VerticalGroup.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.ui;

import com.badlogic.gdx.scenes.scene2d.Actor;
import com.badlogic.gdx.scenes.scene2d.Touchable;
import com.badlogic.gdx.scenes.scene2d.utils.Align;
import com.badlogic.gdx.scenes.scene2d.utils.Layout;
import com.badlogic.gdx.utils.SnapshotArray;

/**
 * A group that lays out its children on top of each other in a single column. This can be easier than using
 * {@link Table} when actors need to be inserted in the middle of the group.
 * <p>
 * The preferred width is the largest preferred width of any child. The preferred height is the sum of the children's
 * preferred heights. The min size is the preferred size and the max size is 0.
 * 
 * @author Nathan Sweet
 */
public class VerticalGroup extends WidgetGroup {
	private float prefWidth, prefHeight;
	private boolean sizeInvalid = true;
	private int alignment;
	private boolean reverse;

	public VerticalGroup() {
		setTouchable(Touchable.childrenOnly);
	}

	/**
	 * Sets the horizontal alignment of the children. Default is center.
	 * 
	 * @see Align
	 */
	public void setAlignment(int alignment) {
		this.alignment = alignment;
	}

	/** If true, the children will be ordered from bottom to top rather than the default top to bottom. */
	public void setReverse(boolean reverse) {
		this.reverse = reverse;
	}

	public void invalidate() {
		super.invalidate();
		sizeInvalid = true;
	}

	private void computeSize() {
		sizeInvalid = false;
		prefWidth = 0;
		prefHeight = 0;
		SnapshotArray<Actor> children = getChildren();
		for (int i = 0, n = children.size; i < n; i++) {
			Actor child = children.get(i);
			if (child instanceof Layout) {
				Layout layout = (Layout) child;
				prefWidth = Math.max(prefWidth, layout.getPrefWidth());
				prefHeight += layout.getPrefHeight();
			} else {
				prefWidth = Math.max(prefWidth, child.getWidth());
				prefHeight += child.getHeight();
			}
		}
	}

	public void layout() {
		float groupWidth = getWidth();
		float y = reverse ? 0 : getHeight();
		float dir = reverse ? 1 : -1;
		SnapshotArray<Actor> children = getChildren();
		for (int i = 0, n = children.size; i < n; i++) {
			Actor child = children.get(i);
			float width, height;
			if (child instanceof Layout) {
				Layout layout = (Layout) child;
				width = layout.getPrefWidth();
				height = layout.getPrefHeight();
			} else {
				width = child.getWidth();
				height = child.getHeight();
			}
			float x;
			if ((alignment & Align.left) != 0)
				x = 0;
			else if ((alignment & Align.right) != 0)
				x = groupWidth - width;
			else
				x = (groupWidth - width) / 2;
			if (!reverse)
				y += height * dir;
			child.setBounds(x, y, width, height);
			if (reverse)
				y += height * dir;
		}
	}

	public float getPrefWidth() {
		if (sizeInvalid)
			computeSize();
		return prefWidth;
	}

	public float getPrefHeight() {
		if (sizeInvalid)
			computeSize();
		return prefHeight;
	}
}