Possible to prevent default behaviour of ALT key?

[makana]

Hey guys!

Everybody knows, if you press ALT key on your keyboard, you activate the keyboard navigation through the main window menu (File, Edit, View etc.). That's what I want to realize for my custom main menu (a top toolbar in my Ext.air.Window).
I defined a KeyMap like this:

new Ext.KeyMap(Ext.getDoc(), {
	key: Ext.EventObject.ALT,
	alt: true,
	stopEvent: true,
	handler: function(k, e) {
		if (mainMenuKeyMap.isEnabled()) {
			activeBtn.onMouseOut(e);
			mainMenuKeyMap.disable();
		} else {
			activeBtn = mainMenu.get(0);
			activeBtn.onMouseOver(e);
			mainMenuKeyMap.enable();
		}
	}
});

Where mainMenuKeyMap is another KeyMap for the navigation through the menu.

It works as far as the first button in the main menu changes its style to a mouseover style. But it hasn't got the focus. If I press the down button now, the default window's menu appears like in the screenshot.

It works like expected, if I press the alt key twice. The same when finishing the keyboard navigation.

Does anybody know, how to prevent the default bevahiour of the ALT key? I don't want to have the default window's menu.

Thanks in advance!
makana

[makana]

Does anybody have any ideas? I don't want to bar users from doing something but implement a common known behaviour. Is it even possible to take priority with the alt key (ctrl, too or similar keys in general) over the browser/adobe air?

Thanks for any hints or ideas!