From 6b2dec91b531dc96d2fe386bccdd4cadbb71ddd2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20Rydg=C3=A5rd?= <hrydgard@gmail.com>
Date: Sun, 24 Apr 2022 22:54:08 +0200
Subject: [PATCH] Finish BlueToAlpha functionality

---
 GPU/Common/FragmentShaderGenerator.cpp | 4 +++-
 GPU/Common/GPUStateUtils.cpp           | 2 +-
 GPU/Common/ShaderId.cpp                | 3 ++-
 assets/compat.ini                      | 1 -
 4 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/GPU/Common/FragmentShaderGenerator.cpp b/GPU/Common/FragmentShaderGenerator.cpp
index 896fb9f439..cb965bf782 100644
--- a/GPU/Common/FragmentShaderGenerator.cpp
+++ b/GPU/Common/FragmentShaderGenerator.cpp
@@ -858,7 +858,9 @@ bool GenerateFragmentShader(const FShaderID &id, char *buffer, const ShaderLangu
 			WRITE(p, "  v.rgb = v.rgb * 2.0;\n");
 		}
 
-		if (replaceBlend == REPLACE_BLEND_PRE_SRC || replaceBlend == REPLACE_BLEND_PRE_SRC_2X_ALPHA) {
+		// In some cases we need to replicate the first half of the blend equation here.
+		// In case of blue-to-alpha, it's since we overwrite alpha with blue before the actual blend equation runs.
+		if (replaceBlend == REPLACE_BLEND_PRE_SRC || replaceBlend == REPLACE_BLEND_PRE_SRC_2X_ALPHA || replaceBlend == REPLACE_BLEND_BLUE_TO_ALPHA) {
 			const char *srcFactor = "ERROR";
 			switch (replaceBlendFuncA) {
 			case GE_SRCBLEND_DSTCOLOR:          srcFactor = "ERROR"; break;
diff --git a/GPU/Common/GPUStateUtils.cpp b/GPU/Common/GPUStateUtils.cpp
index 8a8b7c70ba..8b27be2d34 100644
--- a/GPU/Common/GPUStateUtils.cpp
+++ b/GPU/Common/GPUStateUtils.cpp
@@ -1332,7 +1332,7 @@ void ConvertBlendState(GenericBlendState &blendState, bool allowFramebufferRead,
 			break;
 		}
 	} else if (blueToAlpha) {
-		blendState.setFactors(BlendFactor::ZERO, BlendFactor::ZERO, glBlendFuncA, glBlendFuncB);
+		blendState.setFactors(BlendFactor::ZERO, BlendFactor::ZERO, BlendFactor::ONE, glBlendFuncB);
 		blendState.setEquation(BlendEq::ADD, colorEq);
 		return;
 	} else {
diff --git a/GPU/Common/ShaderId.cpp b/GPU/Common/ShaderId.cpp
index dfaac9a675..e879cec1b9 100644
--- a/GPU/Common/ShaderId.cpp
+++ b/GPU/Common/ShaderId.cpp
@@ -190,7 +190,7 @@ std::string FragmentShaderDesc(const FShaderID &id) {
 	if (blendBits) {
 		switch (blendBits) {
 		case ReplaceBlendType::REPLACE_BLEND_BLUE_TO_ALPHA:
-			desc << "BlueToAlpha";
+			desc << "BlueToAlpha_" << "A:" << id.Bits(FS_BIT_BLENDFUNC_A, 4);
 			break;
 		default:
 			desc << "ReplaceBlend_" << id.Bits(FS_BIT_REPLACE_BLEND, 3)
@@ -325,6 +325,7 @@ void ComputeFragmentShaderID(FShaderID *id_out, const Draw::Bugs &bugs) {
 		// If replaceBlend == REPLACE_BLEND_STANDARD (or REPLACE_BLEND_NO) nothing is done, so we kill these bits.
 		if (replaceBlend == REPLACE_BLEND_BLUE_TO_ALPHA) {
 			id.SetBits(FS_BIT_REPLACE_BLEND, 3, replaceBlend);
+			id.SetBits(FS_BIT_BLENDFUNC_A, 4, gstate.getBlendFuncA());
 		} else if (replaceBlend > REPLACE_BLEND_STANDARD) {
 			// 3 bits.
 			id.SetBits(FS_BIT_REPLACE_BLEND, 3, replaceBlend);
diff --git a/assets/compat.ini b/assets/compat.ini
index 214a470e8a..fc17e3e9b1 100644
--- a/assets/compat.ini
+++ b/assets/compat.ini
@@ -995,7 +995,6 @@ ULES01402 = true
 ULUS10513 = true
 ULJM05812 = true
 NPJH50371 = true
-
 # Some games render first to RGB of a 4444 texture, then they switch to 565 and render masked to blue,
 # just to be able to render to the alpha channel of the 4444. We can detect that and reroute rendering
 # to avoid problems.