/*
* 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.layoutmgr;
import java.util.List;
import java.util.ListIterator;
import org.apache.fop.traits.MinOptMax;
import org.apache.fop.util.ListUtil;
/**
* Utilities for Knuth element lists.
*/
public final class ElementListUtils {
private ElementListUtils() {
// Utility class.
}
/**
* Removes legal breaks in an element list. A constraint can be specified to limit the
* range in which the breaks are removed. Legal breaks occuring before at least
* constraint.opt space is filled will be removed.
* @param elements the element list
* @param constraint min/opt/max value to restrict the range in which the breaks are removed.
* @return true if the opt constraint is bigger than the list contents
*/
public static boolean removeLegalBreaks(List elements, MinOptMax constraint) {
return removeLegalBreaks(elements, constraint.getOpt());
}
/**
* Removes legal breaks in an element list. A constraint can be specified to limit the
* range in which the breaks are removed. Legal breaks occuring before at least
* constraint space is filled will be removed.
* @param elements the element list
* @param constraint value to restrict the range in which the breaks are removed.
* @return true if the constraint is bigger than the list contents
*/
public static boolean removeLegalBreaks(List elements, int constraint) {
return removeLegalBreaks(elements, constraint, false);
}
/**
* Removes legal breaks in an element list. A constraint can be specified to limit the
* range in which the breaks are removed. Legal breaks within the space specified through the
* constraint (starting from the end of the element list) will be removed.
* @param elements the element list
* @param constraint value to restrict the range in which the breaks are removed.
* @return true if the constraint is bigger than the list contents
*/
public static boolean removeLegalBreaksFromEnd(List elements, int constraint) {
return removeLegalBreaks(elements, constraint, true);
}
private static boolean removeLegalBreaks(List elements, int constraint, boolean fromEnd) {
int len = 0;
ListElement el;
for (ListIterator iter = elements.listIterator(fromEnd ? elements.size() : 0);
(fromEnd ? iter.hasPrevious() : iter.hasNext());) {
if (fromEnd) {
el = (ListElement) iter.previous();
} else {
el = (ListElement) iter.next();
}
if (el.isPenalty()) {
KnuthPenalty penalty = (KnuthPenalty)el;
//Convert penalty to break inhibitor
if (penalty.getPenalty() < KnuthPenalty.INFINITE) {
iter.set(new KnuthPenalty(penalty.getWidth(), KnuthPenalty.INFINITE,
penalty.isPenaltyFlagged(), penalty.getPosition(),
penalty.isAuxiliary()));
}
} else if (el.isGlue()) {
KnuthGlue glue = (KnuthGlue)el;
len += glue.getWidth();
//check if previous is a box
if (!fromEnd) {
iter.previous();
}
el = (ListElement)iter.previous();
iter.next();
if (el.isBox()) {
//add break inhibitor
iter.add(new KnuthPenalty(0, KnuthPenalty.INFINITE, false,
null, false));
}
if (!fromEnd) {
iter.next();
}
} else if (el.isUnresolvedElement()) {
if (el instanceof BreakElement) {
BreakElement breakEl = (BreakElement)el;
if (breakEl.getPenaltyValue() < KnuthPenalty.INFINITE) {
breakEl.setPenaltyValue(KnuthPenalty.INFINITE);
}
} else if (el instanceof UnresolvedListElementWithLength) {
UnresolvedListElementWithLength uel = (UnresolvedListElementWithLength)el;
len += uel.getLength().getOpt();
}
} else {
KnuthElement kel = (KnuthElement)el;
len += kel.getWidth();
}
if (len >= constraint) {
return false;
}
}
return true;
}
/**
* Calculates the content length of the given element list. Warning: It doesn't take any
* stretch and shrink possibilities into account.
* @param elems the element list
* @param start element at which to start
* @param end element at which to stop
* @return the content length
*/
public static int calcContentLength(List elems, int start, int end) {
ListIterator iter = elems.listIterator(start);
int count = end - start + 1;
int len = 0;
while (iter.hasNext()) {
ListElement el = (ListElement)iter.next();
if (el.isBox()) {
len += ((KnuthElement)el).getWidth();
} else if (el.isGlue()) {
len += ((KnuthElement)el).getWidth();
} else {
//log.debug("Ignoring penalty: " + el);
//ignore penalties
}
count--;
if (count == 0) {
break;
}
}
return len;
}
/**
* Calculates the content length of the given element list. Warning: It doesn't take any
* stretch and shrink possibilities into account.
* @param elems the element list
* @return the content length
*/
public static int calcContentLength(List elems) {
return calcContentLength(elems, 0, elems.size() - 1);
}
/**
* Indicates whether the given element list ends with a forced break.
* @param elems the element list
* @return true if the list ends with a forced break
*/
public static boolean endsWithForcedBreak(List elems) {
return ((ListElement) ListUtil.getLast(elems)).isForcedBreak();
}
/**
* Indicates whether the given element list starts with a forced break.
* @param elems the element list
* @return true if the list starts with a forced break
*/
public static boolean startsWithForcedBreak(List elems) {
return !elems.isEmpty() && ((ListElement) elems.get(0)).isForcedBreak();
}
/**
* Indicates whether the given element list ends with a penalty with a non-infinite penalty
* value.
* @param elems the element list
* @return true if the list ends with a non-infinite penalty
*/
public static boolean endsWithNonInfinitePenalty(List elems) {
ListElement last = (ListElement) ListUtil.getLast(elems);
if (last.isPenalty() && ((KnuthPenalty)last).getPenalty() < KnuthElement.INFINITE) {
return true;
} else if (last instanceof BreakElement
&& ((BreakElement)last).getPenaltyValue() < KnuthElement.INFINITE) {
return true;
}
return false;
}
/**
* Determines the position of the previous break before the start index on an
* element list.
* @param elems the element list
* @param startIndex the start index
* @return the position of the previous break, or -1 if there was no previous break
*/
public static int determinePreviousBreak(List elems, int startIndex) {
int prevBreak = startIndex - 1;
while (prevBreak >= 0) {
KnuthElement el = (KnuthElement)elems.get(prevBreak);
if (el.isPenalty() && el.getPenalty() < KnuthElement.INFINITE) {
break;
}
prevBreak--;
}
return prevBreak;
}
public static boolean isEmptyBox(List elements) {
if (elements.size() == 1 && elements.get(0) instanceof KnuthBox) {
KnuthBox kb = (KnuthBox) elements.get(0);
if (kb.getWidth() == 0) {
return true;
}
}
return false;
}
}