Pause demo playback when no spectators are watching

svdemo_pauseEmpty (default: 1) pauses frame processing when no
client is CS_ACTIVE during demo playback. Prevents the demo from
advancing with nobody watching. Time residual is cleared so the
demo resumes from where it paused when a spectator connects.

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

code/server/server.h

@@ -357,6 +357,7 @@ void		SVD_Stop_f( void );
 qboolean	SVD_PlaybackFrame( void );
 qboolean	SVD_IsRecording( void );
 qboolean	SVD_IsPlaying( void );
+qboolean	SVD_ShouldPause( void );
 
 //============================================================
 //

code/server/sv_init.c

@@ -624,6 +624,7 @@ void SV_Init (void) {
 	// server-side demo settings
 	Cvar_Get ("svdemo_autorecord", "0", CVAR_ARCHIVE);
 	Cvar_Get ("svdemo_compress", "1", CVAR_ARCHIVE);
+	Cvar_Get ("svdemo_pauseEmpty", "1", CVAR_ARCHIVE);
 
 	// initialize bot cvars so they are listed and can be set before loading the botlib
 	SV_BotInitCvars();

code/server/sv_main.c

@@ -828,6 +828,12 @@ void SV_Frame( int msec ) {
 
 	if (com_dedicated->integer) SV_BotFrame( svs.time );
 
+	// demo playback: pause if no spectators are watching
+	if ( SVD_IsPlaying() && SVD_ShouldPause() ) {
+		sv.timeResidual = 0;
+		return;
+	}
+
 	// run the game simulation in chunks
 	while ( sv.timeResidual >= frameMsec ) {
 		sv.timeResidual -= frameMsec;

code/server/sv_netdemo.c

@@ -1017,3 +1017,23 @@ qboolean SVD_IsPlaying( void ) {
 	return demo.playing;
 }
 
+/*
+Returns qtrue if demo playback should pause (no active spectators).
+Controlled by svdemo_pauseEmpty cvar.
+*/
+qboolean SVD_ShouldPause( void ) {
+	int i;
+
+	if ( !Cvar_VariableIntegerValue( "svdemo_pauseEmpty" ) ) {
+		return qfalse;
+	}
+
+	for ( i = 0; i < sv_maxclients->integer; i++ ) {
+		if ( svs.clients[i].state == CS_ACTIVE ) {
+			return qfalse;  // someone is watching
+		}
+	}
+
+	return qtrue;  // nobody connected, pause
+}
+