From 70e3a041f1890e63855fad693891652b36f48195 Mon Sep 17 00:00:00 2001
From: Mike Bostock <mbostock@gmail.com>
Date: Mon, 28 Mar 2022 10:30:51 -0700
Subject: [PATCH] clamp HSL format (#101)

---
 src/color.js     | 12 ++++++++----
 test/hsl-test.js |  7 +++++++
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/color.js b/src/color.js
index 3e3ad49..3af25a9 100644
--- a/src/color.js
+++ b/src/color.js
@@ -353,11 +353,15 @@ define(Hsl, hsl, extend(Color, {
         && (0 <= this.opacity && this.opacity <= 1);
   },
   formatHsl: function() {
-    var a = this.opacity; a = isNaN(a) ? 1 : Math.max(0, Math.min(1, a));
+    var a = this.opacity,
+        h = (this.h || 0) % 360,
+        s = Math.max(0, Math.min(1, this.s || 0)),
+        l = Math.max(0, Math.min(1, this.l || 0));
+    a = isNaN(a) ? 1 : Math.max(0, Math.min(1, a));
     return (a === 1 ? "hsl(" : "hsla(")
-        + (this.h || 0) + ", "
-        + (this.s || 0) * 100 + "%, "
-        + (this.l || 0) * 100 + "%"
+        + (h < 0 ? h + 360 : h) + ", "
+        + s * 100 + "%, "
+        + l * 100 + "%"
         + (a === 1 ? ")" : ", " + a + ")");
   }
 }));
diff --git a/test/hsl-test.js b/test/hsl-test.js
index 5f5b9c7..d963916 100644
--- a/test/hsl-test.js
+++ b/test/hsl-test.js
@@ -38,6 +38,13 @@ it("hsl.formatHsl() formats as hsl(…) or hsla(…)", () => {
   assert.strictEqual(hsl("hsla(60, 100%, 20%, 0.4)").formatHsl(), "hsla(60, 100%, 20%, 0.4)");
 });
 
+it("hsl.formatHsl() clamps to the expected range", () => {
+  assert.strictEqual(hsl(180, -100, -50).formatHsl(), "hsl(180, 0%, 0%)");
+  assert.strictEqual(hsl(180, 150, 200).formatHsl(), "hsl(180, 100%, 100%)");
+  assert.strictEqual(hsl(-90, 50, 50).formatHsl(), "hsl(270, 100%, 100%)");
+  assert.strictEqual(hsl(420, 50, 50).formatHsl(), "hsl(60, 100%, 100%)");
+});
+
 it("hsl.formatHex() formats as #rrggbb", () => {
   assert.strictEqual(hsl("#abcdef").formatHex(), "#abcdef");
   assert.strictEqual(hsl("hsl(60, 100%, 20%)").formatHex(), "#666600");