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	/*
	* Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/
	package javax.swing.text;

	import java.util.Vector;
	import java.awt.*;
	import javax.swing.event.*;

	/**
	* ZoneView is a View implementation that creates zones for which
	* the child views are not created or stored until they are needed
	* for display or model/view translations. This enables a substantial
	* reduction in memory consumption for situations where the model
	* being represented is very large, by building view objects only for
	* the region being actively viewed/edited. The size of the children
	* can be estimated in some way, or calculated asynchronously with
	* only the result being saved.
	* <p>
	* ZoneView extends BoxView to provide a box that implements
	* zones for its children. The zones are special View implementations
	* (the children of an instance of this class) that represent only a
	* portion of the model that an instance of ZoneView is responsible
	* for. The zones don't create child views until an attempt is made
	* to display them. A box shaped view is well suited to this because:
	* <ul>
	* <li>
	* Boxes are a heavily used view, and having a box that
	* provides this behavior gives substantial opportunity
	* to plug the behavior into a view hierarchy from the
	* view factory.
	* <li>
	* Boxes are tiled in one direction, so it is easy to
	* divide them into zones in a reliable way.
	* <li>
	* Boxes typically have a simple relationship to the model (i.e. they
	* create child views that directly represent the child elements).
	* <li>
	* Boxes are easier to estimate the size of than some other shapes.
	* </ul>
	* <p>
	* The default behavior is controlled by two properties, maxZoneSize
	* and maxZonesLoaded. Setting maxZoneSize to Integer.MAX_VALUE would
	* have the effect of causing only one zone to be created. This would
	* effectively turn the view into an implementation of the decorator
	* pattern. Setting maxZonesLoaded to a value of Integer.MAX_VALUE would
	* cause zones to never be unloaded. For simplicity, zones are created on
	* boundaries represented by the child elements of the element the view is
	* responsible for. The zones can be any View implementation, but the
	* default implementation is based upon AsyncBoxView which supports fairly
	* large zones efficiently.
	*
	* @author Timothy Prinzing
	* @see View
	* @since 1.3
	*/
	public class ZoneView extends BoxView {

	int maxZoneSize = 8 * 1024;
	int maxZonesLoaded = 3;
	Vector<View> loadedZones;

	/**
	* Constructs a ZoneView.
	*
	* @param elem the element this view is responsible for
	* @param axis either View.X_AXIS or View.Y_AXIS
	*/
	public ZoneView(Element elem, int axis) {
	super(elem, axis);
	loadedZones = new Vector<View>();
	}

	/**
	* Get the current maximum zone size.
	*/
	public int getMaximumZoneSize() {
	return maxZoneSize;
	}

	/**
	* Set the desired maximum zone size. A
	* zone may get larger than this size if
	* a single child view is larger than this
	* size since zones are formed on child view
	* boundaries.
	*
	* @param size the number of characters the zone
	* may represent before attempting to break
	* the zone into a smaller size.
	*/
	public void setMaximumZoneSize(int size) {
	maxZoneSize = size;
	}

	/**
	* Get the current setting of the number of zones
	* allowed to be loaded at the same time.
	*/
	public int getMaxZonesLoaded() {
	return maxZonesLoaded;
	}

	/**
	* Sets the current setting of the number of zones
	* allowed to be loaded at the same time. This will throw an
	* <code>IllegalArgumentException</code> if <code>mzl</code> is less
	* than 1.
	*
	* @param mzl the desired maximum number of zones
	* to be actively loaded, must be greater than 0
	* @exception IllegalArgumentException if <code>mzl</code> is < 1
	*/
	public void setMaxZonesLoaded(int mzl) {
	if (mzl < 1) {
	throw new IllegalArgumentException("ZoneView.setMaxZonesLoaded must be greater than 0.");
	}
	maxZonesLoaded = mzl;
	unloadOldZones();
	}

	/**
	* Called by a zone when it gets loaded. This happens when
	* an attempt is made to display or perform a model/view
	* translation on a zone that was in an unloaded state.
	* This is implemented to check if the maximum number of
	* zones was reached and to unload the oldest zone if so.
	*
	* @param zone the child view that was just loaded.
	*/
	protected void zoneWasLoaded(View zone) {
	//System.out.println("loading: " + zone.getStartOffset() + "," + zone.getEndOffset());
	loadedZones.addElement(zone);
	unloadOldZones();
	}

	void unloadOldZones() {
	while (loadedZones.size() > getMaxZonesLoaded()) {
	View zone = loadedZones.elementAt(0);
	loadedZones.removeElementAt(0);
	unloadZone(zone);
	}
	}

	/**
	* Unload a zone (Convert the zone to its memory saving state).
	* The zones are expected to represent a subset of the
	* child elements of the element this view is responsible for.
	* Therefore, the default implementation is to simple remove
	* all the children.
	*
	* @param zone the child view desired to be set to an
	* unloaded state.
	*/
	protected void unloadZone(View zone) {
	//System.out.println("unloading: " + zone.getStartOffset() + "," + zone.getEndOffset());
	zone.removeAll();
	}

	/**
	* Determine if a zone is in the loaded state.
	* The zones are expected to represent a subset of the
	* child elements of the element this view is responsible for.
	* Therefore, the default implementation is to return
	* true if the view has children.
	*/
	protected boolean isZoneLoaded(View zone) {
	return (zone.getViewCount() > 0);
	}

	/**
	* Create a view to represent a zone for the given
	* range within the model (which should be within
	* the range of this objects responsibility). This
	* is called by the zone management logic to create
	* new zones. Subclasses can provide a different
	* implementation for a zone by changing this method.
	*
	* @param p0 the start of the desired zone. This should
	* be >= getStartOffset() and < getEndOffset(). This
	* value should also be < p1.
	* @param p1 the end of the desired zone. This should
	* be > getStartOffset() and <= getEndOffset(). This
	* value should also be > p0.
	*/
	protected View createZone(int p0, int p1) {
	Document doc = getDocument();
	View zone;
	try {
	zone = new Zone(getElement(),
	doc.createPosition(p0),
	doc.createPosition(p1));
	} catch (BadLocationException ble) {
	// this should puke in some way.
	throw new StateInvariantError(ble.getMessage());
	}
	return zone;
	}

	/**
	* Loads all of the children to initialize the view.
	* This is called by the <code>setParent</code> method.
	* This is reimplemented to not load any children directly
	* (as they are created by the zones). This method creates
	* the initial set of zones. Zones don't actually get
	* populated however until an attempt is made to display
	* them or to do model/view coordinate translation.
	*
	* @param f the view factory
	*/
	protected void loadChildren(ViewFactory f) {
	// build the first zone.
	Document doc = getDocument();
	int offs0 = getStartOffset();
	int offs1 = getEndOffset();
	append(createZone(offs0, offs1));
	handleInsert(offs0, offs1 - offs0);
	}

	/**
	* Returns the child view index representing the given position in
	* the model.
	*
	* @param pos the position >= 0
	* @return index of the view representing the given position, or
	* -1 if no view represents that position
	*/
	protected int getViewIndexAtPosition(int pos) {
	// PENDING(prinz) this could be done as a binary
	// search, and probably should be.
	int n = getViewCount();
	if (pos == getEndOffset()) {
	return n - 1;
	}
	for(int i = 0; i < n; i++) {
	View v = getView(i);
	if(pos >= v.getStartOffset() &&
	pos < v.getEndOffset()) {
	return i;
	}
	}
	return -1;
	}

	void handleInsert(int pos, int length) {
	int index = getViewIndex(pos, Position.Bias.Forward);
	View v = getView(index);
	int offs0 = v.getStartOffset();
	int offs1 = v.getEndOffset();
	if ((offs1 - offs0) > maxZoneSize) {
	splitZone(index, offs0, offs1);
	}
	}

	void handleRemove(int pos, int length) {
	// IMPLEMENT
	}

	/**
	* Break up the zone at the given index into pieces
	* of an acceptable size.
	*/
	void splitZone(int index, int offs0, int offs1) {
	// divide the old zone into a new set of bins
	Element elem = getElement();
	Document doc = elem.getDocument();
	Vector<View> zones = new Vector<View>();
	int offs = offs0;
	do {
	offs0 = offs;
	offs = Math.min(getDesiredZoneEnd(offs0), offs1);
	zones.addElement(createZone(offs0, offs));
	} while (offs < offs1);
	View oldZone = getView(index);
	View[] newZones = new View[zones.size()];
	zones.copyInto(newZones);
	replace(index, 1, newZones);
	}

	/**
	* Returns the zone position to use for the
	* end of a zone that starts at the given
	* position. By default this returns something
	* close to half the max zone size.
	*/
	int getDesiredZoneEnd(int pos) {
	Element elem = getElement();
	int index = elem.getElementIndex(pos + (maxZoneSize / 2));
	Element child = elem.getElement(index);
	int offs0 = child.getStartOffset();
	int offs1 = child.getEndOffset();
	if ((offs1 - pos) > maxZoneSize) {
	if (offs0 > pos) {
	return offs0;
	}
	}
	return offs1;
	}

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

	/**
	* The superclass behavior will try to update the child views
	* which is not desired in this case, since the children are
	* zones and not directly effected by the changes to the
	* associated element. This is reimplemented to do nothing
	* and return false.
	*/
	protected boolean updateChildren(DocumentEvent.ElementChange ec,
	DocumentEvent e, ViewFactory f) {
	return false;
	}

	/**
	* Gives notification that something was inserted into the document
	* in a location that this view is responsible for. This is largely
	* delegated to the superclass, but is reimplemented to update the
	* relevant zone (i.e. determine if a zone needs to be split into a
	* set of 2 or more zones).
	*
	* @param changes the change information from the associated document
	* @param a the current allocation of the view
	* @param f the factory to use to rebuild if the view has children
	* @see View#insertUpdate
	*/
	public void insertUpdate(DocumentEvent changes, Shape a, ViewFactory f) {
	handleInsert(changes.getOffset(), changes.getLength());
	super.insertUpdate(changes, a, f);
	}

	/**
	* Gives notification that something was removed from the document
	* in a location that this view is responsible for. This is largely
	* delegated to the superclass, but is reimplemented to update the
	* relevant zones (i.e. determine if zones need to be removed or
	* joined with another zone).
	*
	* @param changes the change information from the associated document
	* @param a the current allocation of the view
	* @param f the factory to use to rebuild if the view has children
	* @see View#removeUpdate
	*/
	public void removeUpdate(DocumentEvent changes, Shape a, ViewFactory f) {
	handleRemove(changes.getOffset(), changes.getLength());
	super.removeUpdate(changes, a, f);
	}

	/**
	* Internally created view that has the purpose of holding
	* the views that represent the children of the ZoneView
	* that have been arranged in a zone.
	*/
	class Zone extends AsyncBoxView {

	private Position start;
	private Position end;

	public Zone(Element elem, Position start, Position end) {
	super(elem, ZoneView.this.getAxis());
	this.start = start;
	this.end = end;
	}

	/**
	* Creates the child views and populates the
	* zone with them. This is done by translating
	* the positions to child element index locations
	* and building views to those elements. If the
	* zone is already loaded, this does nothing.
	*/
	public void load() {
	if (! isLoaded()) {
	setEstimatedMajorSpan(true);
	Element e = getElement();
	ViewFactory f = getViewFactory();
	int index0 = e.getElementIndex(getStartOffset());
	int index1 = e.getElementIndex(getEndOffset());
	View[] added = new View[index1 - index0 + 1];
	for (int i = index0; i <= index1; i++) {
	added[i - index0] = f.create(e.getElement(i));
	}
	replace(0, 0, added);

	zoneWasLoaded(this);
	}
	}

	/**
	* Removes the child views and returns to a
	* state of unloaded.
	*/
	public void unload() {
	setEstimatedMajorSpan(true);
	removeAll();
	}

	/**
	* Determines if the zone is in the loaded state
	* or not.
	*/
	public boolean isLoaded() {
	return (getViewCount() != 0);
	}

	/**
	* This method is reimplemented to not build the children
	* since the children are created when the zone is loaded
	* rather then when it is placed in the view hierarchy.
	* The major span is estimated at this point by building
	* the first child (but not storing it), and calling
	* setEstimatedMajorSpan(true) followed by setSpan for
	* the major axis with the estimated span.
	*/
	protected void loadChildren(ViewFactory f) {
	// mark the major span as estimated
	setEstimatedMajorSpan(true);

	// estimate the span
	Element elem = getElement();
	int index0 = elem.getElementIndex(getStartOffset());
	int index1 = elem.getElementIndex(getEndOffset());
	int nChildren = index1 - index0;

	// replace this with something real
	//setSpan(getMajorAxis(), nChildren * 10);

	View first = f.create(elem.getElement(index0));
	first.setParent(this);
	float w = first.getPreferredSpan(X_AXIS);
	float h = first.getPreferredSpan(Y_AXIS);
	if (getMajorAxis() == X_AXIS) {
	w *= nChildren;
	} else {
	h += nChildren;
	}

	setSize(w, h);
	}

	/**
	* Publish the changes in preferences upward to the parent
	* view.
	* <p>
	* This is reimplemented to stop the superclass behavior
	* if the zone has not yet been loaded. If the zone is
	* unloaded for example, the last seen major span is the
	* best estimate and a calculated span for no children
	* is undesirable.
	*/
	protected void flushRequirementChanges() {
	if (isLoaded()) {
	super.flushRequirementChanges();
	}
	}

	/**
	* Returns the child view index representing the given position in
	* the model. Since the zone contains a cluster of the overall
	* set of child elements, we can determine the index fairly
	* quickly from the model by subtracting the index of the
	* start offset from the index of the position given.
	*
	* @param pos the position >= 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) {
	boolean isBackward = (b == Position.Bias.Backward);
	pos = (isBackward) ? Math.max(0, pos - 1) : pos;
	Element elem = getElement();
	int index1 = elem.getElementIndex(pos);
	int index0 = elem.getElementIndex(getStartOffset());
	return index1 - index0;
	}

	protected boolean updateChildren(DocumentEvent.ElementChange ec,
	DocumentEvent e, ViewFactory f) {
	// the structure of this element changed.
	Element[] removedElems = ec.getChildrenRemoved();
	Element[] addedElems = ec.getChildrenAdded();
	Element elem = getElement();
	int index0 = elem.getElementIndex(getStartOffset());
	int index1 = elem.getElementIndex(getEndOffset()-1);
	int index = ec.getIndex();
	if ((index >= index0) && (index <= index1)) {
	// The change is in this zone
	int replaceIndex = index - index0;
	int nadd = Math.min(index1 - index0 + 1, addedElems.length);
	int nremove = Math.min(index1 - index0 + 1, removedElems.length);
	View[] added = new View[nadd];
	for (int i = 0; i < nadd; i++) {
	added[i] = f.create(addedElems[i]);
	}
	replace(replaceIndex, nremove, added);
	}
	return true;
	}

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

	/**
	* Fetches the attributes to use when rendering. This view
	* isn't directly responsible for an element so it returns
	* the outer classes attributes.
	*/
	public AttributeSet getAttributes() {
	return ZoneView.this.getAttributes();
	}

	/**
	* Renders using the given rendering surface and area on that
	* surface. This is implemented to load the zone if its not
	* already loaded, and then perform the superclass behavior.
	*
	* @param g the rendering surface to use
	* @param a the allocated region to render into
	* @see View#paint
	*/
	public void paint(Graphics g, Shape a) {
	load();
	super.paint(g, a);
	}

	/**
	* Provides a mapping from the view coordinate space to the logical
	* coordinate space of the model. This is implemented to first
	* make sure the zone is loaded before providing the superclass
	* behavior.
	*
	* @param x x coordinate of the view location to convert >= 0
	* @param y y coordinate of the view location to convert >= 0
	* @param a the allocated region to render into
	* @return the location within the model that best represents the
	* given point in the view >= 0
	* @see View#viewToModel
	*/
	public int viewToModel(float x, float y, Shape a, Position.Bias[] bias) {
	load();
	return super.viewToModel(x, y, a, bias);
	}

	/**
	* Provides a mapping from the document model coordinate space
	* to the coordinate space of the view mapped to it. This is
	* implemented to provide the superclass behavior after first
	* making sure the zone is loaded (The zone must be loaded to
	* make this calculation).
	*
	* @param pos the position to convert
	* @param a the allocated region to render into
	* @return the bounding box of the given position
	* @exception BadLocationException if the given position does not represent a
	* valid location in the associated document
	* @see View#modelToView
	*/
	public Shape modelToView(int pos, Shape a, Position.Bias b) throws BadLocationException {
	load();
	return super.modelToView(pos, a, b);
	}

	/**
	* Start of the zones range.
	*
	* @see View#getStartOffset
	*/
	public int getStartOffset() {
	return start.getOffset();
	}

	/**
	* End of the zones range.
	*/
	public int getEndOffset() {
	return end.getOffset();
	}

	/**
	* Gives notification that something was inserted into
	* the document in a location that this view is responsible for.
	* If the zone has been loaded, the superclass behavior is
	* invoked, otherwise this does nothing.
	*
	* @param e the change information from the associated document
	* @param a the current allocation of the view
	* @param f the factory to use to rebuild if the view has children
	* @see View#insertUpdate
	*/
	public void insertUpdate(DocumentEvent e, Shape a, ViewFactory f) {
	if (isLoaded()) {
	super.insertUpdate(e, a, f);
	}
	}

	/**
	* Gives notification that something was removed from the document
	* in a location that this view is responsible for.
	* If the zone has been loaded, the superclass behavior is
	* invoked, otherwise this does nothing.
	*
	* @param e the change information from the associated document
	* @param a the current allocation of the view
	* @param f the factory to use to rebuild if the view has children
	* @see View#removeUpdate
	*/
	public void removeUpdate(DocumentEvent e, Shape a, ViewFactory f) {
	if (isLoaded()) {
	super.removeUpdate(e, a, f);
	}
	}

	/**
	* Gives notification from the document that attributes were changed
	* in a location that this view is responsible for.
	* If the zone has been loaded, the superclass behavior is
	* invoked, otherwise this does nothing.
	*
	* @param e the change information from the associated document
	* @param a the current allocation of the view
	* @param f the factory to use to rebuild if the view has children
	* @see View#removeUpdate
	*/
	public void changedUpdate(DocumentEvent e, Shape a, ViewFactory f) {
	if (isLoaded()) {
	super.changedUpdate(e, a, f);
	}
	}

	}
	}

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