Fixes formatting and abstraction in GameMath

sky/sdk/example/game/lib/sprites.dart

@@ -7,6 +7,7 @@ library sprites;
 import 'dart:async';
 import 'dart:convert';
 import 'dart:math' as math;
+import 'dart:typed_data';
 import 'dart:sky';
 
 import 'package:sky/animation/curves.dart';

sky/sdk/example/game/lib/util.dart

@@ -19,67 +19,64 @@ int randomInt(int max) {
 
 // atan2
 
-class GameMath {
-  static bool _inited = false;
-
-  static final int size = 1024;
-  static final double stretch = math.PI;
-
-  static final int ezis = -size;
-
-  static Float64List atan2_table_ppy = new Float64List(size + 1);
-  static Float64List atan2_table_ppx = new Float64List(size + 1);
-  static Float64List atan2_table_pny = new Float64List(size + 1);
-  static Float64List atan2_table_pnx = new Float64List(size + 1);
-  static Float64List atan2_table_npy = new Float64List(size + 1);
-  static Float64List atan2_table_npx = new Float64List(size + 1);
-  static Float64List atan2_table_nny = new Float64List(size + 1);
-  static Float64List atan2_table_nnx = new Float64List(size + 1);
-
-  static void init() {
-    if (_inited) return;
+class _Atan2Constants {
 
+  _Atan2Constants() {
     for (int i = 0; i <= size; i++) {
       double f = i.toDouble() / size.toDouble();
-      atan2_table_ppy[i] = math.atan(f) * stretch / math.PI;
-      atan2_table_ppx[i] = stretch * 0.5 - atan2_table_ppy[i];
-      atan2_table_pny[i] = -atan2_table_ppy[i];
-      atan2_table_pnx[i] = atan2_table_ppy[i] - stretch * 0.5;
-      atan2_table_npy[i] = stretch - atan2_table_ppy[i];
-      atan2_table_npx[i] = atan2_table_ppy[i] + stretch * 0.5;
-      atan2_table_nny[i] = atan2_table_ppy[i] - stretch;
-      atan2_table_nnx[i] = -stretch * 0.5 - atan2_table_ppy[i];
+      ppy[i] = math.atan(f) * stretch / math.PI;
+      ppx[i] = stretch * 0.5 - ppy[i];
+      pny[i] = -ppy[i];
+      pnx[i] = ppy[i] - stretch * 0.5;
+      npy[i] = stretch - ppy[i];
+      npx[i] = ppy[i] + stretch * 0.5;
+      nny[i] = ppy[i] - stretch;
+      nnx[i] = -stretch * 0.5 - ppy[i];
     }
-    _inited = true;
   }
 
-  static double atan2(double y, double x) {
-    if (!_inited)
-      init();
+  static const int size = 1024;
+  static const double stretch = math.PI;
 
+  static const int ezis = -size;
+
+  final Float64List ppy = new Float64List(size + 1);
+  final Float64List ppx = new Float64List(size + 1);
+  final Float64List pny = new Float64List(size + 1);
+  final Float64List pnx = new Float64List(size + 1);
+  final Float64List npy = new Float64List(size + 1);
+  final Float64List npx = new Float64List(size + 1);
+  final Float64List nny = new Float64List(size + 1);
+  final Float64List nnx = new Float64List(size + 1);
+}
+
+class GameMath {
+  static final _Atan2Constants _atan2 = new _Atan2Constants();
+
+  static double atan2(double y, double x) {
     if (x >= 0) {
       if (y >= 0) {
         if (x >= y)
-          return atan2_table_ppy[(size * y / x + 0.5).toInt()];
+          return _atan2.ppy[(_Atan2Constants.size * y / x + 0.5).floor()];
         else
-          return atan2_table_ppx[(size * x / y + 0.5).toInt()];
+          return _atan2.ppx[(_Atan2Constants.size * x / y + 0.5).floor()];
       } else {
         if (x >= -y)
-          return atan2_table_pny[(ezis * y / x + 0.5).toInt()];
+          return _atan2.pny[(_Atan2Constants.ezis * y / x + 0.5).floor()];
         else
-          return atan2_table_pnx[(ezis * x / y + 0.5).toInt()];
+          return _atan2.pnx[(_Atan2Constants.ezis * x / y + 0.5).floor()];
       }
     } else {
       if (y >= 0) {
         if (-x >= y)
-          return atan2_table_npy[(ezis * y / x + 0.5).toInt()];
+          return _atan2.npy[(_Atan2Constants.ezis * y / x + 0.5).floor()];
         else
-          return atan2_table_npx[(ezis * x / y + 0.5).toInt()];
+          return _atan2.npx[(_Atan2Constants.ezis * x / y + 0.5).floor()];
       } else {
         if (x <= y)
-          return atan2_table_nny[(size * y / x + 0.5).toInt()];
+          return _atan2.nny[(_Atan2Constants.size * y / x + 0.5).floor()];
         else
-          return atan2_table_nnx[(size * x / y + 0.5).toInt()];
+          return _atan2.nnx[(_Atan2Constants.size * x / y + 0.5).floor()];
       }
     }
   }