From b34243fa7bf7e7ce9643840e5ea75b0988ee0b1b Mon Sep 17 00:00:00 2001
From: Gregory Hainaut <gregory.hainaut@gmail.com>
Date: Sun, 4 Sep 2016 12:21:12 +0200
Subject: [PATCH] gsdx state: TEX0 write behavior might depends on the context

Game: harley davidson
* write tex0 ctx0
* write tex0 ctx1
* draw  ctx 0

Previous GSdx behavior will load the clut every write of TEX0. In the
above case the draw will take the wrong clut.

To be honest, it could be a wrong emulation on the EE core emulation.
The hardware likely got a single clut (1KB cache is quite expensive)
So clut loading must be skipped if the context is wrong.

Next draw will use the ctx1 clut so I apply TEX0 when the context is switched

Please test harley davidson :)

v2: detect context switch from UpdateContext function
V3: always set m_env.CTXT[i].offset.tex, avoid crash (Thanks to FlatOutPS2 that spot the issue)
V4: move bad psm correction code (rebase put it in the wrong place)
---
 plugins/GSdx/GSState.cpp | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/plugins/GSdx/GSState.cpp b/plugins/GSdx/GSState.cpp
index 8104910d50..ff4ca1440e 100644
--- a/plugins/GSdx/GSState.cpp
+++ b/plugins/GSdx/GSState.cpp
@@ -821,7 +821,8 @@ void GSState::GIFRegHandlerXYZ2(const GIFReg* RESTRICT r)
 
 template<int i> void GSState::ApplyTEX0(GIFRegTEX0& TEX0)
 {
-	// even if TEX0 did not change, a new palette may have been uploaded and will overwrite the currently queued for drawing
+	// Mask invalid bit before any comparison
+	TEX0.CPSM &= 0xa; // 1010b
 
 	// Handle invalid PSM here
 	switch (TEX0.PSM) {
@@ -832,6 +833,20 @@ template<int i> void GSState::ApplyTEX0(GIFRegTEX0& TEX0)
 			break;
 	}
 
+	if (PRIM->CTXT != i) {
+		// Context isn't current. Only update the register value.
+		// Handling (real write of the clut buffer) will be done when ctxt will be switched
+		if((TEX0.u32[0] ^ m_env.CTXT[i].TEX0.u32[0]) & 0x3ffffff) // TBP0 TBW PSM
+		{
+			m_env.CTXT[i].offset.tex = m_mem.GetOffset(TEX0.TBP0, TEX0.TBW, TEX0.PSM);
+		}
+
+		m_env.CTXT[i].TEX0 = (GSVector4i)TEX0;
+		return;
+	}
+
+	// even if TEX0 did not change, a new palette may have been uploaded and will overwrite the currently queued for drawing
+
 	bool wt = m_mem.m_clut.WriteTest(TEX0, m_env.TEXCLUT);
 
 	// clut loading already covered with WriteTest, for drawing only have to check CPSM and CSA (MGS3 intro skybox would be drawn piece by piece without this)
@@ -843,7 +858,6 @@ template<int i> void GSState::ApplyTEX0(GIFRegTEX0& TEX0)
 		Flush();
 	}
 
-	TEX0.CPSM &= 0xa; // 1010b
 
 	if((TEX0.u32[0] ^ m_env.CTXT[i].TEX0.u32[0]) & 0x3ffffff) // TBP0 TBW PSM
 	{
@@ -2416,9 +2430,21 @@ void GSState::SetGameCRC(uint32 crc, int options)
 
 void GSState::UpdateContext()
 {
+	bool context_switch = (m_context != &m_env.CTXT[PRIM->CTXT]);
+
 	m_context = &m_env.CTXT[PRIM->CTXT];
 
 	UpdateScissor();
+
+	if (context_switch) {
+		// Harley davidson sets TEX0 register before the context. Re-apply it now
+		// so clut is properly loaded
+		if (m_context == &m_env.CTXT[1]) {
+			ApplyTEX0<1>(m_env.CTXT[PRIM->CTXT].TEX0);
+		} else {
+			ApplyTEX0<0>(m_env.CTXT[PRIM->CTXT].TEX0);
+		}
+	}
 }
 
 void GSState::UpdateScissor()