BlTransformAnimation: calculate from and to matrices only on first loop

Fix #188
Pair-programmed with Pablo last week

src/Bloc-Animation/BlTransformAnimation.class.st

@@ -68,26 +68,25 @@ BlTransformAnimation >> initStart [
 
 	super initStart.
 
-	isAbsolute
-		ifTrue: [ elementTransformation := elementTransformation asCachedTransformation ]
-		ifFalse: [ 
-			| aCompositeTransformation |
-			aCompositeTransformation :=
-				BlElementCompositeTransformation new
-					add: self target transformation asElementTransformation;
-					add: elementTransformation;
-					yourself.
-			elementTransformation := aCompositeTransformation asCachedTransformation ].
+	isAbsolute ifFalse: [ 
+		elementTransformation :=
+			BlElementCompositeTransformation new
+				add: self target transformation asElementTransformation;
+				add: elementTransformation asElementTransformation;
+				yourself ].
+	elementTransformation := elementTransformation asCachedTransformation.
 
 	"matrix depends on computed layout bounds, we should manually trigger layout recomputation"
 	self target space isLayoutRequested ifTrue: [ 
 		self target space doLayout ].
-
+	
 	elementTransformation boundingRectangle:
 		self target bounds inLocal asRectangle.
 
-	fromMatrix := self target transformation matrix.
-	toMatrix := elementTransformation matrix
+	"Calculate matrix only on start of first loop"
+	fromMatrix ifNil: [
+		fromMatrix := self target transformation matrix copy.
+		toMatrix := elementTransformation matrix ]
 ]
 
 { #category : #initialization }
@@ -118,13 +117,8 @@ BlTransformAnimation >> transformation: aBlElementTransformation [
 ]
 
 { #category : #pulse }
-BlTransformAnimation >> valueForStep: aDelta [
-	"we should recompute destination matrix every step because transformation origins may have changed"
-
-	toMatrix := elementTransformation
-		boundingRectangle: self target bounds inLocal asRectangle;
-		matrix.
+BlTransformAnimation >> valueForStep: aNumber [
 
 	^ BlElementAbsoluteTransformation matrix:
-		  (fromMatrix interpolate: aDelta to: toMatrix)
+		  (fromMatrix interpolate: aNumber to: toMatrix)
 ]