diva.canvas

Class TransformContext

java.lang.Object

diva.canvas.TransformContext

public class TransformContext
extends java.lang.Object

A transform context defines a transformed coordinate system. Each transform context is associated with a component in the display tree. This class provides the support for most of the transform-related operations on the display tree.

Version:

$Id$

Author:

John Reekie

Pt.AcceptedRating:

Yellow

Constructor Summary

Constructors

Constructor and Description
TransformContext(CanvasComponent component) Create a transform context associated with the given display component.

Method Summary

Modifier and Type	Method and Description
void	checkCacheValid(TransformContext ancestor) Check transform cache validity.
void	concatenate(java.awt.geom.AffineTransform at) Concatenate this transform context with the given transform.
CanvasComponent	getComponent() Get the component that this context is associated with.
java.awt.geom.AffineTransform	getInverseTransform() Get the transform from parent coordinates into local coordinates.
TransformContext	getParent() Get the parent transform context of this one, or null if this context is at the root of the transform tree.
java.awt.geom.AffineTransform	getScreenTransform() Get the transform from local coordinates into screen coordinates.
java.awt.geom.AffineTransform	getTransform() Get the transform of this context.
java.awt.geom.AffineTransform	getTransform(TransformContext context) Get the transform of this context, relative to the given context.
int	getVersion() Get the version number of the transform context.
void	invalidateCache() Notify that cached data based on the transform is now invalid.
boolean	isCacheValid() Test if the cache is valid.
void	pop(java.awt.Graphics2D g) Pop this transform off the graphics stack.
void	preConcatenate(java.awt.geom.AffineTransform at) Pre-concatenate this transform context with the given transform.
void	push(java.awt.Graphics2D g) Push this transform onto the graphics stack.
void	setTransform(java.awt.geom.AffineTransform at) Set the transform that maps local coordinates into the parent's coordinates.
void	translate(double x, double y) Translate this context the given distance.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TransformContext

public TransformContext(CanvasComponent component)

Create a transform context associated with the given display component.

Parameters:

component - The given display component

Method Detail

checkCacheValid

public void checkCacheValid(TransformContext ancestor)

Check transform cache validity. The argument is an ancestor context of this context. If the ancestor is not valid, then all of the contexts from this one up to the ancestor are marked invalid.

Parameters:

ancestor - The ancestor context

concatenate

public void concatenate(java.awt.geom.AffineTransform at)

Concatenate this transform context with the given transform.

Parameters:

at - The transform

getComponent

public CanvasComponent getComponent()

Get the component that this context is associated with. The component is set in the constructor and cannot be changed.

Returns:

The component

getInverseTransform

public java.awt.geom.AffineTransform getInverseTransform()

Get the transform from parent coordinates into local coordinates.

Returns:

the transform

getParent

public TransformContext getParent()

Get the parent transform context of this one, or null if this context is at the root of the transform tree.

Returns:

The parent transform

getScreenTransform

public java.awt.geom.AffineTransform getScreenTransform()

Get the transform from local coordinates into screen coordinates.

Returns:

The transform

getTransform

public java.awt.geom.AffineTransform getTransform()

Get the transform of this context. This is the transform from this context into the parent's context.

Returns:

The transform

See Also:

setTransform(AffineTransform), getTransform(TransformContext)

getTransform

public java.awt.geom.AffineTransform getTransform(TransformContext context)

Get the transform of this context, relative to the given context. This is the transform from this context into the given context, which must enclose this one.

Parameters:

context - The context

Returns:

The transform

See Also:

setTransform(AffineTransform), getTransform()

getVersion

public int getVersion()

Get the version number of the transform context. The version number is incremented whenever the transform changes, so can be used by client components to figure out when to update cached data based upon the transform.

Returns:

The version number of the transform context.

invalidateCache

public void invalidateCache()

Notify that cached data based on the transform is now invalid. Increment the version number so that clients can use it to tell if they need to update data based on the transform.

isCacheValid

public boolean isCacheValid()

Test if the cache is valid.

Returns:

true if the cache is valid.

push

public void push(java.awt.Graphics2D g)

Push this transform onto the graphics stack.

Parameters:

g - The graphics context

pop

public void pop(java.awt.Graphics2D g)

Pop this transform off the graphics stack.

Parameters:

g - The graphics context

preConcatenate

public void preConcatenate(java.awt.geom.AffineTransform at)

Pre-concatenate this transform context with the given transform.

Parameters:

at - The given transform

setTransform

public void setTransform(java.awt.geom.AffineTransform at)

Set the transform that maps local coordinates into the parent's coordinates. If there is no parent, the "parent" is taken to be the screen. An exception will be thrown if the transform is null. This method invalidates any cached transforms. Note that the transform may be remembered by this context, so the caller must make sure that it will not be subsequently modified.

Parameters:

at - The AffineTransform

See Also:

getTransform()

translate

public void translate(double x,
                      double y)

Translate this context the given distance.

Parameters:

x - The x distance to be translated

y - The y distance to be translated