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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);
}
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