Adds action classes

Refactors clamp function

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1215413002.

sdk/example/game/lib/action.dart

+part of sprites;
+
+typedef void PointSetter(Point point);
+
+abstract class Action {
+  bool _finished = false;
+
+  void step(double dt);
+  void update(double t) {
+  }
+}
+
+abstract class ActionInterval extends Action {
+  double _duration;
+
+  bool _firstTick = true;
+  double _elapsed = 0.0;
+
+  double get duration => _duration;
+
+  ActionInterval([this._duration = 0.0]);
+
+  void step(double dt) {
+    if (_firstTick) {
+      _firstTick = false;
+    } else {
+      _elapsed += dt;
+    }
+
+    double t;
+    if (this._duration == 0.0) {
+      t = 1.0;
+    } else {
+      t = (_elapsed / _duration).clamp(0.0, 1.0);
+    }
+
+    update(t);
+
+    if (t >= 1.0) _finished = true;
+  }
+}
+
+class ActionRepeat extends ActionInterval {
+  final int numRepeats;
+  final ActionInterval action;
+
+  ActionRepeat(this.action, this.numRepeats) {
+    _duration = action.duration * numRepeats;
+  }
+
+  void update(double t) {
+    action.update((t * numRepeats.toDouble()) % numRepeats.toDouble());
+  }
+}
+
+// TODO: Implement
+class ActionSequence extends ActionInterval {
+  final List<ActionInterval> actions;
+
+  ActionSequence(this.actions) {
+    for (Action action in actions) {
+      _duration += action._duration;
+    }
+  }
+}
+
+class ActionRepeatForever extends Action {
+  final ActionInterval action;
+  double _elapsedInAction = 0.0;
+
+  ActionRepeatForever(this.action);
+
+  step(double dt) {
+    _elapsedInAction += dt;
+    while (_elapsedInAction > action.duration) {
+      _elapsedInAction -= action.duration;
+    }
+    _elapsedInAction = Math.max(_elapsedInAction, 0.0);
+
+    double t;
+    if (action._duration == 0.0) {
+      t = 1.0;
+    } else {
+      t = (_elapsedInAction / action._duration).clamp(0.0, 1.0);
+    }
+
+    action.update(t);
+  }
+}
+
+class ActionTween extends ActionInterval {
+  final Function setter;
+  final startVal;
+  final endVal;
+
+  var _delta;
+
+  ActionTween(this.setter, this.startVal, this.endVal, double duration) : super(duration) {
+    _computeDelta();
+  }
+
+  void _computeDelta() {
+    if (startVal is Point) {
+      double xStart = startVal.x;
+      double yStart = startVal.y;
+      double xEnd = endVal.x;
+      double yEnd = endVal.y;
+      _delta = new Point(xEnd - xStart, yEnd - yStart);
+    } else if (startVal is double) {
+      _delta = endVal - startVal;
+    } else {
+      assert(false);
+    }
+  }
+
+  void update(double t) {
+    var newVal;
+
+    if (startVal is Point) {
+      double xStart = startVal.x;
+      double yStart = startVal.y;
+      double xDelta = _delta.x;
+      double yDelta = _delta.y;
+
+      newVal = new Point(xStart + xDelta * t, yStart + yDelta * t);
+    } else if (startVal is double) {
+      newVal = startVal + _delta * t;
+    } else {
+      assert(false);
+    }
+
+    setter(newVal);
+  }
+}
+
+class ActionController {
+
+  List<Action> _actions = [];
+
+  ActionController();
+
+  void run(Action action) {
+    _actions.add(action);
+  }
+
+  void step(double dt) {
+    for (int i = _actions.length - 1; i >= 0; i--) {
+      Action action = _actions[i];
+      action.step(dt);
+
+      if (action._finished) {
+        _actions.removeAt(i);
+      }
+    }
+  }
+}
\ No newline at end of file

sdk/example/game/lib/color_secuence.dart

@@ -32,21 +32,15 @@ class ColorSequence {
       int gDelta = ((rand.nextDouble() * 2.0 - 1.0) * greenVar).toInt();
       int bDelta = ((rand.nextDouble() * 2.0 - 1.0) * blueVar).toInt();
 
-      int aNew = _clamp(color.alpha + aDelta, 0, 255);
-      int rNew = _clamp(color.red + rDelta, 0, 255);
-      int gNew = _clamp(color.green + gDelta, 0, 255);
-      int bNew = _clamp(color.blue + bDelta, 0, 255);
+      int aNew = (color.alpha + aDelta).clamp(0, 255);
+      int rNew = (color.red + rDelta).clamp(0, 255);
+      int gNew = (color.green + gDelta).clamp(0, 255);
+      int bNew = (color.blue + bDelta).clamp(0, 255);
 
       colors.add(new Color.fromARGB(aNew, rNew, gNew, bNew));
     }
   }
 
-  int _clamp(int val, int min, int max) {
-    if (val < min) return min;
-    if (val > max) return max;
-    return val;
-  }
-
   Color colorAtPosition(double pos) {
     assert(pos >= 0.0 && pos <= 1.0);
 

sdk/example/game/lib/game_demo_world.dart

@@ -303,6 +303,12 @@ class Asteroid extends Sprite {
                                 _rand.nextDouble() * _maxAsteroidSpeed * 2 - _maxAsteroidSpeed);
 
     userInteractionEnabled = true;
+
+    // Rotate forever
+    double direction = (_rand.nextBool()) ? 360.0 : -360.0;
+    ActionTween rot = new ActionTween( (a) => rotation = a, 0.0, direction, 2.0 * _rand.nextDouble() + 2.0);
+    ActionRepeatForever repeat = new ActionRepeatForever(rot);
+    actions.run(repeat);
   }
 
   bool handleEvent(SpriteBoxEvent event) {

sdk/example/game/lib/node.dart

@@ -59,6 +59,15 @@ class Node {
 
   List<Node>_children = [];
 
+  ActionController _actions;
+
+  ActionController get actions {
+    if (_actions == null) {
+      _actions = new ActionController();
+    }
+    return _actions;
+  }
+
   // Constructors
 
   /// Creates a new [Node] without any transformation.

sdk/example/game/lib/sprite_box.dart

@@ -287,10 +287,21 @@ class SpriteBox extends RenderBox {
     // Print frame rate
     if (_numFrames % 60 == 0) print("delta: $delta fps: $_frameRate");
 
+    _runActions(_rootNode, delta);
     _callUpdate(_rootNode, delta);
     _scheduleTick();
   }
 
+  void _runActions(Node node, double dt) {
+    if (node._actions != null) {
+      node._actions.step(dt);
+    }
+    for (int i = node.children.length - 1; i >= 0; i--) {
+      Node child = node.children[i];
+      _runActions(child, dt);
+    }
+  }
+
   void _callUpdate(Node node, double dt) {
     node.update(dt);
     for (int i = node.children.length - 1; i >= 0; i--) {

sdk/example/game/lib/sprites.dart

@@ -21,3 +21,5 @@ part 'texture.dart';
 part 'spritesheet.dart';
 part 'particle_system.dart';
 part 'color_secuence.dart';
+part 'action.dart';
+part 'util.dart';

sdk/example/game/lib/util.dart

+part of sprites;
+