Add scrollbars to canvas
Canvas is not like other html elements. Html scrollbars cannot effectively scroll through canvas content that is larger than the canvas's css size.
One fallback is to use jquery-ui to draw the scrollbars.
Here is how to add a vertical scrollbar to canvas that allows scrolling up/down over a larger image: http://jsfiddle.net/m1erickson/a9KDB/
You can add a horizontal scrollbar the same way.
Here is the code:
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script src="http://code.jquery.com/jquery-1.9.1.js"></script>
<script src="http://code.jquery.com/ui/1.10.1/jquery-ui.js"></script>
<style>
body{ background-color: ivory; }
div, canvas {
position:absolute;
}
.wrapper {
top:10px;
left:10px;
width: 300px;
height: 300px;
border: 2px solid black;
margin:30px 0 2;
overflow: hidden;
background-color:green;
}
.vertical-scroll {
left:320px;
top:10px;
border: 1px solid green;
width: 20px;
height: 300px;
}
.vertical-scroll div.bar {
left:0px;
top:0px;
width: 20px;
background-color: blue;
height: 20px;
}
#mycanvas {
left:0px;
top:0px;
}
</style>
<script>
$(function(){
var canvas=document.getElementById("mycanvas");
var ctx=canvas.getContext("2d");
var wrapper;
var canvasHeight;
var vScrollHeight;
var canvasWrapperHeight=300;
$(".bar").draggable({
containment: "parent"
});
$(".bar").on("drag", function (event, ui) {
var ctop=(-ui.position.top * canvasHeight / canvasWrapperHeight);
canvas.style.top = ctop + "px"
});
var img=new Image();
img.onload=function(){
canvas.width=this.width;
canvas.height=this.height;
canvasHeight=this.height;
vbarHeight=canvasWrapperHeight*canvasWrapperHeight/canvasHeight;
document.getElementById("vbar").style.height=vbarHeight+"px";
ctx.drawImage(this,260,0,300,this.height,0,0,300,this.height);
}
img.src="http://sciencedude.blog.ocregister.com/files/2008/02/zot1-copy.jpg";
}); // end $(function(){});
</script>
</head>
<body>
<div class="wrapper" id="wrap1">
<canvas id="mycanvas" width="300px" height="300px" />
</div>
<div class="vertical-scroll" id="vscroll">
<div class="bar" id="vbar"></div>
</div>
</body>
</html>
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