Class: TranslationTransform

• Inheritance
• Description
• Class protocol
  • instance creation
• Instance protocol
  • accessing
  • applying transform
  • printing & storing
  • private
  • testing
  • transformations
• Examples

Inheritance:

   Object
   |
   +--DisplayTransform
      |
      +--TranslationTransform

Package:

stx:libview

Category:

Graphics-Transformations

Version:

rev: 1.5 date: 2022/03/08 22:45:22

user: cg

file: TranslationTransform.st directory: libview

module: stx stc-classLibrary: libview

Description:

instances of WindowingTransformation can be used to scale, translate or
generally transform other objects in 2D space. 
They can also be set as the translation in a graphic context, 
which will then apply this to all of its drawing operations 
(see GraphicContext>>transformation:).

All 2-D objects are supposed to be able to be transformed using
instances of me.  Multiple instances of me can also be combined to form a
single composite transformation.

[Instance variables:]
    scale           <Number> or <Point> representing a linear scaling factor.
                    nil is interpreted as 1@1

    translation     <Number> or <Point> representing a translation in 2-D.
                    nil is interpreted as 0@0

copyright
COPYRIGHT (c) 1992 by Claus Gittinger
             All Rights Reserved

This software is furnished under a license and may be used
only in accordance with the terms of that license and with the
inclusion of the above copyright notice.   This software may not
be provided or otherwise made available to, or used by, any
other person.  No title to or ownership of the software is
hereby transferred.

Class protocol:

 identity

returns a windowing transformation with no scaling (1@1)
and no translation (0@0).

Usage example(s):

WindowingTransformation identity

 translation: aTranslation

returns a windowing transformation with no scaling and a translation offset of aTranslation.

Usage example(s):

|v| v := View new openAndWaitUntilVisible. v displayLineFrom:10@10 to:30@30. v transformation:(WindowingTransformation scale:2 translation:0). 'now, everything is magnfied by 2'. v displayLineFrom:10@10 to:30@30.

Usage example(s):

|v| v := View new openAndWaitUntilVisible. v displayLineFrom:10@10 to:30@30. v transformation:(WindowingTransformation translation:50). 'now, everything is offset by 50 pixels'. v displayLineFrom:10@10 to:30@30.

Instance protocol:

 translation

return a copy of the receiver's translation.

 translation: aTranslation

Set the receiver's translation to aTranslation, a Point or Number.

 translationX

return the receiver's x-translation.

 translationY

return the receiver's x-translation.

 applyInverseTo: anObject

Apply the inverse of the receiver to anObject
and return the result. This can be used to map back from logical
to physical coordinates, for example.

 applyInverseToX: aNumber

Apply the receiver to a number representing an x-coordinate
and return the result.

 applyInverseToY: aNumber

Apply the receiver to a number representing an y-coordinate
and return the result.

 applyTo: anObject

Apply the receiver to anObject and return the result.

 applyToX: aNumber

Apply the receiver to a number representing an x-coordinate
and return the result.

 applyToY: aNumber

Apply the receiver to a number representing an y-coordinate
and return the result.

 compose: aTransformation

return a new WindowingTransformation that is the
composition of the receiver and aTransformation.
The effect of applying the resulting WindowingTransformation
to an object is the same as that of first applying
aTransformation to the object and then applying the
receiver to its result.

 composedWithLocal: aTransformation

(comment from inherited method)
Return the composition of the receiver and the local transformation passed in.
A 'local' transformation is defined as a transformation that takes place
between the receiver (the 'global') transformation and any 'local' point
computations, e.g., for the methods

globalPointToLocal: globalPoint
globalPoint -> globalTransform -> localTransform -> locaPoint

localPointToGlobal: localPoint
localPoint -> localTransform -> globalTransform -> globalPoint

 transformPoint: p

Apply the receiver to a point, returning a new point.

 transformRectangle: aRectangle

Apply the receiver to a rectangle, returning a new rectangle.

 printOn: aStream

append a user printed representation of the receiver to aStream.
The format is suitable for a human - not meant to be read back.

 inverseTranslation

return with a Point or Number representing the inverse of my translation.

 isIdentityTransformation

return true if this is an identity transformation;
return false, otherwise.

 isNoScale

return true if the identity scale is in effect (i.e. saleFactor is 1);
return false, otherwise.

 scaleBy: aScale

scale the receiver.
This is a destructive operation, modifying the transformation
represented by the receiver

 scaledBy: aScale

return a new WindowingTransformation with the scale and translation of
the receiver both scaled by aScale.

 translateBy: aTranslation

translate the receiver.
This is a destructive operation, modifying the transformation
represented by the receiver

 translatedBy: aPoint

return a new WindowingTransformation with the same scale and
rotations as the receiver and with a translation of the current
translation plus aPoint.

Examples:

 |v|

 v := View new realize.
 (Delay forSeconds:3) wait.
 v transformation:(WindowingTransformation unit:#inch on:Display).
 'now, we can think of drawing in inches ...'.
 v displayLineFrom:0.5@0.5 to:1@1 

 |v|

 v := View new realize.
 (Delay forSeconds:3) wait.
 v transformation:(WindowingTransformation unit:#mm on:Display).
 'now, we can think of drawing in millimeters ...'.
 v displayLineFrom:5@5 to:20@5 

 |v|

 v := View new realize.
 (Delay forSeconds:3) wait.
 v transformation:(WindowingTransformation scale:2 translation:0).
 'now, everything is magnfied by 2'.
 v displayLineFrom:10@10 to:30@30 

 |v|

 v := View new realize.
 (Delay forSeconds:3) wait.
 v transformation:(WindowingTransformation scale:0.5 translation:0).
 'now, everything is shrunk by 2'.
 v displayLineFrom:10@10 to:30@30