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TextMeasurer.javaAPI DocJava SE 5 API27000Fri Aug 26 14:56:52 BST 2005java.awt.font

TextMeasurer

public final class TextMeasurer extends Object implements Cloneable
The TextMeasurer class provides the primitive operations needed for line break: measuring up to a given advance, determining the advance of a range of characters, and generating a TextLayout for a range of characters. It also provides methods for incremental editing of paragraphs.

A TextMeasurer object is constructed with an {@link java.text.AttributedCharacterIterator AttributedCharacterIterator} representing a single paragraph of text. The value returned by the {@link AttributedCharacterIterator#getBeginIndex() getBeginIndex} method of AttributedCharacterIterator defines the absolute index of the first character. The value returned by the {@link AttributedCharacterIterator#getEndIndex() getEndIndex} method of AttributedCharacterIterator defines the index past the last character. These values define the range of indexes to use in calls to the TextMeasurer. For example, calls to get the advance of a range of text or the line break of a range of text must use indexes between the beginning and end index values. Calls to {@link #insertChar(java.text.AttributedCharacterIterator, int) insertChar} and {@link #deleteChar(java.text.AttributedCharacterIterator, int) deleteChar} reset the TextMeasurer to use the beginning index and end index of the AttributedCharacterIterator passed in those calls.

Most clients will use the more convenient LineBreakMeasurer, which implements the standard line break policy (placing as many words as will fit on each line).

author
John Raley
version
1.31, 04/20/01
see
LineBreakMeasurer
since
1.3

Fields Summary
private static float
EST_LINES
private FontRenderContext
fFrc
private int
fStart
private char[]
fChars
private Bidi
fBidi
private byte[]
fLevels
private TextLineComponent[]
fComponents
private int
fComponentStart
private int
fComponentLimit
private boolean
haveLayoutWindow
private BreakIterator
fLineBreak
private CharArrayIterator
charIter
int
layoutCount
int
layoutCharCount
private StyledParagraph
fParagraph
private boolean
fIsDirectionLTR
private byte
fBaseline
private float[]
fBaselineOffsets
private float
fJustifyRatio
private int
formattedChars
private static boolean
wantStats
private boolean
collectStats
Constructors Summary
public TextMeasurer(AttributedCharacterIterator text, FontRenderContext frc)
Constructs a TextMeasurer from the source text. The source text should be a single entire paragraph.

param
text the source paragraph. Cannot be null.
param
frc the information about a graphics device which is needed to measure the text correctly. Cannot be null.


                                                               
         

        fFrc = frc;
        initAll(text);
Methods Summary
private intcalcLineBreak(int pos, float maxAdvance)


        // either of these statements removes the bug:
        //generateComponents(0, fChars.length);
        //generateComponents(pos, fChars.length);
        
        int startPos = pos;
        float width = maxAdvance;
        
        int tlcIndex;
        int tlcStart = fComponentStart;

        for (tlcIndex = 0; tlcIndex < fComponents.length; tlcIndex++) {
            int gaLimit = tlcStart + fComponents[tlcIndex].getNumCharacters();
            if (gaLimit > startPos) {
                break;
            }
            else {
                tlcStart = gaLimit;
            }
        }
        
        // tlcStart is now the start of the tlc at tlcIndex

        for (; tlcIndex < fComponents.length; tlcIndex++) {
            
            TextLineComponent tlc = fComponents[tlcIndex];
            int numCharsInGa = tlc.getNumCharacters();

            int lineBreak = tlc.getLineBreakIndex(startPos - tlcStart, width);
            if (lineBreak == numCharsInGa && tlcIndex < fComponents.length) {
                width -= tlc.getAdvanceBetween(startPos - tlcStart, lineBreak);
                tlcStart += numCharsInGa;
                startPos = tlcStart;
            }
            else {
                return tlcStart + lineBreak;
            }
        }

        if (fComponentLimit < fChars.length) {
            // format more text and try again
            //if (haveLayoutWindow) {
            //    outOfWindow++;
            //}
            
            generateComponents(pos, fChars.length);
            return calcLineBreak(pos, maxAdvance);
        }
        
        return fChars.length;
protected java.lang.Objectclone()

        TextMeasurer other;
        try {
            other = (TextMeasurer) super.clone();
        }
        catch(CloneNotSupportedException e) {
            throw new Error();
        }
        if (fComponents != null) {
            other.fComponents = (TextLineComponent[]) fComponents.clone();
        }
        return other;
public voiddeleteChar(java.text.AttributedCharacterIterator newParagraph, int deletePos)
Updates the TextMeasurer after a single character has been deleted from the paragraph currently represented by this TextMeasurer. After this call, this TextMeasurer is equivalent to a new TextMeasurer created from the text; however, it will usually be more efficient to update an existing TextMeasurer than to create a new one from scratch.

param
newParagraph the text of the paragraph after performing the deletion. Cannot be null.
param
deletePos the position in the text where the character was removed. Must not be less than the start of newParagraph, and must not be greater than the end of newParagraph.
throws
IndexOutOfBoundsException if deletePos is less than the start of newParagraph or greater than the end of newParagraph
throws
NullPointerException if newParagraph is null


        fStart = newParagraph.getBeginIndex();
        int end = newParagraph.getEndIndex();
        if (end - fStart != fChars.length-1) {
            initAll(newParagraph);
        }
        
        char[] newChars = new char[end-fStart];
        int changedIndex = deletePos-fStart;
        
        System.arraycopy(fChars, 0, newChars, 0, deletePos-fStart);
        System.arraycopy(fChars, changedIndex+1, newChars, changedIndex, end-deletePos);
        fChars = newChars;
        
        if (fBidi != null) {
            fBidi = new Bidi(newParagraph);
	    if (fBidi.isLeftToRight()) {
		fBidi = null;
	    }
        }
        
        fParagraph = StyledParagraph.deleteChar(newParagraph, 
                                                fChars,
                                                deletePos,
                                                fParagraph);
        invalidateComponents();
private voidensureComponents(int start, int limit)

        
        if (start < fComponentStart || limit > fComponentLimit) {
            generateComponents(start, limit);
        }
private voidgenerateComponents(int startingAt, int endingAt)
Generate components for the paragraph. fChars, fBidi should have been initialized already.

        
        if (collectStats) {
            formattedChars += (endingAt-startingAt);
        }
	int layoutFlags = 0; // no extra info yet, bidi determines run and line direction
        TextLabelFactory factory = new TextLabelFactory(fFrc, fChars, fBidi, layoutFlags);

        int[] charsLtoV = null;
        
        if (fBidi != null) {
            fLevels = BidiUtils.getLevels(fBidi);
	    int[] charsVtoL = BidiUtils.createVisualToLogicalMap(fLevels);
            charsLtoV = BidiUtils.createInverseMap(charsVtoL);
            fIsDirectionLTR = fBidi.baseIsLeftToRight();
        }
        else {
            fLevels = null;
            fIsDirectionLTR = true;
        }
        
        try {
            fComponents = TextLine.getComponents(
                fParagraph, fChars, startingAt, endingAt, charsLtoV, fLevels, factory);
        }
        catch(IllegalArgumentException e) {
            System.out.println("startingAt="+startingAt+"; endingAt="+endingAt);
            System.out.println("fComponentLimit="+fComponentLimit);
            throw e;
        }
        
        fComponentStart = startingAt;
        fComponentLimit = endingAt;
        //debugFormatCount += (endingAt-startingAt);
public floatgetAdvanceBetween(int start, int limit)
Returns the graphical width of a line beginning at start and including characters up to limit. start and limit are absolute indices, not relative to the start of the paragraph.

param
start the character index at which to start measuring
param
limit the character index at which to stop measuring
return
the graphical width of a line beginning at start and including characters up to limit
throws
IndexOutOfBoundsException if limit is less than start
throws
IllegalArgumentException if start or limit is not between the beginning of the paragraph and the end of the paragraph.

        
        int localStart = start - fStart;
        int localLimit = limit - fStart;
        
        ensureComponents(localStart, localLimit);
        TextLine line = makeTextLineOnRange(localStart, localLimit);
        return line.getMetrics().advance;
        // could cache line in case getLayout is called with same start, limit
char[]getChars()
NOTE: This method is only for LineBreakMeasurer's use. It is package- private because it returns internal data.


        return fChars;
public java.awt.font.TextLayoutgetLayout(int start, int limit)
Returns a TextLayout on the given character range.

param
start the index of the first character
param
limit the index after the last character. Must be greater than start
return
a TextLayout for the characters beginning at start up to (but not including) limit
throws
IndexOutOfBoundsException if limit is less than start
throws
IllegalArgumentException if start or limit is not between the beginning of the paragraph and the end of the paragraph.

        
        int localStart = start - fStart;
        int localLimit = limit - fStart;
        
        ensureComponents(localStart, localLimit);        
        TextLine textLine = makeTextLineOnRange(localStart, localLimit);

        if (localLimit < fChars.length) {
            layoutCharCount += limit-start;
            layoutCount++;
        }
        
        return new TextLayout(textLine, 
                              fBaseline,
                              fBaselineOffsets,
                              fJustifyRatio);
public intgetLineBreakIndex(int start, float maxAdvance)
Returns the index of the first character which will not fit on on a line beginning at start and possible measuring up to maxAdvance in graphical width.

param
start the character index at which to start measuring. start is an absolute index, not relative to the start of the paragraph
param
maxAdvance the graphical width in which the line must fit
return
the index after the last character that will fit on a line beginning at start, which is not longer than maxAdvance in graphical width
throws
IllegalArgumentException if start is less than the beginning of the paragraph.

        
        int localStart = start - fStart;

        if (!haveLayoutWindow || 
                localStart < fComponentStart || 
                localStart >= fComponentLimit) {
            makeLayoutWindow(localStart);
        }
        
        return calcLineBreak(localStart, maxAdvance) + fStart;
private voidinitAll(java.text.AttributedCharacterIterator text)
Initialize state, including fChars array, direction, and fBidi.


        fStart = text.getBeginIndex();

        // extract chars
        fChars = new char[text.getEndIndex() - fStart];

        int n = 0;
        for (char c = text.first(); c != text.DONE; c = text.next()) {
            fChars[n++] = c;
        }
        
        text.first();
                
        fBidi = new Bidi(text);
	if (fBidi.isLeftToRight()) {
	    fBidi = null;
	}

        text.first();
        Map paragraphAttrs = text.getAttributes();
        if (paragraphAttrs != null) {
            try {
                NumericShaper shaper = (NumericShaper)paragraphAttrs.get(TextAttribute.NUMERIC_SHAPING);
                if (shaper != null) {
                    shaper.shape(fChars, 0, fChars.length);
                }
            }
            catch (ClassCastException e) {
            }
        }

        fParagraph = new StyledParagraph(text, fChars);
        
        // set paragraph attributes
        {
            // If there's an embedded graphic at the start of the
            // paragraph, look for the first non-graphic character
            // and use it and its font to initialize the paragraph.
            // If not, use the first graphic to initialize.
            fJustifyRatio = TextLine.getJustifyRatio(paragraphAttrs);
            
            boolean haveFont = TextLine.advanceToFirstFont(text);

            if (haveFont) {
                Font defaultFont = TextLine.getFontAtCurrentPos(text);
                int charsStart = text.getIndex() - text.getBeginIndex();
                LineMetrics lm = defaultFont.getLineMetrics(fChars, charsStart, charsStart+1, fFrc);
                fBaseline = (byte) lm.getBaselineIndex();
                fBaselineOffsets = lm.getBaselineOffsets();
            }
            else {
                // hmmm what to do here?  Just try to supply reasonable
                // values I guess.

                GraphicAttribute graphic = (GraphicAttribute)
                                paragraphAttrs.get(TextAttribute.CHAR_REPLACEMENT);
                fBaseline = TextLayout.getBaselineFromGraphic(graphic);
                Font dummyFont = new Font(new Hashtable(5, (float)0.9));
                LineMetrics lm = dummyFont.getLineMetrics(" ", 0, 1, fFrc);
                fBaselineOffsets = lm.getBaselineOffsets();
            }
            fBaselineOffsets = TextLine.getNormalizedOffsets(fBaselineOffsets, fBaseline);
        }
        
        invalidateComponents();
public voidinsertChar(java.text.AttributedCharacterIterator newParagraph, int insertPos)
Updates the TextMeasurer after a single character has been inserted into the paragraph currently represented by this TextMeasurer. After this call, this TextMeasurer is equivalent to a new TextMeasurer created from the text; however, it will usually be more efficient to update an existing TextMeasurer than to create a new one from scratch.

param
newParagraph the text of the paragraph after performing the insertion. Cannot be null.
param
insertPos the position in the text where the character was inserted. Must not be less than the start of newParagraph, and must be less than the end of newParagraph.
throws
IndexOutOfBoundsException if insertPos is less than the start of newParagraph or greater than or equal to the end of newParagraph
throws
NullPointerException if newParagraph is null


        if (collectStats) {
            printStats();
        }
        if (wantStats) {
            collectStats = true;
        }
        
        fStart = newParagraph.getBeginIndex();
        int end = newParagraph.getEndIndex();
        if (end - fStart != fChars.length+1) {
            initAll(newParagraph);
        }
        
        char[] newChars = new char[end-fStart];
        int newCharIndex = insertPos - fStart;
        System.arraycopy(fChars, 0, newChars, 0, newCharIndex);
        
        char newChar = newParagraph.setIndex(insertPos);
        newChars[newCharIndex] = newChar;
        System.arraycopy(fChars, 
                         newCharIndex, 
                         newChars, 
                         newCharIndex+1, 
                         end-insertPos-1);
        fChars = newChars;
        
        if (fBidi != null || Bidi.requiresBidi(newChars, newCharIndex, newCharIndex + 1) || 
                newParagraph.getAttribute(TextAttribute.BIDI_EMBEDDING) != null) {

            fBidi = new Bidi(newParagraph);
	    if (fBidi.isLeftToRight()) {
		fBidi = null;
	    }
        }
        
        fParagraph = StyledParagraph.insertChar(newParagraph, 
                                                fChars,
                                                insertPos,
                                                fParagraph);
        invalidateComponents();
private voidinvalidateComponents()

        fComponentStart = fComponentLimit = fChars.length;
        fComponents = null;
        haveLayoutWindow = false;
private sun.font.TextLineComponent[]makeComponentsOnRange(int startPos, int limitPos)


        // sigh I really hate to do this here since it's part of the
        // bidi algorithm.
        // cdWsStart is the start of the trailing counterdirectional
        // whitespace
        final int cdWsStart = trailingCdWhitespaceStart(startPos, limitPos);

        int tlcIndex;
        int tlcStart = fComponentStart;

        for (tlcIndex = 0; tlcIndex < fComponents.length; tlcIndex++) {
            int gaLimit = tlcStart + fComponents[tlcIndex].getNumCharacters();
            if (gaLimit > startPos) {
                break;
            }
            else {
                tlcStart = gaLimit;
            }
        }

        // tlcStart is now the start of the tlc at tlcIndex

        int componentCount;
        {
            boolean split = false;
            int compStart = tlcStart;
            int lim=tlcIndex;
            for (boolean cont=true; cont; lim++) {
                int gaLimit = compStart + fComponents[lim].getNumCharacters();
                if (cdWsStart > Math.max(compStart, startPos) 
                            && cdWsStart < Math.min(gaLimit, limitPos)) {
                    split = true;
                }
                if (gaLimit >= limitPos) {
                    cont=false;
                }
                else {
                    compStart = gaLimit;
                }
            }
            componentCount = lim-tlcIndex;
            if (split) {
                componentCount++;
            }
        }

        TextLineComponent[] components = new TextLineComponent[componentCount];
        int newCompIndex = 0;
        int linePos = startPos;

        int breakPt = cdWsStart;

        int subsetFlag;
        if (breakPt == startPos) {
            subsetFlag = fIsDirectionLTR? TextLineComponent.LEFT_TO_RIGHT :
                                          TextLineComponent.RIGHT_TO_LEFT;
            breakPt = limitPos;
        }
        else {
            subsetFlag = TextLineComponent.UNCHANGED;
        }

        while (linePos < limitPos) {
            
            int compLength = fComponents[tlcIndex].getNumCharacters();
            int tlcLimit = tlcStart + compLength;

            int start = Math.max(linePos, tlcStart);
            int limit = Math.min(breakPt, tlcLimit);
            
            components[newCompIndex++] = fComponents[tlcIndex].getSubset(
                                                                start-tlcStart,
                                                                limit-tlcStart,
                                                                subsetFlag);
            linePos += (limit-start);
            if (linePos == breakPt) {
                breakPt = limitPos;
                subsetFlag = fIsDirectionLTR? TextLineComponent.LEFT_TO_RIGHT :
                                              TextLineComponent.RIGHT_TO_LEFT;
            }
            if (linePos == tlcLimit) {
                tlcIndex++;
                tlcStart = tlcLimit;
            }
        }

        return components;
private voidmakeLayoutWindow(int localStart)

        
        int compStart = localStart;
        int compLimit = fChars.length;
        
        // If we've already gone past the layout window, format to end of paragraph
        if (layoutCount > 0 && !haveLayoutWindow) {
            float avgLineLength = Math.max(layoutCharCount / layoutCount, 1);
            compLimit = Math.min(localStart + (int)(avgLineLength*EST_LINES), fChars.length);
        }
        
        if (localStart > 0 || compLimit < fChars.length) {
            if (charIter == null) {
                charIter = new CharArrayIterator(fChars);
            }
            else {
                charIter.reset(fChars);
            }
            if (fLineBreak == null) {
                fLineBreak = BreakIterator.getLineInstance();
            }
            fLineBreak.setText(charIter);
            if (localStart > 0) {
                if (!fLineBreak.isBoundary(localStart)) {
                    compStart = fLineBreak.preceding(localStart);
                }
            }
            if (compLimit < fChars.length) {
                if (!fLineBreak.isBoundary(compLimit)) {
                    compLimit = fLineBreak.following(compLimit);
                }
            }
        }

        ensureComponents(compStart, compLimit);
        haveLayoutWindow = true;
private java.awt.font.TextLinemakeTextLineOnRange(int startPos, int limitPos)


        int[] charsLtoV = null;
        byte[] charLevels = null;

        if (fBidi != null) {
            Bidi lineBidi = fBidi.createLineBidi(startPos, limitPos);
            charLevels = BidiUtils.getLevels(lineBidi);
	    int[] charsVtoL = BidiUtils.createVisualToLogicalMap(charLevels);
            charsLtoV = BidiUtils.createInverseMap(charsVtoL);
        }

        TextLineComponent[] components = makeComponentsOnRange(startPos, limitPos);

        return new TextLine(components, 
                            fBaselineOffsets,
                            fChars,
                            startPos,
                            limitPos,
                            charsLtoV,
                            charLevels,
                            fIsDirectionLTR);
private voidprintStats()

    
       
        System.out.println("formattedChars: " + formattedChars);
        //formattedChars = 0;
        collectStats = false;
private inttrailingCdWhitespaceStart(int startPos, int limitPos)
According to the Unicode Bidirectional Behavior specification (Unicode Standard 2.0, section 3.11), whitespace at the ends of lines which would naturally flow against the base direction must be made to flow with the line direction, and moved to the end of the line. This method returns the start of the sequence of trailing whitespace characters to move to the end of a line taken from the given range.


        if (fLevels != null) {
            // Back up over counterdirectional whitespace
            final byte baseLevel = (byte) (fIsDirectionLTR? 0 : 1); 
            for (int cdWsStart = limitPos; --cdWsStart >= startPos;) {
                if ((fLevels[cdWsStart] % 2) == baseLevel || 
                        Character.getDirectionality(fChars[cdWsStart]) != Character.DIRECTIONALITY_WHITESPACE) {
                    return ++cdWsStart;
                }
            }
        }

        return startPos;