From a90bc82959f3443ab98a88133e7ef2ca09b201b4 Mon Sep 17 00:00:00 2001
From: Rachael Alexanderson <madame-rachelle@users.noreply.github.com>
Date: Thu, 22 Dec 2022 15:45:16 -0500
Subject: [PATCH] - implement ability to change GameTicRate

---
 src/common/engine/startupinfo.h |  1 +
 src/d_iwad.cpp                  |  7 +++++++
 src/d_main.cpp                  | 36 ++++++++++++++++++++++++++++++++-
 src/d_main.h                    |  4 ++++
 4 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/src/common/engine/startupinfo.h b/src/common/engine/startupinfo.h
index c0dd608c10..a132862ff2 100644
--- a/src/common/engine/startupinfo.h
+++ b/src/common/engine/startupinfo.h
@@ -13,6 +13,7 @@ struct FStartupInfo
 	FString def;
 	FString DiscordAppId = nullptr;
 	FString SteamAppId = nullptr;
+	int TicRate = -1;
 	int Type;
 	int LoadLights = -1;
 	int LoadBrightmaps = -1;
diff --git a/src/d_iwad.cpp b/src/d_iwad.cpp
index 431c37813c..95afe670ee 100644
--- a/src/d_iwad.cpp
+++ b/src/d_iwad.cpp
@@ -255,6 +255,12 @@ void FIWadManager::ParseIWadInfo(const char *fn, const char *data, int datasize,
 					sc.MustGetString();
 					iwad->SteamAppId = sc.String;
 				}
+				else if (sc.Compare("TicRate"))
+				{
+					sc.MustGetStringName("=");
+					sc.MustGetNumber();
+					iwad->TicRate = sc.Number;
+				}
 				else
 				{
 					sc.ScriptError("Unknown keyword '%s'", sc.String);
@@ -859,6 +865,7 @@ const FIWADInfo *FIWadManager::FindIWAD(TArray<FString> &wadfiles, const char *i
 	if (GameStartupInfo.Song.IsEmpty()) GameStartupInfo.Song = iwad_info->Song;
 	if (GameStartupInfo.DiscordAppId.IsEmpty()) GameStartupInfo.DiscordAppId = iwad_info->DiscordAppId;
 	if (GameStartupInfo.SteamAppId.IsEmpty()) GameStartupInfo.SteamAppId = iwad_info->SteamAppId;
+	if (GameStartupInfo.TicRate == -1) GameStartupInfo.TicRate = iwad_info->TicRate;
 	I_SetIWADInfo();
 	return iwad_info;
 }
diff --git a/src/d_main.cpp b/src/d_main.cpp
index d9177fbb47..a1b217f8ca 100644
--- a/src/d_main.cpp
+++ b/src/d_main.cpp
@@ -1876,6 +1876,11 @@ static FString ParseGameInfo(TArray<FString> &pwads, const char *fn, const char
 			sc.MustGetString();
 			GameStartupInfo.SteamAppId = sc.String;
 		}
+		else if (!nextKey.CompareNoCase("TICRATE"))
+		{
+			sc.MustGetNumber();
+			GameStartupInfo.TicRate = sc.Number;
+		}
 		else
 		{
 			// Silently ignore unknown properties
@@ -3654,9 +3659,16 @@ static int D_DoomMain_Internal (void)
 		delete iwad_man;	// now we won't need this anymore
 		iwad_man = NULL;
 		if (ret != 0) return ret;
-
+		if ((GameStartupInfo.TicRate) != -1)
+		{
+			if (((GameStartupInfo.TicRate) < TICRATEMIN) || ((GameStartupInfo.TicRate) > TICRATEMAX))
+				I_FatalError("TicRate can only be in the range of %i to %i! (Default TicRate for Doom engine games: 35)", TICRATEMIN, TICRATEMAX);
+			else
+				GameTicRate = GameStartupInfo.TicRate;
+		}
 		D_DoAnonStats();
 		I_UpdateWindowTitle();
+		
 		D_DoomLoop ();		// this only returns if a 'restart' CCMD is given.
 		// 
 		// Clean up after a restart
@@ -3669,6 +3681,28 @@ static int D_DoomMain_Internal (void)
 	while (1);
 }
 
+CCMD(debug_SetTicRate)
+{
+	if (argv.argc() < 2)
+		Printf("Current game ticrate is: %i\n", GameTicRate);
+	else
+	{
+		uint32_t value = atoi(argv[1]);
+		if (netgame)
+			Printf("Time scale cannot be changed in net games.\n");
+		else if (value < TICRATEMIN)
+			Printf("TicRate must be at least %i!\n", TICRATEMIN);
+		else if (value > TICRATEMAX)
+			Printf("TicRate must be at most %i!\n", TICRATEMAX);
+		else
+		{
+			GameTicRate = value;
+			I_ResetFrameTime();
+			Printf("Testing game tic rate: %i\n", value);
+		}
+	}
+}
+
 int GameMain()
 {
 	int ret = 0;
diff --git a/src/d_main.h b/src/d_main.h
index a6f76a8d89..e8c658c61e 100644
--- a/src/d_main.h
+++ b/src/d_main.h
@@ -33,6 +33,9 @@
 #include "startupinfo.h"
 #include "c_cvars.h"
 
+#define TICRATEMIN 25
+#define TICRATEMAX 50
+
 extern bool		advancedemo;
 extern bool hud_toggled;
 void D_ToggleHud();
@@ -95,6 +98,7 @@ struct FIWADInfo
 	int LoadLights = -1;
 	FString DiscordAppId = nullptr;
 	FString SteamAppId = nullptr;
+	int TicRate = -1;
 };
 
 struct FFoundWadInfo