Extreme|FX Marcelo Volmaro on Programming, User Experience and anything else.

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Fixing Flash External Interface inside Forms on Internet Explorer

As you all may know (or may not), if you want to use External Interface on a flash object that lives inside an "HTML" form, it will not work.

I will show you a simple test:

	<object id="flashElement1" width="256" height="64" data="files/bug4.swf" type="application/x-shockwave-flash">
		<param name="movie" value="files/bug4.swf" />
		<param name="allowScriptAccess" value="always" />
	<p><a onclick="document.getElementById('flashElement1').testFunction(); return false;" href="#">Click to test</a></p>

First of all, you will get a javascript error saying that the element flashElement1 is undefined. And while in the flash window you will see the CallBack added Ok, if you click on the Click to test link you will get another error saying that the Object doesn't support that property or method.

Why?: Easy. The way the javascript bridge with flash was coded is really awful. In IE, every time you add an ID attribute to an HTML element, that element is added to the window element so you can access it directly using window.elementID... but if you place the element inside an HTML form, the element is added to the form element (document.forms[0].elementID if you have only one form) and not window element. I suppose the person who did the bridge knowns nothing about this... I will not get into the details here, but you can believe me: The bridge it's screaming for a rewriting.

How?: Well, this will depend on how are you embedding the object on the HTML page. If you use SwfObject you should add the following line after the line 105 (the line that reads n.innerHTML = this.getSWFHTML();):

if(!(navigator.plugins && navigator.mimeTypes.length))
    window[this.getAttribute('id')] = document.getElementById(this.getAttribute('id'));

That applies to the current version of SwfObject (1.4.4).

If you use UFO you should add the following line after the line 230 (the line that reads _e.innerHTML = '<object classid="...):

if (_fo["id"]) window[_fo["id"]] = document.getElementById(_fo["id"]);

That applies to UFO 3.20.

And if you use Adobe's Active Content you should add the following line after the line 24 (the line that reads document.write(str);):

if (objAttrs["id"]) window[objAttrs["id"]] = document.getElementById(objAttrs["id"]);

Posted under Flash Javascript