Edit in JSFiddle

window.onload = function() {

    $("canvas").attr({height:$("#wrapper").height()});
    $("canvas").attr({width:$("#wrapper").width()});

    var stage = new Stage($("canvas")[0]);
    var g = new Graphics();
    
    g.beginStroke(Graphics.getRGB(0,0,0));

    //べベルな線
    g.setStrokeStyle(10,1,1);
    g.moveTo(-100,-150)
        .lineTo(0,50).lineTo(100,-150).lineTo(120,-150);
    
    //ラウンドな線
    g.setStrokeStyle(10,2,2);
    g.moveTo(-100,-200)
        .lineTo(0,0).lineTo(100,-200).lineTo(120,-200);  
    
    //マイターな線
    g.setStrokeStyle(10,0,0,2);

    g.moveTo(-100,-100)
        .lineTo(0,100).lineTo(100,-100).lineTo(120,-100);
    
    //マイターな線２
    g.setStrokeStyle(10,0,0,5);
    g.moveTo(-100,-50)
        .lineTo(0,150).lineTo(100,-50).lineTo(120,-50);
    
    var s = new Shape(g);
    s.x = $(window).width()/2;
    s.y = $(window).height()/2+30;
    
    stage.addChild(s);
    stage.update();

}

<div id="wrapper">
<canvas></canvas>
</div>

html{
    min-height: 100%;
    overflow: auto;
    position:relative;
    z-index: 1;
}

body{
    min-height: 100%;
    margin: 0;
    padding: 0;
    overflow: auto;
    position: relative;
    z-index: 1;
}

#wrapper{
    height: auto;
    overflow: auto;
    position: fixed;
    z-index: 1;
    width: 100%;
    height:100%;
    min-height:100%;
}

canvas{
    position: fixed;
}