001// Copyright 2009, 2011 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.corelib.mixins;
016
017import org.apache.tapestry5.MarkupWriter;
018import org.apache.tapestry5.annotations.MixinAfter;
019import org.apache.tapestry5.dom.Element;
020
021/**
022 * A mixin that attaches to an element that renders an element.  At the end of the render, if the element is empty, then
023 * a non-breaking space ( ) is injected into the element. This is often necessary for proper rendering on the
024 * client.
025 * <p/>
026 * Often used in conjunction with the {@link org.apache.tapestry5.corelib.components.Any} component.
027 *
028 * @since 5.1.0.0
029 * @tapestrydoc
030 */
031@MixinAfter
032public class NotEmpty
033{
034    private Element element;
035
036    void beginRender(MarkupWriter writer)
037    {
038        element = writer.getElement();
039    }
040
041    void afterRender()
042    {
043        if (element.isEmpty())
044        {
045            element.removeChildren();
046            element.raw("&nbsp;");
047        }
048    }
049}