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World Wind is a collection of components that interactively display 3D geographic information within Java applications or applets.
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/*
 * Copyright (C) 2012 United States Government as represented by the Administrator of the
 * National Aeronautics and Space Administration.
 * All Rights Reserved.
 */

package gov.nasa.worldwind.ogc.kml.impl;

import gov.nasa.worldwind.ogc.kml.KMLRegion;
import gov.nasa.worldwind.util.Logging;

import java.util.*;

/**
 * KMLTraversalContext provides a suitcase of KML specific state used to render a hierarchy of KML
 * features.
 *
 * @author tag
 * @version $Id: KMLTraversalContext.java 1171 2013-02-11 21:45:02Z dcollins $
 */
public class KMLTraversalContext
{
    /**
     * The Deque as this KML traversal context's Region stack. The region stack is used to implement
     * Regions inheritance of from a KML containers to their descendant KML features.
     */
    protected Deque regionStack = new ArrayDeque();
    /**
     * Indicates this KML traversal context's detail hint. Modifies the default relationship of KML scene resolution to
     * screen resolution as viewing distance changes. Values greater than 0 increase the resolution. Values less than 0
     * decrease the resolution. Initially 0.
     */
    protected double detailHint;

    /** Constructs a new KML traversal context in a default state, but otherwise does nothing. */
    public KMLTraversalContext()
    {
    }

    /**
     * Initializes this KML traversal context to its default state. This should be called at the beginning of each frame
     * to prepare this traversal context for the coming render pass.
     */
    public void initialize()
    {
        this.regionStack.clear();
        this.detailHint = 0.0;
    }

    /**
     * Adds the specified region to the top of this KML traversal context's Region stack. The specified
     * region is returned by any subsequent calls to peekRegion until either pushRegion or
     * popRegion are called. The region is removed from the stack by calling
     * popRegion.
     *
     * @param region the KML Region to add to the top of the stack.
     *
     * @throws IllegalArgumentException if region is null.
     */
    public void pushRegion(KMLRegion region)
    {
        if (region == null)
        {
            String message = Logging.getMessage("nullValue.RegionIsNull");
            Logging.logger().severe(message);
            throw new IllegalArgumentException(message);
        }

        this.regionStack.push(region);
    }

    /**
     * Returns the KML Region on the top of this KML traversal context's Region stack, or null if the
     * Region stack is empty. The Region on the top of the stack the last region added with a call to
     * pushRegion. This does not modify the contents of the stack.
     *
     * @return the Region on the top of this context's stack, or null if the stack is empty.
     */
    public KMLRegion peekRegion()
    {
        return this.regionStack.peek();
    }

    /**
     * Removes the KML Region from the top of this KML traversal context's Region stack. This throws an exception if the
     * Region stack is empty, otherwise this removes and returns the last Region added to the stack by a call to
     * pushRegion.
     *
     * @return the Region removed from the top of the stack.
     *
     * @throws NoSuchElementException if the Region stack is empty.
     */
    public KMLRegion popRegion()
    {
        return this.regionStack.pop();
    }

    /**
     * Indicates this KML traversal context's detail hint, which is described in {@link
     * #setDetailHint(double)}.
     *
     * @return the detail hint.
     *
     * @see #setDetailHint(double)
     */
    public double getDetailHint()
    {
        return this.detailHint;
    }

    /**
     * Specifies this KML traversal context's detail hint. The detail hint modifies the default relationship of KML
     * scene resolution to screen resolution as the viewing distance changes. Values greater than 0 cause KML elements
     * with a level of detail to appear at higher resolution at greater distances than normal, but at an increased
     * performance cost. Values less than 0 decrease the default resolution at any given distance. The default value is
     * 0. Values typically range between -0.5 and 0.5.
     *
     * @param detailHint the degree to modify the default relationship of KML scene resolution to screen resolution as
     *                   viewing distance changes. Values greater than 0 increase the resolution. Values less than 0
     *                   decrease the resolution. The default value is 0.
     */
    public void setDetailHint(double detailHint)
    {
        this.detailHint = detailHint;
    }
}