001    // Copyright 2006, 2008, 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    
015    package org.apache.tapestry5.runtime;
016    
017    import org.apache.tapestry5.ComponentResources;
018    
019    /**
020     * A stateful object that manages the process of rendering a page. Rending a page in Tapestry is based on a command
021     * queue.
022     */
023    public interface RenderQueue
024    {
025        /**
026         * Adds the new command to the front of the queue.
027         */
028        void push(RenderCommand command);
029    
030        /**
031         * Indicates that a component is starting its render. A stack of active components is used for exception reporting.
032         * 
033         * @param resources
034         *            identifies the component that is rendering
035         */
036        void startComponent(ComponentResources resources);
037    
038        /**
039         * Corresponds to {@link #startComponent(ComponentResources)}, used to denote when the most recently started
040         * component finishes
041         * rendering.
042         */
043        void endComponent();
044    }