java/8 : javax/swing/text/AsyncBoxView.java

AsyncBoxView
https://openjdk.java.net/
GPLv2 + Classpath Exception
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package javax.swing.text;

import java.util.*;
import java.util.List;
import java.awt.*;
import javax.swing.SwingUtilities;
import javax.swing.event.DocumentEvent;

A box that does layout asynchronously.  This
is useful to keep the GUI event thread moving by
not doing any layout on it.  The layout is done
on a granularity of operations on the child views.
After each child view is accessed for some part
of layout (a potentially time consuming operation)
the remaining tasks can be abandoned or a new higher
priority task (i.e. to service a synchronous request
or a visible area) can be taken on.

While the child view is being accessed
a read lock is acquired on the associated document
so that the model is stable while being accessed.
Author:  Timothy Prinzing
Since:   1.3/**
 * A box that does layout asynchronously.  This
 * is useful to keep the GUI event thread moving by
 * not doing any layout on it.  The layout is done
 * on a granularity of operations on the child views.
 * After each child view is accessed for some part
 * of layout (a potentially time consuming operation)
 * the remaining tasks can be abandoned or a new higher
 * priority task (i.e. to service a synchronous request
 * or a visible area) can be taken on.
 * <p>
 * While the child view is being accessed
 * a read lock is acquired on the associated document
 * so that the model is stable while being accessed.
 *
 * @author  Timothy Prinzing
 * @since   1.3
 */
public class AsyncBoxView extends View {

    Construct a box view that does asynchronous layout.
Params: elem – the element of the model to represent
axis – the axis to tile along.  This can be
 either X_AXIS or Y_AXIS./**
     * Construct a box view that does asynchronous layout.
     *
     * @param elem the element of the model to represent
     * @param axis the axis to tile along.  This can be
     *  either X_AXIS or Y_AXIS.
     */
    public AsyncBoxView(Element elem, int axis) {
        super(elem);
        stats = new ArrayList<ChildState>();
        this.axis = axis;
        locator = new ChildLocator();
        flushTask = new FlushTask();
        minorSpan = Short.MAX_VALUE;
        estimatedMajorSpan = false;
    }

    Fetch the major axis (the axis the children
are tiled along).  This will have a value of
either X_AXIS or Y_AXIS.
/**
     * Fetch the major axis (the axis the children
     * are tiled along).  This will have a value of
     * either X_AXIS or Y_AXIS.
     */
    public int getMajorAxis() {
        return axis;
    }

    Fetch the minor axis (the axis orthogonal
to the tiled axis).  This will have a value of
either X_AXIS or Y_AXIS.
/**
     * Fetch the minor axis (the axis orthogonal
     * to the tiled axis).  This will have a value of
     * either X_AXIS or Y_AXIS.
     */
    public int getMinorAxis() {
        return (axis == X_AXIS) ? Y_AXIS : X_AXIS;
    }

    Get the top part of the margin around the view.
/**
     * Get the top part of the margin around the view.
     */
    public float getTopInset() {
        return topInset;
    }

    Set the top part of the margin around the view.
Params: i – the value of the inset/**
     * Set the top part of the margin around the view.
     *
     * @param i the value of the inset
     */
    public void setTopInset(float i) {
        topInset = i;
    }

    Get the bottom part of the margin around the view.
/**
     * Get the bottom part of the margin around the view.
     */
    public float getBottomInset() {
        return bottomInset;
    }

    Set the bottom part of the margin around the view.
Params: i – the value of the inset/**
     * Set the bottom part of the margin around the view.
     *
     * @param i the value of the inset
     */
    public void setBottomInset(float i) {
        bottomInset = i;
    }

    Get the left part of the margin around the view.
/**
     * Get the left part of the margin around the view.
     */
    public float getLeftInset() {
        return leftInset;
    }

    Set the left part of the margin around the view.
Params: i – the value of the inset/**
     * Set the left part of the margin around the view.
     *
     * @param i the value of the inset
     */
    public void setLeftInset(float i) {
        leftInset = i;
    }

    Get the right part of the margin around the view.
/**
     * Get the right part of the margin around the view.
     */
    public float getRightInset() {
        return rightInset;
    }

    Set the right part of the margin around the view.
Params: i – the value of the inset/**
     * Set the right part of the margin around the view.
     *
     * @param i the value of the inset
     */
    public void setRightInset(float i) {
        rightInset = i;
    }

    Fetch the span along an axis that is taken up by the insets.
Params: axis – the axis to determine the total insets along,
 either X_AXIS or Y_AXIS.
Since: 1.4/**
     * Fetch the span along an axis that is taken up by the insets.
     *
     * @param axis the axis to determine the total insets along,
     *  either X_AXIS or Y_AXIS.
     * @since 1.4
     */
    protected float getInsetSpan(int axis) {
        float margin = (axis == X_AXIS) ?
            getLeftInset() + getRightInset() : getTopInset() + getBottomInset();
        return margin;
    }

    Set the estimatedMajorSpan property that determines if the
major span should be treated as being estimated.  If this
property is true, the value of setSize along the major axis
will change the requirements along the major axis and incremental
changes will be ignored until all of the children have been updated
(which will cause the property to automatically be set to false).
If the property is false the value of the majorSpan will be
considered to be accurate and incremental changes will be
added into the total as they are calculated.
Since: 1.4/**
     * Set the estimatedMajorSpan property that determines if the
     * major span should be treated as being estimated.  If this
     * property is true, the value of setSize along the major axis
     * will change the requirements along the major axis and incremental
     * changes will be ignored until all of the children have been updated
     * (which will cause the property to automatically be set to false).
     * If the property is false the value of the majorSpan will be
     * considered to be accurate and incremental changes will be
     * added into the total as they are calculated.
     *
     * @since 1.4
     */
    protected void setEstimatedMajorSpan(boolean isEstimated) {
        estimatedMajorSpan = isEstimated;
    }

    Is the major span currently estimated?
Since: 1.4/**
     * Is the major span currently estimated?
     *
     * @since 1.4
     */
    protected boolean getEstimatedMajorSpan() {
        return estimatedMajorSpan;
    }

    Fetch the object representing the layout state of
of the child at the given index.
Params: index – the child index.  This should be a
  value >= 0 and < getViewCount()./**
     * Fetch the object representing the layout state of
     * of the child at the given index.
     *
     * @param index the child index.  This should be a
     *   value &gt;= 0 and &lt; getViewCount().
     */
    protected ChildState getChildState(int index) {
        synchronized(stats) {
            if ((index >= 0) && (index < stats.size())) {
                return stats.get(index);
            }
            return null;
        }
    }

    Fetch the queue to use for layout.
/**
     * Fetch the queue to use for layout.
     */
    protected LayoutQueue getLayoutQueue() {
        return LayoutQueue.getDefaultQueue();
    }

    New ChildState records are created through
this method to allow subclasses the extend
the ChildState records to do/hold more
/**
     * New ChildState records are created through
     * this method to allow subclasses the extend
     * the ChildState records to do/hold more
     */
    protected ChildState createChildState(View v) {
        return new ChildState(v);
    }

    Requirements changed along the major axis.
This is called by the thread doing layout for
the given ChildState object when it has completed
fetching the child views new preferences.
Typically this would be the layout thread, but
might be the event thread if it is trying to update
something immediately (such as to perform a
model/view translation).

This is implemented to mark the major axis as having
changed so that a future check to see if the requirements
need to be published to the parent view will consider
the major axis.  If the span along the major axis is
not estimated, it is updated by the given delta to reflect
the incremental change.  The delta is ignored if the
major span is estimated.
/**
     * Requirements changed along the major axis.
     * This is called by the thread doing layout for
     * the given ChildState object when it has completed
     * fetching the child views new preferences.
     * Typically this would be the layout thread, but
     * might be the event thread if it is trying to update
     * something immediately (such as to perform a
     * model/view translation).
     * <p>
     * This is implemented to mark the major axis as having
     * changed so that a future check to see if the requirements
     * need to be published to the parent view will consider
     * the major axis.  If the span along the major axis is
     * not estimated, it is updated by the given delta to reflect
     * the incremental change.  The delta is ignored if the
     * major span is estimated.
     */
    protected synchronized void majorRequirementChange(ChildState cs, float delta) {
        if (estimatedMajorSpan == false) {
            majorSpan += delta;
        }
        majorChanged = true;
    }

    Requirements changed along the minor axis.
This is called by the thread doing layout for
the given ChildState object when it has completed
fetching the child views new preferences.
Typically this would be the layout thread, but
might be the GUI thread if it is trying to update
something immediately (such as to perform a
model/view translation).
/**
     * Requirements changed along the minor axis.
     * This is called by the thread doing layout for
     * the given ChildState object when it has completed
     * fetching the child views new preferences.
     * Typically this would be the layout thread, but
     * might be the GUI thread if it is trying to update
     * something immediately (such as to perform a
     * model/view translation).
     */
    protected synchronized void minorRequirementChange(ChildState cs) {
        minorChanged = true;
    }

    Publish the changes in preferences upward to the parent
view.  This is normally called by the layout thread.
/**
     * Publish the changes in preferences upward to the parent
     * view.  This is normally called by the layout thread.
     */
    protected void flushRequirementChanges() {
        AbstractDocument doc = (AbstractDocument) getDocument();
        try {
            doc.readLock();

            View parent = null;
            boolean horizontal = false;
            boolean vertical = false;

            synchronized(this) {
                // perform tasks that iterate over the children while
                // preventing the collection from changing.
                synchronized(stats) {
                    int n = getViewCount();
                    if ((n > 0) && (minorChanged || estimatedMajorSpan)) {
                        LayoutQueue q = getLayoutQueue();
                        ChildState min = getChildState(0);
                        ChildState pref = getChildState(0);
                        float span = 0f;
                        for (int i = 1; i < n; i++) {
                            ChildState cs = getChildState(i);
                            if (minorChanged) {
                                if (cs.min > min.min) {
                                    min = cs;
                                }
                                if (cs.pref > pref.pref) {
                                    pref = cs;
                                }
                            }
                            if (estimatedMajorSpan) {
                                span += cs.getMajorSpan();
                            }
                        }

                        if (minorChanged) {
                            minRequest = min;
                            prefRequest = pref;
                        }
                        if (estimatedMajorSpan) {
                            majorSpan = span;
                            estimatedMajorSpan = false;
                            majorChanged = true;
                        }
                    }
                }

                // message preferenceChanged
                if (majorChanged || minorChanged) {
                    parent = getParent();
                    if (parent != null) {
                        if (axis == X_AXIS) {
                            horizontal = majorChanged;
                            vertical = minorChanged;
                        } else {
                            vertical = majorChanged;
                            horizontal = minorChanged;
                        }
                    }
                    majorChanged = false;
                    minorChanged = false;
                }
            }

            // propagate a preferenceChanged, using the
            // layout thread.
            if (parent != null) {
                parent.preferenceChanged(this, horizontal, vertical);

                // probably want to change this to be more exact.
                Component c = getContainer();
                if (c != null) {
                    c.repaint();
                }
            }
        } finally {
            doc.readUnlock();
        }
    }

    Calls the superclass to update the child views, and
updates the status records for the children.  This
is expected to be called while a write lock is held
on the model so that interaction with the layout
thread will not happen (i.e. the layout thread
acquires a read lock before doing anything).
Params: offset – the starting offset into the child views >= 0
length – the number of existing views to replace >= 0
views – the child views to insert/**
     * Calls the superclass to update the child views, and
     * updates the status records for the children.  This
     * is expected to be called while a write lock is held
     * on the model so that interaction with the layout
     * thread will not happen (i.e. the layout thread
     * acquires a read lock before doing anything).
     *
     * @param offset the starting offset into the child views &gt;= 0
     * @param length the number of existing views to replace &gt;= 0
     * @param views the child views to insert
     */
    public void replace(int offset, int length, View[] views) {
        synchronized(stats) {
            // remove the replaced state records
            for (int i = 0; i < length; i++) {
                ChildState cs = stats.remove(offset);
                float csSpan = cs.getMajorSpan();

                cs.getChildView().setParent(null);
                if (csSpan != 0) {
                    majorRequirementChange(cs, -csSpan);
                }
            }

            // insert the state records for the new children
            LayoutQueue q = getLayoutQueue();
            if (views != null) {
                for (int i = 0; i < views.length; i++) {
                    ChildState s = createChildState(views[i]);
                    stats.add(offset + i, s);
                    q.addTask(s);
                }
            }

            // notify that the size changed
            q.addTask(flushTask);
        }
    }

    Loads all of the children to initialize the view. This is called by the setParent method. Subclasses can reimplement this to initialize their child views in a different manner. The default implementation creates a child view for each child element. 
Normally a write-lock is held on the Document while
the children are being changed, which keeps the rendering
and layout threads safe.  The exception to this is when
the view is initialized to represent an existing element
(via this method), so it is synchronized to exclude
preferenceChanged while we are initializing.
Params: f – the view factory
See Also: setParent/**
     * Loads all of the children to initialize the view.
     * This is called by the {@link #setParent setParent}
     * method.  Subclasses can reimplement this to initialize
     * their child views in a different manner.  The default
     * implementation creates a child view for each
     * child element.
     * <p>
     * Normally a write-lock is held on the Document while
     * the children are being changed, which keeps the rendering
     * and layout threads safe.  The exception to this is when
     * the view is initialized to represent an existing element
     * (via this method), so it is synchronized to exclude
     * preferenceChanged while we are initializing.
     *
     * @param f the view factory
     * @see #setParent
     */
    protected void loadChildren(ViewFactory f) {
        Element e = getElement();
        int n = e.getElementCount();
        if (n > 0) {
            View[] added = new View[n];
            for (int i = 0; i < n; i++) {
                added[i] = f.create(e.getElement(i));
            }
            replace(0, 0, added);
        }
    }

    Fetches the child view index representing the given position in
the model.  This is implemented to fetch the view in the case
where there is a child view for each child element.
Params: pos – the position >= 0
Returns:  index of the view representing the given position, or
  -1 if no view represents that position/**
     * Fetches the child view index representing the given position in
     * the model.  This is implemented to fetch the view in the case
     * where there is a child view for each child element.
     *
     * @param pos the position &gt;= 0
     * @return  index of the view representing the given position, or
     *   -1 if no view represents that position
     */
    protected synchronized int getViewIndexAtPosition(int pos, Position.Bias b) {
        boolean isBackward = (b == Position.Bias.Backward);
        pos = (isBackward) ? Math.max(0, pos - 1) : pos;
        Element elem = getElement();
        return elem.getElementIndex(pos);
    }

    Update the layout in response to receiving notification of
change from the model.  This is implemented to note the
change on the ChildLocator so that offsets of the children
will be correctly computed.
Params: ec – changes to the element this view is responsible
 for (may be null if there were no changes).
e – the change information from the associated document
a – the current allocation of the view
See Also: View.insertUpdate
View.removeUpdate
View.changedUpdate/**
     * Update the layout in response to receiving notification of
     * change from the model.  This is implemented to note the
     * change on the ChildLocator so that offsets of the children
     * will be correctly computed.
     *
     * @param ec changes to the element this view is responsible
     *  for (may be null if there were no changes).
     * @param e the change information from the associated document
     * @param a the current allocation of the view
     * @see #insertUpdate
     * @see #removeUpdate
     * @see #changedUpdate
     */
    protected void updateLayout(DocumentEvent.ElementChange ec,
                                    DocumentEvent e, Shape a) {
        if (ec != null) {
            // the newly inserted children don't have a valid
            // offset so the child locator needs to be messaged
            // that the child prior to the new children has
            // changed size.
            int index = Math.max(ec.getIndex() - 1, 0);
            ChildState cs = getChildState(index);
            locator.childChanged(cs);
        }
    }

    // --- View methods ------------------------------------

    Sets the parent of the view.
This is reimplemented to provide the superclass
behavior as well as calling the loadChildren
method if this view does not already have children.
The children should not be loaded in the
constructor because the act of setting the parent
may cause them to try to search up the hierarchy
(to get the hosting Container for example).
If this view has children (the view is being moved
from one place in the view hierarchy to another),
the loadChildren method will not be called.
Params: parent – the parent of the view, null if none/**
     * Sets the parent of the view.
     * This is reimplemented to provide the superclass
     * behavior as well as calling the <code>loadChildren</code>
     * method if this view does not already have children.
     * The children should not be loaded in the
     * constructor because the act of setting the parent
     * may cause them to try to search up the hierarchy
     * (to get the hosting Container for example).
     * If this view has children (the view is being moved
     * from one place in the view hierarchy to another),
     * the <code>loadChildren</code> method will not be called.
     *
     * @param parent the parent of the view, null if none
     */
    public void setParent(View parent) {
        super.setParent(parent);
        if ((parent != null) && (getViewCount() == 0)) {
            ViewFactory f = getViewFactory();
            loadChildren(f);
        }
    }

    Child views can call this on the parent to indicate that
the preference has changed and should be reconsidered
for layout.  This is reimplemented to queue new work
on the layout thread.  This method gets messaged from
multiple threads via the children.
Params: child – the child view
width – true if the width preference has changed
height – true if the height preference has changed
See Also: JComponent.revalidate/**
     * Child views can call this on the parent to indicate that
     * the preference has changed and should be reconsidered
     * for layout.  This is reimplemented to queue new work
     * on the layout thread.  This method gets messaged from
     * multiple threads via the children.
     *
     * @param child the child view
     * @param width true if the width preference has changed
     * @param height true if the height preference has changed
     * @see javax.swing.JComponent#revalidate
     */
    public synchronized void preferenceChanged(View child, boolean width, boolean height) {
        if (child == null) {
            getParent().preferenceChanged(this, width, height);
        } else {
            if (changing != null) {
                View cv = changing.getChildView();
                if (cv == child) {
                    // size was being changed on the child, no need to
                    // queue work for it.
                    changing.preferenceChanged(width, height);
                    return;
                }
            }
            int index = getViewIndex(child.getStartOffset(),
                                     Position.Bias.Forward);
            ChildState cs = getChildState(index);
            cs.preferenceChanged(width, height);
            LayoutQueue q = getLayoutQueue();
            q.addTask(cs);
            q.addTask(flushTask);
        }
    }

    Sets the size of the view.  This should cause
layout of the view if the view caches any layout
information.

Since the major axis is updated asynchronously and should be
the sum of the tiled children the call is ignored for the major
axis.  Since the minor axis is flexible, work is queued to resize
the children if the minor span changes.
Params: width – the width >= 0
height – the height >= 0/**
     * Sets the size of the view.  This should cause
     * layout of the view if the view caches any layout
     * information.
     * <p>
     * Since the major axis is updated asynchronously and should be
     * the sum of the tiled children the call is ignored for the major
     * axis.  Since the minor axis is flexible, work is queued to resize
     * the children if the minor span changes.
     *
     * @param width the width &gt;= 0
     * @param height the height &gt;= 0
     */
    public void setSize(float width, float height) {
        setSpanOnAxis(X_AXIS, width);
        setSpanOnAxis(Y_AXIS, height);
    }

    Retrieves the size of the view along an axis.
Params: axis – may be either View.X_AXIS or
         View.Y_AXIS
Returns: the current span of the view along the given axis, >= 0/**
     * Retrieves the size of the view along an axis.
     *
     * @param axis may be either <code>View.X_AXIS</code> or
     *          <code>View.Y_AXIS</code>
     * @return the current span of the view along the given axis, >= 0
     */
    float getSpanOnAxis(int axis) {
        if (axis == getMajorAxis()) {
            return majorSpan;
        }
        return minorSpan;
    }

    Sets the size of the view along an axis.  Since the major
axis is updated asynchronously and should be the sum of the
tiled children the call is ignored for the major axis.  Since
the minor axis is flexible, work is queued to resize the
children if the minor span changes.
Params: axis – may be either View.X_AXIS or
         View.Y_AXIS
span – the span to layout to >= 0/**
     * Sets the size of the view along an axis.  Since the major
     * axis is updated asynchronously and should be the sum of the
     * tiled children the call is ignored for the major axis.  Since
     * the minor axis is flexible, work is queued to resize the
     * children if the minor span changes.
     *
     * @param axis may be either <code>View.X_AXIS</code> or
     *          <code>View.Y_AXIS</code>
     * @param span the span to layout to >= 0
     */
    void setSpanOnAxis(int axis, float span) {
        float margin = getInsetSpan(axis);
        if (axis == getMinorAxis()) {
            float targetSpan = span - margin;
            if (targetSpan != minorSpan) {
                minorSpan = targetSpan;

                // mark all of the ChildState instances as needing to
                // resize the child, and queue up work to fix them.
                int n = getViewCount();
                if (n != 0) {
                    LayoutQueue q = getLayoutQueue();
                    for (int i = 0; i < n; i++) {
                        ChildState cs = getChildState(i);
                        cs.childSizeValid = false;
                        q.addTask(cs);
                    }
                    q.addTask(flushTask);
                }
            }
        } else {
            // along the major axis the value is ignored
            // unless the estimatedMajorSpan property is
            // true.
            if (estimatedMajorSpan) {
                majorSpan = span - margin;
            }
        }
    }

    Render the view using the given allocation and
rendering surface.

This is implemented to determine whether or not the
desired region to be rendered (i.e. the unclipped
area) is up to date or not.  If up-to-date the children
are rendered.  If not up-to-date, a task to build
the desired area is placed on the layout queue as
a high priority task.  This keeps by event thread
moving by rendering if ready, and postponing until
a later time if not ready (since paint requests
can be rescheduled).
Params: g – the rendering surface to use
alloc – the allocated region to render into
See Also: View.paint/**
     * Render the view using the given allocation and
     * rendering surface.
     * <p>
     * This is implemented to determine whether or not the
     * desired region to be rendered (i.e. the unclipped
     * area) is up to date or not.  If up-to-date the children
     * are rendered.  If not up-to-date, a task to build
     * the desired area is placed on the layout queue as
     * a high priority task.  This keeps by event thread
     * moving by rendering if ready, and postponing until
     * a later time if not ready (since paint requests
     * can be rescheduled).
     *
     * @param g the rendering surface to use
     * @param alloc the allocated region to render into
     * @see View#paint
     */
    public void paint(Graphics g, Shape alloc) {
        synchronized (locator) {
            locator.setAllocation(alloc);
            locator.paintChildren(g);
        }
    }

    Determines the preferred span for this view along an
axis.
Params: axis – may be either View.X_AXIS or View.Y_AXIS
Throws: IllegalArgumentException – for an invalid axis type
Returns:   the span the view would like to be rendered into >= 0.
          Typically the view is told to render into the span
          that is returned, although there is no guarantee.
          The parent may choose to resize or break the view./**
     * Determines the preferred span for this view along an
     * axis.
     *
     * @param axis may be either View.X_AXIS or View.Y_AXIS
     * @return   the span the view would like to be rendered into &gt;= 0.
     *           Typically the view is told to render into the span
     *           that is returned, although there is no guarantee.
     *           The parent may choose to resize or break the view.
     * @exception IllegalArgumentException for an invalid axis type
     */
    public float getPreferredSpan(int axis) {
        float margin = getInsetSpan(axis);
        if (axis == this.axis) {
            return majorSpan + margin;
        }
        if (prefRequest != null) {
            View child = prefRequest.getChildView();
            return child.getPreferredSpan(axis) + margin;
        }

        // nothing is known about the children yet
        return margin + 30;
    }

    Determines the minimum span for this view along an
axis.
Params: axis – may be either View.X_AXIS or View.Y_AXIS
Throws: IllegalArgumentException – for an invalid axis type
Returns:  the span the view would like to be rendered into >= 0.
          Typically the view is told to render into the span
          that is returned, although there is no guarantee.
          The parent may choose to resize or break the view./**
     * Determines the minimum span for this view along an
     * axis.
     *
     * @param axis may be either View.X_AXIS or View.Y_AXIS
     * @return  the span the view would like to be rendered into &gt;= 0.
     *           Typically the view is told to render into the span
     *           that is returned, although there is no guarantee.
     *           The parent may choose to resize or break the view.
     * @exception IllegalArgumentException for an invalid axis type
     */
    public float getMinimumSpan(int axis) {
        if (axis == this.axis) {
            return getPreferredSpan(axis);
        }
        if (minRequest != null) {
            View child = minRequest.getChildView();
            return child.getMinimumSpan(axis);
        }

        // nothing is known about the children yet
        if (axis == X_AXIS) {
            return getLeftInset() + getRightInset() + 5;
        } else {
            return getTopInset() + getBottomInset() + 5;
        }
    }

    Determines the maximum span for this view along an
axis.
Params: axis – may be either View.X_AXIS or View.Y_AXIS
Throws: IllegalArgumentException – for an invalid axis type
Returns:   the span the view would like to be rendered into >= 0.
          Typically the view is told to render into the span
          that is returned, although there is no guarantee.
          The parent may choose to resize or break the view./**
     * Determines the maximum span for this view along an
     * axis.
     *
     * @param axis may be either View.X_AXIS or View.Y_AXIS
     * @return   the span the view would like to be rendered into &gt;= 0.
     *           Typically the view is told to render into the span
     *           that is returned, although there is no guarantee.
     *           The parent may choose to resize or break the view.
     * @exception IllegalArgumentException for an invalid axis type
     */
    public float getMaximumSpan(int axis) {
        if (axis == this.axis) {
            return getPreferredSpan(axis);
        }
        return Integer.MAX_VALUE;
    }


    Returns the number of views in this view.  Since
the default is to not be a composite view this
returns 0.
See Also: View.getViewCount
Returns: the number of views >= 0/**
     * Returns the number of views in this view.  Since
     * the default is to not be a composite view this
     * returns 0.
     *
     * @return the number of views &gt;= 0
     * @see View#getViewCount
     */
    public int getViewCount() {
        synchronized(stats) {
            return stats.size();
        }
    }

    Gets the nth child view.  Since there are no
children by default, this returns null.
Params: n – the number of the view to get, >= 0 && < getViewCount()
Returns: the view/**
     * Gets the nth child view.  Since there are no
     * children by default, this returns null.
     *
     * @param n the number of the view to get, &gt;= 0 &amp;&amp; &lt; getViewCount()
     * @return the view
     */
    public View getView(int n) {
        ChildState cs = getChildState(n);
        if (cs != null) {
            return cs.getChildView();
        }
        return null;
    }

    Fetches the allocation for the given child view.
This enables finding out where various views
are located, without assuming the views store
their location.  This returns null since the
default is to not have any child views.
Params: index – the index of the child, >= 0 && < getViewCount()
a –  the allocation to this view.
Returns: the allocation to the child/**
     * Fetches the allocation for the given child view.
     * This enables finding out where various views
     * are located, without assuming the views store
     * their location.  This returns null since the
     * default is to not have any child views.
     *
     * @param index the index of the child, &gt;= 0 &amp;&amp; &lt; getViewCount()
     * @param a  the allocation to this view.
     * @return the allocation to the child
     */
    public Shape getChildAllocation(int index, Shape a) {
        Shape ca = locator.getChildAllocation(index, a);
        return ca;
    }

    Returns the child view index representing the given position in
the model.  By default a view has no children so this is implemented
to return -1 to indicate there is no valid child index for any
position.
Params: pos – the position >= 0
Returns:  index of the view representing the given position, or
  -1 if no view represents that position
Since: 1.3/**
     * Returns the child view index representing the given position in
     * the model.  By default a view has no children so this is implemented
     * to return -1 to indicate there is no valid child index for any
     * position.
     *
     * @param pos the position &gt;= 0
     * @return  index of the view representing the given position, or
     *   -1 if no view represents that position
     * @since 1.3
     */
    public int getViewIndex(int pos, Position.Bias b) {
        return getViewIndexAtPosition(pos, b);
    }

    Provides a mapping from the document model coordinate space
to the coordinate space of the view mapped to it.
Params: pos – the position to convert >= 0
a – the allocated region to render into
b – the bias toward the previous character or the
 next character represented by the offset, in case the
 position is a boundary of two views.
Throws: BadLocationException –  if the given position does
  not represent a valid location in the associated document
IllegalArgumentException – for an invalid bias argument
See Also: View.viewToModel
Returns: the bounding box of the given position is returned/**
     * Provides a mapping from the document model coordinate space
     * to the coordinate space of the view mapped to it.
     *
     * @param pos the position to convert &gt;= 0
     * @param a the allocated region to render into
     * @param b the bias toward the previous character or the
     *  next character represented by the offset, in case the
     *  position is a boundary of two views.
     * @return the bounding box of the given position is returned
     * @exception BadLocationException  if the given position does
     *   not represent a valid location in the associated document
     * @exception IllegalArgumentException for an invalid bias argument
     * @see View#viewToModel
     */
    public Shape modelToView(int pos, Shape a, Position.Bias b) throws BadLocationException {
        int index = getViewIndex(pos, b);
        Shape ca = locator.getChildAllocation(index, a);

        // forward to the child view, and make sure we don't
        // interact with the layout thread by synchronizing
        // on the child state.
        ChildState cs = getChildState(index);
        synchronized (cs) {
            View cv = cs.getChildView();
            Shape v = cv.modelToView(pos, ca, b);
            return v;
        }
    }

    Provides a mapping from the view coordinate space to the logical
coordinate space of the model.  The biasReturn argument will be
filled in to indicate that the point given is closer to the next
character in the model or the previous character in the model.

This is expected to be called by the GUI thread, holding a
read-lock on the associated model.  It is implemented to
locate the child view and determine it's allocation with a
lock on the ChildLocator object, and to call viewToModel
on the child view with a lock on the ChildState object
to avoid interaction with the layout thread.
Params: x – the X coordinate >= 0
y – the Y coordinate >= 0
a – the allocated region to render into
Returns: the location within the model that best represents the
 given point in the view >= 0.  The biasReturn argument will be
filled in to indicate that the point given is closer to the next
character in the model or the previous character in the model./**
     * Provides a mapping from the view coordinate space to the logical
     * coordinate space of the model.  The biasReturn argument will be
     * filled in to indicate that the point given is closer to the next
     * character in the model or the previous character in the model.
     * <p>
     * This is expected to be called by the GUI thread, holding a
     * read-lock on the associated model.  It is implemented to
     * locate the child view and determine it's allocation with a
     * lock on the ChildLocator object, and to call viewToModel
     * on the child view with a lock on the ChildState object
     * to avoid interaction with the layout thread.
     *
     * @param x the X coordinate &gt;= 0
     * @param y the Y coordinate &gt;= 0
     * @param a the allocated region to render into
     * @return the location within the model that best represents the
     *  given point in the view &gt;= 0.  The biasReturn argument will be
     * filled in to indicate that the point given is closer to the next
     * character in the model or the previous character in the model.
     */
    public int viewToModel(float x, float y, Shape a, Position.Bias[] biasReturn) {
        int pos;    // return position
        int index;  // child index to forward to
        Shape ca;   // child allocation

        // locate the child view and it's allocation so that
        // we can forward to it.  Make sure the layout thread
        // doesn't change anything by trying to flush changes
        // to the parent while the GUI thread is trying to
        // find the child and it's allocation.
        synchronized (locator) {
            index = locator.getViewIndexAtPoint(x, y, a);
            ca = locator.getChildAllocation(index, a);
        }

        // forward to the child view, and make sure we don't
        // interact with the layout thread by synchronizing
        // on the child state.
        ChildState cs = getChildState(index);
        synchronized (cs) {
            View v = cs.getChildView();
            pos = v.viewToModel(x, y, ca, biasReturn);
        }
        return pos;
    }

    Provides a way to determine the next visually represented model location that one might place a caret. Some views may not be visible, they might not be in the same order found in the model, or they just might not allow access to some of the locations in the model. This method enables specifying a position to convert within the range of >=0. If the value is -1, a position will be calculated automatically. If the value < -1, the BadLocationException will be thrown. 
Params: pos – the position to convert
a – the allocated region to render into
direction – the direction from the current position that can
 be thought of as the arrow keys typically found on a keyboard;
 this may be one of the following:
 
 SwingConstants.WEST
 SwingConstants.EAST
 SwingConstants.NORTH
 SwingConstants.SOUTH
 
biasRet – an array contain the bias that was checked
Throws: BadLocationException – the given position is not a valid
                                position within the document
IllegalArgumentException – if direction is invalid
Returns: the location within the model that best represents the next
 location visual position/**
     * Provides a way to determine the next visually represented model
     * location that one might place a caret.  Some views may not be visible,
     * they might not be in the same order found in the model, or they just
     * might not allow access to some of the locations in the model.
     * This method enables specifying a position to convert
     * within the range of &gt;=0.  If the value is -1, a position
     * will be calculated automatically.  If the value &lt; -1,
     * the {@code BadLocationException} will be thrown.
     *
     * @param pos the position to convert
     * @param a the allocated region to render into
     * @param direction the direction from the current position that can
     *  be thought of as the arrow keys typically found on a keyboard;
     *  this may be one of the following:
     *  <ul style="list-style-type:none">
     *  <li><code>SwingConstants.WEST</code></li>
     *  <li><code>SwingConstants.EAST</code></li>
     *  <li><code>SwingConstants.NORTH</code></li>
     *  <li><code>SwingConstants.SOUTH</code></li>
     *  </ul>
     * @param biasRet an array contain the bias that was checked
     * @return the location within the model that best represents the next
     *  location visual position
     * @exception BadLocationException the given position is not a valid
     *                                 position within the document
     * @exception IllegalArgumentException if <code>direction</code> is invalid
     */
    public int getNextVisualPositionFrom(int pos, Position.Bias b, Shape a,
                                         int direction,
                                         Position.Bias[] biasRet)
                                                  throws BadLocationException {
        if (pos < -1) {
            throw new BadLocationException("invalid position", pos);
        }
        return Utilities.getNextVisualPositionFrom(
                            this, pos, b, a, direction, biasRet);
    }

    // --- variables -----------------------------------------

    The major axis against which the children are
tiled.
/**
     * The major axis against which the children are
     * tiled.
     */
    int axis;

    The children and their layout statistics.
/**
     * The children and their layout statistics.
     */
    List<ChildState> stats;

    Current span along the major axis.  This
is also the value returned by getMinimumSize,
getPreferredSize, and getMaximumSize along
the major axis.
/**
     * Current span along the major axis.  This
     * is also the value returned by getMinimumSize,
     * getPreferredSize, and getMaximumSize along
     * the major axis.
     */
    float majorSpan;

    Is the span along the major axis estimated?
/**
     * Is the span along the major axis estimated?
     */
    boolean estimatedMajorSpan;

    Current span along the minor axis.  This
is what layout was done against (i.e. things
are flexible in this direction).
/**
     * Current span along the minor axis.  This
     * is what layout was done against (i.e. things
     * are flexible in this direction).
     */
    float minorSpan;

    Object that manages the offsets of the
children.  All locking for management of
child locations is on this object.
/**
     * Object that manages the offsets of the
     * children.  All locking for management of
     * child locations is on this object.
     */
    protected ChildLocator locator;

    float topInset;
    float bottomInset;
    float leftInset;
    float rightInset;

    ChildState minRequest;
    ChildState prefRequest;
    boolean majorChanged;
    boolean minorChanged;
    Runnable flushTask;

    Child that is actively changing size.  This often
causes a preferenceChanged, so this is a cache to
possibly speed up the marking the state.  It also
helps flag an opportunity to avoid adding to flush
task to the layout queue.
/**
     * Child that is actively changing size.  This often
     * causes a preferenceChanged, so this is a cache to
     * possibly speed up the marking the state.  It also
     * helps flag an opportunity to avoid adding to flush
     * task to the layout queue.
     */
    ChildState changing;

    A class to manage the effective position of the
child views in a localized area while changes are
being made around the localized area.  The AsyncBoxView
may be continuously changing, but the visible area
needs to remain fairly stable until the layout thread
decides to publish an update to the parent.
Since: 1.3/**
     * A class to manage the effective position of the
     * child views in a localized area while changes are
     * being made around the localized area.  The AsyncBoxView
     * may be continuously changing, but the visible area
     * needs to remain fairly stable until the layout thread
     * decides to publish an update to the parent.
     * @since 1.3
     */
    public class ChildLocator {

        construct a child locator.
/**
         * construct a child locator.
         */
        public ChildLocator() {
            lastAlloc = new Rectangle();
            childAlloc = new Rectangle();
        }

        Notification that a child changed.  This can effect
whether or not new offset calculations are needed.
This is called by a ChildState object that has
changed it's major span.  This can therefore be
called by multiple threads.
/**
         * Notification that a child changed.  This can effect
         * whether or not new offset calculations are needed.
         * This is called by a ChildState object that has
         * changed it's major span.  This can therefore be
         * called by multiple threads.
         */
        public synchronized void childChanged(ChildState cs) {
            if (lastValidOffset == null) {
                lastValidOffset = cs;
            } else if (cs.getChildView().getStartOffset() <
                       lastValidOffset.getChildView().getStartOffset()) {
                lastValidOffset = cs;
            }
        }

        Paint the children that intersect the clip area.
/**
         * Paint the children that intersect the clip area.
         */
        public synchronized void paintChildren(Graphics g) {
            Rectangle clip = g.getClipBounds();
            float targetOffset = (axis == X_AXIS) ?
                clip.x - lastAlloc.x : clip.y - lastAlloc.y;
            int index = getViewIndexAtVisualOffset(targetOffset);
            int n = getViewCount();
            float offs = getChildState(index).getMajorOffset();
            for (int i = index; i < n; i++) {
                ChildState cs = getChildState(i);
                cs.setMajorOffset(offs);
                Shape ca = getChildAllocation(i);
                if (intersectsClip(ca, clip)) {
                    synchronized (cs) {
                        View v = cs.getChildView();
                        v.paint(g, ca);
                    }
                } else {
                    // done painting intersection
                    break;
                }
                offs += cs.getMajorSpan();
            }
        }

        Fetch the allocation to use for a child view.
This will update the offsets for all children
not yet updated before the given index.
/**
         * Fetch the allocation to use for a child view.
         * This will update the offsets for all children
         * not yet updated before the given index.
         */
        public synchronized Shape getChildAllocation(int index, Shape a) {
            if (a == null) {
                return null;
            }
            setAllocation(a);
            ChildState cs = getChildState(index);
            if (lastValidOffset == null) {
                lastValidOffset = getChildState(0);
            }
            if (cs.getChildView().getStartOffset() >
                lastValidOffset.getChildView().getStartOffset()) {
                // offsets need to be updated
                updateChildOffsetsToIndex(index);
            }
            Shape ca = getChildAllocation(index);
            return ca;
        }

        Fetches the child view index at the given point.
This is called by the various View methods that
need to calculate which child to forward a message
to.  This should be called by a block synchronized
on this object, and would typically be followed
with one or more calls to getChildAllocation that
should also be in the synchronized block.
Params: x – the X coordinate >= 0
y – the Y coordinate >= 0
a – the allocation to the View
Returns: the nearest child index/**
         * Fetches the child view index at the given point.
         * This is called by the various View methods that
         * need to calculate which child to forward a message
         * to.  This should be called by a block synchronized
         * on this object, and would typically be followed
         * with one or more calls to getChildAllocation that
         * should also be in the synchronized block.
         *
         * @param x the X coordinate &gt;= 0
         * @param y the Y coordinate &gt;= 0
         * @param a the allocation to the View
         * @return the nearest child index
         */
        public int getViewIndexAtPoint(float x, float y, Shape a) {
            setAllocation(a);
            float targetOffset = (axis == X_AXIS) ? x - lastAlloc.x : y - lastAlloc.y;
            int index = getViewIndexAtVisualOffset(targetOffset);
            return index;
        }

        Fetch the allocation to use for a child view.
This does not update the offsets in the ChildState
records.
/**
         * Fetch the allocation to use for a child view.
         * <em>This does not update the offsets in the ChildState
         * records.</em>
         */
        protected Shape getChildAllocation(int index) {
            ChildState cs = getChildState(index);
            if (! cs.isLayoutValid()) {
                cs.run();
            }
            if (axis == X_AXIS) {
                childAlloc.x = lastAlloc.x + (int) cs.getMajorOffset();
                childAlloc.y = lastAlloc.y + (int) cs.getMinorOffset();
                childAlloc.width = (int) cs.getMajorSpan();
                childAlloc.height = (int) cs.getMinorSpan();
            } else {
                childAlloc.y = lastAlloc.y + (int) cs.getMajorOffset();
                childAlloc.x = lastAlloc.x + (int) cs.getMinorOffset();
                childAlloc.height = (int) cs.getMajorSpan();
                childAlloc.width = (int) cs.getMinorSpan();
            }
            childAlloc.x += (int)getLeftInset();
            childAlloc.y += (int)getRightInset();
            return childAlloc;
        }

        Copy the currently allocated shape into the Rectangle
used to store the current allocation.  This would be
a floating point rectangle in a Java2D-specific implementation.
/**
         * Copy the currently allocated shape into the Rectangle
         * used to store the current allocation.  This would be
         * a floating point rectangle in a Java2D-specific implementation.
         */
        protected void setAllocation(Shape a) {
            if (a instanceof Rectangle) {
                lastAlloc.setBounds((Rectangle) a);
            } else {
                lastAlloc.setBounds(a.getBounds());
            }
            setSize(lastAlloc.width, lastAlloc.height);
        }

        Locate the view responsible for an offset into the box
along the major axis.  Make sure that offsets are set
on the ChildState objects up to the given target span
past the desired offset.
Returns:   index of the view representing the given visual
  location (targetOffset), or -1 if no view represents
  that location/**
         * Locate the view responsible for an offset into the box
         * along the major axis.  Make sure that offsets are set
         * on the ChildState objects up to the given target span
         * past the desired offset.
         *
         * @return   index of the view representing the given visual
         *   location (targetOffset), or -1 if no view represents
         *   that location
         */
        protected int getViewIndexAtVisualOffset(float targetOffset) {
            int n = getViewCount();
            if (n > 0) {
                boolean lastValid = (lastValidOffset != null);

                if (lastValidOffset == null) {
                    lastValidOffset = getChildState(0);
                }
                if (targetOffset > majorSpan) {
                    // should only get here on the first time display.
                    if (!lastValid) {
                        return 0;
                    }
                    int pos = lastValidOffset.getChildView().getStartOffset();
                    int index = getViewIndex(pos, Position.Bias.Forward);
                    return index;
                } else if (targetOffset > lastValidOffset.getMajorOffset()) {
                    // roll offset calculations forward
                    return updateChildOffsets(targetOffset);
                } else {
                    // no changes prior to the needed offset
                    // this should be a binary search
                    float offs = 0f;
                    for (int i = 0; i < n; i++) {
                        ChildState cs = getChildState(i);
                        float nextOffs = offs + cs.getMajorSpan();
                        if (targetOffset < nextOffs) {
                            return i;
                        }
                        offs = nextOffs;
                    }
                }
            }
            return n - 1;
        }

        Move the location of the last offset calculation forward
to the desired offset.
/**
         * Move the location of the last offset calculation forward
         * to the desired offset.
         */
        int updateChildOffsets(float targetOffset) {
            int n = getViewCount();
            int targetIndex = n - 1;
            int pos = lastValidOffset.getChildView().getStartOffset();
            int startIndex = getViewIndex(pos, Position.Bias.Forward);
            float start = lastValidOffset.getMajorOffset();
            float lastOffset = start;
            for (int i = startIndex; i < n; i++) {
                ChildState cs = getChildState(i);
                cs.setMajorOffset(lastOffset);
                lastOffset += cs.getMajorSpan();
                if (targetOffset < lastOffset) {
                    targetIndex = i;
                    lastValidOffset = cs;
                    break;
                }
            }

            return targetIndex;
        }

        Move the location of the last offset calculation forward
to the desired index.
/**
         * Move the location of the last offset calculation forward
         * to the desired index.
         */
        void updateChildOffsetsToIndex(int index) {
            int pos = lastValidOffset.getChildView().getStartOffset();
            int startIndex = getViewIndex(pos, Position.Bias.Forward);
            float lastOffset = lastValidOffset.getMajorOffset();
            for (int i = startIndex; i <= index; i++) {
                ChildState cs = getChildState(i);
                cs.setMajorOffset(lastOffset);
                lastOffset += cs.getMajorSpan();
            }
        }

        boolean intersectsClip(Shape childAlloc, Rectangle clip) {
            Rectangle cs = (childAlloc instanceof Rectangle) ?
                (Rectangle) childAlloc : childAlloc.getBounds();
            if (cs.intersects(clip)) {
                // Make sure that lastAlloc also contains childAlloc,
                // this will be false if haven't yet flushed changes.
                return lastAlloc.intersects(cs);
            }
            return false;
        }

        The location of the last offset calculation
that is valid.
/**
         * The location of the last offset calculation
         * that is valid.
         */
        protected ChildState lastValidOffset;

        The last seen allocation (for repainting when changes
are flushed upward).
/**
         * The last seen allocation (for repainting when changes
         * are flushed upward).
         */
        protected Rectangle lastAlloc;

        A shape to use for the child allocation to avoid
creating a lot of garbage.
/**
         * A shape to use for the child allocation to avoid
         * creating a lot of garbage.
         */
        protected Rectangle childAlloc;
    }

    A record representing the layout state of a
child view.  It is runnable as a task on another
thread.  All access to the child view that is
based upon a read-lock on the model should synchronize
on this object (i.e. The layout thread and the GUI
thread can both have a read lock on the model at the
same time and are not protected from each other).
Access to a child view hierarchy is serialized via
synchronization on the ChildState instance.
Since: 1.3/**
     * A record representing the layout state of a
     * child view.  It is runnable as a task on another
     * thread.  All access to the child view that is
     * based upon a read-lock on the model should synchronize
     * on this object (i.e. The layout thread and the GUI
     * thread can both have a read lock on the model at the
     * same time and are not protected from each other).
     * Access to a child view hierarchy is serialized via
     * synchronization on the ChildState instance.
     * @since 1.3
     */
    public class ChildState implements Runnable {

        Construct a child status.  This needs to start
out as fairly large so we don't falsely begin with
the idea that all of the children are visible.
Since: 1.4/**
         * Construct a child status.  This needs to start
         * out as fairly large so we don't falsely begin with
         * the idea that all of the children are visible.
         * @since 1.4
         */
        public ChildState(View v) {
            child = v;
            minorValid = false;
            majorValid = false;
            childSizeValid = false;
            child.setParent(AsyncBoxView.this);
        }

        Fetch the child view this record represents
/**
         * Fetch the child view this record represents
         */
        public View getChildView() {
            return child;
        }

        Update the child state.  This should be
called by the thread that desires to spend
time updating the child state (intended to
be the layout thread).

This acquires a read lock on the associated
document for the duration of the update to
ensure the model is not changed while it is
operating.  The first thing to do would be
to see if any work actually needs to be done.
The following could have conceivably happened
while the state was waiting to be updated:

The child may have been removed from the
view hierarchy.
The child may have been updated by a
higher priority operation (i.e. the child
may have become visible).

/**
         * Update the child state.  This should be
         * called by the thread that desires to spend
         * time updating the child state (intended to
         * be the layout thread).
         * <p>
         * This acquires a read lock on the associated
         * document for the duration of the update to
         * ensure the model is not changed while it is
         * operating.  The first thing to do would be
         * to see if any work actually needs to be done.
         * The following could have conceivably happened
         * while the state was waiting to be updated:
         * <ol>
         * <li>The child may have been removed from the
         * view hierarchy.
         * <li>The child may have been updated by a
         * higher priority operation (i.e. the child
         * may have become visible).
         * </ol>
         */
        public void run () {
            AbstractDocument doc = (AbstractDocument) getDocument();
            try {
                doc.readLock();
                if (minorValid && majorValid && childSizeValid) {
                    // nothing to do
                    return;
                }
                if (child.getParent() == AsyncBoxView.this) {
                    // this may overwrite anothers threads cached
                    // value for actively changing... but that just
                    // means it won't use the cache if there is an
                    // overwrite.
                    synchronized(AsyncBoxView.this) {
                        changing = this;
                    }
                    updateChild();
                    synchronized(AsyncBoxView.this) {
                        changing = null;
                    }

                    // setting the child size on the minor axis
                    // may have caused it to change it's preference
                    // along the major axis.
                    updateChild();
                }
            } finally {
                doc.readUnlock();
            }
        }

        void updateChild() {
            boolean minorUpdated = false;
            synchronized(this) {
                if (! minorValid) {
                    int minorAxis = getMinorAxis();
                    min = child.getMinimumSpan(minorAxis);
                    pref = child.getPreferredSpan(minorAxis);
                    max = child.getMaximumSpan(minorAxis);
                    minorValid = true;
                    minorUpdated = true;
                }
            }
            if (minorUpdated) {
                minorRequirementChange(this);
            }

            boolean majorUpdated = false;
            float delta = 0.0f;
            synchronized(this) {
                if (! majorValid) {
                    float old = span;
                    span = child.getPreferredSpan(axis);
                    delta = span - old;
                    majorValid = true;
                    majorUpdated = true;
                }
            }
            if (majorUpdated) {
                majorRequirementChange(this, delta);
                locator.childChanged(this);
            }

            synchronized(this) {
                if (! childSizeValid) {
                    float w;
                    float h;
                    if (axis == X_AXIS) {
                        w = span;
                        h = getMinorSpan();
                    } else {
                        w = getMinorSpan();
                        h = span;
                    }
                    childSizeValid = true;
                    child.setSize(w, h);
                }
            }

        }

        What is the span along the minor axis.
/**
         * What is the span along the minor axis.
         */
        public float getMinorSpan() {
            if (max < minorSpan) {
                return max;
            }
            // make it the target width, or as small as it can get.
            return Math.max(min, minorSpan);
        }

        What is the offset along the minor axis
/**
         * What is the offset along the minor axis
         */
        public float getMinorOffset() {
            if (max < minorSpan) {
                // can't make the child this wide, align it
                float align = child.getAlignment(getMinorAxis());
                return ((minorSpan - max) * align);
            }
            return 0f;
        }

        What is the span along the major axis.
/**
         * What is the span along the major axis.
         */
        public float getMajorSpan() {
            return span;
        }

        Get the offset along the major axis
/**
         * Get the offset along the major axis
         */
        public float getMajorOffset() {
            return offset;
        }

        This method should only be called by the ChildLocator,
it is simply a convenient place to hold the cached
location.
/**
         * This method should only be called by the ChildLocator,
         * it is simply a convenient place to hold the cached
         * location.
         */
        public void setMajorOffset(float offs) {
            offset = offs;
        }

        Mark preferences changed for this child.
Params: width – true if the width preference has changed
height – true if the height preference has changed
See Also: JComponent.revalidate/**
         * Mark preferences changed for this child.
         *
         * @param width true if the width preference has changed
         * @param height true if the height preference has changed
         * @see javax.swing.JComponent#revalidate
         */
        public void preferenceChanged(boolean width, boolean height) {
            if (axis == X_AXIS) {
                if (width) {
                    majorValid = false;
                }
                if (height) {
                    minorValid = false;
                }
            } else {
                if (width) {
                    minorValid = false;
                }
                if (height) {
                    majorValid = false;
                }
            }
            childSizeValid = false;
        }

        Has the child view been laid out.
/**
         * Has the child view been laid out.
         */
        public boolean isLayoutValid() {
            return (minorValid && majorValid && childSizeValid);
        }

        // minor axis
        private float min;
        private float pref;
        private float max;
        private boolean minorValid;

        // major axis
        private float span;
        private float offset;
        private boolean majorValid;

        private View child;
        private boolean childSizeValid;
    }

    Task to flush requirement changes upward
/**
     * Task to flush requirement changes upward
     */
    class FlushTask implements Runnable {

        public void run() {
            flushRequirementChanges();
        }

    }

}
Params:	axis – the axis to determine the total insets along, either X_AXIS or Y_AXIS.
Since:	1.4
Params:	pos – the position >= 0
Returns:	index of the view representing the given position, or -1 if no view represents that position
Params:	ec – changes to the element this view is responsible for (may be null if there were no changes). e – the change information from the associated document a – the current allocation of the view
See Also:	View.insertUpdate View.removeUpdate View.changedUpdate
Params:	child – the child view width – true if the width preference has changed height – true if the height preference has changed
See Also:	JComponent.revalidate
Params:	axis – may be either `View.X_AXIS` or `View.Y_AXIS`
Returns:	the current span of the view along the given axis, >= 0
Params:	g – the rendering surface to use alloc – the allocated region to render into
See Also:	View.paint
Params:	axis – may be either View.X_AXIS or View.Y_AXIS
Throws:	IllegalArgumentException – for an invalid axis type
Returns:	the span the view would like to be rendered into >= 0. Typically the view is told to render into the span that is returned, although there is no guarantee. The parent may choose to resize or break the view.
Params:	n – the number of the view to get, >= 0 && < getViewCount()
Returns:	the view
Params:	index – the index of the child, >= 0 && < getViewCount() a – the allocation to this view.
Returns:	the allocation to the child
Params:	pos – the position to convert >= 0 a – the allocated region to render into b – the bias toward the previous character or the next character represented by the offset, in case the position is a boundary of two views.
Throws:	BadLocationException – if the given position does not represent a valid location in the associated document IllegalArgumentException – for an invalid bias argument
See Also:	View.viewToModel
Returns:	the bounding box of the given position is returned
Params:	x – the X coordinate >= 0 y – the Y coordinate >= 0 a – the allocated region to render into
Returns:	the location within the model that best represents the given point in the view >= 0. The biasReturn argument will be filled in to indicate that the point given is closer to the next character in the model or the previous character in the model.
Params:	pos – the position to convert a – the allocated region to render into direction – the direction from the current position that can be thought of as the arrow keys typically found on a keyboard; this may be one of the following: `SwingConstants.WEST` `SwingConstants.EAST` `SwingConstants.NORTH` `SwingConstants.SOUTH` biasRet – an array contain the bias that was checked
Throws:	BadLocationException – the given position is not a valid position within the document IllegalArgumentException – if `direction` is invalid
Returns:	the location within the model that best represents the next location visual position
Params:	width – true if the width preference has changed height – true if the height preference has changed
See Also:	JComponent.revalidate
/

java/ 8/ javax/swing/text/AsyncBoxView.java
