From dc9346a45df2e5f9e7711846cd198c6d150e5537 Mon Sep 17 00:00:00 2001
From: Sally Coolatta <tehrealsalt@gmail.com>
Date: Wed, 26 Jul 2023 07:50:47 -0400
Subject: [PATCH] Add forwardmove rng backwards compat with demos

---
 src/g_demo.c | 3 +++
 src/g_demo.h | 1 +
 src/p_user.c | 7 +++++++
 3 files changed, 11 insertions(+)

diff --git a/src/g_demo.c b/src/g_demo.c
index a7b9098fa..adb8e891d 100644
--- a/src/g_demo.c
+++ b/src/g_demo.c
@@ -58,6 +58,7 @@ static UINT8 demoflags;
 static UINT16 demoversion;
 boolean singledemo; // quit after playing a demo from cmdline
 boolean demo_start; // don't start playing demo right away
+boolean demo_forwardmove_rng; // old demo backwards compatibility
 boolean demosynced = true; // console warning message
 
 boolean metalrecording; // recording as metal sonic
@@ -2028,6 +2029,7 @@ void G_DoPlayDemo(char *defdemoname)
 	version = READUINT8(demo_p);
 	subversion = READUINT8(demo_p);
 	demoversion = READUINT16(demo_p);
+	demo_forwardmove_rng = (demoversion < 0x0010);
 	switch(demoversion)
 	{
 	case 0x000f:
@@ -2339,6 +2341,7 @@ UINT8 G_CheckDemoForError(char *defdemoname)
 	demo_p++; // version
 	demo_p++; // subversion
 	demoversion = READUINT16(demo_p);
+	demo_forwardmove_rng = (demoversion < 0x0010);
 	switch(demoversion)
 	{
 	case 0x000d:
diff --git a/src/g_demo.h b/src/g_demo.h
index 383d2719b..379c57428 100644
--- a/src/g_demo.h
+++ b/src/g_demo.h
@@ -38,6 +38,7 @@ extern demo_file_override_e demofileoverride;
 // Quit after playing a demo from cmdline.
 extern boolean singledemo;
 extern boolean demo_start;
+extern boolean demo_forwardmove_rng;
 extern boolean demosynced;
 
 extern mobj_t *metalplayback;
diff --git a/src/p_user.c b/src/p_user.c
index dcb84451b..1c2e4f7c9 100644
--- a/src/p_user.c
+++ b/src/p_user.c
@@ -11623,6 +11623,13 @@ void P_PlayerThink(player_t *player)
 
 	cmd = &player->cmd;
 
+	if (demoplayback && demo_forwardmove_rng)
+	{
+		// Smelly demo backwards compatibility
+		if (cmd->forwardmove)
+			P_RandomFixed();
+	}
+
 #ifdef PARANOIA
 	if (player->playerstate == PST_REBORN)
 		I_Error("player %s is in PST_REBORN\n", sizeu1(playeri));