From 58cb6ab7284c1631806dab8d686c8513c6bb8232 Mon Sep 17 00:00:00 2001
From: lightningterror <18107717+lightningterror@users.noreply.github.com>
Date: Sun, 26 Feb 2023 21:59:04 +0100
Subject: [PATCH] GS-ogl: Add clr3 case for blend mix 2.

When Cs*(Alpha + 1) overflows compensate with adjusting Alpha output for Cd*Alpha.
---
 bin/resources/shaders/opengl/tfx_fs.glsl | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/bin/resources/shaders/opengl/tfx_fs.glsl b/bin/resources/shaders/opengl/tfx_fs.glsl
index 10ebf9ce62..5666fe6145 100644
--- a/bin/resources/shaders/opengl/tfx_fs.glsl
+++ b/bin/resources/shaders/opengl/tfx_fs.glsl
@@ -777,10 +777,8 @@ float As = As_rgba.a;
 #endif
 
 #if PS_CLR_HW == 1
-    // Replace Af with As so we can do proper compensation for Alpha.
-#if PS_BLEND_C == 2
-    As_rgba = vec4(Af);
-#endif
+    // As or Af
+    As_rgba.rgb = vec3(C);
     // Subtract 1 for alpha to compensate for the changed equation,
     // if c.rgb > 255.0f then we further need to adjust alpha accordingly,
     // we pick the lowest overflow from all colors because it's the safest,
@@ -796,6 +794,14 @@ float As = As_rgba.a;
     // blended value it can be.
     float color_compensate = 1.0f * (C + 1.0f);
     Color.rgb -= vec3(color_compensate);
+#elif PS_CLR_HW == 3
+    // As, Ad or Af clamped.
+    As_rgba.rgb = vec3(C_clamped);
+    // Cs*(Alpha + 1) might overflow, if it does then adjust alpha value
+    // that is sent on second output to compensate.
+    vec3 overflow_check = (Color.rgb - vec3(255.0f)) / 255.0f;
+    vec3 alpha_compensate = max(vec3(0.0f), overflow_check);
+    As_rgba.rgb -= alpha_compensate;
 #endif
 
 #else