Detect Zoom in Firefox

I want to detect if the browser is zoomed in or out (don't really care to know the value, but I assume it will need to be found anyway in the decision process). I have read a lot of other SO posts 开发者_如何学JAVAon the topic, but none of the solutions given work on FF (although there is an IE7/8 and chrome solution).

Oh, and I can't use flash, so the flash solution is out of the question.

Edit: And I must be able to detect this on the initial page load

With modern versions of FireFox, you can now do the following:

DPR = window.devicePixelRatio;
if ( DPR <= 0.999 || DPR >= 1.001 ){
   // User has zoomed in or zoomed out
}

If by zoom you mean that the user pressed ctrl/cmd+[plus] and not css transformation you can detect computed font-size. Just checked in FF 4.0.1/Mac and it worked for me. To detect computed font-size I used code from this question: Get computed font size for DOM element in JS .

The value changed after zooming. You need to know what the font-size of a certain element should be (as set in css) and compare it with what it really is.

I suggest you look at this generic question. And possibly close your own as a duplicate (not voting to do this myself, since it's not "an exact dup".

Did you try to detect the resolution, which may help you to detect the zoom.

Maybe instead of detecting the zoom you could detect the error.

For example if your layout expects an elements' offset to be at 100,200 and a query shows it's at 300,450 you'll know it's in the wrong place and you can apply your fixup/workaround.

This has the added benefit that if the zoom issue is fixed in a future version of the browser you won't be applying your fix needlessly or incorrectly.