Package org.apache.fop.layoutmgr

Class BreakingAlgorithm

java.lang.Object
org.apache.fop.layoutmgr.BreakingAlgorithm
Direct Known Subclasses:
BalancingColumnBreakingAlgorithm
public abstract class BreakingAlgorithm extends Object
The set of nodes is sorted into lines indexed into activeLines. The nodes in each line are linked together in a single linked list by the BreakingAlgorithm.KnuthNode.next field. The activeLines array contains a link to the head of the linked list in index 'line*2' and a link to the tail at index 'line*2+1'.

The set of active nodes can be traversed by 

 for (int line = startLine; line < endLine; line++) {
     for (KnuthNode node = getNode(line); node != null; node = node.next) {
         // Do something with 'node'
     }
 }

  • Field Details

    • log

      protected static final org.apache.commons.logging.Log log
      the logger for the class

    • INFINITE_RATIO

      protected static final int INFINITE_RATIO
      Maximum adjustment ration
      See Also:

    • ALL_BREAKS

      public static final int ALL_BREAKS
      All feasible breaks are ok.
      See Also:

    • NO_FLAGGED_PENALTIES

      public static final int NO_FLAGGED_PENALTIES
      This forbids hyphenation.
      See Also:

    • ONLY_FORCED_BREAKS

      public static final int ONLY_FORCED_BREAKS
      wrap-option = "no-wrap".
      See Also:

    • repeatedFlaggedDemerit

      protected int repeatedFlaggedDemerit
      Demerit for consecutive lines ending at flagged penalties.

    • incompatibleFitnessDemerit

      protected int incompatibleFitnessDemerit
      Demerit for consecutive lines belonging to incompatible fitness classes .

    • maxFlaggedPenaltiesCount

      protected int maxFlaggedPenaltiesCount
      Maximum number of consecutive lines ending with a flagged penalty. Only a value >= 1 is a significant limit.

    • par

      protected KnuthSequence par
      The paragraph of KnuthElements.

    • lineWidth

      protected int lineWidth
      The width of a line (or height of a column in page-breaking mode). -1 indicates that the line widths are different for each line.

    • considerTooShort

      protected boolean considerTooShort
      If set to true, doesn't ignore break possibilities which are definitely too short.

    • alignment

      protected int alignment
      Alignment of the paragraph/page. One of EN_START, EN_JUSTIFY, etc.

    • alignmentLast

      protected int alignmentLast
      Alignment of the paragraph's last line.

    • indentFirstPart

      protected boolean indentFirstPart
      Used to handle the text-indent property (indent the first line of a paragraph).

    • activeLines

      protected BreakingAlgorithm.KnuthNode[] activeLines
      The set of active nodes in ascending line order. For each line l, activeLines[2l] contains a link to l's first active node, and activeLines[2l+1] a link to l's last active node. The line number l corresponds to the number of the line ending at the node's breakpoint.

    • activeNodeCount

      protected int activeNodeCount
      The number of active nodes.

    • startLine

      protected int startLine
      The lowest available line in the set of active nodes.

    • endLine

      protected int endLine
      The highest + 1 available line in the set of active nodes.

    • totalWidth

      protected int totalWidth
      The total width of all elements handled so far.

    • totalStretch

      protected int totalStretch
      The total stretch of all elements handled so far.

    • totalShrink

      protected int totalShrink
      The total shrink of all elements handled so far.

    • best

      protected BreakingAlgorithm.BestRecords best
      Best records.

  • Constructor Details

    • BreakingAlgorithm

      public BreakingAlgorithm(int align, int alignLast, boolean first, boolean partOverflowRecovery, int maxFlagCount)
      Create a new instance.
      Parameters:
      align - alignment of the paragraph/page. One of Constants.EN_START, Constants.EN_JUSTIFY, Constants.EN_CENTER, Constants.EN_END. For pages, Constants.EN_BEFORE and Constants.EN_AFTER are mapped to the corresponding inline properties, Constants.EN_START and Constants.EN_END.
      alignLast - alignment of the paragraph's last line
      first - for the text-indent property (true if the first line of a paragraph should be indented)
      partOverflowRecovery - true if too long elements should be moved to the next line/part
      maxFlagCount - maximum allowed number of consecutive lines ending at a flagged penalty item

  • Method Details

    • getMaxRecoveryAttempts

      protected int getMaxRecoveryAttempts()
      Returns:
      the number of times the algorithm should try to move overflowing content to the next line/page.

    • isPartOverflowRecoveryActivated

      protected boolean isPartOverflowRecoveryActivated()
      Controls the behaviour of the algorithm in cases where the first element of a part overflows a line/page.
      Returns:
      true if the algorithm should try to send the element to the next line/page.

    • getLastTooLong

      protected BreakingAlgorithm.KnuthNode getLastTooLong()

    • updateData1

      public abstract void updateData1(int total, double demerits)
      Empty method, hook for subclasses. Called before determining the optimal breakpoints corresponding to a given active node.
      Parameters:
      total - number of lines for the active node
      demerits - total demerits of the paragraph for the active node

    • updateData2

      public abstract void updateData2(BreakingAlgorithm.KnuthNode bestActiveNode, KnuthSequence sequence, int total)
      Empty method, hook for subclasses. Called when determining the optimal breakpoints for a given active node.
      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

    • setConstantLineWidth

      public void setConstantLineWidth(int lineWidth)
      Parameters:
      lineWidth - the line width

    • findBreakingPoints

      public int findBreakingPoints(KnuthSequence par, double threshold, boolean force, int allowedBreaks)
      Parameters:
      par - the paragraph to break
      threshold - upper bound of the adjustment ratio
      force - true if a set of breakpoints must be found, even if there are no feasible ones
      allowedBreaks - the type(s) of breaks allowed. One of ONLY_FORCED_BREAKS, NO_FLAGGED_PENALTIES or ALL_BREAKS.
      Returns:
      the number of effective breaks
      See Also:

    • findBreakingPoints

      public int findBreakingPoints(KnuthSequence par, int startIndex, double threshold, boolean force, int allowedBreaks)
      Finds an optimal set of breakpoints for the given paragraph.
      Parameters:
      par - the paragraph to break
      startIndex - index of the Knuth element at which the breaking must start
      threshold - upper bound of the adjustment ratio
      force - true if a set of breakpoints must be found, even if there are no feasible ones
      allowedBreaks - the type(s) of breaks allowed. One of ONLY_FORCED_BREAKS, NO_FLAGGED_PENALTIES or ALL_BREAKS.
      Returns:
      the number of effective breaks

    • getIPDdifference

      protected int getIPDdifference()
      obtain ipd difference
      Returns:
      an integer

    • handleIpdChange

      protected int handleIpdChange()
      handle ipd change
      Returns:
      an integer

    • recoverFromTooLong

      protected BreakingAlgorithm.KnuthNode recoverFromTooLong(BreakingAlgorithm.KnuthNode lastTooLong)
      Recover from a BreakingAlgorithm.KnuthNode leading to a line that is too long. The default implementation creates a new node corresponding to a break point after the previous node that led to a line that was too short.
      Parameters:
      lastTooLong - the node that leads to a "too long" line
      Returns:
      node corresponding to a breakpoint after the previous "too short" line

    • initialize

      protected void initialize()
      Initializes the algorithm's variables.

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

    • createNode

      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.
      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
      Returns:
      a new node
      See Also:

    • getLastTooShort

      protected final BreakingAlgorithm.KnuthNode getLastTooShort()
      Return the last node that yielded a too short line.
      Returns:
      the node corresponding to the last too short line

    • handleElementAt

      protected final KnuthElement handleElementAt(int position, boolean previousIsBox, int allowedBreaks)
      Generic handler for a KnuthElement at the given position, taking into account whether the preceding element was a box, and which type(s) of breaks are allowed. Non-overridable. This method simply serves to route the call to one of the more specific handlers (handleBox(KnuthBox), handleGlueAt(KnuthGlue,int,boolean,int) or handlePenaltyAt(KnuthPenalty,int,int). The specialized handlers can be overridden by subclasses to add to or modify the default behavior for the different types of elements.
      Parameters:
      position - the position index of the element in the paragraph
      previousIsBox - true if the previous element is a box
      allowedBreaks - the type(s) of breaks allowed; should be one of ALL_BREAKS, NO_FLAGGED_PENALTIES or ONLY_FORCED_BREAKS
      Returns:
      the handled element

    • handleBox

      protected void handleBox(KnuthBox box)
      Handle a KnuthBox.
      Note: default implementation just adds the box's width to the total content width. Subclasses that do not keep track of this themselves, but override this method, should remember to call super.handleBox(box) to avoid unwanted side-effects.
      Parameters:
      box - the KnuthBox to handle

    • handleGlueAt

      protected void handleGlueAt(KnuthGlue glue, int position, boolean previousIsBox, int allowedBreaks)
      Handle a KnuthGlue at the given position, taking into account the additional parameters.
      Parameters:
      glue - the KnuthGlue to handle
      position - the position of the glue in the list
      previousIsBox - true if the preceding element is a box
      allowedBreaks - the type of breaks that are allowed

    • handlePenaltyAt

      protected void handlePenaltyAt(KnuthPenalty penalty, int position, int allowedBreaks)
      Handle a KnuthPenalty at the given position, taking into account the type of breaks allowed.
      Parameters:
      penalty - the KnuthPenalty to handle
      position - the position of the penalty in the list
      allowedBreaks - the type of breaks that are allowed

    • replaceLastDeactivated

      protected final void replaceLastDeactivated()
      Replace the last too-long or too-short node by the last deactivated node, if applicable.

    • recoverFromOverflow

      protected BreakingAlgorithm.KnuthNode recoverFromOverflow()
      Recover from an overflow condition.
      Returns:
      the new lastForced node

    • restartFrom

      protected int restartFrom(BreakingAlgorithm.KnuthNode restartingNode, int currentIndex)
      Restart from the given node at the given index.
      Parameters:
      restartingNode - the BreakingAlgorithm.KnuthNode to restart from
      currentIndex - the current position index
      Returns:
      the index of the restart point

    • considerLegalBreak

      protected void considerLegalBreak(KnuthElement element, int elementIdx)
      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.
      Parameters:
      element - the paragraph's element to consider
      elementIdx - the element's index inside the paragraph

    • elementCanEndLine

      protected boolean elementCanEndLine(KnuthElement element, int line, int difference)
      Check if the given KnuthElement can end the line with the given number.
      Parameters:
      element - the element
      line - the line number
      difference - an integer
      Returns:
      true if the element can end the line

    • forceNode

      protected void forceNode(BreakingAlgorithm.KnuthNode node, int line, int elementIdx, int difference, double r, double demerits, int fitnessClass, int availableShrink, int availableStretch)
      Force the given BreakingAlgorithm.KnuthNode, and register it.
      Parameters:
      node - the node
      line - the line number
      elementIdx - the position index of the element
      difference - the difference between content-length and available width
      r - the adjustment ratio
      demerits - demerits produced by the node
      fitnessClass - the fitness class
      availableShrink - the available amount of shrink
      availableStretch - tha available amount of stretch

    • createForcedNodes

      protected void createForcedNodes(BreakingAlgorithm.KnuthNode node, int line, int elementIdx, int difference, double r, double demerits, int fitnessClass, int availableShrink, int availableStretch, int newWidth, int newStretch, int newShrink)

    • activateNode

      protected void activateNode(BreakingAlgorithm.KnuthNode node, int difference, double r, double demerits, int fitnessClass, int availableShrink, int availableStretch)
      Activate the given node. Will result in the given BreakingAlgorithm.KnuthNode being registered as a feasible breakpoint, if the demerits are better than that of the best node registered for the given fitnessClass.
      Parameters:
      node - the node
      difference - the difference between content-length and available width
      r - the adjustment ratio
      demerits - demerits produced by the node
      fitnessClass - the fitness class
      availableShrink - the available amount of shrink
      availableStretch - the available amount of stretch

    • deactivateNode

      protected void deactivateNode(BreakingAlgorithm.KnuthNode node, int line)
      Deactivate the given node
      Parameters:
      node - the node
      line - the line number

    • computeDifference

      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.
      Parameters:
      activeNode - node for the previous breakpoint
      element - currently considered breakpoint
      elementIndex - index of the element that is considered as a 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)
      Return the adjustment ratio needed to make up for the difference. A ratio 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.
      Parameters:
      activeNode - the currently active node
      difference - the difference between content-length and available width
      Returns:
      The adjustment ratio.

    • 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

    • finish

      protected void finish()
      Hook for subclasses to trigger special behavior after ending the main loop in findBreakingPoints(KnuthSequence,int,double,boolean,int)

    • getElement

      protected KnuthElement getElement(int idx)
      Return the element at index idx in the paragraph.
      Parameters:
      idx - index of the element.
      Returns:
      the element at index idx in the paragraph.

    • compareNodes

      protected BreakingAlgorithm.KnuthNode compareNodes(BreakingAlgorithm.KnuthNode node1, BreakingAlgorithm.KnuthNode node2)
      Compare two KnuthNodes and return the node with the least demerit.
      Parameters:
      node1 - The first knuth node.
      node2 - The other knuth node.
      Returns:
      the node with the least demerit.

    • addNode

      protected void addNode(int line, BreakingAlgorithm.KnuthNode node)
      Add a node at the end of the given line's existing active nodes. If this is the first node in the line, adjust endLine accordingly.
      Parameters:
      line - number of the line ending at the node's corresponding breakpoint
      node - the active node to add

    • removeNode

      protected void removeNode(int line, BreakingAlgorithm.KnuthNode node)
      Remove the given active node registered for the given line. If there are no more active nodes for this line, adjust the startLine accordingly.
      Parameters:
      line - number of the line ending at the node's corresponding breakpoint
      node - the node to deactivate

    • getNode

      protected BreakingAlgorithm.KnuthNode getNode(int line)
      Returns the first active node for the given line.
      Parameters:
      line - the line/part number
      Returns:
      the requested active node

    • getLineWidth

      protected int getLineWidth(int line)
      Returns the line/part width of a given line/part.
      Parameters:
      line - the line/part number
      Returns:
      the width/length in millipoints

    • getLineWidth

      protected int getLineWidth()
      Returns:
      the constant line/part width or -1 if there is no such value

    • toString

      public String toString(String prepend)
      Creates a string representation of the active nodes. Used for debugging.
      Parameters:
      prepend - a string to prepend on each entry
      Returns:
      the requested string

    • filterActiveNodes

      protected abstract int filterActiveNodes()
      Filter active nodes.
      Returns:
      an integer

    • calculateBreakPoints

      protected void calculateBreakPoints(BreakingAlgorithm.KnuthNode node, KnuthSequence par, int total)
      Determines the set of optimal breakpoints corresponding to the given active node.
      Parameters:
      node - the active node
      par - the corresponding paragraph
      total - the number of lines into which the paragraph will be broken

    • getAlignment

      public int getAlignment()
      Returns:
      the alignment for normal lines/parts

    • getAlignmentLast

      public int getAlignmentLast()
      Returns:
      the alignment for the last line/part

    • handlingFloat

      protected boolean handlingFloat()

    • handleFloat

      protected int handleFloat()

    • disableFloatHandling

      protected void disableFloatHandling()