/*
 * 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: PropertyInfo.java 985537 2010-08-14 17:17:00Z jeremias $ */

package org.apache.fop.fo.expr;

import java.util.Stack;

import org.apache.fop.apps.FOUserAgent;
import org.apache.fop.datatypes.Length;
import org.apache.fop.datatypes.PercentBase;
import org.apache.fop.fo.Constants;
import org.apache.fop.fo.FObj;
import org.apache.fop.fo.PropertyList;
import org.apache.fop.fo.properties.PropertyMaker;


This class holds context information needed during property expression
evaluation.
It holds the Maker object for the property, the PropertyList being
built, and the FObj parent of the FObj for which the property is being set.
/**
 * This class holds context information needed during property expression
 * evaluation.
 * It holds the Maker object for the property, the PropertyList being
 * built, and the FObj parent of the FObj for which the property is being set.
 */
public class PropertyInfo {
    private PropertyMaker maker;
    private PropertyList plist;
    private FObj fo;
    private Stack stkFunction;    // Stack of functions being evaluated

    
Constructor
Params:
maker – Property.Maker object
plist – PropertyList object/**
     * Constructor
     * @param maker Property.Maker object
     * @param plist PropertyList object
     */
    public PropertyInfo(PropertyMaker maker, PropertyList plist) {
        this.maker = maker;
        this.plist = plist;
        this.fo = plist.getParentFObj();
    }

    
Return the PercentBase object used to calculate the absolute value from
a percent specification.
Propagates to the Maker.
Throws:
PropertyException – if a property exception occurs
Returns:
The PercentBase object or null if percentLengthOK()=false./**
     * Return the PercentBase object used to calculate the absolute value from
     * a percent specification.
     * Propagates to the Maker.
     * @return The PercentBase object or null if percentLengthOK()=false.
     * @throws PropertyException if a property exception occurs
     */
    public PercentBase getPercentBase() throws PropertyException {
        PercentBase pcbase = getFunctionPercentBase();
        return (pcbase != null) ? pcbase : maker.getPercentBase(plist);
    }

    
Throws:
PropertyException – if a property exception occurs
Returns:
the current font-size value as base units (milli-points)./**
     * @return the current font-size value as base units (milli-points).
     * @throws PropertyException if a property exception occurs
     */
    public Length currentFontSize() throws PropertyException {
        return plist.get(Constants.PR_FONT_SIZE).getLength();
    }

    
accessor for FObj
Returns:
FObj/**
     * accessor for FObj
     * @return FObj
     */
    public FObj getFO() {
        return fo;
    }

    
accessor for PropertyList
Returns:
PropertyList object/**
     * accessor for PropertyList
     * @return PropertyList object
     */
    public PropertyList getPropertyList() {
        return plist;
    }

    
accessor for PropertyMaker
Returns:
PropertyMaker object/**
     * accessor for PropertyMaker
     * @return PropertyMaker object
     */
    public PropertyMaker getPropertyMaker() {
        return maker;
    }

    
push a function onto the function stack
Params:
func – function to push onto stack/**
     * push a function onto the function stack
     * @param func function to push onto stack
     */
    public void pushFunction(Function func) {
        if (stkFunction == null) {
            stkFunction = new Stack();
        }
        stkFunction.push(func);
    }

    
pop a function off of the function stack
/**
     * pop a function off of the function stack
     */
    public void popFunction() {
        if (stkFunction != null) {
            stkFunction.pop();
        }
    }

    
Convenience shortcut to get a reference to the FOUserAgent
Returns:
 the FOUserAgent/**
     * Convenience shortcut to get a reference to the FOUserAgent
     *
     * @return  the FOUserAgent
     */
    protected FOUserAgent getUserAgent() {
        return (plist.getFObj() != null)
            ? plist.getFObj().getUserAgent()
                    : null;
    }

    private PercentBase getFunctionPercentBase() {
        if (stkFunction != null) {
            Function f = (Function)stkFunction.peek();
            if (f != null) {
                return f.getPercentBase();
            }
        }
        return null;
    }

}