"{ Package: 'stx:libview' }"

DisplayTransform variableFloatSubclass:#ScaleTransform

	instanceVariableNames:'scale'

	classVariableNames:''

	poolDictionaries:''

	category:'Graphics-Transformations'

!

!ScaleTransform class methodsFor:'documentation'!

documentation

"

    instances of ScaleTransform can be used to scale other objects in 2D space.

    This one is used, if only a scale is applied, but no translation.

    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

    [author:]

        Claus Gittinger

"

!

examples

"

    example :

                                                                        [exBegin]

     |v|

     v := View new extent:200@200; openAndWait.

     v paint:Color green.

     v fillRectangle:(10@10 corner:40@40).

     v displayLineFrom:50@50 to:75@100. 

     v transformation:(ScaleTransform withScale:2).

     v paint:Color red.

     v fillRectangle:(10@10 corner:40@40).

     v displayLineFrom:50@50 to:75@100. 

                                                                        [exEnd]

"

! !

!ScaleTransform class methodsFor:'instance creation'!

scale:scaleFactor

    ^ self new scale:scaleFactor

!

withScale:scaleFactor

    ^ self new scale:scaleFactor

! !

!ScaleTransform methodsFor:'accessing'!

inverseTransformation

    "Return the inverse transformation of the receiver"

    ^ ScaleTransform withScale:(1 / scale)

!

scale

    "return a copy of the Point that represents the

     current scale of the receiver."

    scale isNil ifTrue:[^ Point x:1 y:1 ].

    ^ scale copy

!

scale:aScale

    "Set the receiver's scale to aScale, a Point or Number."

    aScale isNil ifTrue:[

        scale := aScale

    ] ifFalse:[

        aScale = 1 ifTrue:[

            scale := nil

        ] ifFalse:[

            scale := aScale asPoint.

        ]

    ].

    "Modified: / 13.6.1998 / 14:04:51 / cg"

!

scaleOfOne

    "Set the scale of the receiver to the identity scale"

    scale := nil

!

scaleX

    "return the current x-scale of the receiver."

    scale isNil ifTrue:[^ 1].

    ^ scale x

    "Created: 21.5.1996 / 21:13:49 / cg"

!

scaleY

    "return the current x-scale of the receiver."

    scale isNil ifTrue:[^ 1].

    ^ scale y

    "Created: 21.5.1996 / 21:13:59 / cg"

!

translation

    "return a copy of the receiver's translation."

    ^ Point x:0 y:0

!

translationX

    "return the x part of the receiver's translation."

    ^ 0 

!

translationY

    "return the y part of the receiver's translation."

    ^ 0 

! !

!ScaleTransform methodsFor:'applying transform'!

applyInverseScaleX:aNumber

    "apply the scale only (if widths are to be transformed)"

    scale isNil ifTrue:[^ aNumber].

    ^ aNumber / scale x

!

applyInverseScaleY:aNumber

    "apply the scale only (if heights are to be transformed)"

    scale isNil ifTrue:[^ aNumber].

    ^ aNumber / scale y

!

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."

    scale isNil ifTrue:[

        ^ anObject

    ].

    ^ anObject scaledBy:self inverseScale 

!

applyInverseToX:aNumber

    "Apply the receiver to a number representing an x-coordinate

     and return the result."

    |s|

    scale isNil ifTrue:[s := 1] ifFalse:[s := scale x].

    ^ aNumber / s

!

applyInverseToY:aNumber

    "Apply the receiver to a number representing an y-coordinate

     and return the result."

    |s|

    scale isNil ifTrue:[s := 1] ifFalse:[s := scale y].

    ^ aNumber / s

!

applyScaleX:aNumber

    "apply the scale only (if widths are to be transformed)"

    scale isNil ifTrue:[^ aNumber].

    ^ aNumber * scale x

!

applyScaleY:aNumber

    "apply the scale only (if heights are to be transformed)"

    scale isNil ifTrue:[^ aNumber].

    ^ aNumber * scale y

!

transformPoint:p 

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

    scale isNil ifTrue:[

        ^ p

    ].

    ^ p * scale

! !

!ScaleTransform methodsFor:'printing & storing'!

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."

    aStream nextPutAll:self class name.

    aStream nextPutAll:' scale: '.

    scale printOn:aStream.

! !

!ScaleTransform methodsFor:'private'!

checkScale:aScale

    "Converts aScale to the internal format of a floating-point Point."

    |checkedScale|

    checkedScale := aScale asPoint.

!

inverseScale

    "return with a Point representing the inverse of my

     scale."

    |newScale|

    newScale := self checkScale:scale.

    ^ (1.0 / newScale x) @ (1.0 / newScale y)

! !

!ScaleTransform methodsFor:'testing'!

isNoScale

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

     return false, otherwise."

    scale isNil ifTrue:[^ true].

    ^ scale x = 1 and:[scale y = 1]

! !

!ScaleTransform methodsFor:'transformations'!

scaleBy:aScale 

    "scale the receiver.

     This is a destructive operation, modifying the transformation

     represented by the receiver"

    |newScale|

    aScale isNil ifTrue:[^ self].

    scale isNil ifTrue:[

        newScale := aScale asPoint

    ] ifFalse:[

        newScale := scale * aScale

    ].

    scale := newScale.

!

scaledBy:aScale 

    "return a new WindowingTransformation with the scale and translation of 

     the receiver both scaled by aScale."

    |checkedScale newScale|

    aScale isNil ifTrue:[

        newScale := scale.

    ] ifFalse:[

        checkedScale := self checkScale:aScale.

        scale isNil ifTrue:[

            newScale := checkedScale

        ] ifFalse:[

            newScale := scale * checkedScale

        ].

    ].

    ^ (self class) withScale:newScale

!

translateBy:aTranslation 

    "translate the receiver.

     This is a destructive operation, modifying the transformation

     represented by the receiver"

    self error:'not allowed'

!

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."

    ^ WindowingTransformation

          scale:scale

          translation:aPoint

! !

!ScaleTransform class methodsFor:'documentation'!

version

!

version_CVS

! !