Canvas distorts drawing. How do I get the scale factor between the set size and the styled size?

I have this canvas:

<canvas id="game" width="2开发者_StackOverflow中文版80" height="280"></canvas>

The css styles the canvas via:

canvas
{
    width: inherit;
    height: 280px;
}

As the width can change, the canvas distorts the drawing. I need to know how to compensate for this. Anyone who can help me?

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This is the same problem that the Mozilla Bespin team ran into. (back when they were using Canvas, before it merged with Ace)

Don't give the Canvas any CSS width/height rules. Doing so usually ends up as a pain. Put the Canvas in a Div that only has a single thing in it (the canvas itself)

As the canvas-parent div changes size, change the size of the canvas (canvas.width and canvas.height) to match the size of the div.

Since most browsers do not fire an event when a div changes size, you'll simply have to check, say, every half second with a timer to see if the div has changed size. If it has, then you resize the canvas accordingly.