org.eclipse.swt.graphics

Class Transform

java.lang.Object

org.eclipse.swt.graphics.Resource

org.eclipse.swt.graphics.Transform

public class Transform
extends Resource

Instances of this class represent transformation matrices for points expressed as (x, y) pairs of floating point numbers.

Application code must explicitly invoke the Transform.dispose() method to release the operating system resources managed by each instance when those instances are no longer required.

This class requires the operating system's advanced graphics subsystem which may not be available on some platforms.

Since:

3.1

See Also:

SWT Example: GraphicsExample, Sample code and further information

Structure Diagram

Field Summary

Fields

Modifier and Type	Field and Description
int	handle the OS resource for the Transform (Warning: This field is platform dependent) IMPORTANT: This field is not part of the SWT public API.

Fields inherited from class org.eclipse.swt.graphics.Resource

device

Constructor Summary

Constructors

Constructor and Description
Transform(Device device) Constructs a new identity Transform.
Transform(Device device, float[] elements) Constructs a new Transform given an array of elements that represent the matrix that describes the transformation.
Transform(Device device, float m11, float m12, float m21, float m22, float dx, float dy) Constructs a new Transform given all of the elements that represent the matrix that describes the transformation.

Method Summary

Methods

Modifier and Type	Method and Description
(package private) static float[]	checkTransform(float[] elements)
(package private) void	destroy()
void	getElements(float[] elements) Fills the parameter with the values of the transformation matrix that the receiver represents, in the order {m11, m12, m21, m22, dx, dy}.
void	identity() Modifies the receiver such that the matrix it represents becomes the identity matrix.
void	invert() Modifies the receiver such that the matrix it represents becomes the mathematical inverse of the matrix it previously represented.
boolean	isDisposed() Returns true if the Transform has been disposed, and false otherwise.
boolean	isIdentity() Returns true if the Transform represents the identity matrix and false otherwise.
void	multiply(Transform matrix) Modifies the receiver such that the matrix it represents becomes the the result of multiplying the matrix it previously represented by the argument.
void	rotate(float angle) Modifies the receiver so that it represents a transformation that is equivalent to its previous transformation rotated by the specified angle.
void	scale(float scaleX, float scaleY) Modifies the receiver so that it represents a transformation that is equivalent to its previous transformation scaled by (scaleX, scaleY).
void	setElements(float m11, float m12, float m21, float m22, float dx, float dy) Modifies the receiver to represent a new transformation given all of the elements that represent the matrix that describes that transformation.
void	shear(float shearX, float shearY) Modifies the receiver so that it represents a transformation that is equivalent to its previous transformation sheared by (shearX, shearY).
java.lang.String	toString() Returns a string containing a concise, human-readable description of the receiver.
void	transform(float[] pointArray) Given an array containing points described by alternating x and y values, modify that array such that each point has been replaced with the result of applying the transformation represented by the receiver to that point.
void	translate(float offsetX, float offsetY) Modifies the receiver so that it represents a transformation that is equivalent to its previous transformation translated by (offsetX, offsetY).

Methods inherited from class org.eclipse.swt.graphics.Resource

dispose, getDevice, init

Methods inherited from class java.lang.Object

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

Field Detail

handle

public int handle

the OS resource for the Transform (Warning: This field is platform dependent)

IMPORTANT: This field is not part of the SWT public API. It is marked public only so that it can be shared within the packages provided by SWT. It is not available on all platforms and should never be accessed from application code.

Constructor Detail

Transform

public Transform(Device device)

Constructs a new identity Transform.

This operation requires the operating system's advanced graphics subsystem which may not be available on some platforms.

Parameters:

device - the device on which to allocate the Transform

Throws:

java.lang.IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if device is null and there is no current device

SWTException -

• ERROR_NO_GRAPHICS_LIBRARY - if advanced graphics are not available

SWTError -

• ERROR_NO_HANDLES if a handle for the Transform could not be obtained

See Also:

Resource.dispose()

Transform

public Transform(Device device,
         float[] elements)

Constructs a new Transform given an array of elements that represent the matrix that describes the transformation.

This operation requires the operating system's advanced graphics subsystem which may not be available on some platforms.

Parameters:

device - the device on which to allocate the Transform

elements - an array of floats that describe the transformation matrix

Throws:

java.lang.IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if device is null and there is no current device, or the elements array is null
• ERROR_INVALID_ARGUMENT - if the elements array is too small to hold the matrix values

SWTException -

• ERROR_NO_GRAPHICS_LIBRARY - if advanced graphics are not available

SWTError -

• ERROR_NO_HANDLES if a handle for the Transform could not be obtained

See Also:

Resource.dispose()

Transform

public Transform(Device device,
         float m11,
         float m12,
         float m21,
         float m22,
         float dx,
         float dy)

Constructs a new Transform given all of the elements that represent the matrix that describes the transformation.

This operation requires the operating system's advanced graphics subsystem which may not be available on some platforms.

Parameters:

device - the device on which to allocate the Transform

m11 - the first element of the first row of the matrix

m12 - the second element of the first row of the matrix

m21 - the first element of the second row of the matrix

m22 - the second element of the second row of the matrix

dx - the third element of the first row of the matrix

dy - the third element of the second row of the matrix

Throws:

java.lang.IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if device is null and there is no current device

SWTException -

• ERROR_NO_GRAPHICS_LIBRARY - if advanced graphics are not available

SWTError -

• ERROR_NO_HANDLES if a handle for the Transform could not be obtained

See Also:

Resource.dispose()

Method Detail

checkTransform

static float[] checkTransform(float[] elements)

destroy

void destroy()

Overrides:

destroy in class Resource

getElements

public void getElements(float[] elements)

Fills the parameter with the values of the transformation matrix that the receiver represents, in the order {m11, m12, m21, m22, dx, dy}.

Parameters:

elements - array to hold the matrix values

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

java.lang.IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the parameter is null
• ERROR_INVALID_ARGUMENT - if the parameter is too small to hold the matrix values

identity

public void identity()

Modifies the receiver such that the matrix it represents becomes the identity matrix.

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

Since:

3.4

invert

public void invert()

Modifies the receiver such that the matrix it represents becomes the mathematical inverse of the matrix it previously represented.

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed
• ERROR_CANNOT_INVERT_MATRIX - if the matrix is not invertible

isDisposed

public boolean isDisposed()

Returns true if the Transform has been disposed, and false otherwise.

This method gets the dispose state for the Transform. When a Transform has been disposed, it is an error to invoke any other method (except Resource.dispose()) using the Transform.

Specified by:

isDisposed in class Resource

Returns:

true when the Transform is disposed, and false otherwise

isIdentity

public boolean isIdentity()

Returns true if the Transform represents the identity matrix and false otherwise.

Returns:

true if the receiver is an identity Transform, and false otherwise

multiply

public void multiply(Transform matrix)

Modifies the receiver such that the matrix it represents becomes the the result of multiplying the matrix it previously represented by the argument.

Parameters:

matrix - the matrix to multiply the receiver by

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

java.lang.IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the parameter is null
• ERROR_INVALID_ARGUMENT - if the parameter has been disposed

rotate

public void rotate(float angle)

Modifies the receiver so that it represents a transformation that is equivalent to its previous transformation rotated by the specified angle. The angle is specified in degrees and for the identity transform 0 degrees is at the 3 o'clock position. A positive value indicates a clockwise rotation while a negative value indicates a counter-clockwise rotation.

Parameters:

angle - the angle to rotate the transformation by

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

scale

public void scale(float scaleX,
         float scaleY)

Modifies the receiver so that it represents a transformation that is equivalent to its previous transformation scaled by (scaleX, scaleY).

Parameters:

scaleX - the amount to scale in the X direction

scaleY - the amount to scale in the Y direction

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

setElements

public void setElements(float m11,
               float m12,
               float m21,
               float m22,
               float dx,
               float dy)

Modifies the receiver to represent a new transformation given all of the elements that represent the matrix that describes that transformation.

Parameters:

m11 - the first element of the first row of the matrix

m12 - the second element of the first row of the matrix

m21 - the first element of the second row of the matrix

m22 - the second element of the second row of the matrix

dx - the third element of the first row of the matrix

dy - the third element of the second row of the matrix

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

shear

public void shear(float shearX,
         float shearY)

Modifies the receiver so that it represents a transformation that is equivalent to its previous transformation sheared by (shearX, shearY).

Parameters:

shearX - the shear factor in the X direction

shearY - the shear factor in the Y direction

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

Since:

3.4

transform

public void transform(float[] pointArray)

Given an array containing points described by alternating x and y values, modify that array such that each point has been replaced with the result of applying the transformation represented by the receiver to that point.

Parameters:

pointArray - an array of alternating x and y values to be transformed

Throws:

java.lang.IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the point array is null

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

translate

public void translate(float offsetX,
             float offsetY)

Modifies the receiver so that it represents a transformation that is equivalent to its previous transformation translated by (offsetX, offsetY).

Parameters:

offsetX - the distance to translate in the X direction

offsetY - the distance to translate in the Y direction

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

toString

public java.lang.String toString()

Returns a string containing a concise, human-readable description of the receiver.

Overrides:

toString in class java.lang.Object

Returns:

a string representation of the receiver