From 58ddfc9da08d18c2bbd58b4af4d46f99bf6159b8 Mon Sep 17 00:00:00 2001
From: GenericHeroGuy <genericheroguy@noreply.codeberg.org>
Date: Mon, 11 Aug 2025 15:29:23 +0200
Subject: [PATCH] Change demoheader to BlanReplay, add G_CompatLevel

---
 src/g_demo.c | 69 +++++++++++++++++++++++++++++++++-------------------
 src/g_demo.h |  1 +
 src/p_tick.c |  4 +--
 3 files changed, 47 insertions(+), 27 deletions(-)

diff --git a/src/g_demo.c b/src/g_demo.c
index a573e2b51..2e61ea89d 100644
--- a/src/g_demo.c
+++ b/src/g_demo.c
@@ -112,7 +112,7 @@ demoghost *ghosts = NULL;
 //
 
 #define DEMOVERSION 0x0009
-#define DEMOHEADER  "\xF0" "KartReplay" "\x0F"
+#define DEMOHEADER  "\xF0" "BlanReplay" "\x0F"
 
 #define DF_GHOST        0x01 // This demo contains ghost data too!
 #define DF_TIMEATTACK   0x02 // This demo is from Time Attack and contains its final completion time & best lap!
@@ -672,36 +672,44 @@ static headerstatus_e G_ReadDemoHeader(UINT8 *dp, demoheader_t *header)
 	header->raflags = 0;
 	header->empty = false;
 
-	if (memcmp(dp, DEMOHEADER, 12))
-		return HEADER_BADMAGIC;
 	dp += 12;
-
 	header->version = READUINT8(dp);
 	header->subversion = READUINT8(dp);
 	header->demoversion = READUINT16(dp);
 
-	switch (header->demoversion)
+	if (!memcmp(startdp, DEMOHEADER, 12)) // BlanReplay
 	{
-	case DEMOVERSION: // latest always supported
-		break;
+		switch (header->demoversion)
+		{
+		case DEMOVERSION: // latest always supported
+			break;
 
-	case 0x0008: // BlanKart (Pre-RA mod flags)
-		raflag = false;
-		break;
-
-	case 0x0001: // SRB2Kart 1.0.x (only staff ghosts supported)
-		oldkart = kart = true;
-		raflag = false;
-		break;
-
-	case 0x0002: // SRB2Kart 1.1+
-		kart = true;
-		raflag = false;
-		break;
-
-	default: // too old, cannot support.
-		return HEADER_BADVERSION;
+		default: // too old, cannot support.
+			return HEADER_BADVERSION;
+		}
 	}
+	else if (!memcmp(startdp, "\xF0" "KartReplay" "\x0F", 12))
+	{
+		raflag = false;
+		switch (header->demoversion)
+		{
+		case 0x0001: // SRB2Kart 1.0.x (only staff ghosts supported)
+			oldkart = kart = true;
+			break;
+
+		case 0x0002: // SRB2Kart 1.1+
+			kart = true;
+			break;
+
+		case 0x0008: // BlanKart (Pre-RA mod flags)
+			break;
+
+		default: // too old, cannot support.
+			return HEADER_BADVERSION;
+		}
+	}
+	else
+		return HEADER_BADMAGIC;
 
 	if (oldkart)
 		header->demotitle[0] = '\0';
@@ -947,6 +955,17 @@ static void G_FreeDemoHeader(demoheader_t *header)
 
 // and now, the rest of g_demo.c
 
+boolean G_CompatLevel(UINT16 level)
+{
+	if (demo.playback)
+	{
+		// Check gameplay differences for older ghosts
+		return (demo.version <= level);
+	}
+
+	return false;
+}
+
 static mobj_t oldmetal, oldghost[MAXPLAYERS];
 
 void G_SaveMetal(UINT8 **buffer)
@@ -1850,7 +1869,7 @@ void G_ConsGhostTic(INT32 playernum)
 		else
 			ghostext[playernum].desyncframes = 0;
 
-		if (demo.version != 0x0001 &&
+		if (!G_CompatLevel(0x0001) &&
 		   (players[playernum].itemtype != ghostext[playernum].kartitem
 		 || players[playernum].itemamount != ghostext[playernum].kartamount
 		 || players[playernum].bumper != ghostext[playernum].kartbumpers))
@@ -3745,7 +3764,7 @@ void G_DoPlayDemo(char *defdemoname)
 			LUA_ClearState();
 
 		// No modeattacking check, DF_LUAVARS won't be present here.
-		LUA_UnArchive(&demobuf, false, demo.version <= 0x0002);
+		LUA_UnArchive(&demobuf, false, G_CompatLevel(0x0002));
 	}
 
 	splitscreen = 0;
diff --git a/src/g_demo.h b/src/g_demo.h
index ef592664d..228822085 100644
--- a/src/g_demo.h
+++ b/src/g_demo.h
@@ -101,6 +101,7 @@ struct menudemo_t {
 	} standings[MAXPLAYERS];
 };
 
+boolean G_CompatLevel(UINT16 level);
 
 extern mobj_t *metalplayback;
 
diff --git a/src/p_tick.c b/src/p_tick.c
index 979c06930..76e90552e 100644
--- a/src/p_tick.c
+++ b/src/p_tick.c
@@ -721,7 +721,7 @@ void P_Ticker(boolean run)
 		}
 		if (demo.playback)
 		{
-			if (demo.version == 0x0001 && !multiplayer)
+			if (G_CompatLevel(0x0001) && !multiplayer)
 				G_ReadDemoTiccmd(&players[0].cmd, 0);
 			else
 			{
@@ -899,7 +899,7 @@ void P_Ticker(boolean run)
 		}
 		else if (demo.playback) // Use Ghost data for consistency checks.
 		{
-			if (!multiplayer && demo.version == 0x0001)
+			if (!multiplayer && G_CompatLevel(0x0001))
 				G_ConsGhostTic(0);
 			else
 				G_ConsAllGhostTics();