public class

StyleContext

extends Object
implements Serializable AbstractDocument.AttributeContext
java.lang.Object
   ↳ javax.swing.text.StyleContext
Known Direct Subclasses

Class Overview

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.

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 applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeansTM has been added to the java.beans package. Please see XMLEncoder.

Summary

Nested Classes
class StyleContext.NamedStyle A collection of attributes, typically used to represent character and paragraph styles. 
class StyleContext.SmallAttributeSet This class holds a small number of attributes in an array. 
Constants
String DEFAULT_STYLE The name given to the default logical style attached to paragraphs.
Public Constructors
StyleContext()
Creates a new StyleContext object.
Public Methods
synchronized AttributeSet addAttribute(AttributeSet old, Object name, Object value)
Adds an attribute to the given set, and returns the new representative set.
synchronized AttributeSet addAttributes(AttributeSet old, AttributeSet attr)
Adds a set of attributes to the element.
void addChangeListener(ChangeListener l)
Adds a listener to track when styles are added or removed.
Style addStyle(String nm, Style parent)
Adds a new style into the style hierarchy.
Color getBackground(AttributeSet attr)
Takes a set of attributes and turn it into a background color specification.
ChangeListener[] getChangeListeners()
Returns an array of all the ChangeListeners added to this StyleContext with addChangeListener().
final static StyleContext getDefaultStyleContext()
Returns default AttributeContext shared by all documents that don't bother to define/supply their own context.
AttributeSet getEmptySet()
Fetches an empty AttributeSet.
Font getFont(String family, int style, int size)
Gets a new font.
Font getFont(AttributeSet attr)
Gets the font from an attribute set.
FontMetrics getFontMetrics(Font f)
Returns font metrics for a font.
Color getForeground(AttributeSet attr)
Takes a set of attributes and turn it into a foreground color specification.
static Object getStaticAttribute(Object key)
Returns the object previously registered with registerStaticAttributeKey.
static Object getStaticAttributeKey(Object key)
Returns the String that key will be registered with
Style getStyle(String nm)
Fetches a named style previously added to the document
Enumeration<?> getStyleNames()
Fetches the names of the styles defined.
static void readAttributeSet(ObjectInputStream in, MutableAttributeSet a)
Reads a set of attributes from the given object input stream that have been previously written out with writeAttributeSet.
void readAttributes(ObjectInputStream in, MutableAttributeSet a)
Context-specific handling of reading in attributes
void reclaim(AttributeSet a)
Returns a set no longer needed by the MutableAttributeSet implmentation.
static void registerStaticAttributeKey(Object key)
Registers an object as a static object that is being used as a key in attribute sets.
synchronized AttributeSet removeAttribute(AttributeSet old, Object name)
Removes an attribute from the set.
synchronized AttributeSet removeAttributes(AttributeSet old, Enumeration<?> names)
Removes a set of attributes for the element.
synchronized AttributeSet removeAttributes(AttributeSet old, AttributeSet attrs)
Removes a set of attributes for the element.
void removeChangeListener(ChangeListener l)
Removes a listener that was tracking styles being added or removed.
void removeStyle(String nm)
Removes a named style previously added to the document.
String toString()
Converts a StyleContext to a String.
static void writeAttributeSet(ObjectOutputStream out, AttributeSet a)
Writes a set of attributes to the given object stream for the purpose of serialization.
void writeAttributes(ObjectOutputStream out, AttributeSet a)
Context-specific handling of writing out attributes
Protected Methods
MutableAttributeSet createLargeAttributeSet(AttributeSet a)
Create a large set of attributes that should trade off space for time.
StyleContext.SmallAttributeSet createSmallAttributeSet(AttributeSet a)
Create a compact set of attributes that might be shared.
int getCompressionThreshold()
Returns the maximum number of key/value pairs to try and compress into unique/immutable sets.
[Expand]
Inherited Methods
From class java.lang.Object
From interface javax.swing.text.AbstractDocument.AttributeContext

Constants

public static final String DEFAULT_STYLE

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

Constant Value: "default"

Public Constructors

public StyleContext ()

Creates a new StyleContext object.

Public Methods

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 How to Use Threads 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

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 How to Use Threads for more information.

Parameters
old the old attribute set
attr the attributes to add
Returns
  • the updated attribute set
See Also

public void addChangeListener (ChangeListener l)

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

Parameters
l the change listener

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 Color getBackground (AttributeSet 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.

Parameters
attr the set of attributes
Returns
  • the color

public ChangeListener[] getChangeListeners ()

Returns an array of all the ChangeListeners added to this StyleContext with addChangeListener().

Returns
  • all of the ChangeListeners added or an empty array if no listeners have been added

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 AttributeSet getEmptySet ()

Fetches an empty AttributeSet.

Returns
  • the set

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 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 FontMetrics getFontMetrics (Font f)

Returns font metrics for a font.

Parameters
f the font
Returns
  • the metrics

public Color getForeground (AttributeSet attr)

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.

Parameters
attr the set of attributes
Returns
  • the color

public static Object getStaticAttribute (Object key)

Returns the object previously registered with registerStaticAttributeKey.

public static Object getStaticAttributeKey (Object key)

Returns the String that key will be registered with

See Also

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 static void readAttributeSet (ObjectInputStream in, MutableAttributeSet a)

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.
IOException passed upward if encountered when reading the object stream.

public void readAttributes (ObjectInputStream in, MutableAttributeSet a)

Context-specific handling of reading in attributes

Throws
ClassNotFoundException
IOException

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 How to Use Threads for more information.

Parameters
a the set to reclaim

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

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 How to Use Threads for more information.

Parameters
old the old set of attributes
name the non-null attribute name
Returns
  • the updated attribute set
See Also

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 How to Use Threads for more information.

Parameters
old the old attribute set
names the attribute names
Returns
  • the updated attribute set
See Also

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 How to Use Threads for more information.

Parameters
old the old attribute set
attrs the attributes
Returns
  • the updated attribute set
See Also

public void removeChangeListener (ChangeListener l)

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

Parameters
l the change listener

public void removeStyle (String nm)

Removes a named style previously added to the document.

Parameters
nm the name of the style to remove

public String toString ()

Converts a StyleContext to a String.

Returns
  • the string

public static void writeAttributeSet (ObjectOutputStream out, AttributeSet 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 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 void writeAttributes (ObjectOutputStream out, AttributeSet a)

Context-specific handling of writing out attributes

Throws
IOException

Protected Methods

protected MutableAttributeSet createLargeAttributeSet (AttributeSet 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.

Parameters
a The set of attributes to be represented in the the larger form.

protected StyleContext.SmallAttributeSet createSmallAttributeSet (AttributeSet a)

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.

Parameters
a The set of attributes to be represented in the the compact form.

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