/**
* Adds event delegation support to the library.
*
* @module event
* @submodule event-delegate
*/
var toArray = Y.Array,
YLang = Y.Lang,
isString = YLang.isString,
selectorTest = Y.Selector.test,
detachCategories = Y.Env.evt.handles;
/**
* <p>Sets up event delegation on a container element. The delegated event
* will use a supplied selector or filtering function to test if the event
* references at least one node that should trigger the subscription
* callback.</p>
*
* <p>Selector string filters will trigger the callback if the event originated
* from a node that matches it or is contained in a node that matches it.
* Function filters are called for each Node up the parent axis to the
* subscribing container node, and receive at each level the Node and the event
* object. The function should return true (or a truthy value) if that Node
* should trigger the subscription callback. Note, it is possible for filters
* to match multiple Nodes for a single event. In this case, the delegate
* callback will be executed for each matching Node.</p>
*
* <p>For each matching Node, the callback will be executed with its 'this'
* object set to the Node matched by the filter (unless a specific context was
* provided during subscription), and the provided event's
* <code>currentTarget</code> will also be set to the matching Node. The
* containing Node from which the subscription was originally made can be
* referenced as <code>e.container</code>.
*
* @method delegate
* @param type {String} the event type to delegate
* @param fn {Function} the callback function to execute. This function
* will be provided the event object for the delegated event.
* @param el {String|node} the element that is the delegation container
* @param spec {string|Function} a selector that must match the target of the
* event or a function to test target and its parents for a match
* @param context optional argument that specifies what 'this' refers to.
* @param args* 0..n additional arguments to pass on to the callback function.
* These arguments will be added after the event object.
* @return {EventHandle} the detach handle
* @for YUI
*/
function delegate(type, fn, el, filter) {
var args = toArray(arguments, 0, true),
query = isString(el) ? el : null,
typeBits = type.split(/\|/),
synth, container, categories, cat, handle;
if (typeBits.length > 1) {
cat = typeBits.shift();
type = typeBits.shift();
}
synth = Y.Node.DOM_EVENTS[type];
if (YLang.isObject(synth) && synth.delegate) {
handle = synth.delegate.apply(synth, arguments);
}
if (!handle) {
if (!type || !fn || !el || !filter) {
Y.log("delegate requires type, callback, parent, & filter", "warn");
return;
}
container = (query) ? Y.Selector.query(query, null, true) : el;
if (!container && isString(el)) {
handle = Y.on('available', function () {
Y.mix(handle, Y.delegate.apply(Y, args), true);
}, el);
}
if (!handle && container) {
args.splice(2, 2, container); // remove the filter
if (isString(filter)) {
filter = Y.delegate.compileFilter(filter);
}
handle = Y.on.apply(Y, args);
handle.sub.filter = filter;
handle.sub._notify = delegate.notifySub;
}
}
if (handle && cat) {
categories = detachCategories[cat] || (detachCategories[cat] = {});
categories = categories[type] || (categories[type] = []);
categories.push(handle);
}
return handle;
}
/**
* Overrides the <code>_notify</code> method on the normal DOM subscription to inject the filtering logic and only proceed in the case of a match.
*
* @method delegate.notifySub
* @param thisObj {Object} default 'this' object for the callback
* @param args {Array} arguments passed to the event's <code>fire()</code>
* @param ce {CustomEvent} the custom event managing the DOM subscriptions for
* the subscribed event on the subscribing node.
* @return {Boolean} false if the event was stopped
* @private
* @static
* @since 3.2.0
*/
delegate.notifySub = function (thisObj, args, ce) {
// Preserve args for other subscribers
args = args.slice();
if (this.args) {
args.push.apply(args, this.args);
}
// Only notify subs if the event occurred on a targeted element
var e = args[0],
currentTarget = delegate._applyFilter(this.filter, args),
container = e.currentTarget,
i, ret, target;
if (currentTarget) {
// Support multiple matches up the the container subtree
currentTarget = toArray(currentTarget);
for (i = currentTarget.length - 1; i >= 0; --i) {
target = currentTarget[i];
// New facade to avoid corrupting facade sent to direct subs
args[0] = new Y.DOMEventFacade(e, target, ce);
args[0].container = container;
thisObj = this.context || target;
ret = this.fn.apply(thisObj, args);
if (ret === false) { // stop further notifications
break;
}
}
return ret;
}
};
/**
* <p>Compiles a selector string into a filter function to identify whether
* Nodes along the parent axis of an event's target should trigger event
* notification.</p>
*
* <p>This function is memoized, so previously compiled filter functions are
* returned if the same selector string is provided.</p>
*
* <p>This function may be useful when defining synthetic events for delegate
* handling.</p>
*
* @method delegate.compileFilter
* @param selector {String} the selector string to base the filtration on
* @return {Function}
* @since 3.2.0
* @static
*/
delegate.compileFilter = Y.cached(function (selector) {
return function (target, e) {
return selectorTest(target._node, selector, e.currentTarget._node);
};
});
/**
* Walks up the parent axis of an event's target, and tests each element
* against a supplied filter function. If any Nodes satisfy the filter, the
* delegated callback will be triggered for each.
*
* @method delegate._applyFilter
* @param filter {Function} boolean function to test for inclusion in event
* notification
* @param args {Array} the arguments that would be passed to subscribers
* @return {Node|Node[]|undefined} The Node or Nodes that satisfy the filter
* @protected
*/
delegate._applyFilter = function (filter, args) {
var e = args[0],
container = e.currentTarget,
target = e.target,
match = [];
// passing target as the first arg rather than leaving well enough alone
// making 'this' in the filter function refer to the target. This is to
// support bound filter functions.
args.unshift(target);
while (target && target !== container) {
// filter(target, e, extra args...) - this === target
if (filter.apply(target, args)) {
match.push(target);
}
args[0] = target = target.get('parentNode');
}
if (match.length <= 1) {
match = match[0]; // single match or undefined
}
// remove the target
args.shift();
return match;
};
/**
* Sets up event delegation on a container element. The delegated event
* will use a supplied filter to test if the callback should be executed.
* This filter can be either a selector string or a function that returns
* a Node to use as the currentTarget for the event.
*
* The event object for the delegated event is supplied to the callback
* function. It is modified slightly in order to support all properties
* that may be needed for event delegation. 'currentTarget' is set to
* the element that matched the selector string filter or the Node returned
* from the filter function. 'container' is set to the element that the
* listener is delegated from (this normally would be the 'currentTarget').
*
* Filter functions will be called with the arguments that would be passed to
* the callback function, including the event object as the first parameter.
* The function should return false (or a falsey value) if the success criteria
* aren't met, and the Node to use as the event's currentTarget and 'this'
* object if they are.
*
* @method delegate
* @param type {string} the event type to delegate
* @param fn {function} the callback function to execute. This function
* will be provided the event object for the delegated event.
* @param el {string|node} the element that is the delegation container
* @param filter {string|function} a selector that must match the target of the
* event or a function that returns a Node or false.
* @param context optional argument that specifies what 'this' refers to.
* @param args* 0..n additional arguments to pass on to the callback function.
* These arguments will be added after the event object.
* @return {EventHandle} the detach handle
* @for YUI
*/
Y.delegate = Y.Event.delegate = delegate;