Merge pull request #1833 from Hixie/progress-nits

SawTooth

packages/flutter/lib/src/animation/curves.dart

@@ -28,6 +28,16 @@ class Linear implements Curve {
   double transform(double t) => t;
 }
 
+/// A sawtooth curve that repeats a given number of times over the unit interval.
+class SawTooth implements Curve {
+  const SawTooth(this.count);
+  final int count;
+  double transform(double t) {
+    t *= count;
+    return t - t.truncateToDouble();
+  }
+}
+
 /// A curve that is 0.0 until start, then curved from 0.0 to 1.0 at end, then 1.0.
 class Interval implements Curve {
   const Interval(this.start, this.end, { this.curve: Curves.linear });

packages/flutter/lib/src/material/progress_indicator.dart

@@ -191,42 +191,22 @@ class CircularProgressIndicator extends ProgressIndicator {
   _CircularProgressIndicatorState createState() => new _CircularProgressIndicatorState();
 }
 
-// This class assumes that the incoming animation is a linear 0.0..1.0.
-class _RepeatingCurveTween extends Animatable<double> {
-  _RepeatingCurveTween({ this.curve, this.repeats });
-
-  Curve curve;
-  int repeats;
-
-  double evaluate(Animation<double> animation) {
-    double t = animation.value;
-    t *= repeats;
-    t -= t.truncateToDouble();
-    if (t == 0.0 || t == 1.0) {
-      assert(curve.transform(t).round() == t);
-      return t;
-    }
-    return curve.transform(t);
-  }
-}
-
 // Tweens used by circular progress indicator
-final _RepeatingCurveTween _kStrokeHeadTween = new _RepeatingCurveTween(
-  curve: new Interval(0.0, 0.5, curve: Curves.fastOutSlowIn),
-  repeats: 5
-);
-
-final _RepeatingCurveTween _kStrokeTailTween = new _RepeatingCurveTween(
-  curve: new Interval(0.5, 1.0, curve: Curves.fastOutSlowIn),
-  repeats: 5
-);
-
-final StepTween _kStepTween = new StepTween(begin: 0, end: 5);
-
-final _RepeatingCurveTween _kRotationTween = new _RepeatingCurveTween(
-  curve: Curves.linear,
-  repeats: 5
-);
+final Animatable<double> _kStrokeHeadTween = new CurveTween(
+  curve: new Interval(0.0, 0.5, curve: Curves.fastOutSlowIn)
+).chain(new CurveTween(
+  curve: new SawTooth(5)
+));
+
+final Animatable<double> _kStrokeTailTween = new CurveTween(
+  curve: new Interval(0.5, 1.0, curve: Curves.fastOutSlowIn)
+).chain(new CurveTween(
+  curve: new SawTooth(5)
+));
+
+final Animatable<int> _kStepTween = new StepTween(begin: 0, end: 5);
+
+final Animatable<double> _kRotationTween = new CurveTween(curve: new SawTooth(5));
 
 class _CircularProgressIndicatorState extends State<CircularProgressIndicator> {
   AnimationController _animationController;