From a3cb79912612463d989c1bb2bff2aae3d49146a7 Mon Sep 17 00:00:00 2001
From: erixreyes <ebreyes2@up.edu.ph>
Date: Fri, 25 Jul 2025 04:47:13 +0800
Subject: [PATCH] Issue #2489: Fix CSS color-mix() percentage parsing

---
 layout/style/nsCSSParser.cpp | 42 ++++++++++++++++++++++++++++++++++--
 1 file changed, 40 insertions(+), 2 deletions(-)

diff --git a/layout/style/nsCSSParser.cpp b/layout/style/nsCSSParser.cpp
index d27763d03c..0aad8add3f 100644
--- a/layout/style/nsCSSParser.cpp
+++ b/layout/style/nsCSSParser.cpp
@@ -7477,7 +7477,21 @@ CSSParserImpl::ParseColor(nsCSSValue& aValue)
           SkipUntil(')');
           return CSSParseResult::Error;
         }
-        colorMix->mColor1 = color1;
+        
+        // parse optional weight for first color
+        bool w1_specified = false;
+        float w1 = 0.5f; // Default to 50%
+        if (GetToken(true)) {
+          if (mToken.mType == eCSSToken_Percentage) {
+            w1 = mToken.mNumber; // percentage tokens are already normalized (0.0-1.0)
+            w1_specified = true;
+            // clamp to valid range [0, 1]
+            if (w1 < 0.0f) w1 = 0.0f;
+            if (w1 > 1.0f) w1 = 1.0f;
+          } else {
+            UngetToken();
+          }
+        }
         
         if (!ExpectSymbol(',', true)) {
           SkipUntil(')');
@@ -7489,13 +7503,37 @@ CSSParserImpl::ParseColor(nsCSSValue& aValue)
           SkipUntil(')');
           return CSSParseResult::Error;
         }
-        colorMix->mColor2 = color2;
+        
+        // parse optional weight for second color
+        bool w2_specified = false;
+        float w2 = 0.5f; // default to 50%
+        if (GetToken(true)) {
+          if (mToken.mType == eCSSToken_Percentage) {
+            w2 = mToken.mNumber; // percentage tokens are already normalized (0.0-1.0)
+            w2_specified = true;
+            // Clamp to valid range [0, 1]
+            if (w2 < 0.0f) w2 = 0.0f;
+            if (w2 > 1.0f) w2 = 1.0f;
+          } else {
+            UngetToken();
+          }
+        }
+        
+        if (w1_specified && !w2_specified) {
+          // first specified, second should be complement
+          w2 = 1.0f - w1;
+        } else if (!w1_specified && w2_specified) {
+          // second specified, first should be complement
+          w1 = 1.0f - w2;
+        }
         
         if (!ExpectSymbol(')', true)) {
           SkipUntil(')');
           return CSSParseResult::Error;
         }
         
+        RefPtr<mozilla::css::ColorMixValue> colorMix = new mozilla::css::ColorMixValue(
+          mozilla::css::ColorMixColorSpace::sRGB, color1, color2, w1, w2);
         aValue.SetColorMixValue(colorMix.forget());
         return CSSParseResult::Ok;
       }