From 6a2255160f78f79bac93bccc01bbc127096340fb Mon Sep 17 00:00:00 2001
From: narzoul <narzoul@users.noreply.github.com>
Date: Sat, 15 Jul 2017 12:41:21 +0200
Subject: [PATCH] Add extra rows to system memory primary surface buffers

Fixes a memory corruption issue in Diablo 1, reported in issue #3.
---
 DDrawCompat/Config/Config.h                   |  1 +
 DDrawCompat/DDraw/Surfaces/PrimarySurface.cpp | 33 +++++++++++++++++++
 DDrawCompat/DDraw/Surfaces/PrimarySurface.h   |  7 ++++
 3 files changed, 41 insertions(+)

diff --git a/DDrawCompat/Config/Config.h b/DDrawCompat/Config/Config.h
index 6df3d79..6b1bb08 100644
--- a/DDrawCompat/Config/Config.h
+++ b/DDrawCompat/Config/Config.h
@@ -7,4 +7,5 @@ namespace Config
 	const int maxPaletteUpdatesPerMs = 5;
 	const int minExpectedFlipsPerSec = 5;
 	const DWORD preallocatedGdiDcCount = 4;
+	const DWORD primarySurfaceExtraRows = 2;
 }
diff --git a/DDrawCompat/DDraw/Surfaces/PrimarySurface.cpp b/DDrawCompat/DDraw/Surfaces/PrimarySurface.cpp
index 1ad1db6..e438c29 100644
--- a/DDrawCompat/DDraw/Surfaces/PrimarySurface.cpp
+++ b/DDrawCompat/DDraw/Surfaces/PrimarySurface.cpp
@@ -1,4 +1,5 @@
 #include "Common/CompatPtr.h"
+#include "Config/Config.h"
 #include "DDraw/DirectDraw.h"
 #include "DDraw/RealPrimarySurface.h"
 #include "DDraw/Surfaces/PrimarySurface.h"
@@ -25,6 +26,7 @@ namespace DDraw
 		g_gdiSurface = nullptr;
 		g_primarySurface = nullptr;
 		s_palette = nullptr;
+		s_surfaceBuffers.clear();
 		ZeroMemory(&s_paletteEntries, sizeof(s_paletteEntries));
 		ZeroMemory(&g_primarySurfaceDesc, sizeof(g_primarySurfaceDesc));
 
@@ -70,6 +72,11 @@ namespace DDraw
 		g_primarySurfaceDesc.dwSize = sizeof(g_primarySurfaceDesc);
 		CompatVtable<IDirectDrawSurface7Vtbl>::s_origVtable.GetSurfaceDesc(surface7, &g_primarySurfaceDesc);
 
+		if (g_primarySurfaceDesc.ddsCaps.dwCaps & DDSCAPS_SYSTEMMEMORY)
+		{
+			resizeBuffers(*surface7);
+		}
+
 		return DD_OK;
 	}
 
@@ -120,6 +127,31 @@ namespace DDraw
 			Compat::queryInterface<IDirectDrawSurface7>(g_primarySurface.get()));
 	}
 
+	void PrimarySurface::resizeBuffers(CompatRef<IDirectDrawSurface7> surface)
+	{
+		DDSCAPS2 flipCaps = {};
+		flipCaps.dwCaps = DDSCAPS_FLIP;
+
+		DDSURFACEDESC2 desc = {};
+		desc.dwSize = sizeof(desc);
+		desc.dwFlags = DDSD_LPSURFACE;
+
+		const DWORD newBufferSize = g_primarySurfaceDesc.lPitch *
+			(g_primarySurfaceDesc.dwHeight + Config::primarySurfaceExtraRows);
+
+		auto surfacePtr(CompatPtr<IDirectDrawSurface7>::from(&surface));
+		do
+		{
+			s_surfaceBuffers.push_back(std::vector<unsigned char>(newBufferSize));
+			desc.lpSurface = s_surfaceBuffers.back().data();
+			surfacePtr->SetSurfaceDesc(surfacePtr, &desc, 0);
+
+			CompatPtr<IDirectDrawSurface7> nextSurface;
+			surfacePtr->GetAttachedSurface(surfacePtr, &flipCaps, &nextSurface.getRef());
+			surfacePtr.swap(nextSurface);
+		} while (surfacePtr && surfacePtr != &surface);
+	}
+
 	void PrimarySurface::updateGdiSurfacePtr(IDirectDrawSurface* flipTargetOverride)
 	{
 		auto primary(CompatPtr<IDirectDrawSurface>::from(m_surface->getDirectDrawSurface().get()));
@@ -153,4 +185,5 @@ namespace DDraw
 
 	CompatWeakPtr<IDirectDrawPalette> PrimarySurface::s_palette;
 	PALETTEENTRY PrimarySurface::s_paletteEntries[256] = {};
+	std::vector<std::vector<unsigned char>> PrimarySurface::s_surfaceBuffers;
 }
diff --git a/DDrawCompat/DDraw/Surfaces/PrimarySurface.h b/DDrawCompat/DDraw/Surfaces/PrimarySurface.h
index b64775b..9ae577f 100644
--- a/DDrawCompat/DDraw/Surfaces/PrimarySurface.h
+++ b/DDrawCompat/DDraw/Surfaces/PrimarySurface.h
@@ -1,6 +1,9 @@
 #pragma once
 
+#include <vector>
+
 #include "Common/CompatPtr.h"
+#include "Common/CompatRef.h"
 #include "DDraw/Surfaces/Surface.h"
 
 namespace DDraw
@@ -28,6 +31,10 @@ namespace DDraw
 
 		virtual void createImpl() override;
 
+		static void resizeBuffers(CompatRef<IDirectDrawSurface7> surface);
+
 		std::unique_ptr<Surface> m_surface;
+
+		static std::vector<std::vector<unsigned char>> s_surfaceBuffers;
 	};
 }