From 83c9090d67e23a8d361a7467ae1647001ca43144 Mon Sep 17 00:00:00 2001
From: Eric Willigers <ericwilligers@chromium.org>
Date: Mon, 18 Apr 2016 16:54:22 +1000
Subject: [PATCH] Increase Bezier timing function accuracy

The polyfill evaluation of cubic Bezier timing functions
gives slightly different results than the native Blink
implementation.

In my testing, this change reduced the absolute error by 63%
while only increasing the number of cubic function evaluations
by 31%

This closes #139
---
 src/timing-utilities.js     | 2 +-
 test/js/timing-utilities.js | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/timing-utilities.js b/src/timing-utilities.js
index 3a30276..85c2484 100644
--- a/src/timing-utilities.js
+++ b/src/timing-utilities.js
@@ -168,7 +168,7 @@
         var mid = (start + end) / 2;
         function f(a, b, m) { return 3 * a * (1 - m) * (1 - m) * m + 3 * b * (1 - m) * m * m + m * m * m};
         var xEst = f(a, c, mid);
-        if (Math.abs(x - xEst) < 0.001) {
+        if (Math.abs(x - xEst) < 0.0001) {
           return f(b, d, mid);
         }
         if (xEst < x) {
diff --git a/test/js/timing-utilities.js b/test/js/timing-utilities.js
index 3ffceb5..ba8b4d4 100644
--- a/test/js/timing-utilities.js
+++ b/test/js/timing-utilities.js
@@ -23,15 +23,15 @@ suite('timing-utilities', function() {
     var f = toTimingFunction('ease');
     var g = toTimingFunction('cubic-bezier(.25, 0.1, 0.25, 1.0)');
     assertTimingFunctionsEqual(f, g, 'ease should map onto preset cubic-bezier');
-    assert.closeTo(f(0.1844), 0.2601, 0.01);
-    assert.closeTo(g(0.1844), 0.2601, 0.01);
+    assert.closeTo(f(0.1844), 0.2599, 0.001);
+    assert.closeTo(g(0.1844), 0.2599, 0.001);
     assert.equal(f(0), 0);
     assert.equal(f(1), 1);
     assert.equal(g(0), 0);
     assert.equal(g(1), 1);
 
     f = toTimingFunction('cubic-bezier(0, 1, 1, 0)');
-    assert.closeTo(f(0.104), 0.392, 0.01);
+    assert.closeTo(f(0.104), 0.3920, 0.001);
 
     function assertIsLinear(easing) {
       var f = toTimingFunction(easing);