Java example source code file (StyleContext.java)
The StyleContext.java Java example source code
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* 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).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
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package javax.swing.text;
import java.awt.*;
import java.util.*;
import java.io.*;
import javax.swing.SwingUtilities;
import javax.swing.event.ChangeListener;
import javax.swing.event.EventListenerList;
import javax.swing.event.ChangeEvent;
import java.lang.ref.WeakReference;
import java.util.WeakHashMap;
import sun.font.FontUtilities;
/**
* A pool of styles and their associated resources. This class determines
* the lifetime of a group of resources by being a container that holds
* caches for various resources such as font and color that get reused
* by the various style definitions. This can be shared by multiple
* documents if desired to maximize the sharing of related resources.
* <p>
* This class also provides efficient support for small sets of attributes
* and compresses them by sharing across uses and taking advantage of
* their immutable nature. Since many styles are replicated, the potential
* for sharing is significant, and copies can be extremely cheap.
* Larger sets reduce the possibility of sharing, and therefore revert
* automatically to a less space-efficient implementation.
* <p>
* <strong>Warning:
* Serialized objects of this class will not be compatible with
* future Swing releases. The current serialization support is
* appropriate for short term storage or RMI between applications running
* the same version of Swing. As of 1.4, support for long term storage
* of all JavaBeans™
* has been added to the <code>java.beans package.
* Please see {@link java.beans.XMLEncoder}.
*
* @author Timothy Prinzing
*/
public class StyleContext implements Serializable, AbstractDocument.AttributeContext {
/**
* Returns default AttributeContext shared by all documents that
* don't bother to define/supply their own context.
*
* @return the context
*/
public static final StyleContext getDefaultStyleContext() {
if (defaultContext == null) {
defaultContext = new StyleContext();
}
return defaultContext;
}
private static StyleContext defaultContext;
/**
* Creates a new StyleContext object.
*/
public StyleContext() {
styles = new NamedStyle(null);
addStyle(DEFAULT_STYLE, null);
}
/**
* Adds a new style into the style hierarchy. Style attributes
* resolve from bottom up so an attribute specified in a child
* will override an attribute specified in the parent.
*
* @param nm the name of the style (must be unique within the
* collection of named styles in the document). The name may
* be null if the style is unnamed, but the caller is responsible
* for managing the reference returned as an unnamed style can't
* be fetched by name. An unnamed style may be useful for things
* like character attribute overrides such as found in a style
* run.
* @param parent the parent style. This may be null if unspecified
* attributes need not be resolved in some other style.
* @return the created style
*/
public Style addStyle(String nm, Style parent) {
Style style = new NamedStyle(nm, parent);
if (nm != null) {
// add a named style, a class of attributes
styles.addAttribute(nm, style);
}
return style;
}
/**
* Removes a named style previously added to the document.
*
* @param nm the name of the style to remove
*/
public void removeStyle(String nm) {
styles.removeAttribute(nm);
}
/**
* Fetches a named style previously added to the document
*
* @param nm the name of the style
* @return the style
*/
public Style getStyle(String nm) {
return (Style) styles.getAttribute(nm);
}
/**
* Fetches the names of the styles defined.
*
* @return the list of names as an enumeration
*/
public Enumeration<?> getStyleNames() {
return styles.getAttributeNames();
}
/**
* Adds a listener to track when styles are added
* or removed.
*
* @param l the change listener
*/
public void addChangeListener(ChangeListener l) {
styles.addChangeListener(l);
}
/**
* Removes a listener that was tracking styles being
* added or removed.
*
* @param l the change listener
*/
public void removeChangeListener(ChangeListener l) {
styles.removeChangeListener(l);
}
/**
* Returns an array of all the <code>ChangeListeners added
* to this StyleContext with addChangeListener().
*
* @return all of the <code>ChangeListeners added or an empty
* array if no listeners have been added
* @since 1.4
*/
public ChangeListener[] getChangeListeners() {
return ((NamedStyle)styles).getChangeListeners();
}
/**
* Gets the font from an attribute set. This is
* implemented to try and fetch a cached font
* for the given AttributeSet, and if that fails
* the font features are resolved and the
* font is fetched from the low-level font cache.
*
* @param attr the attribute set
* @return the font
*/
public Font getFont(AttributeSet attr) {
// PENDING(prinz) add cache behavior
int style = Font.PLAIN;
if (StyleConstants.isBold(attr)) {
style |= Font.BOLD;
}
if (StyleConstants.isItalic(attr)) {
style |= Font.ITALIC;
}
String family = StyleConstants.getFontFamily(attr);
int size = StyleConstants.getFontSize(attr);
/**
* if either superscript or subscript is
* is set, we need to reduce the font size
* by 2.
*/
if (StyleConstants.isSuperscript(attr) ||
StyleConstants.isSubscript(attr)) {
size -= 2;
}
return getFont(family, style, size);
}
/**
* Takes a set of attributes and turn it into a foreground color
* specification. This might be used to specify things
* like brighter, more hue, etc. By default it simply returns
* the value specified by the StyleConstants.Foreground attribute.
*
* @param attr the set of attributes
* @return the color
*/
public Color getForeground(AttributeSet attr) {
return StyleConstants.getForeground(attr);
}
/**
* Takes a set of attributes and turn it into a background color
* specification. This might be used to specify things
* like brighter, more hue, etc. By default it simply returns
* the value specified by the StyleConstants.Background attribute.
*
* @param attr the set of attributes
* @return the color
*/
public Color getBackground(AttributeSet attr) {
return StyleConstants.getBackground(attr);
}
/**
* Gets a new font. This returns a Font from a cache
* if a cached font exists. If not, a Font is added to
* the cache. This is basically a low-level cache for
* 1.1 font features.
*
* @param family the font family (such as "Monospaced")
* @param style the style of the font (such as Font.PLAIN)
* @param size the point size >= 1
* @return the new font
*/
public Font getFont(String family, int style, int size) {
fontSearch.setValue(family, style, size);
Font f = fontTable.get(fontSearch);
if (f == null) {
// haven't seen this one yet.
Style defaultStyle =
getStyle(StyleContext.DEFAULT_STYLE);
if (defaultStyle != null) {
final String FONT_ATTRIBUTE_KEY = "FONT_ATTRIBUTE_KEY";
Font defaultFont =
(Font) defaultStyle.getAttribute(FONT_ATTRIBUTE_KEY);
if (defaultFont != null
&& defaultFont.getFamily().equalsIgnoreCase(family)) {
f = defaultFont.deriveFont(style, size);
}
}
if (f == null) {
f = new Font(family, style, size);
}
if (! FontUtilities.fontSupportsDefaultEncoding(f)) {
f = FontUtilities.getCompositeFontUIResource(f);
}
FontKey key = new FontKey(family, style, size);
fontTable.put(key, f);
}
return f;
}
/**
* Returns font metrics for a font.
*
* @param f the font
* @return the metrics
*/
public FontMetrics getFontMetrics(Font f) {
// The Toolkit implementations cache, so we just forward
// to the default toolkit.
return Toolkit.getDefaultToolkit().getFontMetrics(f);
}
// --- AttributeContext methods --------------------
/**
* Adds an attribute to the given set, and returns
* the new representative set.
* <p>
* This method is thread safe, although most Swing methods
* are not. Please see
* <A HREF="http://docs.oracle.com/javase/tutorial/uiswing/concurrency/index.html">Concurrency
* in Swing</A> for more information.
*
* @param old the old attribute set
* @param name the non-null attribute name
* @param value the attribute value
* @return the updated attribute set
* @see MutableAttributeSet#addAttribute
*/
public synchronized AttributeSet addAttribute(AttributeSet old, Object name, Object value) {
if ((old.getAttributeCount() + 1) <= getCompressionThreshold()) {
// build a search key and find/create an immutable and unique
// set.
search.removeAttributes(search);
search.addAttributes(old);
search.addAttribute(name, value);
reclaim(old);
return getImmutableUniqueSet();
}
MutableAttributeSet ma = getMutableAttributeSet(old);
ma.addAttribute(name, value);
return ma;
}
/**
* Adds a set of attributes to the element.
* <p>
* This method is thread safe, although most Swing methods
* are not. Please see
* <A HREF="http://docs.oracle.com/javase/tutorial/uiswing/concurrency/index.html">Concurrency
* in Swing</A> for more information.
*
* @param old the old attribute set
* @param attr the attributes to add
* @return the updated attribute set
* @see MutableAttributeSet#addAttribute
*/
public synchronized AttributeSet addAttributes(AttributeSet old, AttributeSet attr) {
if ((old.getAttributeCount() + attr.getAttributeCount()) <= getCompressionThreshold()) {
// build a search key and find/create an immutable and unique
// set.
search.removeAttributes(search);
search.addAttributes(old);
search.addAttributes(attr);
reclaim(old);
return getImmutableUniqueSet();
}
MutableAttributeSet ma = getMutableAttributeSet(old);
ma.addAttributes(attr);
return ma;
}
/**
* Removes an attribute from the set.
* <p>
* This method is thread safe, although most Swing methods
* are not. Please see
* <A HREF="http://docs.oracle.com/javase/tutorial/uiswing/concurrency/index.html">Concurrency
* in Swing</A> for more information.
*
* @param old the old set of attributes
* @param name the non-null attribute name
* @return the updated attribute set
* @see MutableAttributeSet#removeAttribute
*/
public synchronized AttributeSet removeAttribute(AttributeSet old, Object name) {
if ((old.getAttributeCount() - 1) <= getCompressionThreshold()) {
// build a search key and find/create an immutable and unique
// set.
search.removeAttributes(search);
search.addAttributes(old);
search.removeAttribute(name);
reclaim(old);
return getImmutableUniqueSet();
}
MutableAttributeSet ma = getMutableAttributeSet(old);
ma.removeAttribute(name);
return ma;
}
/**
* Removes a set of attributes for the element.
* <p>
* This method is thread safe, although most Swing methods
* are not. Please see
* <A HREF="http://docs.oracle.com/javase/tutorial/uiswing/concurrency/index.html">Concurrency
* in Swing</A> for more information.
*
* @param old the old attribute set
* @param names the attribute names
* @return the updated attribute set
* @see MutableAttributeSet#removeAttributes
*/
public synchronized AttributeSet removeAttributes(AttributeSet old, Enumeration<?> names) {
if (old.getAttributeCount() <= getCompressionThreshold()) {
// build a search key and find/create an immutable and unique
// set.
search.removeAttributes(search);
search.addAttributes(old);
search.removeAttributes(names);
reclaim(old);
return getImmutableUniqueSet();
}
MutableAttributeSet ma = getMutableAttributeSet(old);
ma.removeAttributes(names);
return ma;
}
/**
* Removes a set of attributes for the element.
* <p>
* This method is thread safe, although most Swing methods
* are not. Please see
* <A HREF="http://docs.oracle.com/javase/tutorial/uiswing/concurrency/index.html">Concurrency
* in Swing</A> for more information.
*
* @param old the old attribute set
* @param attrs the attributes
* @return the updated attribute set
* @see MutableAttributeSet#removeAttributes
*/
public synchronized AttributeSet removeAttributes(AttributeSet old, AttributeSet attrs) {
if (old.getAttributeCount() <= getCompressionThreshold()) {
// build a search key and find/create an immutable and unique
// set.
search.removeAttributes(search);
search.addAttributes(old);
search.removeAttributes(attrs);
reclaim(old);
return getImmutableUniqueSet();
}
MutableAttributeSet ma = getMutableAttributeSet(old);
ma.removeAttributes(attrs);
return ma;
}
/**
* Fetches an empty AttributeSet.
*
* @return the set
*/
public AttributeSet getEmptySet() {
return SimpleAttributeSet.EMPTY;
}
/**
* Returns a set no longer needed by the MutableAttributeSet implementation.
* This is useful for operation under 1.1 where there are no weak
* references. This would typically be called by the finalize method
* of the MutableAttributeSet implementation.
* <p>
* This method is thread safe, although most Swing methods
* are not. Please see
* <A HREF="http://docs.oracle.com/javase/tutorial/uiswing/concurrency/index.html">Concurrency
* in Swing</A> for more information.
*
* @param a the set to reclaim
*/
public void reclaim(AttributeSet a) {
if (SwingUtilities.isEventDispatchThread()) {
attributesPool.size(); // force WeakHashMap to expunge stale entries
}
// if current thread is not event dispatching thread
// do not bother with expunging stale entries.
}
// --- local methods -----------------------------------------------
/**
* Returns the maximum number of key/value pairs to try and
* compress into unique/immutable sets. Any sets above this
* limit will use hashtables and be a MutableAttributeSet.
*
* @return the threshold
*/
protected int getCompressionThreshold() {
return THRESHOLD;
}
/**
* Create a compact set of attributes that might be shared.
* This is a hook for subclasses that want to alter the
* behavior of SmallAttributeSet. This can be reimplemented
* to return an AttributeSet that provides some sort of
* attribute conversion.
*
* @param a The set of attributes to be represented in the
* the compact form.
*/
protected SmallAttributeSet createSmallAttributeSet(AttributeSet a) {
return new SmallAttributeSet(a);
}
/**
* Create a large set of attributes that should trade off
* space for time. This set will not be shared. This is
* a hook for subclasses that want to alter the behavior
* of the larger attribute storage format (which is
* SimpleAttributeSet by default). This can be reimplemented
* to return a MutableAttributeSet that provides some sort of
* attribute conversion.
*
* @param a The set of attributes to be represented in the
* the larger form.
*/
protected MutableAttributeSet createLargeAttributeSet(AttributeSet a) {
return new SimpleAttributeSet(a);
}
/**
* Clean the unused immutable sets out of the hashtable.
*/
synchronized void removeUnusedSets() {
attributesPool.size(); // force WeakHashMap to expunge stale entries
}
/**
* Search for an existing attribute set using the current search
* parameters. If a matching set is found, return it. If a match
* is not found, we create a new set and add it to the pool.
*/
AttributeSet getImmutableUniqueSet() {
// PENDING(prinz) should consider finding a alternative to
// generating extra garbage on search key.
SmallAttributeSet key = createSmallAttributeSet(search);
WeakReference<SmallAttributeSet> reference = attributesPool.get(key);
SmallAttributeSet a;
if (reference == null || (a = reference.get()) == null) {
a = key;
attributesPool.put(a, new WeakReference<SmallAttributeSet>(a));
}
return a;
}
/**
* Creates a mutable attribute set to hand out because the current
* needs are too big to try and use a shared version.
*/
MutableAttributeSet getMutableAttributeSet(AttributeSet a) {
if (a instanceof MutableAttributeSet &&
a != SimpleAttributeSet.EMPTY) {
return (MutableAttributeSet) a;
}
return createLargeAttributeSet(a);
}
/**
* Converts a StyleContext to a String.
*
* @return the string
*/
public String toString() {
removeUnusedSets();
String s = "";
for (SmallAttributeSet set : attributesPool.keySet()) {
s = s + set + "\n";
}
return s;
}
// --- serialization ---------------------------------------------
/**
* Context-specific handling of writing out attributes
*/
public void writeAttributes(ObjectOutputStream out,
AttributeSet a) throws IOException {
writeAttributeSet(out, a);
}
/**
* Context-specific handling of reading in attributes
*/
public void readAttributes(ObjectInputStream in,
MutableAttributeSet a) throws ClassNotFoundException, IOException {
readAttributeSet(in, a);
}
/**
* Writes a set of attributes to the given object stream
* for the purpose of serialization. This will take
* special care to deal with static attribute keys that
* have been registered wit the
* <code>registerStaticAttributeKey method.
* Any attribute key not registered as a static key
* will be serialized directly. All values are expected
* to be serializable.
*
* @param out the output stream
* @param a the attribute set
* @exception IOException on any I/O error
*/
public static void writeAttributeSet(ObjectOutputStream out,
AttributeSet a) throws IOException {
int n = a.getAttributeCount();
out.writeInt(n);
Enumeration keys = a.getAttributeNames();
while (keys.hasMoreElements()) {
Object key = keys.nextElement();
if (key instanceof Serializable) {
out.writeObject(key);
} else {
Object ioFmt = freezeKeyMap.get(key);
if (ioFmt == null) {
throw new NotSerializableException(key.getClass().
getName() + " is not serializable as a key in an AttributeSet");
}
out.writeObject(ioFmt);
}
Object value = a.getAttribute(key);
Object ioFmt = freezeKeyMap.get(value);
if (value instanceof Serializable) {
out.writeObject((ioFmt != null) ? ioFmt : value);
} else {
if (ioFmt == null) {
throw new NotSerializableException(value.getClass().
getName() + " is not serializable as a value in an AttributeSet");
}
out.writeObject(ioFmt);
}
}
}
/**
* Reads a set of attributes from the given object input
* stream that have been previously written out with
* <code>writeAttributeSet. This will try to restore
* keys that were static objects to the static objects in
* the current virtual machine considering only those keys
* that have been registered with the
* <code>registerStaticAttributeKey method.
* The attributes retrieved from the stream will be placed
* into the given mutable set.
*
* @param in the object stream to read the attribute data from.
* @param a the attribute set to place the attribute
* definitions in.
* @exception ClassNotFoundException passed upward if encountered
* when reading the object stream.
* @exception IOException passed upward if encountered when
* reading the object stream.
*/
public static void readAttributeSet(ObjectInputStream in,
MutableAttributeSet a) throws ClassNotFoundException, IOException {
int n = in.readInt();
for (int i = 0; i < n; i++) {
Object key = in.readObject();
Object value = in.readObject();
if (thawKeyMap != null) {
Object staticKey = thawKeyMap.get(key);
if (staticKey != null) {
key = staticKey;
}
Object staticValue = thawKeyMap.get(value);
if (staticValue != null) {
value = staticValue;
}
}
a.addAttribute(key, value);
}
}
/**
* Registers an object as a static object that is being
* used as a key in attribute sets. This allows the key
* to be treated specially for serialization.
* <p>
* For operation under a 1.1 virtual machine, this
* uses the value returned by <code>toString
* concatenated to the classname. The value returned
* by toString should not have the class reference
* in it (ie it should be reimplemented from the
* definition in Object) in order to be the same when
* recomputed later.
*
* @param key the non-null object key
*/
public static void registerStaticAttributeKey(Object key) {
String ioFmt = key.getClass().getName() + "." + key.toString();
if (freezeKeyMap == null) {
freezeKeyMap = new Hashtable<Object, String>();
thawKeyMap = new Hashtable<String, Object>();
}
freezeKeyMap.put(key, ioFmt);
thawKeyMap.put(ioFmt, key);
}
/**
* Returns the object previously registered with
* <code>registerStaticAttributeKey.
*/
public static Object getStaticAttribute(Object key) {
if (thawKeyMap == null || key == null) {
return null;
}
return thawKeyMap.get(key);
}
/**
* Returns the String that <code>key will be registered with
* @see #getStaticAttribute
* @see #registerStaticAttributeKey
*/
public static Object getStaticAttributeKey(Object key) {
return key.getClass().getName() + "." + key.toString();
}
private void writeObject(java.io.ObjectOutputStream s)
throws IOException
{
// clean out unused sets before saving
removeUnusedSets();
s.defaultWriteObject();
}
private void readObject(ObjectInputStream s)
throws ClassNotFoundException, IOException
{
fontSearch = new FontKey(null, 0, 0);
fontTable = new Hashtable<FontKey, Font>();
search = new SimpleAttributeSet();
attributesPool = Collections.
synchronizedMap(new WeakHashMap<SmallAttributeSet, WeakReference
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