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Apache FOP (Formatting Objects Processor) is the world's first print formatter driven by XSL formatting objects (XSL-FO) and the world's first output independent formatter. It is a Java application that reads a formatting object (FO) tree and renders the resulting pages to a specified output. Output formats currently supported include PDF, PCL, PS, AFP, TIFF, PNG, SVG, XML (area tree representation), Print, AWT and TXT. The primary output target is PDF.
/*
* 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: Function.java 679326 2008-07-24 09:35:34Z vhennebert $ */
package org.apache.fop.fo.expr;
import org.apache.fop.fo.properties.Property;
import org.apache.fop.datatypes.PercentBase;
/**
* Interface for managing XSL-FO Functions
*/
public interface Function {
/**
* @return the number of arguments that must be passed to this function. For
* example, if the function should determine the minimum of two numbers, it
* must be passed two arguments, one for each of the two values.
*/
int nbArgs();
/**
* @return the basis for percentage calculations
*/
PercentBase getPercentBase();
/**
* Evaluate the function
* @param args an array of Properties that should be evaluated
* @param propInfo the PropertyInfo
* @return the Property satisfying the function
* @throws PropertyException for problems when evaluating the function
*/
Property eval(Property[] args,
PropertyInfo propInfo) throws PropertyException;
/**
* @return if it is allowed to fill up the property list with
* the property name if only one arg is missing.
*/
boolean padArgsWithPropertyName();
}