From adebfb000c9b277e2f35c3406db2ccb9e120ed97 Mon Sep 17 00:00:00 2001
From: James R <justsomejames2@gmail.com>
Date: Fri, 1 Mar 2024 06:05:52 -0800
Subject: [PATCH] Replays: keep party in sync with current viewpoints

- More and more parts of the game rely on parties
- Parties are assumed to match the displayplayers
- This fixes A/B/C/D nametags
---
 src/d_netcmd.c                     | 11 +++++++++--
 src/g_demo.cpp                     | 31 ++++++++++++++++++++++++++++++
 src/g_demo.h                       |  2 ++
 src/g_game.c                       |  9 +++++++--
 src/menus/transient/pause-replay.c |  6 +++---
 5 files changed, 52 insertions(+), 7 deletions(-)

diff --git a/src/d_netcmd.c b/src/d_netcmd.c
index 5f68e5961..768c461de 100644
--- a/src/d_netcmd.c
+++ b/src/d_netcmd.c
@@ -1838,8 +1838,15 @@ static void Command_SetViews_f(void)
 		// Even if the splits go beyond the real number of
 		// splitscreen players, displayplayers was filled
 		// with duplicates of P1 (see Got_AddPlayer).
-		r_splitscreen = newsplits-1;
-		R_ExecuteSetViewSize();
+		if (demo.playback)
+		{
+			G_SyncDemoParty(consoleplayer, newsplits-1);
+		}
+		else
+		{
+			r_splitscreen = newsplits-1;
+			R_ExecuteSetViewSize();
+		}
 
 		// If promoting (outside of replays), make sure the
 		// camera is in the correct position.
diff --git a/src/g_demo.cpp b/src/g_demo.cpp
index 650aa4d53..c649320df 100644
--- a/src/g_demo.cpp
+++ b/src/g_demo.cpp
@@ -47,6 +47,7 @@
 #include "lua_hook.h"
 #include "md5.h" // demo checksums
 #include "p_saveg.h" // savebuffer_t
+#include "g_party.h"
 
 // SRB2Kart
 #include "d_netfil.h" // nameonly
@@ -4096,3 +4097,33 @@ boolean G_CheckDemoTitleEntry(void)
 
 	return true;
 }
+
+void G_SyncDemoParty(INT32 rem, INT32 newsplitscreen)
+{
+	int r_splitscreen_copy = r_splitscreen;
+	INT32 displayplayers_copy[MAXSPLITSCREENPLAYERS];
+	memcpy(displayplayers_copy, displayplayers, sizeof displayplayers);
+
+	// If we switch away from someone's view, that player
+	// should be removed from the party.
+	// However, it is valid to have the player on multiple
+	// viewports.
+
+	// Remove this player
+	G_LeaveParty(rem);
+
+	// And reset the rest of the party
+	for (int i = 0; i <= r_splitscreen_copy; ++i)
+		G_LeaveParty(displayplayers_copy[i]);
+
+	// Restore the party, without the removed player, and
+	// with the order matching displayplayers
+	for (int i = 0; i <= newsplitscreen; ++i)
+		G_JoinParty(consoleplayer, displayplayers_copy[i]);
+
+	// memcpy displayplayers back to preserve duplicates
+	// (G_JoinParty will not create duplicates itself)
+	r_splitscreen = newsplitscreen;
+	memcpy(displayplayers, displayplayers_copy, sizeof displayplayers);
+	R_ExecuteSetViewSize();
+}
diff --git a/src/g_demo.h b/src/g_demo.h
index 68d7bb6ed..4405589e1 100644
--- a/src/g_demo.h
+++ b/src/g_demo.h
@@ -243,6 +243,8 @@ typedef enum
 	DEMO_ATTRACT_CREDITS
 } demoAttractMode_t;
 
+void G_SyncDemoParty(INT32 rem, INT32 newsplitscreen);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif
diff --git a/src/g_game.c b/src/g_game.c
index 1ce8c1dbe..26a2c387a 100644
--- a/src/g_game.c
+++ b/src/g_game.c
@@ -1685,8 +1685,13 @@ void G_ResetView(UINT8 viewnum, INT32 playernum, boolean onlyactive)
 		}
 	}
 
-	if (viewnum == 1 && demo.playback)
-		consoleplayer = displayplayers[0];
+	if (demo.playback)
+	{
+		if (viewnum == 1)
+			consoleplayer = displayplayers[0];
+
+		G_SyncDemoParty(olddisplayplayer, r_splitscreen);
+	}
 
 	// change statusbar also if playing back demo
 	if (demo.quitafterplaying)
diff --git a/src/menus/transient/pause-replay.c b/src/menus/transient/pause-replay.c
index 138127e8e..9c0c777a7 100644
--- a/src/menus/transient/pause-replay.c
+++ b/src/menus/transient/pause-replay.c
@@ -9,6 +9,7 @@
 #include "../../p_local.h" // P_InitCameraCmd
 #include "../../d_main.h" // D_StartTitle
 #include "../../k_credits.h"
+#include "../../g_demo.h"
 
 static void M_PlaybackTick(void);
 
@@ -220,13 +221,12 @@ void M_PlaybackSetViews(INT32 choice)
 	{
 		if (choice == 0)
 		{
-			r_splitscreen--;
+			G_SyncDemoParty(displayplayers[r_splitscreen], r_splitscreen - 1);
 		}
 		else
 		{
-			r_splitscreen = 0;
+			G_SyncDemoParty(consoleplayer, 0);
 		}
-		R_ExecuteSetViewSize();
 	}
 }