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package java.awt.geom;

import java.util.*;


The FlatteningPathIterator class returns a flattened view of another PathIterator object. Other Shape classes can use this class to provide flattening behavior for their paths without having to perform the interpolation calculations themselves. 
Author:Jim Graham
/**
 * The {@code FlatteningPathIterator} class returns a flattened view of
 * another {@link PathIterator} object.  Other {@link java.awt.Shape Shape}
 * classes can use this class to provide flattening behavior for their paths
 * without having to perform the interpolation calculations themselves.
 *
 * @author Jim Graham
 */
public class FlatteningPathIterator implements PathIterator {
    static final int GROW_SIZE = 24;    // Multiple of cubic & quad curve size

    PathIterator src;                   // The source iterator

    double squareflat;                  // Square of the flatness parameter
                                        // for testing against squared lengths

    int limit;                          // Maximum number of recursion levels

    double hold[] = new double[14];     // The cache of interpolated coords
                                        // Note that this must be long enough
                                        // to store a full cubic segment and
                                        // a relative cubic segment to avoid
                                        // aliasing when copying the coords
                                        // of a curve to the end of the array.
                                        // This is also serendipitously equal
                                        // to the size of a full quad segment
                                        // and 2 relative quad segments.

    double curx, cury;                  // The ending x,y of the last segment

    double movx, movy;                  // The x,y of the last move segment

    int holdType;                       // The type of the curve being held
                                        // for interpolation

    int holdEnd;                        // The index of the last curve segment
                                        // being held for interpolation

    int holdIndex;                      // The index of the curve segment
                                        // that was last interpolated.  This
                                        // is the curve segment ready to be
                                        // returned in the next call to
                                        // currentSegment().

    int levels[];                       // The recursion level at which
                                        // each curve being held in storage
                                        // was generated.

    int levelIndex;                     // The index of the entry in the
                                        // levels array of the curve segment
                                        // at the holdIndex

    boolean done;                       // True when iteration is done

    
Constructs a new FlatteningPathIterator object that flattens a path as it iterates over it. The iterator does not subdivide any curve read from the source iterator to more than 10 levels of subdivision which yields a maximum of 1024 line segments per curve. 
Params:
  • src – the original unflattened path being iterated over
  • flatness – the maximum allowable distance between the
control points and the flattened curve
/**
     * Constructs a new {@code FlatteningPathIterator} object that
     * flattens a path as it iterates over it.  The iterator does not
     * subdivide any curve read from the source iterator to more than
     * 10 levels of subdivision which yields a maximum of 1024 line
     * segments per curve.
     * @param src the original unflattened path being iterated over
     * @param flatness the maximum allowable distance between the
     * control points and the flattened curve
     */
    public FlatteningPathIterator(PathIterator src, double flatness) {
        this(src, flatness, 10);
    }

    
Constructs a new FlatteningPathIterator object that flattens a path as it iterates over it. The limit parameter allows you to control the maximum number of recursive subdivisions that the iterator can make before it assumes that the curve is flat enough without measuring against the flatness parameter. The flattened iteration therefore never generates more than a maximum of (2^limit) line segments per curve. 
Params:
  • src – the original unflattened path being iterated over
  • flatness – the maximum allowable distance between the
control points and the flattened curve
  • limit – the maximum number of recursive subdivisions
allowed for any curved segment
Throws:
/**
     * Constructs a new {@code FlatteningPathIterator} object
     * that flattens a path as it iterates over it.
     * The {@code limit} parameter allows you to control the
     * maximum number of recursive subdivisions that the iterator
     * can make before it assumes that the curve is flat enough
     * without measuring against the {@code flatness} parameter.
     * The flattened iteration therefore never generates more than
     * a maximum of {@code (2^limit)} line segments per curve.
     * @param src the original unflattened path being iterated over
     * @param flatness the maximum allowable distance between the
     * control points and the flattened curve
     * @param limit the maximum number of recursive subdivisions
     * allowed for any curved segment
     * @exception IllegalArgumentException if
     *          {@code flatness} or {@code limit}
     *          is less than zero
     */
    public FlatteningPathIterator(PathIterator src, double flatness,
                                  int limit) {
        if (flatness < 0.0) {
            throw new IllegalArgumentException("flatness must be >= 0");
        }
        if (limit < 0) {
            throw new IllegalArgumentException("limit must be >= 0");
        }
        this.src = src;
        this.squareflat = flatness * flatness;
        this.limit = limit;
        this.levels = new int[limit + 1];
        // prime the first path segment
        next(false);
    }

    
Returns the flatness of this iterator.

Returns:the flatness of this FlatteningPathIterator.
/**
     * Returns the flatness of this iterator.
     * @return the flatness of this {@code FlatteningPathIterator}.
     */
    public double getFlatness() {
        return Math.sqrt(squareflat);
    }

    
Returns the recursion limit of this iterator.

Returns:the recursion limit of this FlatteningPathIterator.
/**
     * Returns the recursion limit of this iterator.
     * @return the recursion limit of this
     * {@code FlatteningPathIterator}.
     */
    public int getRecursionLimit() {
        return limit;
    }

    
Returns the winding rule for determining the interior of the
path.

See Also:
Returns:the winding rule of the original unflattened path being
iterated over.
/**
     * Returns the winding rule for determining the interior of the
     * path.
     * @return the winding rule of the original unflattened path being
     * iterated over.
     * @see PathIterator#WIND_EVEN_ODD
     * @see PathIterator#WIND_NON_ZERO
     */
    public int getWindingRule() {
        return src.getWindingRule();
    }

    
Tests if the iteration is complete.

Returns:true if all the segments have been read; false otherwise.
/**
     * Tests if the iteration is complete.
     * @return {@code true} if all the segments have
     * been read; {@code false} otherwise.
     */
    public boolean isDone() {
        return done;
    }

    /*
     * Ensures that the hold array can hold up to (want) more values.
     * It is currently holding (hold.length - holdIndex) values.
     */
    void ensureHoldCapacity(int want) {
        if (holdIndex - want < 0) {
            int have = hold.length - holdIndex;
            int newsize = hold.length + GROW_SIZE;
            double newhold[] = new double[newsize];
            System.arraycopy(hold, holdIndex,
                             newhold, holdIndex + GROW_SIZE,
                             have);
            hold = newhold;
            holdIndex += GROW_SIZE;
            holdEnd += GROW_SIZE;
        }
    }

    
Moves the iterator to the next segment of the path forwards
along the primary direction of traversal as long as there are
more points in that direction.

/**
     * Moves the iterator to the next segment of the path forwards
     * along the primary direction of traversal as long as there are
     * more points in that direction.
     */
    public void next() {
        next(true);
    }

    private void next(boolean doNext) {
        int level;

        if (holdIndex >= holdEnd) {
            if (doNext) {
                src.next();
            }
            if (src.isDone()) {
                done = true;
                return;
            }
            holdType = src.currentSegment(hold);
            levelIndex = 0;
            levels[0] = 0;
        }

        switch (holdType) {
        case SEG_MOVETO:
        case SEG_LINETO:
            curx = hold[0];
            cury = hold[1];
            if (holdType == SEG_MOVETO) {
                movx = curx;
                movy = cury;
            }
            holdIndex = 0;
            holdEnd = 0;
            break;
        case SEG_CLOSE:
            curx = movx;
            cury = movy;
            holdIndex = 0;
            holdEnd = 0;
            break;
        case SEG_QUADTO:
            if (holdIndex >= holdEnd) {
                // Move the coordinates to the end of the array.
                holdIndex = hold.length - 6;
                holdEnd = hold.length - 2;
                hold[holdIndex + 0] = curx;
                hold[holdIndex + 1] = cury;
                hold[holdIndex + 2] = hold[0];
                hold[holdIndex + 3] = hold[1];
                hold[holdIndex + 4] = curx = hold[2];
                hold[holdIndex + 5] = cury = hold[3];
            }

            level = levels[levelIndex];
            while (level < limit) {
                if (QuadCurve2D.getFlatnessSq(hold, holdIndex) < squareflat) {
                    break;
                }

                ensureHoldCapacity(4);
                QuadCurve2D.subdivide(hold, holdIndex,
                                      hold, holdIndex - 4,
                                      hold, holdIndex);
                holdIndex -= 4;

                // Now that we have subdivided, we have constructed
                // two curves of one depth lower than the original
                // curve.  One of those curves is in the place of
                // the former curve and one of them is in the next
                // set of held coordinate slots.  We now set both
                // curves level values to the next higher level.
                level++;
                levels[levelIndex] = level;
                levelIndex++;
                levels[levelIndex] = level;
            }

            // This curve segment is flat enough, or it is too deep
            // in recursion levels to try to flatten any more.  The
            // two coordinates at holdIndex+4 and holdIndex+5 now
            // contain the endpoint of the curve which can be the
            // endpoint of an approximating line segment.
            holdIndex += 4;
            levelIndex--;
            break;
        case SEG_CUBICTO:
            if (holdIndex >= holdEnd) {
                // Move the coordinates to the end of the array.
                holdIndex = hold.length - 8;
                holdEnd = hold.length - 2;
                hold[holdIndex + 0] = curx;
                hold[holdIndex + 1] = cury;
                hold[holdIndex + 2] = hold[0];
                hold[holdIndex + 3] = hold[1];
                hold[holdIndex + 4] = hold[2];
                hold[holdIndex + 5] = hold[3];
                hold[holdIndex + 6] = curx = hold[4];
                hold[holdIndex + 7] = cury = hold[5];
            }

            level = levels[levelIndex];
            while (level < limit) {
                if (CubicCurve2D.getFlatnessSq(hold, holdIndex) < squareflat) {
                    break;
                }

                ensureHoldCapacity(6);
                CubicCurve2D.subdivide(hold, holdIndex,
                                       hold, holdIndex - 6,
                                       hold, holdIndex);
                holdIndex -= 6;

                // Now that we have subdivided, we have constructed
                // two curves of one depth lower than the original
                // curve.  One of those curves is in the place of
                // the former curve and one of them is in the next
                // set of held coordinate slots.  We now set both
                // curves level values to the next higher level.
                level++;
                levels[levelIndex] = level;
                levelIndex++;
                levels[levelIndex] = level;
            }

            // This curve segment is flat enough, or it is too deep
            // in recursion levels to try to flatten any more.  The
            // two coordinates at holdIndex+6 and holdIndex+7 now
            // contain the endpoint of the curve which can be the
            // endpoint of an approximating line segment.
            holdIndex += 6;
            levelIndex--;
            break;
        }
    }

    
Returns the coordinates and type of the current path segment in
the iteration.
The return value is the path segment type:
SEG_MOVETO, SEG_LINETO, or SEG_CLOSE.
A float array of length 6 must be passed in and can be used to
store the coordinates of the point(s).
Each point is stored as a pair of float x,y coordinates.
SEG_MOVETO and SEG_LINETO types return one point,
and SEG_CLOSE does not return any points.

Params:
  • coords – an array that holds the data returned from
this method
Throws:
See Also:
Returns:the path segment type of the current path segment.
/**
     * Returns the coordinates and type of the current path segment in
     * the iteration.
     * The return value is the path segment type:
     * SEG_MOVETO, SEG_LINETO, or SEG_CLOSE.
     * A float array of length 6 must be passed in and can be used to
     * store the coordinates of the point(s).
     * Each point is stored as a pair of float x,y coordinates.
     * SEG_MOVETO and SEG_LINETO types return one point,
     * and SEG_CLOSE does not return any points.
     * @param coords an array that holds the data returned from
     * this method
     * @return the path segment type of the current path segment.
     * @exception NoSuchElementException if there
     *          are no more elements in the flattening path to be
     *          returned.
     * @see PathIterator#SEG_MOVETO
     * @see PathIterator#SEG_LINETO
     * @see PathIterator#SEG_CLOSE
     */
    public int currentSegment(float[] coords) {
        if (isDone()) {
            throw new NoSuchElementException("flattening iterator out of bounds");
        }
        int type = holdType;
        if (type != SEG_CLOSE) {
            coords[0] = (float) hold[holdIndex + 0];
            coords[1] = (float) hold[holdIndex + 1];
            if (type != SEG_MOVETO) {
                type = SEG_LINETO;
            }
        }
        return type;
    }

    
Returns the coordinates and type of the current path segment in
the iteration.
The return value is the path segment type:
SEG_MOVETO, SEG_LINETO, or SEG_CLOSE.
A double array of length 6 must be passed in and can be used to
store the coordinates of the point(s).
Each point is stored as a pair of double x,y coordinates.
SEG_MOVETO and SEG_LINETO types return one point,
and SEG_CLOSE does not return any points.

Params:
  • coords – an array that holds the data returned from
this method
Throws:
See Also:
Returns:the path segment type of the current path segment.
/**
     * Returns the coordinates and type of the current path segment in
     * the iteration.
     * The return value is the path segment type:
     * SEG_MOVETO, SEG_LINETO, or SEG_CLOSE.
     * A double array of length 6 must be passed in and can be used to
     * store the coordinates of the point(s).
     * Each point is stored as a pair of double x,y coordinates.
     * SEG_MOVETO and SEG_LINETO types return one point,
     * and SEG_CLOSE does not return any points.
     * @param coords an array that holds the data returned from
     * this method
     * @return the path segment type of the current path segment.
     * @exception NoSuchElementException if there
     *          are no more elements in the flattening path to be
     *          returned.
     * @see PathIterator#SEG_MOVETO
     * @see PathIterator#SEG_LINETO
     * @see PathIterator#SEG_CLOSE
     */
    public int currentSegment(double[] coords) {
        if (isDone()) {
            throw new NoSuchElementException("flattening iterator out of bounds");
        }
        int type = holdType;
        if (type != SEG_CLOSE) {
            coords[0] = hold[holdIndex + 0];
            coords[1] = hold[holdIndex + 1];
            if (type != SEG_MOVETO) {
                type = SEG_LINETO;
            }
        }
        return type;
    }
}