From 02cd43e27f2aafd7c332d7672a837e1b11cce120 Mon Sep 17 00:00:00 2001
From: +merlan #flirora <flirora@flirora.xyz>
Date: Wed, 12 Feb 2025 07:38:40 -0500
Subject: [PATCH] `Gradient::repeat`: Fix floating-point error in stop
 calculation (#5837)

---
 crates/typst-library/src/visualize/gradient.rs | 7 +++----
 tests/suite/visualize/gradient.typ             | 8 ++++++++
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/crates/typst-library/src/visualize/gradient.rs b/crates/typst-library/src/visualize/gradient.rs
index 431f07dd4..d6530dd09 100644
--- a/crates/typst-library/src/visualize/gradient.rs
+++ b/crates/typst-library/src/visualize/gradient.rs
@@ -582,12 +582,11 @@ impl Gradient {
                 let mut stops = stops
                     .iter()
                     .map(move |&(color, offset)| {
-                        let t = i as f64 / n as f64;
                         let r = offset.get();
                         if i % 2 == 1 && mirror {
-                            (color, Ratio::new(t + (1.0 - r) / n as f64))
+                            (color, Ratio::new((i as f64 + 1.0 - r) / n as f64))
                         } else {
-                            (color, Ratio::new(t + r / n as f64))
+                            (color, Ratio::new((i as f64 + r) / n as f64))
                         }
                     })
                     .collect::<Vec<_>>();
@@ -1230,7 +1229,7 @@ fn process_stops(stops: &[Spanned<GradientStop>]) -> SourceResult<Vec<(Color, Ra
             };
 
             if stop.get() < last_stop {
-                bail!(*span, "offsets must be in strictly monotonic order");
+                bail!(*span, "offsets must be in monotonic order");
             }
 
             last_stop = stop.get();
diff --git a/tests/suite/visualize/gradient.typ b/tests/suite/visualize/gradient.typ
index b221f411d..811b8b605 100644
--- a/tests/suite/visualize/gradient.typ
+++ b/tests/suite/visualize/gradient.typ
@@ -658,3 +658,11 @@ $ A = mat(
   height: 10pt,
   fill: gradient.linear(violet, blue, space: cmyk)
 )
+
+--- issue-5819-gradient-repeat ---
+// Ensure the gradient constructor generates monotonic stops which can be fed
+// back into the gradient constructor itself.
+#let my-gradient = gradient.linear(red, blue).repeat(5)
+#let _ = gradient.linear(..my-gradient.stops())
+#let my-gradient2 = gradient.linear(red, blue).repeat(5, mirror: true)
+#let _ = gradient.linear(..my-gradient2.stops())