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Class com.sun.java.swing.text.StyleContext

java.lang.Object
   |
   +----com.sun.java.swing.text.StyleContext

public class StyleContext

extends Object

implements Serializable, AbstractDocument. AttributeContext

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.

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 Swing1.0 applications. It will not be possible to load serialized Swing1.0 objects with future releases of Swing. The JDK1.2 release of Swing will be the compatibility baseline for the serialized form of Swing objects.

DEFAULT_STYLE

The name given to the default logical style attached to paragraphs.

StyleContext()

Creates a new StyleContext object.

addAttribute(AttributeSet, Object, Object)

Adds an attribute to the given set, and returns the new representative set.

addAttributes(AttributeSet, AttributeSet)

Adds a set of attributes to the element.

addChangeListener(ChangeListener)

Adds a listener to track when styles are added or removed.

addStyle(String, Style)

Adds a new style into the style hierarchy.

getCompressionThreshold()

Returns the maximum number of key/value pairs to try and compress into unique/immutable sets.

getDefaultStyleContext()

Returns default AttributeContext shared by all documents that don't bother to define/supply their own context.

getEmptySet()

Fetches an empty AttributeSet.

getFont(AttributeSet)

Gets the font from an attribute set.

getFont(String, int, int)

Gets a new font.

getFontMetrics(Font)

Returns font metrics for a font.

getStyle(String)

Fetches a named style previously added to the document

getStyleNames()

Fetches the names of the styles defined.

readAttributeSet(ObjectInputStream, MutableAttributeSet)

Reads a set of attributes from the given object input stream that have been previously written out with writeAttributeSet.

reclaim(AttributeSet)

Returns a set no longer needed by the MutableAttributeSet implmentation.

registerStaticAttributeKey(Object)

Registers an object as a static object that is being used as a key in attribute sets.

removeAttribute(AttributeSet, Object)

Removes an attribute from the set.

removeAttributes(AttributeSet, AttributeSet)

Removes a set of attributes for the element.

removeAttributes(AttributeSet, Enumeration)

Removes a set of attributes for the element.

removeChangeListener(ChangeListener)

Removes a listener that was tracking styles being added or removed.

removeStyle(String)

Removes a named style previously added to the document.

toString()

Converts a StyleContext to a String.

writeAttributeSet(ObjectOutputStream, AttributeSet)

Writes a set of attributes to the given object stream for the purpose of serialization.

 public static final String DEFAULT_STYLE

The name given to the default logical style attached to paragraphs.

 public StyleContext()

Creates a new StyleContext object.

 public static final StyleContext getDefaultStyleContext()

Returns default AttributeContext shared by all documents that don't bother to define/supply their own context.

Returns:

the context

 public Style addStyle(String nm,
                       Style parent)

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.

Parameters:

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.

parent - the parent style. This may be null if unspecified attributes need not be resolved in some other style.

Returns:

the created style

 public void removeStyle(String nm)

Removes a named style previously added to the document.

Parameters:

nm - the name of the style to remove

 public Style getStyle(String nm)

Fetches a named style previously added to the document

Parameters:

nm - the name of the style

Returns:

the style

 public Enumeration getStyleNames()

Fetches the names of the styles defined.

Returns:

the list of names as an enumeration

 public void addChangeListener(ChangeListener l)

Adds a listener to track when styles are added or removed.

Parameters:

l - the change listener

 public void removeChangeListener(ChangeListener l)

Removes a listener that was tracking styles being added or removed.

Parameters:

l - the change listener

 public Font getFont(AttributeSet attr)

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.

Parameters:

attr - the attribute set

Returns:

the font

 public Font getFont(String family,
                     int style,
                     int size)

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.

Parameters:

family - the font family (such as "Monospaced")

style - the style of the font (such as Font.PLAIN)

size - the point size >= 1

Returns:

the new font

 public FontMetrics getFontMetrics(Font f)

Returns font metrics for a font.

Parameters:

f - the font

Returns:

the metrics

 public synchronized AttributeSet addAttribute(AttributeSet old,
                                               Object name,
                                               Object value)

Adds an attribute to the given set, and returns the new representative set.

This method is thread safe, although most Swing methods are not. Please see Threads and Swing for more information.

Parameters:

old - the old attribute set

name - the non-null attribute name

value - the attribute value

Returns:

the updated attribute set

See Also:

addAttribute

 public synchronized AttributeSet addAttributes(AttributeSet old,
                                                AttributeSet attr)

Adds a set of attributes to the element.

This method is thread safe, although most Swing methods are not. Please see Threads and Swing for more information.

Parameters:

old - the old attribute set

attr - the attributes to add

Returns:

the updated attribute set

See Also:

addAttribute

 public synchronized AttributeSet removeAttribute(AttributeSet old,
                                                  Object name)

Removes an attribute from the set.

This method is thread safe, although most Swing methods are not. Please see Threads and Swing for more information.

Parameters:

old - the old set of attributes

name - the non-null attribute name

Returns:

the updated attribute set

See Also:

removeAttribute

 public synchronized AttributeSet removeAttributes(AttributeSet old,
                                                   Enumeration names)

Removes a set of attributes for the element.

This method is thread safe, although most Swing methods are not. Please see Threads and Swing for more information.

Parameters:

old - the old attribute set

names - the attribute names

Returns:

the updated attribute set

See Also:

removeAttributes

 public synchronized AttributeSet removeAttributes(AttributeSet old,
                                                   AttributeSet attrs)

Removes a set of attributes for the element.

This method is thread safe, although most Swing methods are not. Please see Threads and Swing for more information.

Parameters:

old - the old attribute set

attrs - the attributes

Returns:

the updated attribute set

See Also:

removeAttributes

 public AttributeSet getEmptySet()

Fetches an empty AttributeSet.

Returns:

the set

 public void reclaim(AttributeSet a)

Returns a set no longer needed by the MutableAttributeSet implmentation. 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.

This method is thread safe, although most Swing methods are not. Please see Threads and Swing for more information.

Parameters:

a - the set to reclaim

 protected int getCompressionThreshold()

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.

Returns:

the threshold

 public String toString()

Converts a StyleContext to a String.

Returns:

the string

Overrides:

toString in class Object

 public static void writeAttributeSet(ObjectOutputStream out,
                                      AttributeSet a) throws IOException

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 registerStaticAttributeKey method. Any attribute key not regsitered as a static key will be serialized directly. All values are expected to be serializable.

Parameters:

out - the output stream

a - the attribute set

Throws: IOException

on any I/O error

 public static void readAttributeSet(ObjectInputStream in,
                                     MutableAttributeSet a) throws ClassNotFoundException, IOException

Reads a set of attributes from the given object input stream that have been previously written out with 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 registerStaticAttributeKey method. The attributes retrieved from the stream will be placed into the given mutable set.

Parameters:

in - the object stream to read the attribute data from.

a - the attribute set to place the attribute definitions in.

Throws: ClassNotFoundException

passed upward if encountered when reading the object stream.

Throws: IOException

passed upward if encountered when reading the object stream.

 public static void registerStaticAttributeKey(Object key)

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.

For operation under a 1.1 virtual machine, this uses the value returned by 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.

Parameters:

key - the non-null object key

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