From f2cecc78ea16616b0f7215bd9ab014c511471b57 Mon Sep 17 00:00:00 2001
From: Guillaume Ayoub <guillaume@courtbouillon.org>
Date: Sun, 10 Jul 2022 20:37:33 +0200
Subject: [PATCH] Fix gradients with opacity set

Fix #1678.
---
 tests/draw/svg/test_gradients.py | 31 +++++++++++++++++++++++++++++++
 weasyprint/svg/defs.py           |  2 +-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/tests/draw/svg/test_gradients.py b/tests/draw/svg/test_gradients.py
index cd138919b..a58660cf2 100644
--- a/tests/draw/svg/test_gradients.py
+++ b/tests/draw/svg/test_gradients.py
@@ -490,3 +490,34 @@ def test_radial_gradient_reflect(assert_pixels):
         <rect x="0" y="0" width="10" height="10" fill="url(#grad)" />
       </svg>
     ''')
+
+
+@assert_no_logs
+def test_linear_gradient_opacity(assert_pixels):
+    assert_pixels('''
+        BBBBBBBBBB
+        BBBBBBBBBB
+        BBBBBBBBBB
+        BBBBBBBBBB
+        BBBBBBBBBB
+        ssssssssss
+        ssssssssss
+        ssssssssss
+        ssssssssss
+        ssssssssss
+    ''', '''
+      <style>
+        @page { size: 10px }
+        svg { display: block }
+      </style>
+      <svg width="10px" height="10px" xmlns="https://www.w3.org/2000/svg">
+        <defs>
+          <linearGradient id="grad" x1="0" y1="0" x2="0" y2="1"
+            gradientUnits="objectBoundingBox">
+            <stop stop-color="blue" offset="50%"></stop>
+            <stop stop-color="red" stop-opacity="0.502" offset="50%"></stop>
+          </linearGradient>
+        </defs>
+        <rect x="0" y="0" width="10" height="10" fill="url(#grad)" />
+      </svg>
+    ''')
diff --git a/weasyprint/svg/defs.py b/weasyprint/svg/defs.py
index c98e682a8..34481dd9d 100644
--- a/weasyprint/svg/defs.py
+++ b/weasyprint/svg/defs.py
@@ -236,7 +236,7 @@ def draw_gradient(svg, node, gradient, font_size, opacity, stroke):
         encode = (len(colors) - 1) * (0, 1)
         bounds = positions[1:-1]
         sub_functions = (
-            group.create_interpolation_function((0, 1), c0, c1, 1)
+            group.create_interpolation_function((0, 1), [c0], [c1], 1)
             for c0, c1 in alpha_couples)
         function = group.create_stitching_function(
             domain, encode, bounds, sub_functions)