From 55281cebd218896443ddedaa774d4086cc8bfe5c Mon Sep 17 00:00:00 2001
From: Chris Pable <chris.pable@gmail.com>
Date: Thu, 25 May 2017 02:34:33 -0500
Subject: [PATCH] keep xp on life support a bit longer, check for vista+ stuff
 (#1456)

---
 src/arch/Sound/DSoundHelpers.cpp       | 10 ++++++++-
 src/archutils/Win32/DirectXHelpers.h   | 19 +++++++++++++++++
 src/archutils/Win32/GraphicsWindow.cpp | 29 ++++++++++++++++++++++----
 src/archutils/Win32/GraphicsWindow.h   |  5 +++++
 4 files changed, 58 insertions(+), 5 deletions(-)

diff --git a/src/arch/Sound/DSoundHelpers.cpp b/src/arch/Sound/DSoundHelpers.cpp
index 111816d534..74a27ec41a 100644
--- a/src/arch/Sound/DSoundHelpers.cpp
+++ b/src/arch/Sound/DSoundHelpers.cpp
@@ -210,7 +210,15 @@ RString DSoundBuf::Init( DSound &ds, DSoundBuf::hw hardware,
 	DSBUFFERDESC format;
 	memset( &format, 0, sizeof(format) );
 	format.dwSize = sizeof(format);
-	format.dwFlags = DSBCAPS_GETCURRENTPOSITION2 | DSBCAPS_GLOBALFOCUS | DSBCAPS_CTRLVOLUME;
+
+	if (at_least_vista())
+	{
+		format.dwFlags = DSBCAPS_GETCURRENTPOSITION2 | DSBCAPS_GLOBALFOCUS | DSBCAPS_CTRLVOLUME | DSBCAPS_TRUEPLAYPOSITION;
+	}
+	else
+	{
+		format.dwFlags = DSBCAPS_GETCURRENTPOSITION2 | DSBCAPS_GLOBALFOCUS | DSBCAPS_CTRLVOLUME;
+	}
 
 	/* Don't use DSBCAPS_STATIC.  It's meant for static buffers, and we
 	 * only use streaming buffers. */
diff --git a/src/archutils/Win32/DirectXHelpers.h b/src/archutils/Win32/DirectXHelpers.h
index 7729751e44..b8438f1fce 100644
--- a/src/archutils/Win32/DirectXHelpers.h
+++ b/src/archutils/Win32/DirectXHelpers.h
@@ -1,8 +1,27 @@
 #ifndef DIRECTX_HELPERS_H
 #define DIRECTX_HELPERS_H
+#include "windows.h"
 
 RString hr_ssprintf( int hr, const char *fmt, ... );
 
+//Keep XP on life support
+static bool at_least_vista()
+{
+OSVERSIONINFOEXW osvi = { sizeof(osvi), 0, 0, 0, 0, { 0 }, 0, 0 };
+DWORDLONG        const dwlConditionMask = VerSetConditionMask(
+	VerSetConditionMask(
+	VerSetConditionMask(
+	0, VER_MAJORVERSION, VER_GREATER_EQUAL),
+	VER_MINORVERSION, VER_GREATER_EQUAL),
+	VER_SERVICEPACKMAJOR, VER_GREATER_EQUAL);
+
+osvi.dwMajorVersion = 0x0600;
+osvi.dwMinorVersion = 0x0;
+osvi.wServicePackMajor = 0;
+
+return VerifyVersionInfoW(&osvi, VER_MAJORVERSION | VER_MINORVERSION | VER_SERVICEPACKMAJOR, dwlConditionMask) != false;
+}
+
 #endif
 
 /*
diff --git a/src/archutils/Win32/GraphicsWindow.cpp b/src/archutils/Win32/GraphicsWindow.cpp
index 5722701ed2..81f5836270 100644
--- a/src/archutils/Win32/GraphicsWindow.cpp
+++ b/src/archutils/Win32/GraphicsWindow.cpp
@@ -12,8 +12,7 @@
 #include "archutils/Win32/WindowIcon.h"
 #include "archutils/Win32/GetFileInformation.h"
 #include "CommandLineActions.h"
-#include <dwmapi.h>
-#pragma comment(lib, "dwmapi.lib")
+#include "DirectXHelpers.h"
 
 #include <set>
 
@@ -417,6 +416,19 @@ void GraphicsWindow::Initialize( bool bD3D )
 	// A few things need to be handled differently for D3D.
 	g_bD3D = bD3D;
 
+	//keeping xp on life support -- check for vista+ for dwm
+	if (at_least_vista())
+	{
+		hInstanceDwmapi = LoadLibraryA("dwmapi.dll");
+	}
+
+	//if we have dwm, get function pointers to the dll functions
+	if( hInstanceDwmapi != NULL )
+	{
+		PFN_DwmFlush =					(HRESULT (WINAPI *)(VOID))GetProcAddress( hInstanceDwmapi, "DwmFlush" );
+		PFN_DwmIsCompositionEnabled =	(HRESULT (WINAPI *)(BOOL*))GetProcAddress( hInstanceDwmapi, "DwmIsCompositionEnabled" );
+	}
+
 	AppInstance inst;
 	do
 	{
@@ -498,8 +510,17 @@ void GraphicsWindow::Update()
 	HOOKS->SetHasFocus( g_bHasFocus );
 
 	if (g_CurrentParams.vsync)
-	{
-		DwmFlush();
+	{
+		//if we can use DWM
+		if( hInstanceDwmapi != NULL )
+		{
+			BOOL compositeEnabled = true;
+			PFN_DwmIsCompositionEnabled(&compositeEnabled);
+			if (compositeEnabled)
+			{
+				PFN_DwmFlush();
+			}
+		}
 	}
 
 	if( g_bResolutionChanged && DISPLAY != NULL )
diff --git a/src/archutils/Win32/GraphicsWindow.h b/src/archutils/Win32/GraphicsWindow.h
index 6e1e6ebcef..7d3cd08e6a 100644
--- a/src/archutils/Win32/GraphicsWindow.h
+++ b/src/archutils/Win32/GraphicsWindow.h
@@ -35,6 +35,11 @@ namespace GraphicsWindow
 	void Update();
 
 	HWND GetHwnd();
+
+	//dwm functions for vista+
+	static HINSTANCE hInstanceDwmapi = NULL;
+	static HRESULT(WINAPI* PFN_DwmIsCompositionEnabled)(BOOL*);
+	static HRESULT (WINAPI* PFN_DwmFlush)(VOID);
 };
 
 #endif