gamecore/src/mightypork/gamecore/gui/screens/LayeredScreen.java

package mightypork.gamecore.gui.screens;


import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

import mightypork.utils.eventbus.clients.DelegatingClient;


/**
 * Screen with multiple instances of {@link ScreenLayer}. Layers specify their
 * rendering and event priority.
 *
 * @author Ondřej Hruška (MightyPork)
 */
public abstract class LayeredScreen extends Screen {

	/**
	 * Wrapper for delegating client, to use custom client ordering.
	 *
	 * @author Ondřej Hruška (MightyPork)
	 */
	private class LayersClient implements DelegatingClient {

		@SuppressWarnings({ "unchecked", "rawtypes" })
		@Override
		public Collection getChildClients()
		{
			return layersByEventPriority;
		}


		@Override
		public boolean doesDelegate()
		{
			return true;
		}

	}

	private final List<ScreenLayer> layersByZIndex = new ArrayList<>();
	private final List<ScreenLayer> layersByEventPriority = new ArrayList<>();

	private final LayersClient layersClient = new LayersClient();


	/**
	 * Create a layered screen
	 */
	public LayeredScreen()
	{
		addChildClient(layersClient);
	}


	@Override
	protected void renderScreen()
	{
		for (final ScreenLayer layer : layersByZIndex) {
			if (layer.isVisible()) layer.render();
		}
	}


	/**
	 * Add a layer to the screen.
	 *
	 * @param layer the layer to add
	 */
	protected void addLayer(ScreenLayer layer)
	{
		this.layersByZIndex.add(layer);
		this.layersByEventPriority.add(layer);

		Collections.sort(layersByEventPriority, new Comparator<Overlay>() {

			@Override
			public int compare(Overlay o1, Overlay o2)
			{
				return o2.getEventPriority() - o1.getEventPriority();
			}

		});

		Collections.sort(layersByZIndex, new Comparator<Overlay>() {

			@Override
			public int compare(Overlay o1, Overlay o2)
			{
				return o1.getZIndex() - o2.getZIndex();
			}

		});
	}


	@Override
	protected void onScreenEnter()
	{
		for (final ScreenLayer layer : layersByEventPriority) {
			layer.onScreenEnter();
		}
	}


	@Override
	protected void onScreenLeave()
	{
		for (final ScreenLayer layer : layersByEventPriority) {
			layer.onScreenLeave();
		}
	}

}