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/*
Feathers
Copyright 2012-2015 Bowler Hat LLC. All Rights Reserved.

This program is free software. You can redistribute and/or modify it in
accordance with the terms of the accompanying license agreement.
*/
package feathers.layout
{
	import feathers.core.IFeathersEventDispatcher;

	import flash.geom.Point;

	import starling.display.DisplayObject;

	/**
	 * Dispatched when a property of the layout changes, indicating that a
	 * redraw is probably needed.
	 *
	 * The properties of the event object have the following values:
	 * 
	 * 
	 * 
	 * 
	 * 
	 * 
	 * Property Value
bubbles false
currentTarget The Object that defines the
	 *   event listener that handles the event. For example, if you use
	 *   myButton.addEventListener() to register an event listener,
	 *   myButton is the value of the currentTarget.
data null
target The Object that dispatched the event;
	 *   it is not always the Object listening for the event. Use the
	 *   currentTarget property to always access the Object
	 *   listening for the event.
	 *
	 * @eventType starling.events.Event.CHANGE
	 */
	[Event(name="change",type="starling.events.Event")]

	/**
	 * Interface providing layout capabilities for containers.
	 */
	public interface ILayout extends IFeathersEventDispatcher
	{
		/**
		 * Determines if the container calls layout() when the
		 * scroll position changes. Useful for transforming items as the view
		 * port scrolls. This value should be true for layouts that
		 * implement the IVirtualLayout interface and the
		 * useVirtualLayout property is set to true.
		 * May also be used by layouts that toggle item visibility as the items
		 * scroll into and out of the view port.
		 */
		function get requiresLayoutOnScroll():Boolean;

		/**
		 * Positions (and possibly resizes) the supplied items within the
		 * optional bounds argument. If no bounds are specified, the layout
		 * algorithm will assume that the bounds start a 0,0 and have unbounded
		 * dimensions. Returns the actual bounds of the content, which may
		 * be different than the specified bounds.
		 *
		 * Note: The items are not absolutely
		 * restricted to appear only within the bounds. The bounds can affect
		 * positioning, but the algorithm may very well ignore them completely.
		 *
		 * If a layout implementation needs to access accurate width
		 * and height values from items that are of type
		 * IFeathersControl, it must call validate()
		 * manually. For performance reasons, the container that is the parent
		 * of the items will not call validate() before passing the
		 * items to a layout implementation. Meeting this requirement may be as
		 * simple as looping through the items at the beginning of
		 * layout() and validating all items that are Feathers UI
		 * controls:
		 *
		 * 		 * const itemCount:int = items.length;
		 * for(var i:int = 0; i < itemCount; i++)
		 * {
		 *     var item:IFeathersControl = items[i] as IFeathersControl;
		 *     if(item)
		 *     {
		 *         item.validate();
		 *     }
		 * }
		 * 
		 * @see feathers.core.FeathersControl#validate()
		 */
		function layout(items:Vector., viewPortBounds:ViewPortBounds = null, result:LayoutBoundsResult = null):LayoutBoundsResult;


		/**
		 * Using the item dimensions, calculates a scroll position that will
		 * ensure that the item at a given index will be visible within the
		 * specified bounds.
		 *
		 * Typically, this function is used to show the item in the most
		 * prominent way, such as centering. To scroll a minimum distance
		 * required to display the full bounds of the item in the view port,
		 * use getNearestScrollPositionForIndex() instead.
		 *
		 * This function should always be called after the
		 * layout() function. The width and height arguments are
		 * the final bounds of the view port, which may be calculated in the
		 * layout() function.
		 *
		 * @see #getNearestScrollPositionForIndex()
		 */
		function getScrollPositionForIndex(index:int, items:Vector.,
			x:Number, y:Number, width:Number, height:Number, result:Point = null):Point;

		/**
		 * Calculates the scroll position nearest to the current scroll position
		 * that will display the full bounds of the item within the view port.
		 * If the item is already fully displayed in the view port, the current
		 * scroll position will be returned unchanged.
		 *
		 * While the item will be displayed in the view port without being
		 * clipped in any way, it may not be placed in the most prominent
		 * position possible. To give the item a more prominent location, use
		 * getScrollPositionForIndex() instead.
		 *
		 * This function should always be called after the
		 * layout() function. The width and height arguments are
		 * the final bounds of the view port, which may be calculated in the
		 * layout() function.
		 *
		 * @see #getScrollPositionForIndex()
		 */
		function getNearestScrollPositionForIndex(index:int, scrollX:Number, scrollY:Number,
			items:Vector., x:Number, y:Number, width:Number, height:Number, result:Point = null):Point
	}
}
Property	Value
`bubbles`	false
`currentTarget`	The Object that defines the * event listener that handles the event. For example, if you use * `myButton.addEventListener()` to register an event listener, * myButton is the value of the `currentTarget`.
`data`	null
`target`	The Object that dispatched the event; * it is not always the Object listening for the event. Use the * `currentTarget` property to always access the Object * listening for the event.