CustomListCell.java

/*******************************************************************************
 * Copyright (c) 2006-2010 eBay Inc. All Rights Reserved.
 * 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
 *******************************************************************************/
package org.ebayopensource.turmeric.policy.adminui.client.view.policy;

import java.util.List;

import com.google.gwt.cell.client.AbstractInputCell;
import com.google.gwt.core.client.GWT;
import com.google.gwt.safehtml.client.SafeHtmlTemplates;
import com.google.gwt.safehtml.client.SafeHtmlTemplates.Template;
import com.google.gwt.safehtml.shared.SafeHtml;
import com.google.gwt.safehtml.shared.SafeHtmlBuilder;

/**
 * Custom cell implementation that allows to show a list of Strings as an html select
 * tag or a simple HTML-scaped string list based on the minScrollbarSize attribute.
 * 
 */
public class CustomListCell extends AbstractInputCell<List<String>, String> {
    private int minScrollbarSize = 3;

    interface Template extends SafeHtmlTemplates {
		@Template("<select size=\"{0}\"  tabindex=\"-1\">{1}</select>")
		SafeHtml selectTag(String size, SafeHtml content);
		
		@Template("<option value=\"{0}\">{0}</option>")
		SafeHtml deselected(String option);

		@Template("<option value=\"{0}\" selected=\"selected\">{0}</option>")
		SafeHtml selected(String option);
	}

	private static Template template;

	/**
	 * Instantiates a new custom list cell.
	 */
	public CustomListCell() {
		super("change");
		if (template == null) {
			template = GWT.create(Template.class);
		}
	}

	/**
	 * Instantiates a new custom list cell.
	 * @param minScrollbarSize
	 *            the min scrollbar size
	 */
	public CustomListCell(int minScrollbarSize) {
		this();
		if (minScrollbarSize < 0) {
            throw new IllegalArgumentException("Invalid minScrollbarSize parameter = "
					+ minScrollbarSize);
		}
		this.minScrollbarSize = minScrollbarSize;
	}

	/**
     * Renders the element list. If the list size >= minScrollbarSize then the
	 * cell renders as a select element, else, as a text list of elements,
	 * separated by br tags
     * 
	 * @param value
	 *            the value
	 * @param key
	 *            the key
	 * @param sb
	 *            the sb
	 */
	public final void render(final List<String> value, final Object key, final SafeHtmlBuilder sb) {
		if (value != null) {
			if (value.size() >= minScrollbarSize) {
				renderSelectList(value, sb);
			} else {
				renderSimpleList(value, sb);
			}
		}

	}
	
	private void renderSimpleList(final List<String> value, final SafeHtmlBuilder sb) {
		if (value != null && !value.isEmpty()) {
			for (String option : value) {
				sb.appendEscaped(option).appendHtmlConstant("<br>");
			}
		}
	}

	private void renderSelectList(final List<String> value, final SafeHtmlBuilder sb) {
		SafeHtmlBuilder content = new SafeHtmlBuilder();
		if (value != null && !value.isEmpty()) {
			for (String option : value) {
				content.append(template.deselected(option));
			}
		}
		sb.append(template.selectTag(String.valueOf(this.minScrollbarSize), content.toSafeHtml()));
		
	}

	/* (non-Javadoc)
	 * @see com.google.gwt.cell.client.AbstractCell#render(com.google.gwt.cell.client.Cell.Context, java.lang.Object, com.google.gwt.safehtml.shared.SafeHtmlBuilder)
	 */
	@Override
	public final void render(com.google.gwt.cell.client.Cell.Context paramContext,
			List<String> paramC, SafeHtmlBuilder paramSafeHtmlBuilder) {
		this.render(paramC, paramContext.getKey(), paramSafeHtmlBuilder);
	}

}