Class StyleContext
- java.lang.Object
-
- javax.swing.text.StyleContext
- All Implemented Interfaces:
-
Serializable
,AbstractDocument.AttributeContext
- Direct Known Subclasses:
StyleSheet
public class StyleContext extends Object implements Serializable, AbstractDocument.AttributeContext
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 JavaBeans™ has been added to the java.beans
package. Please see XMLEncoder
.
- See Also:
- Serialized Form
Nested Class Summary
Modifier and Type | Class | Description |
---|---|---|
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. |
Field Summary
Modifier and Type | Field | Description |
---|---|---|
static String | DEFAULT_STYLE | The name given to the default logical style attached to paragraphs. |
Constructor Summary
Constructor | Description |
---|---|
StyleContext() | Creates a new StyleContext object. |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
AttributeSet | addAttribute(AttributeSet old,
Object name,
Object value) | Adds an attribute to the given set, and returns the new representative set. |
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. |
protected MutableAttributeSet | createLargeAttributeSet(AttributeSet a) | Create a large set of attributes that should trade off space for time. |
protected StyleContext.SmallAttributeSet | createSmallAttributeSet(AttributeSet a) | Create a compact set of attributes that might be shared. |
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 |
protected int | getCompressionThreshold() | Returns the maximum number of key/value pairs to try and compress into unique/immutable sets. |
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 |
static Object | getStaticAttributeKey(Object key) | Returns the String that |
Style | getStyle(String nm) | Fetches a named style previously added to the document |
Enumeration<?> | getStyleNames() | Fetches the names of the styles defined. |
void | readAttributes(ObjectInputStream in,
MutableAttributeSet a) | Context-specific handling of reading in attributes |
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 |
void | reclaim(AttributeSet a) | Returns a set no longer needed by the MutableAttributeSet implementation. |
static void | registerStaticAttributeKey(Object key) | Registers an object as a static object that is being used as a key in attribute sets. |
AttributeSet | removeAttribute(AttributeSet old,
Object name) | Removes an attribute from the set. |
AttributeSet | removeAttributes(AttributeSet old,
Enumeration<?> names) | Removes a set of attributes for the element. |
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. |
void | writeAttributes(ObjectOutputStream out,
AttributeSet a) | Context-specific handling of writing out attributes |
static void | writeAttributeSet(ObjectOutputStream out,
AttributeSet a) | Writes a set of attributes to the given object stream for the purpose of serialization. |
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Field Detail
DEFAULT_STYLE
public static final String DEFAULT_STYLE
The name given to the default logical style attached to paragraphs.
- See Also:
- Constant Field Values
Constructor Detail
StyleContext
public StyleContext()
Creates a new StyleContext object.
Method Detail
getDefaultStyleContext
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
addStyle
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
removeStyle
public void removeStyle(String nm)
Removes a named style previously added to the document.
- Parameters:
-
nm
- the name of the style to remove
getStyle
public Style getStyle(String nm)
Fetches a named style previously added to the document
- Parameters:
-
nm
- the name of the style - Returns:
- the style
getStyleNames
public Enumeration<?> getStyleNames()
Fetches the names of the styles defined.
- Returns:
- the list of names as an enumeration
addChangeListener
public void addChangeListener(ChangeListener l)
Adds a listener to track when styles are added or removed.
- Parameters:
-
l
- the change listener
removeChangeListener
public void removeChangeListener(ChangeListener l)
Removes a listener that was tracking styles being added or removed.
- Parameters:
-
l
- the change listener
getChangeListeners
public ChangeListener[] getChangeListeners()
Returns an array of all the ChangeListener
s added to this StyleContext with addChangeListener().
- Returns:
- all of the
ChangeListener
s added or an empty array if no listeners have been added - Since:
- 1.4
getFont
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
getForeground
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
getBackground
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
getFont
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
getFontMetrics
public FontMetrics getFontMetrics(Font f)
Returns font metrics for a font.
- Parameters:
-
f
- the font - Returns:
- the metrics
addAttribute
public 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 Concurrency in Swing for more information.
- Specified by:
-
addAttribute
in interfaceAbstractDocument.AttributeContext
- Parameters:
-
old
- the old attribute set -
name
- the non-null attribute name -
value
- the attribute value - Returns:
- the updated attribute set
- See Also:
MutableAttributeSet.addAttribute(java.lang.Object, java.lang.Object)
addAttributes
public 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 Concurrency in Swing for more information.
- Specified by:
-
addAttributes
in interfaceAbstractDocument.AttributeContext
- Parameters:
-
old
- the old attribute set -
attr
- the attributes to add - Returns:
- the updated attribute set
- See Also:
MutableAttributeSet.addAttribute(java.lang.Object, java.lang.Object)
removeAttribute
public 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 Concurrency in Swing for more information.
- Specified by:
-
removeAttribute
in interfaceAbstractDocument.AttributeContext
- Parameters:
-
old
- the old set of attributes -
name
- the non-null attribute name - Returns:
- the updated attribute set
- See Also:
MutableAttributeSet.removeAttribute(java.lang.Object)
removeAttributes
public 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 Concurrency in Swing for more information.
- Specified by:
-
removeAttributes
in interfaceAbstractDocument.AttributeContext
- Parameters:
-
old
- the old attribute set -
names
- the attribute names - Returns:
- the updated attribute set
- See Also:
MutableAttributeSet.removeAttributes(java.util.Enumeration<?>)
removeAttributes
public 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 Concurrency in Swing for more information.
- Specified by:
-
removeAttributes
in interfaceAbstractDocument.AttributeContext
- Parameters:
-
old
- the old attribute set -
attrs
- the attributes - Returns:
- the updated attribute set
- See Also:
MutableAttributeSet.removeAttributes(java.util.Enumeration<?>)
getEmptySet
public AttributeSet getEmptySet()
Fetches an empty AttributeSet.
- Specified by:
-
getEmptySet
in interfaceAbstractDocument.AttributeContext
- Returns:
- the set
reclaim
public void reclaim(AttributeSet a)
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.
This method is thread safe, although most Swing methods are not. Please see Concurrency in Swing for more information.
- Specified by:
-
reclaim
in interfaceAbstractDocument.AttributeContext
- Parameters:
-
a
- the set to reclaim
getCompressionThreshold
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
createSmallAttributeSet
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. - Returns:
- a compact set of attributes that might be shared
createLargeAttributeSet
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. - Returns:
- a large set of attributes that should trade off space for time
toString
public String toString()
Converts a StyleContext to a String.
writeAttributes
public void writeAttributes(ObjectOutputStream out, AttributeSet a) throws IOException
Context-specific handling of writing out attributes
- Parameters:
-
out
- the output stream -
a
- the attribute set - Throws:
-
IOException
- on any I/O error
readAttributes
public void readAttributes(ObjectInputStream in, MutableAttributeSet a) throws ClassNotFoundException, IOException
Context-specific handling of reading in attributes
- 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.
writeAttributeSet
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 registered 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
readAttributeSet
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. -
IOException
- passed upward if encountered when reading the object stream.
registerStaticAttributeKey
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
getStaticAttribute
public static Object getStaticAttribute(Object key)
Returns the object previously registered with registerStaticAttributeKey
.
- Parameters:
-
key
- the object key - Returns:
- Returns the object previously registered with
registerStaticAttributeKey
getStaticAttributeKey
public static Object getStaticAttributeKey(Object key)
Returns the String that key
will be registered with.
- Parameters:
-
key
- the object key - Returns:
- the String that
key
will be registered with - See Also:
-
getStaticAttribute(java.lang.Object)
,registerStaticAttributeKey(java.lang.Object)