From 9d90bab91ba69e8e67604c2b713a4937304b129b Mon Sep 17 00:00:00 2001
From: Jelle Raaijmakers <jelle@gmta.nl>
Date: Thu, 30 Dec 2021 00:32:17 +0100
Subject: [PATCH] LibSoftGPU: Prevent fog from overwriting the alpha channel

Fog only affects the RGB channels according to the spec.
---
 Userland/Libraries/LibSoftGPU/Device.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Userland/Libraries/LibSoftGPU/Device.cpp b/Userland/Libraries/LibSoftGPU/Device.cpp
index 3602dc5752..0aa9efc912 100644
--- a/Userland/Libraries/LibSoftGPU/Device.cpp
+++ b/Userland/Libraries/LibSoftGPU/Device.cpp
@@ -742,8 +742,10 @@ void Device::submit_triangle(const Triangle& triangle, Vector<size_t> const& ena
                 break;
             }
 
-            // Mix texel with fog
-            fragment = mix(m_options.fog_color, fragment, factor);
+            // Mix texel's RGB with fog's RBG - leave alpha alone
+            fragment.set_x(mix(m_options.fog_color.x(), fragment.x(), factor));
+            fragment.set_y(mix(m_options.fog_color.y(), fragment.y(), factor));
+            fragment.set_z(mix(m_options.fog_color.z(), fragment.z(), factor));
         }
 
         return fragment;