From e6360f656f37b915f43b06f431b397ae2c98f608 Mon Sep 17 00:00:00 2001
From: Apoorva Verma <vermaapoorva0510@gmail.com>
Date: Thu, 2 Jul 2026 08:40:44 +0530
Subject: [PATCH] fix(scale): clamp out-of-domain input before applying gamma

pow(t, gamma) returns NaN for a negative t with a fractional gamma, so an
out-of-domain value threw instead of clamping to the endpoint.
---
 src/generator/scale.js |  4 +++-
 test/scales.test.js    | 14 ++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/generator/scale.js b/src/generator/scale.js
index d60b89da..1220a52e 100644
--- a/src/generator/scale.js
+++ b/src/generator/scale.js
@@ -117,7 +117,9 @@ export default function (colors) {
         }
 
         if (_gamma !== 1) {
-            t = pow(t, _gamma);
+            // clamp before pow: a fractional gamma over a negative base returns
+            // NaN, so out-of-domain values must be pinned to the endpoints first
+            t = pow(limit(t, 0, 1), _gamma);
         }
 
         t = _padding[0] + t * (1 - _padding[0] - _padding[1]);
diff --git a/test/scales.test.js b/test/scales.test.js
index 8213b96d..4b151a69 100644
--- a/test/scales.test.js
+++ b/test/scales.test.js
@@ -430,4 +430,18 @@ describe('Some tests for scale()', () => {
             expect(f(100).hex()).toBe('#000000');
         });
     });
+
+    describe('gamma scale with out-of-domain input', () => {
+        const f = scale('YlGn').domain([5, 15]).gamma(1.2);
+
+        it('clamps below domain to left endpoint', () => {
+            expect(f(4).hex()).toBe('#ffffe5');
+            expect(f(4).hex()).toBe(f(5).hex());
+        });
+
+        it('clamps above domain to right endpoint', () => {
+            expect(f(16).hex()).toBe('#004529');
+            expect(f(16).hex()).toBe(f(15).hex());
+        });
+    });
 });