perf(setRotationCenter): compare new setRotationCenter values after truncating to 32bit

Compare new setRotationCenter values after truncating to 32bit

src/Skin.js

@@ -4,6 +4,19 @@ const twgl = require('twgl.js');
 
 const RenderConstants = require('./RenderConstants');
 
+/**
+ * Truncate a number into what could be stored in a 32 bit floating point value.
+ * @param {number} num Number to truncate.
+ * @return {number} Truncated value.
+ */
+const toFloat32 = (function () {
+    const memory = new Float32Array(1);
+    return function (num) {
+        memory[0] = num;
+        return memory[0];
+    };
+}());
+
 class Skin extends EventEmitter {
     /**
      * Create a Skin, which stores and/or generates textures for use in rendering.
@@ -79,7 +92,11 @@ class Skin extends EventEmitter {
      */
     setRotationCenter (x, y) {
         const emptySkin = this.size[0] === 0 && this.size[1] === 0;
-        const changed = x !== this._rotationCenter[0] || y !== this._rotationCenter[1];
+        // Compare a 32 bit x and y value against the stored 32 bit center
+        // values.
+        const changed = (
+            toFloat32(x) !== this._rotationCenter[0] ||
+            toFloat32(y) !== this._rotationCenter[1]);
         if (!emptySkin && changed) {
             this._rotationCenter[0] = x;
             this._rotationCenter[1] = y;