adding jquery-visibility

https://github.com/mathiasbynens/jquery-visibility
MIT and GPL licensed

apps/files/js/jquery-visibility.js

@@ -0,0 +1,32 @@
+/*! http://mths.be/visibility v1.0.5 by @mathias */
+(function (window, document, $, undefined) {
+
+	var prefix,
+		property,
+// In Opera, `'onfocusin' in document == true`, hence the extra `hasFocus` check to detect IE-like behavior
+		eventName = 'onfocusin' in document && 'hasFocus' in document ? 'focusin focusout' : 'focus blur',
+		prefixes = ['', 'moz', 'ms', 'o', 'webkit'],
+		$support = $.support,
+		$event = $.event;
+
+	while ((property = prefix = prefixes.pop()) != undefined) {
+		property = (prefix ? prefix + 'H' : 'h') + 'idden';
+		if ($support.pageVisibility = typeof document[property] == 'boolean') {
+			eventName = prefix + 'visibilitychange';
+			break;
+		}
+	}
+
+	$(/blur$/.test(eventName) ? window : document).on(eventName, function (event) {
+		var type = event.type,
+			originalEvent = event.originalEvent,
+			toElement = originalEvent.toElement;
+// If it’s a `{focusin,focusout}` event (IE), `fromElement` and `toElement` should both be `null` or `undefined`;
+// else, the page visibility hasn’t changed, but the user just clicked somewhere in the doc.
+// In IE9, we need to check the `relatedTarget` property instead.
+		if (!/^focus./.test(type) || (toElement == undefined && originalEvent.fromElement == undefined && originalEvent.relatedTarget == undefined)) {
+			$event.trigger((property && document[property] || /^(?:blur|focusout)$/.test(type) ? 'hide' : 'show') + '.visibility');
+		}
+	});
+
+}(this, document, jQuery));