org.apache.fop.layoutmgr

Class BalancingColumnBreakingAlgorithm

java.lang.Object

org.apache.fop.layoutmgr.BreakingAlgorithm

org.apache.fop.layoutmgr.BalancingColumnBreakingAlgorithm

public class BalancingColumnBreakingAlgorithm
extends BreakingAlgorithm

This is a the breaking algorithm that is responsible for balancing columns in multi-column layout.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	PageBreakingAlgorithm.PageBreakingLayoutListener Interface to notify about layout events during page breaking.

Nested classes/interfaces inherited from class org.apache.fop.layoutmgr.BreakingAlgorithm

BreakingAlgorithm.BestRecords, BreakingAlgorithm.KnuthNode

Field Summary

Fields inherited from class org.apache.fop.layoutmgr.BreakingAlgorithm

activeLines, activeNodeCount, alignment, alignmentLast, ALL_BREAKS, best, bFirst, considerTooShort, endLine, incompatibleFitnessDemerit, INFINITE_RATIO, lineWidth, maxFlaggedPenaltiesCount, NO_FLAGGED_PENALTIES, ONLY_FORCED_BREAKS, par, repeatedFlaggedDemerit, startLine, totalShrink, totalStretch, totalWidth

Constructor Summary

Constructors

Constructor and Description
BalancingColumnBreakingAlgorithm(LayoutManager topLevelLM, PageProvider pageProvider, PageBreakingAlgorithm.PageBreakingLayoutListener layoutListener, int alignment, int alignmentLast, MinOptMax footnoteSeparatorLength, boolean partOverflowRecovery, int columnCount)

Method Summary

Methods

Modifier and Type	Method and Description
protected double	computeAdjustmentRatio(BreakingAlgorithm.KnuthNode activeNode, int difference) Return the adjust ration needed to make up for the difference.
protected double	computeDemerits(BreakingAlgorithm.KnuthNode activeNode, KnuthElement element, int fitnessClass, double r) Computes the demerits of the current breaking (that is, up to the given element), if the next-to-last chosen breakpoint is the given active node.
protected int	computeDifference(BreakingAlgorithm.KnuthNode activeNode, KnuthElement element, int elementIndex) Return the difference between the natural width of a line that would be made between the given active node and the given element, and the available width of the real line.
protected void	considerLegalBreak(KnuthElement element, int elementIdx) Determines if the given breakpoint is a feasible breakpoint.
protected BreakingAlgorithm.KnuthNode	createNode(int position, int line, int fitness, int totalWidth, int totalStretch, int totalShrink) Creates a new active node for a break from the best active node of the given fitness class to the element at the given position.
protected BreakingAlgorithm.KnuthNode	createNode(int position, int line, int fitness, int totalWidth, int totalStretch, int totalShrink, double adjustRatio, int availableShrink, int availableStretch, int difference, double totalDemerits, BreakingAlgorithm.KnuthNode previous) Creates a new active node for a feasible breakpoint at the given position.
protected int	filterActiveNodes()
protected void	finish()
FObj	getFObj()
java.util.LinkedList	getFootnoteList(int index)
protected int	getLineWidth(int line) Returns the line/part width of a given line/part.
java.util.LinkedList	getPageBreaks()
protected void	handleBox(KnuthBox box) Page-breaking specific handling of the given box.
protected void	initialize() Resets the algorithm's variables.
void	insertPageBreakAsFirst(AbstractBreaker.PageBreakPosition pageBreak)
void	removeAllPageBreaks() Removes all page breaks from the result list.
protected int	restartFrom(BreakingAlgorithm.KnuthNode restartingNode, int currentIndex)
void	updateData1(int total, double demerits) Empty method, hook for subclasses.
void	updateData2(BreakingAlgorithm.KnuthNode bestActiveNode, KnuthSequence sequence, int total) Empty method, hook for subclasses.

Methods inherited from class org.apache.fop.layoutmgr.BreakingAlgorithm

addNode, compareNodes, findBreakingPoints, findBreakingPoints, getAlignment, getAlignmentLast, getElement, getLineWidth, getMaxRecoveryAttempts, getNode, isPartOverflowRecoveryActivated, removeNode, setConstantLineWidth, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BalancingColumnBreakingAlgorithm

public BalancingColumnBreakingAlgorithm(LayoutManager topLevelLM,
                                PageProvider pageProvider,
                                PageBreakingAlgorithm.PageBreakingLayoutListener layoutListener,
                                int alignment,
                                int alignmentLast,
                                MinOptMax footnoteSeparatorLength,
                                boolean partOverflowRecovery,
                                int columnCount)

Method Detail

computeDemerits

protected double computeDemerits(BreakingAlgorithm.KnuthNode activeNode,
                     KnuthElement element,
                     int fitnessClass,
                     double r)

Computes the demerits of the current breaking (that is, up to the given element), if the next-to-last chosen breakpoint is the given active node. This adds to the total demerits of the given active node, the demerits of a line starting at this node and ending at the given element.

Parameters:

activeNode - considered preceding line break

element - considered current line break

fitnessClass - fitness of the current line

r - adjustment ratio for the current line

Returns:

the demerit of the current line

initialize

protected void initialize()

Description copied from class: BreakingAlgorithm

Resets the algorithm's variables.

Overrides:

initialize in class BreakingAlgorithm

createNode

protected BreakingAlgorithm.KnuthNode createNode(int position,
                                     int line,
                                     int fitness,
                                     int totalWidth,
                                     int totalStretch,
                                     int totalShrink,
                                     double adjustRatio,
                                     int availableShrink,
                                     int availableStretch,
                                     int difference,
                                     double totalDemerits,
                                     BreakingAlgorithm.KnuthNode previous)

Description copied from class: BreakingAlgorithm

Creates a new active node for a feasible breakpoint at the given position. Only called in forced mode.

Overrides:

createNode in class BreakingAlgorithm

Parameters:

position - index of the element in the Knuth sequence

line - number of the line ending at the breakpoint

fitness - fitness class of the line ending at the breakpoint. One of 0, 1, 2, 3.

totalWidth - accumulated width of the KnuthElements up to after the breakpoint

totalStretch - accumulated stretchability of the KnuthElements up to after the breakpoint

totalShrink - accumulated shrinkability of the KnuthElements up to after the breakpoint

adjustRatio - adjustment ratio if the line ends at this breakpoint

availableShrink - available stretch of the line ending at this breakpoint

availableStretch - available shrink of the line ending at this breakpoint

difference - difference between target and actual line width

totalDemerits - minimum total demerits up to the breakpoint

previous - active node for the preceding breakpoint

createNode

protected BreakingAlgorithm.KnuthNode createNode(int position,
                                     int line,
                                     int fitness,
                                     int totalWidth,
                                     int totalStretch,
                                     int totalShrink)

Description copied from class: BreakingAlgorithm

Creates a new active node for a break from the best active node of the given fitness class to the element at the given position.

Overrides:

createNode in class BreakingAlgorithm

See Also:

BreakingAlgorithm.createNode(int, int, int, int, int, int, double, int, int, int, double, org.apache.fop.layoutmgr.BreakingAlgorithm.KnuthNode), BreakingAlgorithm.BestRecords

handleBox

protected void handleBox(KnuthBox box)

Page-breaking specific handling of the given box. Currently it adds the footnotes cited in the given box to the list of to-be-handled footnotes.

Overrides:

handleBox in class BreakingAlgorithm

Parameters:

box - a block-level element possibly containing foonotes citations

restartFrom

protected int restartFrom(BreakingAlgorithm.KnuthNode restartingNode,
              int currentIndex)

Overrides:

restartFrom in class BreakingAlgorithm

considerLegalBreak

protected void considerLegalBreak(KnuthElement element,
                      int elementIdx)

Description copied from class: BreakingAlgorithm

Determines if the given breakpoint is a feasible breakpoint. That is, if a decent line may be built between one of the currently active nodes and this breakpoint.

Overrides:

considerLegalBreak in class BreakingAlgorithm

Parameters:

element - the paragraph's element to consider

elementIdx - the element's index inside the paragraph

computeDifference

protected int computeDifference(BreakingAlgorithm.KnuthNode activeNode,
                    KnuthElement element,
                    int elementIndex)

Description copied from class: BreakingAlgorithm

Return the difference between the natural width of a line that would be made between the given active node and the given element, and the available width of the real line.

Overrides:

computeDifference in class BreakingAlgorithm

Parameters:

activeNode - node for the previous breakpoint

element - currently considered breakpoint

Returns:

The difference in width. Positive numbers mean extra space in the line, negative number that the line overflows.

computeAdjustmentRatio

protected double computeAdjustmentRatio(BreakingAlgorithm.KnuthNode activeNode,
                            int difference)

Description copied from class: BreakingAlgorithm

Return the adjust ration needed to make up for the difference. A ration of

• 0 means that the break has the exact right width
• >= -1 && < 0 means that the break is wider than the line, but within the minimim values of the glues.
• >0 && < 1 means that the break is smaller than the line width, but within the maximum values of the glues.
• > 1 means that the break is too small to make up for the glues.

Overrides:

computeAdjustmentRatio in class BreakingAlgorithm

Returns:

The ration.

finish

protected void finish()

Overrides:

finish in class BreakingAlgorithm

getPageBreaks

public java.util.LinkedList getPageBreaks()

Returns:

a list of PageBreakPosition elements

insertPageBreakAsFirst

public void insertPageBreakAsFirst(AbstractBreaker.PageBreakPosition pageBreak)

removeAllPageBreaks

public void removeAllPageBreaks()

Removes all page breaks from the result list. This is used by block-containers and static-content when it is only desired to know where there is an overflow but later the whole content should be painted as one part.

updateData1

public void updateData1(int total,
               double demerits)

Description copied from class: BreakingAlgorithm

Empty method, hook for subclasses. Called before determining the optimal breakpoints corresponding to a given active node.

Specified by:

updateData1 in class BreakingAlgorithm

Parameters:

total - number of lines for the active node

demerits - total demerits of the paragraph for the active node

updateData2

public void updateData2(BreakingAlgorithm.KnuthNode bestActiveNode,
               KnuthSequence sequence,
               int total)

Description copied from class: BreakingAlgorithm

Empty method, hook for subclasses. Called when determining the optimal breakpoints for a given active node.

Specified by:

updateData2 in class BreakingAlgorithm

Parameters:

bestActiveNode - a node in the chain of best active nodes, corresponding to one of the optimal breakpoints

sequence - the corresponding paragraph

total - the number of lines into which the paragraph will be broken

See Also:

BreakingAlgorithm.calculateBreakPoints(KnuthNode, KnuthSequence, int)

filterActiveNodes

protected int filterActiveNodes()

Specified by:

filterActiveNodes in class BreakingAlgorithm

getFootnoteList

public java.util.LinkedList getFootnoteList(int index)

getFObj

public FObj getFObj()

Returns:

the associated top-level formatting object.

getLineWidth

protected int getLineWidth(int line)

Returns the line/part width of a given line/part.

Overrides:

getLineWidth in class BreakingAlgorithm

Parameters:

line - the line/part number

Returns:

the width/length in millipoints