http://jsfiddle.net/cs5Sg/11/

I want to do the scalable canvas. I created two circles (arcs) and one line, when you click on circle and move it, the line will follow and change position. The problem is when I added code for resize:

var canvas = document.getElementById('myCanvas'),
    context = canvas.getContext('2d'),
    radius = 12,
    p = null,
    point = {
        p1: { x:100, y:250 },
        p2: { x:400, y:100 }
    },
    moving = false;

window.addEventListener("resize", OnResizeCalled, false);

function OnResizeCalled() {
    var gameWidth = window.innerWidth;
    var gameHeight = window.innerHeight;
    var scaleToFitX = gameWidth / 800;
    var scaleToFitY = gameHeight / 480;

    var currentScreenRatio = gameWidth / gameHeight;
    var optimalRatio = Math.min(scaleToFitX, scaleToFitY);

    if (currentScreenRatio >= 1.77 && currentScreenRatio <= 1.79) {
        canvas.style.width = gameWidth + "px";
        canvas.style.height = gameHeight + "px";
    }
    else {
        canvas.style.width = 800 * optimalRatio + "px";
        canvas.style.height = 480 * optimalRatio + "px";
    }
}

function init() {
        return setInterval(draw, 10);
}

canvas.addEventListener('mousedown', function(e) {
    for (p in point) {
        var
            mouseX = e.clientX - 1,
            mouseY = e.clientY - 1,
            distance = Math.sqrt(Math.pow(mouseX - point[p].x, 2) + Math.pow(mouseY - point[p].y, 2));

        if (distance <= radius) {
            moving = p;
            break;
        }
    }
});

canvas.addEventListener('mouseup', function(e) {
    moving = false;
});

canvas.addEventListener('mousemove', function(e) {

    if(moving) {
        point[moving].x = e.clientX - 1; 
        point[moving].y = e.clientY - 1;
    }
});


function draw() {
    context.clearRect(0, 0, canvas.width, canvas.height);

    context.beginPath();
    context.moveTo(point.p1.x,point.p1.y);
    context.lineTo(point.p2.x,point.p2.y);

    context.closePath();

    context.fillStyle = '#8ED6FF';
    context.fill();
    context.stroke();

    for (p in point) {
        context.beginPath();
        context.arc(point[p].x,point[p].y,radius,0,2*Math.PI);
        context.fillStyle = 'red';
        context.fill();
        context.stroke();
    }
    context.closePath();
}

init();

The canvas is scalable, but the problem is with the points (circles). When you change the window size, they still have the same position on the canvas area, but the distance change (so the click option fails). How to fix that?