From 3b85a96fddd8fb25e220709e8dcb8ff268d8ded2 Mon Sep 17 00:00:00 2001
From: regorxxx <regorxxx@protonmail.com>
Date: Sun, 10 Mar 2024 11:50:24 +0100
Subject: [PATCH] * fix wrong handling of values outside scale domain due to
 internal Math.pow usage. See [Issue
 331](https://github.com/gka/chroma.js/issues/331)

Signed-off-by: regorxxx <regorxxx@protonmail.com>
---
 src/generator/scale.js |  4 +++-
 test/scales.test.js    | 10 ++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/generator/scale.js b/src/generator/scale.js
index 8da2e0da..9289794b 100644
--- a/src/generator/scale.js
+++ b/src/generator/scale.js
@@ -109,7 +109,9 @@ module.exports = function(colors) {
             t = tMapLightness(t);  // lightness correction
         }
 
-        if (_gamma !== 1) { t = pow(t, _gamma); }
+        if (t > 1) { t = 1; } // pow fails with negative bases, but values are always clamped to the extremes
+        else if (t < 0) { t = 0 }
+        else if (_gamma !== 1) { t = pow(t, _gamma); }
 
         t = _padding[0] + (t * (1 - _padding[0] - _padding[1]));
 
diff --git a/test/scales.test.js b/test/scales.test.js
index ec71979c..ca1043ab 100644
--- a/test/scales.test.js
+++ b/test/scales.test.js
@@ -275,5 +275,15 @@ vows
                 ) 
             }
         },
+        
+        'scale domain': {
+            topic: {
+                f: scale(['white','black']).domain([1, 3]).gamma(1.1)
+            },
+            'should return left color within domain'(topic) { assert.equal(topic.f(1).hex(), '#ffffff'); },
+            'should return right color within domain'(topic) { assert.equal(topic.f(3).hex(), '#000000'); },
+            'should return left color outside domain'(topic) { assert.equal(topic.f(0).hex(), '#ffffff'); },
+            'should return right color outside domain'(topic) { assert.equal(topic.f(4).hex(), '#000000'); }
+        },
 
     }).export(module);