Question

look at examples:

1. jsfiddle.net/Kky6J/5/
2. jsfiddle.net/8t3Nq/2/

The only difference is in which way canvas is cleared, in window.render function:

1. ctx.clearRect(0, 0, width, height);
2. chart.width = chart.width;

In google chrome “23.0.1271.97m” (and firefox 17.0.1) i got performance degradation at each frame in (1.) (number at right side from the red bar – time spent to draw frame in ms)

I think it is my mistake, because in popular manuals the (1.) are faster in examples. (http://www.html5rocks.com/en/tutorials/canvas/performance/)

Answer 1

jsfiddle.net/Kky6J/21/

Solution – use ctx.beginPath() before use ctx.rect(10, 10, 5, 20)