From 931970068c352e047eb53d3a18068a4e425e3a80 Mon Sep 17 00:00:00 2001
From: Luke Usher <luke.usher@outlook.com>
Date: Sun, 21 Jul 2019 12:37:06 +0100
Subject: [PATCH] Fix when CreateDevice doesn't call SetRenderTarget

This allows for the Xbox backbuffer location to be properly determined, even in titles that do not call
SetRenderTarget at all!

Tt also fixes the situation where games didn't call SetRenderTarget internally within CreateDevice.

This works because GetRenderTarget always returns the assigned render target, which immediately after
CreateDevice, is *always* the backbuffer.

This allows us to reliably determine the default backbuffer and depth stencil, even without a CreateDevice call.

This fixed a regresion in Shin Megami Tensei: Nine , and has potential to fix some more blackscreen issues.
---
 src/core/hle/D3D8/Direct3D9/Direct3D9.cpp | 62 +++++++++++++++++++++--
 1 file changed, 59 insertions(+), 3 deletions(-)

diff --git a/src/core/hle/D3D8/Direct3D9/Direct3D9.cpp b/src/core/hle/D3D8/Direct3D9/Direct3D9.cpp
index 08f3ba5ff..c4df4b90e 100644
--- a/src/core/hle/D3D8/Direct3D9/Direct3D9.cpp
+++ b/src/core/hle/D3D8/Direct3D9/Direct3D9.cpp
@@ -2453,11 +2453,67 @@ void Direct3D_CreateDevice_Start
 
 void Direct3D_CreateDevice_End()
 {
-	// Set g_XboxD3DDevice to point to the Xbox D3D Device
-	auto it = g_SymbolAddresses.find("D3DDEVICE");
-	if (it != g_SymbolAddresses.end()) {
+    // Set g_XboxD3DDevice to point to the Xbox D3D Device
+    auto it = g_SymbolAddresses.find("D3DDEVICE");
+    if (it != g_SymbolAddresses.end()) {
         g_XboxD3DDevice = (DWORD*)it->second;
     }
+
+    // If the Xbox version of CreateDevice didn't call SetRenderTarget, we must derive the default backbuffer ourselves
+    // This works because CreateDevice always sets the current render target to the Xbox Backbuffer
+    // In later XDKs, it does this inline rather than by calling D3DDevice_SetRenderTarget
+    // meaning our patch doesn't always get called in these cases.
+    // We fix the situation by calling the Xbox GetRenderTarget function, which immediately after CreateDevice
+    // WILL always return the Backbuffer!
+    // Test Case: Shin Megami Tensei: Nine
+    if (g_XboxBackBufferSurface == xbnullptr || g_XboxDefaultDepthStencilSurface == xbnullptr) {
+        // First, log the test case
+        LOG_TEST_CASE("Xbox CreateDevice did not call SetRenderTarget");
+    }
+
+    if (g_XboxBackBufferSurface == xbnullptr) {
+        // Setup trampolines for both versions of D3DDevice_GetRenderTarget
+        XB_trampoline(HRESULT, WINAPI, D3DDevice_GetRenderTarget, (XTL::X_D3DSurface**));
+        XB_trampoline(XTL::X_D3DSurface*, WINAPI, D3DDevice_GetRenderTarget2, (VOID));
+        if (XB_D3DDevice_GetRenderTarget) {
+            XB_D3DDevice_GetRenderTarget(&g_XboxBackBufferSurface);
+        }
+        else if (XB_D3DDevice_GetRenderTarget2) {
+            g_XboxBackBufferSurface = XB_D3DDevice_GetRenderTarget2();
+        }
+
+        // At this point, pRenderTarget should now point to a valid render target
+        // if it still doesn't, we cannot continue without crashing at draw time
+        if (g_XboxBackBufferSurface == xbnullptr) {
+            CxbxKrnlCleanup("Unable to determine default Xbox backbuffer");
+        }
+
+        // We must also call our SetRenderTarget patch to properly setup the host state
+        // Update only the Back buffer
+        XTL::EMUPATCH(D3DDevice_SetRenderTarget)(g_XboxBackBufferSurface, xbnullptr);
+    }
+
+    // Now do the same, but for the default depth stencil surface
+    if (g_XboxDefaultDepthStencilSurface == xbnullptr) {
+        // Setup trampolines for both versions of D3DDevice_GetDepthStencilSurface
+        XB_trampoline(HRESULT, WINAPI, D3DDevice_GetDepthStencilSurface, (XTL::X_D3DSurface**));
+        XB_trampoline(XTL::X_D3DSurface*, WINAPI, D3DDevice_GetDepthStencilSurface2, (VOID));
+        if (XB_D3DDevice_GetDepthStencilSurface) {
+            XB_D3DDevice_GetDepthStencilSurface(&g_XboxDefaultDepthStencilSurface);
+        }
+        else if (XB_D3DDevice_GetDepthStencilSurface2) {
+            g_XboxDefaultDepthStencilSurface = XB_D3DDevice_GetDepthStencilSurface2();
+        }
+
+        // At this point, g_XboxDefaultDepthStencilSurface should now point to a valid depth stencil
+        // If it doesn't, just log and carry on: Unlike RenderTarget, this situation is not fatal
+        if (g_XboxDefaultDepthStencilSurface == xbnullptr) {
+            LOG_TEST_CASE("Unable to determine default Xbox depth stencil");
+        } else {
+            // Update only the depth stencil
+            XTL::EMUPATCH(D3DDevice_SetRenderTarget)(xbnullptr, g_XboxDefaultDepthStencilSurface);
+        }
+    }
 }
 
 // LTCG specific Direct3D_CreateDevice function...