src/java/org/apache/fop/render/intermediate/IFContext.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

/* $Id$ */

package org.apache.fop.render.intermediate;

import java.util.Collections;
import java.util.Map;

import org.apache.xmlgraphics.util.QName;

import org.apache.fop.apps.FOUserAgent;

/**
 * This class provides a context object that is valid for a single processing run to create
 * an output file using the intermediate format. It allows access to the user agent and other
 * context information, such as foreign attributes for certain elements in the intermediate
 * format.
 * <p>
 * Foreign attributes are usually specific to a particular output format implementation. Most
 * implementations will just ignore all foreign attributes for most elements. That's why the
 * main IF interfaces are not burdened with this.
 */
public class IFContext {

    private FOUserAgent userAgent;

    /** foreign attributes: Map<QName, Object> */
    private Map foreignAttributes = Collections.EMPTY_MAP;

    /**
     * Main constructor.
     * @param ua the user agent
     */
    public IFContext(FOUserAgent ua) {
        setUserAgent(ua);
    }

    /**
     * Set the user agent.
     * @param ua the user agent
     */
    public void setUserAgent(FOUserAgent ua) {
        if (this.userAgent != null) {
            throw new IllegalStateException("The user agent was already set");
        }
        this.userAgent = ua;
    }

    /**
     * Returns the associated user agent.
     * @return the user agent
     */
    public FOUserAgent getUserAgent() {
        return this.userAgent;
    }

    /**
     * Returns the currently applicable foreign attributes.
     * @return a Map<QName, Object>
     */
    public Map getForeignAttributes() {
        return this.foreignAttributes;
    }

    /**
     * Returns a foreign attribute.
     * @param qName the qualified name of the foreign attribute
     * @return the value of the foreign attribute or null if the attribute isn't specified
     */
    public Object getForeignAttribute(QName qName) {
        return this.foreignAttributes.get(qName);
    }

    /**
     * Sets the currently applicable foreign attributes.
     * @param foreignAttributes a Map<QName, Object> or null to reset
     */
    public void setForeignAttributes(Map foreignAttributes) {
        if (foreignAttributes != null) {
            this.foreignAttributes = foreignAttributes;
        } else {
            //Make sure there is always at least an empty map so we don't have to check
            //in the implementation code
            this.foreignAttributes = Collections.EMPTY_MAP;
        }
    }

    /**
     * Resets the foreign attributes to "no foreign attributes".
     */
    public void resetForeignAttributes() {
        setForeignAttributes(null);
    }

}