From dffc89e41cfa5c2ea5efac7ac43677f995e52553 Mon Sep 17 00:00:00 2001
From: Anders Jenbo <anders@jenbo.dk>
Date: Wed, 13 Nov 2019 00:41:38 +0100
Subject: [PATCH] Limit FPS when upscaling is disabled

---
 SourceX/dx.cpp           | 8 ++++++++
 SourceX/miniwin/ddraw.h  | 2 ++
 SourceX/miniwin/misc.cpp | 8 ++++++++
 3 files changed, 18 insertions(+)

diff --git a/SourceX/dx.cpp b/SourceX/dx.cpp
index bb7437d8c..e313759ca 100644
--- a/SourceX/dx.cpp
+++ b/SourceX/dx.cpp
@@ -14,6 +14,8 @@ int locktbl[256];
 static CCritSect sgMemCrit;
 HMODULE ghDiabMod;
 
+int refreshDelay;
+DWORD refreshDelayTc;
 SDL_Window *window;
 SDL_Renderer *renderer;
 SDL_Texture *texture;
@@ -237,6 +239,12 @@ void RenderPresent()
 		}
 		SDL_RenderPresent(renderer);
 	} else {
+		// no VSync when not using upscaling
+		int tc = GetTickCount();
+		if (refreshDelayTc + refreshDelay > tc)
+			Sleep(tc - refreshDelayTc + refreshDelay);
+		refreshDelayTc = tc;
+
 		if (SDL_UpdateWindowSurface(window) <= -1) {
 			ErrSdl();
 		}
diff --git a/SourceX/miniwin/ddraw.h b/SourceX/miniwin/ddraw.h
index 360e4192e..c7e5de987 100644
--- a/SourceX/miniwin/ddraw.h
+++ b/SourceX/miniwin/ddraw.h
@@ -6,6 +6,8 @@
 
 namespace dvl {
 
+extern int refreshDelay;
+extern DWORD refreshDelayTc;
 extern SDL_Window *window;
 extern SDL_Renderer *renderer;
 extern SDL_Texture *texture;
diff --git a/SourceX/miniwin/misc.cpp b/SourceX/miniwin/misc.cpp
index cff312459..a6a9f0007 100644
--- a/SourceX/miniwin/misc.cpp
+++ b/SourceX/miniwin/misc.cpp
@@ -190,6 +190,14 @@ bool SpawnWindow(LPCSTR lpWindowName, int nWidth, int nHeight)
 		if (SDL_RenderSetLogicalSize(renderer, nWidth, nHeight) <= -1) {
 			ErrSdl();
 		}
+#endif
+	} else {
+#ifdef USE_SDL1
+		refreshDelay = 16; // rougly 60hz
+#else
+		SDL_DisplayMode mode;
+		SDL_GetDisplayMode(0, 0, &mode);
+		refreshDelay = 1000 / mode.refresh_rate;
 #endif
 	}