HTML5 Canvas 100% Width Height of Viewport?

Question

I am trying to create a canvas element that takes up 100% of the width and height of the viewport.

You can see in my example here that is occurring, however it is adding scroll bars in both Chrome and FireFox. How can I prevent the extra scroll bars and just provide exactly the width and height of the window to be the size of the canvas?

Answer 1

In order to make the canvas full screen width and height always, meaning even when the browser is resized, you need to run your draw loop within a function that resizes the canvas to the window.innerHeight and window.innerWidth.

Example: http://jsfiddle.net/jaredwilli/qFuDr/

HTML

<canvas id="canvas"></canvas>

JavaScript

(function() {
    var canvas = document.getElementById('canvas'),
            context = canvas.getContext('2d');

    // resize the canvas to fill browser window dynamically
    window.addEventListener('resize', resizeCanvas, false);

    function resizeCanvas() {
            canvas.width = window.innerWidth;
            canvas.height = window.innerHeight;

            /**
             * Your drawings need to be inside this function otherwise they will be reset when 
             * you resize the browser window and the canvas goes will be cleared.
             */
            drawStuff(); 
    }
    resizeCanvas();

    function drawStuff() {
            // do your drawing stuff here
    }
})();

CSS

* { margin:0; padding:0; } /* to remove the top and left whitespace */

html, body { width:100%; height:100%; } /* just to be sure these are full screen*/

canvas { display:block; } /* To remove the scrollbars */

That is how you properly make the canvas full width and height of the browser. You just have to put all the code for drawing to the canvas in the drawStuff() function.