Fix svdemo_play from in-game and devmap from demo playback

Multiple issues fixed for seamless transitions:

Server lifecycle:
- SV_Shutdown before devmap in SVD_Play_f: drops old clients so
  spectator doesn't land in slot 0 (recorded player collision)
- SVD_IsStarting flag prevents cleanup hooks from destroying demo
  state during our own SV_Shutdown/SV_SpawnServer calls
- SV_SpawnServer stops demo playback on non-demo map changes
  via SVD_CleanupPlayback (no disconnect, just state cleanup)
- SVD_CleanupPlayback made non-static for use from sv_init.c

Cvar handling:
- Use Cvar_Set2 with force=qtrue for CVAR_ROM sv_demoplaying
- Set cvar AFTER SV_Shutdown (old game module gone) but BEFORE
  devmap (so new G_InitGame reads correct value)
- Set CS_SVDEMO configstring after devmap as backup for cgame

Game module:
- ClientBegin: set pm_type=PM_SPECTATOR after ClientSpawn (which
  memsets ps). ClientThink_real normally sets this but is disabled
  in demo mode.
- G_WriteSessionData: skip during demo playback so forced
  TEAM_SPECTATOR doesn't persist to next normal game
- ClientThink: return early in demo mode (no server-side movement)

Removed debug prints and unused SVD_GetPlayMaxClients.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

code/game/g_client.c

@@ -1013,7 +1013,6 @@ void ClientBegin( int clientNum ) {
 	client->pers.teamState.state = TEAM_BEGIN;
 
 	// demo playback: force all clients to spectator
-	// demo playback: force to spectator and update configstring
 	if ( g_svDemoPlaying.integer ) {
 		client->sess.sessionTeam = TEAM_SPECTATOR;
 		ClientUserinfoChanged( ent->client - level.clients );
@@ -1031,6 +1030,13 @@ void ClientBegin( int clientNum ) {
 	// locate ent at a spawn point
 	ClientSpawn( ent );
 
+	// demo playback: ClientThink_real (which normally sets pm_type
+	// for spectators) is disabled. Set it explicitly after spawn.
+	if ( g_svDemoPlaying.integer && client->sess.sessionTeam == TEAM_SPECTATOR ) {
+		client->ps.pm_type = PM_SPECTATOR;
+		client->ps.speed = 480;
+	}
+
 	if ( client->sess.sessionTeam != TEAM_SPECTATOR ) {
 		// send event
 		tent = G_TempEntity( ent->client->ps.origin, EV_PLAYER_TELEPORT_IN );

code/game/g_session.c

@@ -183,6 +183,12 @@ G_WriteSessionData
 void G_WriteSessionData( void ) {
 	int		i;
 
+	// don't persist demo spectator sessions — the forced TEAM_SPECTATOR
+	// would carry over to the next normal game
+	if ( g_svDemoPlaying.integer ) {
+		return;
+	}
+
 	trap_Cvar_Set( "session", va("%i", g_gametype.integer) );
 
 	for ( i = 0 ; i < level.maxclients ; i++ ) {

code/server/server.h

@@ -352,12 +352,14 @@ void		SVD_AutoRecord( void );
 void		SVD_CaptureServerCommand( const char *cmd );
 void		SVD_Play_f( void );
 void		SVD_StopPlay_f( void );
+void		SVD_CleanupPlayback( void );
 void		SVD_Stop_f( void );
 void		SVD_Pause_f( void );
 qboolean	SVD_PlaybackFrame( void );
 qboolean	SVD_IsRecording( void );
 qboolean	SVD_IsPlaying( void );
 qboolean	SVD_IsPaused( void );
+qboolean	SVD_IsStarting( void );
 qboolean	SVD_ShouldPause( void );
 
 //============================================================

code/server/sv_init.c

@@ -351,11 +351,17 @@ void SV_SpawnServer( char *server, qboolean killBots ) {
 	char		systemInfo[16384];
 	const char	*p;
 
-	// stop any active demo recording (one demo = one map)
+	// stop any active demo recording/playback (one demo = one map).
+	// SVD_IsStarting() returns true when SVD_Play_f is calling devmap
+	// internally — don't stop our own playback.
 	if ( SVD_IsRecording() ) {
 		Com_Printf( "Map change — stopping demo recording.\n" );
 		SVD_StopRecord_f();
 	}
+	if ( SVD_IsPlaying() && !SVD_IsStarting() ) {
+		Com_Printf( "Map change — stopping demo playback.\n" );
+		SVD_CleanupPlayback();
+	}
 
 	// shut down the existing game if it is running
 	SV_ShutdownGameProgs();
@@ -680,12 +686,13 @@ void SV_Shutdown( char *finalmsg ) {
 
 	Com_Printf( "----- Server Shutdown -----\n" );
 
-	// clean up any active demo recording/playback
+	// clean up any active demo recording/playback.
+	// skip if SVD_Play_f is calling SV_Shutdown internally.
 	if ( SVD_IsRecording() ) {
 		SVD_StopRecord_f();
 	}
-	if ( SVD_IsPlaying() ) {
-		SVD_StopPlay_f();
+	if ( SVD_IsPlaying() && !SVD_IsStarting() ) {
+		SVD_CleanupPlayback();
 	}
 
 	if ( svs.clients && !com_errorEntered ) {

code/server/sv_netdemo.c

@@ -11,6 +11,9 @@ snapshot pipeline delivers them to a spectator client.
 
 #include "server.h"
 
+// Cvar_Set2 not in public header but needed to force-set CVAR_ROM cvars
+extern cvar_t *Cvar_Set2( const char *var_name, const char *value, qboolean force );
+
 // ---------------------------------------------------------------
 //  File format
 // ---------------------------------------------------------------
@@ -97,12 +100,14 @@ typedef struct {
 	char			playMapName[SVDEMO_MAX_MAPNAME];
 	qboolean		endOfDemo;
 	qboolean		needConfigstrings;	// apply saved configstrings on first frame
+	qboolean		starting;			// SVD_Play_f is running devmap internally
 	qboolean		paused;
 	svdEntityState_t	playPrevEntities[MAX_GENTITIES];  // previous frame for delta read
 	svdPlayerState_t	playPrevPlayers[MAX_CLIENTS];     // previous frame player states
 } svDemo_t;
 
 static svDemo_t	demo;
+void SVD_CleanupPlayback( void );
 
 // ---------------------------------------------------------------
 //  Recording helpers
@@ -770,8 +775,8 @@ void SVD_Play_f( void ) {
 	char *s;
 	int len;
 
-	if ( demo.playing ) {
-		Com_Printf( "Already playing a server demo.\n" );
+	if ( demo.recording ) {
+		Com_Printf( "Stop recording first (svdemo_stop).\n" );
 		return;
 	}
 
@@ -781,6 +786,11 @@ void SVD_Play_f( void ) {
 		return;
 	}
 
+	// stop current playback if switching demos
+	if ( demo.playing ) {
+		SVD_CleanupPlayback();
+	}
+
 	Com_sprintf( name, sizeof(name), "svdemos/%s.svdm", s );
 
 	memset( &demo, 0, sizeof(demo) );
@@ -799,42 +809,50 @@ void SVD_Play_f( void ) {
 
 	demo.playing = qtrue;
 	demo.endOfDemo = qfalse;
+	demo.needConfigstrings = qtrue;
 
 	Com_Printf( "Playing server demo: map=%s maxclients=%d fps=%d\n",
 		demo.playMapName, demo.playMaxClients, demo.playFps );
 
-	// Signal demo mode BEFORE map load so the game module knows
-	// during ClientConnect/ClientBegin to force spectator team.
-	Cvar_Set( "sv_demoplaying", "1" );
+	// Shut down current server first so no clients carry over to
+	// reserved slots. SV_Shutdown triggers our cleanup hook, but
+	// demo.starting prevents it from clearing our state.
+	demo.starting = qtrue;
+	if ( com_sv_running->integer ) {
+		SV_Shutdown( "Demo playback\n" );
+	}
+
+	// Set demo cvar BEFORE devmap so G_InitGame can read it.
+	// The previous server is gone so no old game module to conflict with.
+	Cvar_Set2( "sv_demoplaying", "1", qtrue );
 
-	// Load the map with maxclients = MAX_CLIENTS to avoid entity slot collisions.
 	Cbuf_ExecuteText( EXEC_NOW, va("set sv_maxclients %d\n", MAX_CLIENTS) );
 	Cbuf_ExecuteText( EXEC_NOW, va("set sv_fps %d\n", demo.playFps) );
 	Cbuf_ExecuteText( EXEC_NOW, va("devmap %s\n", demo.playMapName) );
+	demo.starting = qfalse;
 
-	// Reserve recorded player slots so the connecting spectator
-	// doesn't land in slot 0 (which collides with recorded player 0).
-	// Mark as CS_ZOMBIE (non-free, won't be reused by SV_DirectConnect).
-	// Set rate and nextSnapshotTime so SV_SendClientMessages doesn't
-	// crash on division by zero or try to send them snapshots.
+	// Also set configstring directly for cgame (must be after devmap
+	// which creates the server and allocates configstrings)
+	if ( sv.state == SS_GAME ) {
+		SV_SetConfigstring( CS_SVDEMO, "1" );
+	}
+
+	// Reserve recorded player slots. Server is fresh (SV_Shutdown cleared
+	// old clients), local client hasn't connected yet.
 	{
 		int i;
 		for ( i = 0; i < demo.playMaxClients; i++ ) {
 			if ( svs.clients[i].state == CS_FREE ) {
 				svs.clients[i].state = CS_ZOMBIE;
 				svs.clients[i].rate = 10000;
-				svs.clients[i].nextSnapshotTime = 0x7FFFFFFF;  // never send
+				svs.clients[i].nextSnapshotTime = 0x7FFFFFFF;
 				svs.clients[i].lastPacketTime = svs.time;
 			}
 		}
 	}
-
-	// Configstrings will be applied on the first playback frame,
-	// after the map has fully loaded.
-	demo.needConfigstrings = qtrue;
 }
 
-static void SVD_CleanupPlayback( void ) {
+void SVD_CleanupPlayback( void ) {
 	int i;
 
 	if ( !demo.playing ) {
@@ -858,7 +876,7 @@ static void SVD_CleanupPlayback( void ) {
 	}
 
 	memset( &demo, 0, sizeof(demo) );
-	Cvar_Set( "sv_demoplaying", "0" );
+	Cvar_Set2( "sv_demoplaying", "0", qtrue );
 }
 
 void SVD_StopPlay_f( void ) {
@@ -957,6 +975,11 @@ qboolean SVD_IsPaused( void ) {
 	return demo.playing && demo.paused;
 }
 
+qboolean SVD_IsStarting( void ) {
+	return demo.starting;
+}
+
+
 /*
 Returns qtrue if demo playback should pause (no active spectators).
 Controlled by svdemo_pauseEmpty cvar.