/* * 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.fo.expr; import org.apache.fop.datatypes.PercentBase; import org.apache.fop.fo.properties.Property; /** * Interface for managing XSL-FO Functions */ public interface Function { /** * @return the number of required (non-optional) arguments that must be specified * in the argument list */ int getRequiredArgsCount(); /** * @return the number of non-required (optional) arguments that may be specified * in the argument list, which, if specified, must follow the required arguments */ int getOptionalArgsCount(); /** * @param index of optional argument * @param pi property information instance that applies to property being evaluated * @return the default property value for the optional argument at INDEX, where * INDEX is with respect to optional arguments; i.e., the first optional argument * position is index 0; if no default for a given index, then null is returned * @throws PropertyException if index is greater than or equal to optional args count */ Property getOptionalArgDefault(int index, PropertyInfo pi) throws PropertyException; /** * Determine if function allows variable arguments. If it does, then they must appear * after required and optional arguments, and all optional arguments must be specified. * @return true if function permits additional variable number of arguments after * required and (completely specified) optional arguments */ boolean hasVariableArgs(); /** * @return the basis for percentage calculations */ PercentBase getPercentBase(); /** * Evaluate the function * @param args an array of Properties that should be evaluated * @param pi property information instance that applies to property being evaluated * @return the Property satisfying the function * @throws PropertyException for problems when evaluating the function */ Property eval(Property[] args, PropertyInfo pi) throws PropertyException; }