QFocuser 0.95 - class for keyboard navigable AJAX widgets for better usability and accessibility

    Features:
            - allow to your widget listen key events when its focused
            - focus can be enabled on any element
            - fires focus and blur events (so your table row will NOT remain highlighted after click out of table for example)
            - make your widget to be accessible by tab key
            - tiny and library agnostic
            - this implementation could serve as a model for the others
            - works also in Safari!

    Tested on: IE6/7, FF2/3, Safari, Webkit, Opera and Chrome
    
Key navigation is important part in overall usability and accessibility of all applications.
    If you have only one widget, key events can be safely attached to document, but if more than one widgets
    are involved, each widget has to react to keyboard separately, which means when it has focus.
    Also, each widget has to react when focus is lost (remove highlighted row for example).
    There is no another solution than listen blur event. Any other solution based e.g. on mouseclick will fail with iframes.

    .. read this: http://dojotoolkit.org/book/dojo-book-0-9/part-3-programmatic-dijit-and-dojo/writing-your-own-widget-class/creating-accessi

    How it should work: 
            Key tab switches between your widgets, in order defined by tabIndex. Focused widget can listen key events.

    How it work: 
            To make elements focusable, set them tabindex. That will allow you to attach keyboard events to them too.
            The tabindex value can allow for some interesting behavior. If given a value of "-1", the element can't be tabbed 
            to but focus can be given to the element programmatically (using element.focus()).
            If given a value of 0, the element can be focused via the keyboard and falls into the tabbing flow of the document.
            Values greater than 0 create a priority level with 1 being the most important.

    Safari issue:
            Current version of safari doesn't support tabIndex for regular elements. WebKit nightly build does.
            This library has a workaround for it, to have almost same behavior.

    Hiding the Browsers Focus Borders issue:
            All browser including IE6/7 will show pesky dotted borders around focused elements for accessibility reasons.
            The dotted visual clutters up the design. To remove them, use options doNotShowBrowserFocusDottedBorder.
            It has to be done in code, because Internet Explorer has no style property for that. If you are remove them, do not
            forget use own focused element highlighting.
    
    Example:

            var focuser = new QFocuser(widgetContainer, {
                    onFocus: function(focusedEl) { .. add highlighted class or whatever }
                    onBlur: function(focusedEl) { .. remove highlighted class or whatever }
                    onKeydown: e.g. handleArrows...
            });
            // attach your own keys listeners
            $(focuser.getEl()).addEvent('keydown', e.g. handleArrows);
            // when your widget decided to set the focus (and then receive key events)
            focuser.focus(tableRowForExample);

    Links:

            http://snook.ca/archives/accessibility_and_usability/elements_focusable_with_tabindex/
            http://wiki.codetalks.org/wiki/index.php/Docs/Keyboard_navigable_JS_widgets
            http://dev.aol.com/dhtml_style_guide - recommended key shortcuts
            http://fluidproject.org/blog/2008/01/09/getting-setting-and-removing-tabindex-values-with-javascript/

    License: MIT-style license. Copyright: Copyright (c) 2009 Daniel Steigerwald, daniel.steigerwald.cz