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Class java.awt.image.renderable.RenderContext

java.lang.Object
    |
    +----java.awt.image.renderable.RenderContext

public class RenderContext
extends Object
implements Cloneable
A RenderContext encapsulates the information needed to produce a specific rendering from a RenderableImage. It contains the area to be rendered specified in rendering-independent terms, the resolution at which the rendering is to be performed, and hints used to control the rendering process. Users create RenderContexts and pass them to the RenderableImage via the getImage method. Most of the methods of RenderContexts are not meant to used by users, but by the RenderableImage and operator classed which it may be passed to. The AffineTransform and Hashtable parameters passed into and out of this class are cloned. The Shape parameters are not necessarily cloneable and are therefore only reference copied. Changing instances of Shape that are also in use by instances of RenderContext may have undesired side effects.


Constructor Summary
 RenderContext(AffineTransform usr2dev, Shape aoi, Hashtable hints)
Constructs a RenderContext with a given transform.
 RenderContext(AffineTransform usr2dev)
Constructs a RenderContext with a given transform.
 RenderContext(AffineTransform usr2dev, Hashtable hints)
Constructs a RenderContext with a given transform and rendering hints.
 RenderContext(AffineTransform usr2dev, Shape aoi)
Constructs a RenderContext with a given transform and area of interest.
 

Method Summary
void  addHintsObserved(Hashtable sourceHints)
Adds hints from a supplied Hashtable to the Hashtable of observed hints.
void  addHintsObserved(RenderContext rc)
Adds the observed hints from another RenderContext to this RenderContext's observed hints table.
Object  clone()
Makes a copy of a RenderContext.
Shape  getAreaOfInterest()
Gets the ares of interest currently contained in the RenderContext.
Object  getHint(Object key)
Returns the value of a hint from the hints Hashtable.
Hashtable  getHintsObserved()
Returns a copy of the Hashtable of hints that have been observed by this renderContext.
Enumeration  getKeys()
Returns an Enumeration of the hint keys.
AffineTransform  getTransform()
Gets the current user-to-device AffineTransform.
Object  observeHint(Object key)
Searches for a key in the Hashtable of rendering hints.
void  setAreaOfInterest(Shape newAoi)
Sets the current area of interest.
void  setHint(Object key, Object value)
Sets a hint in the hints Hashtable.
void  setHintsObserved(Hashtable sourceObserved)
Sets hintsObserved to a new table.
void  setTransform(AffineTransform newTransform)
Sets the current user-to-device AffineTransform contained in the RenderContext to a given transform.
void  transform(AffineTransform modTransform)
Modifies the current user-to-device transform by prepending another transform.
void  unobserveHint(Object key)
Removes a hint from the hintsObserved Hashtable.
 
Methods inherited from class java.lang.Object
 clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

RenderContext

public RenderContext(AffineTransform usr2dev,
                     Shape aoi,
                     Hashtable hints)
Constructs a RenderContext with a given transform. The area of interest is supplied as a Shape, and the rendering hints are supplied as a Hashtable.
Parameters:
usr2dev - an AffineTransform.
aoi - a Shape representing the area of interest.
hints - a Hashtable containing rendering hints.

RenderContext

public RenderContext(AffineTransform usr2dev)
Constructs a RenderContext with a given transform. The area of interest is taken to be the entire renderable area. No rendering hints are used.
Parameters:
usr2dev - an AffineTransform.

RenderContext

public RenderContext(AffineTransform usr2dev,
                     Hashtable hints)
Constructs a RenderContext with a given transform and rendering hints. The area of interest is taken to be the entire renderable area.
Parameters:
usr2dev - an AffineTransform.
hints - a Hashtable containing rendering hints.

RenderContext

public RenderContext(AffineTransform usr2dev,
                     Shape aoi)
Constructs a RenderContext with a given transform and area of interest. The area of interest is supplied as a Shape. No rendering hints are used.
Parameters:
usr2dev - an AffineTransform.
aoi - a Shape representing the area of interest.
Method Detail

getKeys

public Enumeration getKeys()
Returns an Enumeration of the hint keys.
Returns:
returns an enumeration of the keys in the hints Hashtable, or null if no hints are present.

observeHint

public Object observeHint(Object key)
Searches for a key in the Hashtable of rendering hints. If the key is found, the associated value is returned. The key and value are also copied into the hintsObserved Hashtable.
Parameters:
key - the hint's key, as an Object.
Returns:
the Object value associated with the key.

getHint

public Object getHint(Object key)
Returns the value of a hint from the hints Hashtable. If there are no hints, or the desired key is not present, null is returned.
Parameters:
key - the hint's key, as an Object.
Returns:
the hint associated with the key, or null.

setHint

public void setHint(Object key,
                    Object value)
Sets a hint in the hints Hashtable.
Parameters:
key - the hint's key, as an Object.
value - the value to assign to the hint.

getHintsObserved

public Hashtable getHintsObserved()
Returns a copy of the Hashtable of hints that have been observed by this renderContext. The hint keys and values are copied by reference.
Returns:
a Hashtable containing the hints observed.

unobserveHint

public void unobserveHint(Object key)
Removes a hint from the hintsObserved Hashtable.
Parameters:
key - The key for the hint to be removed from the observed hints table.

addHintsObserved

public void addHintsObserved(Hashtable sourceHints)
Adds hints from a supplied Hashtable to the Hashtable of observed hints. The hints will also be copied into the hints hashtable. If the current hints tables are null, new tables will be created. The tables will each be copies of the supplied table, because all the hints will be considered to have been observed.
Parameters:
sourceHints - The source hints to add to this RenderContext's hintsObserved Hashtable.

addHintsObserved

public void addHintsObserved(RenderContext rc)
Adds the observed hints from another RenderContext to this RenderContext's observed hints table.
Parameters:
rc - The RenderContext from which to get the observed hints.

setHintsObserved

public void setHintsObserved(Hashtable sourceObserved)
Sets hintsObserved to a new table. This is accomplished by cloning the input parameter. Any current observed hints are removed from the hints table and discarded. All entries in the new observed hints table are added to the hints table.
Parameters:
sourceObserved - The source of observedHints.

setTransform

public void setTransform(AffineTransform newTransform)
Sets the current user-to-device AffineTransform contained in the RenderContext to a given transform.
Parameters:
newTransform - the new AffineTransform.

transform

public void transform(AffineTransform modTransform)
Modifies the current user-to-device transform by prepending another transform. In matrix notation the operation is:
 [this] = [modTransform] x [this]
 
Parameters:
modTransform - the AffineTransform to prepend to the current usr2dev transform.

getTransform

public AffineTransform getTransform()
Gets the current user-to-device AffineTransform.
Returns:
A reference to the current AffineTransform.

setAreaOfInterest

public void setAreaOfInterest(Shape newAoi)
Sets the current area of interest. The old area is discarded.
Parameters:
newAoi - The new area of interest.

getAreaOfInterest

public Shape getAreaOfInterest()
Gets the ares of interest currently contained in the RenderContext.
Returns:
a reference to the area of interest of the RenderContext, or null if none is specified.

clone

public Object clone()
Makes a copy of a RenderContext. The area of interest is copied by reference. The usr2dev Transform and hints tables are actually cloned.
Returns:
The new cloned RenderContext.
Overrides:
clone in class Object

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