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;
}

Construct a box view that does asynchronous layout.

Parameters:

elem - the element of the model to represent

axis - the axis to tile along. This can be either X_AXIS or Y_AXIS.

 protected ChildState createChildState(View v) 
{
        return new ChildState(v);
}

New ChildState records are created through this method to allow subclasses the extend the ChildState records to do/hold more

 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();
        }
}

Publish the changes in preferences upward to the parent view. This is normally called by the layout thread.

 public float getBottomInset() 
{
        return bottomInset;
}

Get the bottom part of the margin around the view.

 public Shape getChildAllocation(int index,
    Shape a) 
{
        Shape ca = locator.getChildAllocation(index, a);
        return ca;
}

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.

 protected ChildState getChildState(int index) 
{
        synchronized(stats) {
            if ((index  >= 0) && (index <  stats.size())) {
                return stats.get(index);
            }
            return null;
        }
}

Fetch the object representing the layout state of of the child at the given index.

 protected boolean getEstimatedMajorSpan() 
{
        return estimatedMajorSpan;
}

Is the major span currently estimated?

 protected float getInsetSpan(int axis) 
{
        float margin = (axis == X_AXIS) ?
            getLeftInset() + getRightInset() : getTopInset() + getBottomInset();
        return margin;
}

Fetch the span along an axis that is taken up by the insets.

 protected LayoutQueue getLayoutQueue() 
{
        return LayoutQueue.getDefaultQueue();
}

Fetch the queue to use for layout.

 public float getLeftInset() 
{
        return leftInset;
}

Get the left part of the margin around the view.

 public int getMajorAxis() 
{
        return 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 float getMaximumSpan(int axis) 
{
        if (axis == this.axis) {
            return getPreferredSpan(axis);
        }
        return Integer.MAX_VALUE;
}

Determines the maximum span for this view along an axis.

 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 minimum span for this view along an axis.

 public int getMinorAxis() 
{
        return (axis == X_AXIS) ? Y_AXIS : X_AXIS;
}

Fetch the minor axis (the axis orthoginal to the tiled axis). This will have a value of either X_AXIS or Y_AXIS.

 public int getNextVisualPositionFrom(int pos,
    Bias b,
    Shape a,
    int direction,
    Bias[] biasRet) throws BadLocationException 
{
        return Utilities.getNextVisualPositionFrom(
                            this, pos, b, a, direction, biasRet);
}

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.

 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 preferred span for this view along an axis.

 public float getRightInset() 
{
        return rightInset;
}

Get the right part of the margin around the view.

 float getSpanOnAxis(int axis) 
{
        if (axis == getMajorAxis()) {
            return majorSpan;
        }
        return minorSpan;
}

Retrieves the size of the view along an axis.

 public float getTopInset() 
{
        return topInset;
}

Get the top part of the margin around the view.

 public View getView(int n) 
{
        ChildState cs = getChildState(n);
        if (cs != null) {
            return cs.getChildView();
        }
        return null;
}

Gets the nth child view. Since there are no children by default, this returns null.

 public int getViewCount() 
{
        synchronized(stats) {
            return stats.size();
        }
}

Returns the number of views in this view. Since the default is to not be a composite view this returns 0.

 public int getViewIndex(int pos,
    Bias b) 
{
        return getViewIndexAtPosition(pos, b);
}

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.

 protected synchronized int getViewIndexAtPosition(int pos,
    Bias b) 
{
        boolean isBackward = (b == Position.Bias.Backward);
        pos = (isBackward) ? Math.max(0, pos - 1) : pos;
        Element elem = getElement();
        return elem.getElementIndex(pos);
}

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.

 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);
        }
}

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.

 protected synchronized  void majorRequirementChange(ChildState cs,
    float delta) 
{
        if (estimatedMajorSpan == false) {
            majorSpan += delta;
        }
        majorChanged = true;
}

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.

 protected synchronized  void minorRequirementChange(ChildState cs) 
{
        minorChanged = 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).

 public Shape modelToView(int pos,
    Shape a,
    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 document model coordinate space to the coordinate space of the view mapped to it.

 public  void paint(Graphics g,
    Shape alloc) 
{
        synchronized (locator) {
            locator.setAllocation(alloc);
            locator.paintChildren(g);
        }
}

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).

 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);
        }
}

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.

 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);
        }
}

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).

 public  void setBottomInset(float i) 
{
        bottomInset = i;
}

Set the bottom part of the margin around the view.

 protected  void setEstimatedMajorSpan(boolean isEstimated) 
{
        estimatedMajorSpan = isEstimated;
}

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.

 public  void setLeftInset(float i) 
{
        leftInset = i;
}

Set the left part of the margin around the view.

 public  void setParent(View parent) 
{
        super.setParent(parent);
        if ((parent != null) && (getViewCount() == 0)) {
            ViewFactory f = getViewFactory();
            loadChildren(f);
        }
}

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.

 public  void setRightInset(float i) 
{
        rightInset = i;
}

Set the right part of the margin around the view.

 public  void setSize(float width,
    float height) 
{
        setSpanOnAxis(X_AXIS, width);
        setSpanOnAxis(Y_AXIS, height);
}

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.

  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;
            }
        }
}

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.

 public  void setTopInset(float i) 
{
        topInset = i;
}

Set the top part of the margin around the view.

 protected  void updateLayout(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);
        }
}

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.

 public int viewToModel(float x,
    float y,
    Shape a,
    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 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.