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