org.apache.fop.layoutmgr.Keep Maven / Gradle / Ivy
/*
* 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: Keep.java 985537 2010-08-14 17:17:00Z jeremias $ */
package org.apache.fop.layoutmgr;
import org.apache.fop.fo.Constants;
import org.apache.fop.fo.properties.KeepProperty;
import org.apache.fop.fo.properties.Property;
/**
* Object representing a keep constraint, corresponding
* to the XSL-FO keep properties.
*/
public final class Keep {
/** The integer value for "auto" keep strength. */
private static final int STRENGTH_AUTO = Integer.MIN_VALUE;
/** The integer value for "always" keep strength. */
private static final int STRENGTH_ALWAYS = Integer.MAX_VALUE;
/** keep auto */
public static final Keep KEEP_AUTO = new Keep(STRENGTH_AUTO, Constants.EN_AUTO);
/** keep always */
public static final Keep KEEP_ALWAYS = new Keep(STRENGTH_ALWAYS, Constants.EN_LINE);
private int strength;
private int context;
private Keep(int strength, int context) {
this.strength = strength;
this.context = context;
}
private static int getKeepStrength(Property keep) {
if (keep.isAuto()) {
return STRENGTH_AUTO;
} else if (keep.getEnum() == Constants.EN_ALWAYS) {
return STRENGTH_ALWAYS;
} else {
return keep.getNumber().intValue();
}
}
/**
* Obtain a Keep instance corresponding to the given {@link KeepProperty}
*
* @param keepProperty the {@link KeepProperty}
* @return a new instance corresponding to the given property
*/
public static Keep getKeep(KeepProperty keepProperty) {
Keep keep = new Keep(STRENGTH_AUTO, Constants.EN_AUTO);
keep.update(keepProperty.getWithinPage(), Constants.EN_PAGE);
keep.update(keepProperty.getWithinColumn(), Constants.EN_COLUMN);
keep.update(keepProperty.getWithinLine(), Constants.EN_LINE);
return keep;
}
private void update(Property keep, int context) {
if (!keep.isAuto()) {
this.strength = getKeepStrength(keep);
this.context = context;
}
}
/** @return {@code true} if the keep property was specified as "auto" */
public boolean isAuto() {
return strength == STRENGTH_AUTO;
}
/**
* Returns the context of this keep.
*
* @return one of {@link Constants#EN_LINE}, {@link Constants#EN_COLUMN} or
* {@link Constants#EN_PAGE}
*/
public int getContext() {
return context;
}
/** @return the penalty value corresponding to the strength of this Keep */
public int getPenalty() {
if (strength == STRENGTH_AUTO) {
return 0;
} else if (strength == STRENGTH_ALWAYS) {
return KnuthElement.INFINITE;
} else {
return KnuthElement.INFINITE - 1;
}
}
private static int getKeepContextPriority(int context) {
switch (context) {
case Constants.EN_LINE: return 0;
case Constants.EN_COLUMN: return 1;
case Constants.EN_PAGE: return 2;
case Constants.EN_AUTO: return 3;
default: throw new IllegalArgumentException();
}
}
/**
* Compare this Keep instance to another one, and return the
* stronger one if the context is the same
*
* @param other the instance to compare to
* @return the winning Keep instance
*/
public Keep compare(Keep other) {
/* check strength "always" first, regardless of priority */
if (this.strength == STRENGTH_ALWAYS
&& this.strength > other.strength) {
return this;
} else if (other.strength == STRENGTH_ALWAYS
&& other.strength > this.strength) {
return other;
}
int pThis = getKeepContextPriority(this.context);
int pOther = getKeepContextPriority(other.context);
/* equal priority: strongest wins */
if (pThis == pOther) {
return (strength >= other.strength) ? this : other;
}
/* different priority: lowest priority wins */
return (pThis < pOther) ? this : other;
}
/** {@inheritDoc} */
public String toString() {
return (strength == STRENGTH_AUTO) ? "auto"
: (strength == STRENGTH_ALWAYS) ? "always"
: Integer.toString(strength);
}
}