From 75471df7877f23fe39a1e1784186388c6622bf00 Mon Sep 17 00:00:00 2001
From: Braden Obrzut <admin@maniacsvault.net>
Date: Fri, 24 Apr 2015 22:26:57 -0400
Subject: [PATCH] - Made a few Win32 calls optional in order to restore
 capatibility with Windows NT 4.0 (not that anyone is using NT 4, but it was a
 trivial fix)

---
 src/m_specialpaths.cpp   | 26 ++++++++++++--------------
 src/win32/i_system.cpp   | 11 +++++++++--
 src/win32/i_system.h     | 29 +++++++++++++++++++++++++++++
 src/win32/win32video.cpp |  5 ++++-
 4 files changed, 54 insertions(+), 17 deletions(-)

diff --git a/src/m_specialpaths.cpp b/src/m_specialpaths.cpp
index a45c23dc79..086f170f8f 100644
--- a/src/m_specialpaths.cpp
+++ b/src/m_specialpaths.cpp
@@ -22,6 +22,8 @@
 
 #if defined(_WIN32)
 
+#include "i_system.h"
+
 typedef HRESULT (WINAPI *GKFP)(REFKNOWNFOLDERID, DWORD, HANDLE, PWSTR *);
 
 //===========================================================================
@@ -73,18 +75,7 @@ bool UseKnownFolders()
 
 bool GetKnownFolder(int shell_folder, REFKNOWNFOLDERID known_folder, bool create, FString &path)
 {
-	static GKFP SHGetKnownFolderPath = NULL;
-	static bool tested = false;
-
-	if (!tested)
-	{
-		tested = true;
-		HMODULE shell32 = GetModuleHandle("shell32.dll");
-		if (shell32 != NULL)
-		{
-			SHGetKnownFolderPath = (GKFP)GetProcAddress(shell32, "SHGetKnownFolderPath");
-		}
-	}
+	static TOptWin32Proc<GKFP> SHGetKnownFolderPath("shell32.dll", "SHGetKnownFolderPath");
 
 	char pathstr[MAX_PATH];
 
@@ -92,6 +83,13 @@ bool GetKnownFolder(int shell_folder, REFKNOWNFOLDERID known_folder, bool create
 	// new to Vista, hence the reason we support both.
 	if (SHGetKnownFolderPath == NULL)
 	{
+		static TOptWin32Proc<HRESULT(*)(HWND, int, HANDLE, DWORD, LPTSTR)>
+			SHGetFolderPathA("shell32.dll", "SHGetFolderPathA");
+
+		// NT4 doesn't even have this function.
+		if (SHGetFolderPathA == NULL)
+			return false;
+
 		if (shell_folder < 0)
 		{ // Not supported by SHGetFolderPath
 			return false;
@@ -100,7 +98,7 @@ bool GetKnownFolder(int shell_folder, REFKNOWNFOLDERID known_folder, bool create
 		{
 			shell_folder |= CSIDL_FLAG_CREATE;
 		}
-		if (FAILED(SHGetFolderPathA(NULL, shell_folder, NULL, 0, pathstr)))
+		if (FAILED(SHGetFolderPathA.Call(NULL, shell_folder, NULL, 0, pathstr)))
 		{
 			return false;
 		}
@@ -110,7 +108,7 @@ bool GetKnownFolder(int shell_folder, REFKNOWNFOLDERID known_folder, bool create
 	else
 	{
 		PWSTR wpath;
-		if (FAILED(SHGetKnownFolderPath(known_folder, create ? KF_FLAG_CREATE : 0, NULL, &wpath)))
+		if (FAILED(SHGetKnownFolderPath.Call(known_folder, create ? KF_FLAG_CREATE : 0, NULL, &wpath)))
 		{
 			return false;
 		}
diff --git a/src/win32/i_system.cpp b/src/win32/i_system.cpp
index 2dabe7de9a..5b6a69c638 100644
--- a/src/win32/i_system.cpp
+++ b/src/win32/i_system.cpp
@@ -1600,13 +1600,20 @@ unsigned int I_MakeRNGSeed()
 
 FString I_GetLongPathName(FString shortpath)
 {
-	DWORD buffsize = GetLongPathName(shortpath.GetChars(), NULL, 0);
+	static TOptWin32Proc<DWORD (WINAPI*)(LPCTSTR, LPTSTR, DWORD)>
+		GetLongPathName("kernel32.dll", "GetLongPathNameW", "GetLongPathNameA");
+
+	// Doesn't exist on NT4
+	if (GetLongPathName == NULL)
+		return shortpath;
+
+	DWORD buffsize = GetLongPathName.Call(shortpath.GetChars(), NULL, 0);
 	if (buffsize == 0)
 	{ // nothing to change (it doesn't exist, maybe?)
 		return shortpath;
 	}
 	TCHAR *buff = new TCHAR[buffsize];
-	DWORD buffsize2 = GetLongPathName(shortpath.GetChars(), buff, buffsize);
+	DWORD buffsize2 = GetLongPathName.Call(shortpath.GetChars(), buff, buffsize);
 	if (buffsize2 >= buffsize)
 	{ // Failure! Just return the short path
 		delete[] buff;
diff --git a/src/win32/i_system.h b/src/win32/i_system.h
index 647a08d134..6872ca232c 100644
--- a/src/win32/i_system.h
+++ b/src/win32/i_system.h
@@ -51,6 +51,35 @@ typedef enum {
 
 extern os_t OSPlatform;
 
+// Helper template so that we can access newer Win32 functions with a single static
+// variable declaration. If this were C++11 it could be totally transparent.
+template<typename Proto>
+class TOptWin32Proc
+{
+	static Proto GetOptionalWin32Proc(const char* module, const char* function, const char* alt)
+	{
+		HMODULE hmodule = GetModuleHandle(module);
+		if (hmodule == NULL)
+			return NULL;
+
+		Proto ret = (Proto)GetProcAddress(hmodule, function);
+		if(ret != NULL || alt == NULL)
+			return ret;
+
+		// Lookup alternate function name (ex. ProcW -> ProcA)
+		return (Proto)GetProcAddress(hmodule, alt);
+	}
+
+public:
+	const Proto Call;
+
+	TOptWin32Proc(const char* module, const char* function, const char* alt=NULL)
+		: Call(GetOptionalWin32Proc(module, function, alt)) {}
+
+	// Wrapper object can be tested against NULL, but not directly called.
+	operator const void*() const { return Call; }
+};
+
 // Called by DoomMain.
 void I_Init (void);
 
diff --git a/src/win32/win32video.cpp b/src/win32/win32video.cpp
index 8aa74bfb58..690bb5725b 100644
--- a/src/win32/win32video.cpp
+++ b/src/win32/win32video.cpp
@@ -414,7 +414,10 @@ void Win32Video::DumpAdapters()
 		HMONITOR hm = D3D->GetAdapterMonitor(i);
 		MONITORINFOEX mi;
 		mi.cbSize = sizeof(mi);
-		if (GetMonitorInfo(hm, &mi))
+
+		TOptWin32Proc<BOOL(WINAPI*)(HMONITOR, LPMONITORINFO)> GetMonitorInfo("user32.dll", "GetMonitorInfoW");
+		assert(GetMonitorInfo != NULL); // Missing in NT4, but so is D3D
+		if (GetMonitorInfo.Call(hm, &mi))
 		{
 			mysnprintf(moreinfo, countof(moreinfo), " [%ldx%ld @ (%ld,%ld)]%s",
 				mi.rcMonitor.right - mi.rcMonitor.left,