Layout.java

/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 ******************************************************************************/

package com.badlogic.gdx.scenes.scene2d.utils;

import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.scenes.scene2d.Actor;
import com.badlogic.gdx.scenes.scene2d.ui.Table;

/**
 * Provides methods for an actor to participate in layout and to provide a minimum, preferred, and maximum size.
 * 
 * @author Nathan Sweet
 */
public interface Layout {
	/**
	 * Computes and caches any information needed for drawing and, if this actor has children, positions and sizes each
	 * child, calls {@link #invalidate()} any each child whose width or height has changed, and calls
	 * {@link #validate()} on each child. This method should almost never be called directly, instead
	 * {@link #validate()} should be used.
	 */
	public void layout();

	/**
	 * Invalidates this actor's layout, causing {@link #layout()} to happen the next time {@link #validate()} is called.
	 * This method should be called when state changes in the actor that requires a layout but does not change the
	 * minimum, preferred, maximum, or actual size of the actor (meaning it does not affect the parent actor's layout).
	 */
	public void invalidate();

	/**
	 * Invalidates this actor and all its parents, calling {@link #invalidate()} on all involved actors. This method
	 * should be called when state changes in the actor that affects the minimum, preferred, maximum, or actual size of
	 * the actor (meaning it it potentially affects the parent actor's layout).
	 */
	public void invalidateHierarchy();

	/**
	 * Ensures the actor has been laid out. Calls {@link #layout()} if {@link #invalidate()} has called since the last
	 * time {@link #validate()} was called, or if the actor otherwise needs to be laid out. This method is usually
	 * called in {@link Actor#draw(SpriteBatch, float)} before drawing is performed.
	 */
	public void validate();

	/**
	 * Sizes this actor to its preferred width and height and, if this changed the size, causes the actor to be laid out
	 * by calling {@link #invalidate()} then {@link #validate()}.
	 * <p>
	 * Generally this method should not be called in an actor's constructor because it calls {@link #layout()}, which
	 * means a subclass would have layout() called before the subclass' constructor. Instead, in constructors, simply
	 * set the actors width and height to {@link #getPrefWidth()} and {@link #getPrefHeight()}. This allows the actor to
	 * have a size at construction time for more convenient use outside of a {@link Table}.
	 */
	public void pack();

	/**
	 * If true, this actor will be sized to the parent in {@link #validate()}. If the parent is the stage, the actor
	 * will be sized to the stage.
	 */
	public void setFillParent(boolean fillParent);

	/**
	 * Enables or disables the layout for this actor and all child actors, recursively. When false, {@link #validate()}
	 * will not cause a layout to occur. This is useful when an actor will be manipulated externally, such as with
	 * actions. Default is true.
	 */
	public void setLayoutEnabled(boolean enabled);

	public float getMinWidth();

	public float getMinHeight();

	public float getPrefWidth();

	public float getPrefHeight();

	public float getMaxWidth();

	public float getMaxHeight();
}