MouseWheelTrap

MouseWheelTrap – how to stop simultaneous Flash / browser scrolling in AS3

Update: This project is now hosted at GoogleCode

I recently stumbled over a new AS3 gotcha that seems to be bugging a lot of the Flash community. Apparently a new ‘feature’ of AS3, whereby using the mousewheel inside an embedded Flash movie still scrolls the surrounding browser window (if it has enough content, that is).

This didn’t happen in AS2. If a Flash movie had focus, mousewheel events weren’t sent to the browser window. It wasn’t a problem in FireFox either, until a recent update and adversely affects any AS3 Flash app embedded in an HTML page where you might want to scroll or zoom with the mousewheel while over the Flash, instead of the scrolling the browser window.

So, I decided to cook up some code to fix this. While it’s early version and isn’t perfect, it suits my purposes, is easy to set up and doesn’t require any external JavaScript – so I’d thought I’d share it with the world, in case Adobe never get around to addressing this ‘feature’.

Introducing MouseWheelTrap. A handy little utility class that traps mousewheel events while the mouse is over the Flash, so your app scrolls how it was intended to. I’ve tested it with SWFObject on PC IE and FireFox, but not with SWFMacMouseWheel on Mac (if someone could tell me if it works). I decided against using jQuery for trapping mouse events, partly out of laziness, partly because many people have no control over the HTML that embeds their Flash app and therefore can’t add custom JavaScript.

Setting up MouseWheelTrap is easy:

  • Download the MouseWheelTrap ZIP package, or just the AS file.
  • Unzip the package and have a look at the demo, or just take the MouseWheelTrap.as file and put it in the com.spikything.utils folder into your own project or classpath.
  • Import the utility and set it up somewhere in your main class like so:
  • [AS]
    import com.spikything.utils.MouseWheelTrap;
    MouseWheelTrap.setup(stage);
    [/AS]

    Simple huh? Let me know how you get on…

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