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/*
 * Copyright © 1996-2009 GlobalMentor, Inc. 
 *
 * 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.globalmentor.swing;

import java.awt.*;
import javax.swing.*;

/**
 * An class for simple rendering of custom strings and icons in a list cell. A child class should override
 * {@link SimpleListCellRenderer#getListCellRendererString(Object)} and return the correct string for display. If that method is not overridden, the value will
 * be converted to a string by default.
 * 
 * If it is desired that an icon be displayed, a child class should override getListCellRendererIcon() and return the correct icon for display.
 * 
 * @author Garret Wilson
 */
public class SimpleListCellRenderer extends DefaultListCellRenderer {

	/** Default constructor. */
	public SimpleListCellRenderer() {
	}

	/**
	 * @return A renderer with the correct text for this list item.
	 * @param list The list component.
	 * @param value The value of this list item.
	 * @param index The index of this list item.
	 * @param isSelected Whether the list item is selected.
	 * @param cellHasFocus Whether the list item has the focus.
	 */
	public Component getListCellRendererComponent(final JList list, final Object value, final int index, final boolean isSelected, final boolean cellHasFocus) {
		final Component component = super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus); //get the default component
		final String string = getListCellRendererString(list, value, index, isSelected, cellHasFocus); //get the string to display
		final Icon icon = getListCellRendererIcon(list, value, index, isSelected, cellHasFocus); //get the icon to display
		//TODO assert the string is not null
		assert component instanceof JLabel : "List cell renderer component is not a JLabel";
		final JLabel label = (JLabel)component; //cast the component to a label, assuming that the component is a JLabel (which is likely the implementation used by the default)
		label.setText(string); //set the correct text
		if(icon != null) //if we have an icon
			label.setIcon(icon); //set the icon
		return component; //return the component, now using our custom text
	}

	/**
	 * Retrieves text for a list item. This can be overridden in a derived class to return custom text for the specified value. This default version delegates to
	 * the one-parameter version.
	 * @param list The list component.
	 * @param value The value of this list item.
	 * @param index The index of this list item.
	 * @param isSelected Whether the list item is selected.
	 * @param cellHasFocus Whether the list item has the focus.
	 * @return The correct text for this list item.
	 */
	protected String getListCellRendererString(final JList list, final Object value, final int index, final boolean isSelected, final boolean cellHasFocus) {
		return getListCellRendererString(value); //delegate to the simple version
	}

	/**
	 * Retrieves text for a list item. This can be overridden in a derived class to return custom text for the specified value. This default version is called
	 * from the multi-parameter version, and returns the object's default toString() value.
	 * @param value The value of this list item.
	 * @return The correct text for this list item.
	 */
	protected String getListCellRendererString(final Object value) {
		return value.toString(); //return the string value of the object by default
	}

	/**
	 * Retrieves an icon for a list item. This can be overridden in a derived class to return a custom icon for the specified value. This default version
	 * delegates to the one-parameter version.
	 * @param list The list component.
	 * @param value The value of this list item.
	 * @param index The index of this list item.
	 * @param isSelected Whether the list item is selected.
	 * @param cellHasFocus Whether the list item has the focus.
	 * @return The correct icon for this list item, or null if no icon should be displayed.
	 */
	protected Icon getListCellRendererIcon(final JList list, final Object value, final int index, final boolean isSelected, final boolean cellHasFocus) {
		return getListCellRendererIcon(value); //return the result of the simple version
	}

	/**
	 * Retrieves an icon for a list item. This can be overridden in a derived class to return a custom icon for the specified value. This default version is
	 * called from the multi-parameter version, and returns null.
	 * @param value The value of this list item.
	 * @return The correct icon for this list item, or null if no icon should be displayed.
	 */
	protected Icon getListCellRendererIcon(final Object value) {
		return null; //we don't know the icon in this version
	}

}