, this._bottom, this._right, this._bottom, bopts);
                            break;
                        case 'yaxis':
                            drawLine (this._left, this._bottom, this._left, this._top, bopts);
                            break;
                        case 'x2axis':
                            drawLine (this._left, this._bottom, this._right, this._bottom, bopts);
                            break;
                        case 'y2axis':
                            drawLine (this._right, this._bottom, this._right, this._top, bopts);
                            break;
                    }
                }
                for (var j=numticks; j>0; j--) {
                    var t = ticks[j-1];
                    if (t.show) {
                        var pos = Math.round(axis.u2p(t.value)) + 0.5;
                        switch (name) {
                            case 'xaxis':
                                // draw the grid line if we should
                                if (t.showGridline && this.drawGridlines && ((!t.isMinorTick && axis.drawMajorGridlines) || (t.isMinorTick && axis.drawMinorGridlines)) ) {
                                    drawLine(pos, this._top, pos, this._bottom);
                                }
                                // draw the mark
                                if (t.showMark && t.mark && ((!t.isMinorTick && axis.drawMajorTickMarks) || (t.isMinorTick && axis.drawMinorTickMarks)) ) {
                                    s = t.markSize;
                                    m = t.mark;
                                    var pos = Math.round(axis.u2p(t.value)) + 0.5;
                                    switch (m) {
                                        case 'outside':
                                            b = this._bottom;
                                            e = this._bottom+s;
                                            break;
                                        case 'inside':
                                            b = this._bottom-s;
                                            e = this._bottom;
                                            break;
                                        case 'cross':
                                            b = this._bottom-s;
                                            e = this._bottom+s;
                                            break;
                                        default:
                                            b = this._bottom;
                                            e = this._bottom+s;
                                            break;
                                    }
                                    // draw the shadow
                                    if (this.shadow) {
                                        this.renderer.shadowRenderer.draw(ctx, [[pos,b],[pos,e]], {lineCap:'butt', lineWidth:this.gridLineWidth, offset:this.gridLineWidth*0.75, depth:2, fill:false, closePath:false});
                                    }
                                    // draw the line
                                    drawLine(pos, b, pos, e);
                                }
                                break;
                            case 'yaxis':
                                // draw the grid line
                                if (t.showGridline && this.drawGridlines && ((!t.isMinorTick && axis.drawMajorGridlines) || (t.isMinorTick && axis.drawMinorGridlines)) ) {
                                    drawLine(this._right, pos, this._left, pos);
                                }
                                // draw the mark
                                if (t.showMark && t.mark && ((!t.isMinorTick && axis.drawMajorTickMarks) || (t.isMinorTick && axis.drawMinorTickMarks)) ) {
                                    s = t.markSize;
                                    m = t.mark;
                                    var pos = Math.round(axis.u2p(t.value)) + 0.5;
                                    switch (m) {
                                        case 'outside':
                                            b = this._left-s;
                                            e = this._left;
                                            break;
                                        case 'inside':
                                            b = this._left;
                                            e = this._left+s;
                                            break;
                                        case 'cross':
                                            b = this._left-s;
                                            e = this._left+s;
                                            break;
                                        default:
                                            b = this._left-s;
                                            e = this._left;
                                            break;
                                            }
                                    // draw the shadow
                                    if (this.shadow) {
                                        this.renderer.shadowRenderer.draw(ctx, [[b, pos], [e, pos]], {lineCap:'butt', lineWidth:this.gridLineWidth*1.5, offset:this.gridLineWidth*0.75, fill:false, closePath:false});
                                    }
                                    drawLine(b, pos, e, pos, {strokeStyle:axis.borderColor});
                                }
                                break;
                            case 'x2axis':
                                // draw the grid line
                                if (t.showGridline && this.drawGridlines && ((!t.isMinorTick && axis.drawMajorGridlines) || (t.isMinorTick && axis.drawMinorGridlines)) ) {
                                    drawLine(pos, this._bottom, pos, this._top);
                                }
                                // draw the mark
                                if (t.showMark && t.mark && ((!t.isMinorTick && axis.drawMajorTickMarks) || (t.isMinorTick && axis.drawMinorTickMarks)) ) {
                                    s = t.markSize;
                                    m = t.mark;
                                    var pos = Math.round(axis.u2p(t.value)) + 0.5;
                                    switch (m) {
                                        case 'outside':
                                            b = this._top-s;
                                            e = this._top;
                                            break;
                                        case 'inside':
                                            b = this._top;
                                            e = this._top+s;
                                            break;
                                        case 'cross':
                                            b = this._top-s;
                                            e = this._top+s;
                                            break;
                                        default:
                                            b = this._top-s;
                                            e = this._top;
                                            break;
                                            }
                                    // draw the shadow
                                    if (this.shadow) {
                                        this.renderer.shadowRenderer.draw(ctx, [[pos,b],[pos,e]], {lineCap:'butt', lineWidth:this.gridLineWidth, offset:this.gridLineWidth*0.75, depth:2, fill:false, closePath:false});
                                    }
                                    drawLine(pos, b, pos, e);
                                }
                                break;
                            case 'y2axis':
                                // draw the grid line
                                if (t.showGridline && this.drawGridlines && ((!t.isMinorTick && axis.drawMajorGridlines) || (t.isMinorTick && axis.drawMinorGridlines)) ) {
                                    drawLine(this._left, pos, this._right, pos);
                                }
                                // draw the mark
                                if (t.showMark && t.mark && ((!t.isMinorTick && axis.drawMajorTickMarks) || (t.isMinorTick && axis.drawMinorTickMarks)) ) {
                                    s = t.markSize;
                                    m = t.mark;
                                    var pos = Math.round(axis.u2p(t.value)) + 0.5;
                                    switch (m) {
                                        case 'outside':
                                            b = this._right;
                                            e = this._right+s;
                                            break;
                                        case 'inside':
                                            b = this._right-s;
                                            e = this._right;
                                            break;
                                        case 'cross':
                                            b = this._right-s;
                                            e = this._right+s;
                                            break;
                                        default:
                                            b = this._right;
                                            e = this._right+s;
                                            break;
                                            }
                                    // draw the shadow
                                    if (this.shadow) {
                                        this.renderer.shadowRenderer.draw(ctx, [[b, pos], [e, pos]], {lineCap:'butt', lineWidth:this.gridLineWidth*1.5, offset:this.gridLineWidth*0.75, fill:false, closePath:false});
                                    }
                                    drawLine(b, pos, e, pos, {strokeStyle:axis.borderColor});
                                }
                                break;
                            default:
                                break;
                        }
                    }
                }
                t = null;
            }
            axis = null;
            ticks = null;
        }
        // Now draw grid lines for additional y axes
        //////
        // TO DO: handle yMidAxis
        //////
        ax = ['y3axis', 'y4axis', 'y5axis', 'y6axis', 'y7axis', 'y8axis', 'y9axis', 'yMidAxis'];
        for (var i=7; i>0; i--) {
            var axis = axes[ax[i-1]];
            var ticks = axis._ticks;
            if (axis.show) {
                var tn = ticks[axis.numberTicks-1];
                var t0 = ticks[0];
                var left = axis.getLeft();
                var points = [[left, tn.getTop() + tn.getHeight()/2], [left, t0.getTop() + t0.getHeight()/2 + 1.0]];
                // draw the shadow
                if (this.shadow) {
                    this.renderer.shadowRenderer.draw(ctx, points, {lineCap:'butt', fill:false, closePath:false});
                }
                // draw the line
                drawLine(points[0][0], points[0][1], points[1][0], points[1][1], {lineCap:'butt', strokeStyle:axis.borderColor, lineWidth:axis.borderWidth});
                // draw the tick marks
                for (var j=ticks.length; j>0; j--) {
                    var t = ticks[j-1];
                    s = t.markSize;
                    m = t.mark;
                    var pos = Math.round(axis.u2p(t.value)) + 0.5;
                    if (t.showMark && t.mark) {
                        switch (m) {
                            case 'outside':
                                b = left;
                                e = left+s;
                                break;
                            case 'inside':
                                b = left-s;
                                e = left;
                                break;
                            case 'cross':
                                b = left-s;
                                e = left+s;
                                break;
                            default:
                                b = left;
                                e = left+s;
                                break;
                        }
                        points = [[b,pos], [e,pos]];
                        // draw the shadow
                        if (this.shadow) {
                            this.renderer.shadowRenderer.draw(ctx, points, {lineCap:'butt', lineWidth:this.gridLineWidth*1.5, offset:this.gridLineWidth*0.75, fill:false, closePath:false});
                        }
                        // draw the line
                        drawLine(b, pos, e, pos, {strokeStyle:axis.borderColor});
                    }
                    t = null;
                }
                t0 = null;
            }
            axis = null;
            ticks =  null;
        }
        
        ctx.restore();
        
        function drawLine(bx, by, ex, ey, opts) {
            ctx.save();
            opts = opts || {};
            if (opts.lineWidth == null || opts.lineWidth != 0){
                $.extend(true, ctx, opts);
                ctx.beginPath();
                ctx.moveTo(bx, by);
                ctx.lineTo(ex, ey);
                ctx.stroke();
                ctx.restore();
            }
        }
        
        if (this.shadow) {
            var points = [[this._left, this._bottom], [this._right, this._bottom], [this._right, this._top]];
            this.renderer.shadowRenderer.draw(ctx, points);
        }
        // Now draw border around grid.  Use axis border definitions. start at
        // upper left and go clockwise.
        if (this.borderWidth != 0 && this.drawBorder) {
            drawLine (this._left, this._top, this._right, this._top, {lineCap:'round', strokeStyle:axes.x2axis.borderColor, lineWidth:axes.x2axis.borderWidth});
            drawLine (this._right, this._top, this._right, this._bottom, {lineCap:'round', strokeStyle:axes.y2axis.borderColor, lineWidth:axes.y2axis.borderWidth});
            drawLine (this._right, this._bottom, this._left, this._bottom, {lineCap:'round', strokeStyle:axes.xaxis.borderColor, lineWidth:axes.xaxis.borderWidth});
            drawLine (this._left, this._bottom, this._left, this._top, {lineCap:'round', strokeStyle:axes.yaxis.borderColor, lineWidth:axes.yaxis.borderWidth});
        }
        // ctx.lineWidth = this.borderWidth;
        // ctx.strokeStyle = this.borderColor;
        // ctx.strokeRect(this._left, this._top, this._width, this._height);
        
        ctx.restore();
        ctx =  null;
        axes = null;
    };
 