scaffold.libs_as.feathers.layout.IVirtualLayout.as Maven / Gradle / Ivy
/*
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 flash.geom.Point;
import starling.display.DisplayObject;
/**
* A layout algorithm that supports virtualization of items so that only
* the visible items need to be created. Useful in lists with dozens or
* hundreds of items are needed, but only a small subset of the items are
* visible at any given moment.
*/
public interface IVirtualLayout extends ILayout
{
/**
* Determines if virtual layout should be used. Some components don't
* support virtual layouts, and they will always change this property to
* false. In those cases, the virtual layout options
* will be ignored.
*/
function get useVirtualLayout():Boolean;
/**
* @private
*/
function set useVirtualLayout(value:Boolean):void;
/**
* Used internally by a component that supports layout virtualization,
* such as List, to provide a display object with
* dimensions that represent a "typical" item in the layout. These
* dimensions will be used to fill in blanks for the layout when an
* item is virtual and isn't actually on the display list. If you are
* simply passing a layout to a component, setting this property will
* have no effect. It is meant to be used by the component, and the
* component will replace any value you pass to this property.
*/
function get typicalItem():DisplayObject;
/**
* @private
*/
function set typicalItem(value:DisplayObject):void;
/**
* Used internally by a component, such as List, to measure
* the view port based on the typical item dimensions or cached
* dimensions, if available.
*
* This function is meant to be called by the List or
* other component that uses the virtual layout. If you're simply
* creating a layout for a List or another component, do
* not call this function. It is meant for developers creating custom
* components only.
*
* @see #typicalItemWidth
* @see #typicalItemHeight
*/
function measureViewPort(itemCount:int, viewPortBounds:ViewPortBounds = null, result:Point = null):Point;
/**
* Used internally by a component, such as List, to
* determines which indices are visible with the specified view port
* bounds and scroll position. Indices that aren't returned are
* typically not displayed and can be replaced virtually. Uses the
* typical items dimensions, or cached dimensions, if available.
*
* This function is meant to be called by the List or
* other component that uses the virtual layout. If you're simply
* creating a layout for a List or another component, do
* not call this function. It is meant for developers creating custom
* components only.
*/
function getVisibleIndicesAtScrollPosition(scrollX:Number, scrollY:Number, width:Number, height:Number, itemCount:int, result:Vector. = null):Vector.;
}
}