From 490fcd9bde873a9e81b220079e32106c711b4ace Mon Sep 17 00:00:00 2001
From: serge_shubin <serge@generalarcade.com>
Date: Tue, 24 Mar 2026 03:59:44 +0800
Subject: [PATCH] Smooth unpause: reset client time delta and entity
 interpolation

On unpause, toggle SNAPFLAG_SERVERCOUNT and set SNAPFLAG_RESET_ENTITIES.
In CL_ParseSnapshot, detect SERVERCOUNT toggle and hard-reset
cl.serverTimeDelta instead of letting CL_AdjustTimeDelta slowly drift.
During pause, the delta drifted because snapshots had frozen serverTime
while cls.realtime advanced. Without the hard reset, it took 1-2 seconds
of choppy interpolation to re-sync.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 code/client/cl_parse.c   | 30 +++++++++++++++++++++---------
 code/server/sv_netdemo.c |  8 ++++++++
 2 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/code/client/cl_parse.c b/code/client/cl_parse.c
index 9de3588..6c55476 100644
--- a/code/client/cl_parse.c
+++ b/code/client/cl_parse.c
@@ -288,17 +288,29 @@ void CL_ParseSnapshot( msg_t *msg ) {
 		cl.snapshots[oldMessageNum & PACKET_MASK].valid = qfalse;
 	}
 
-	// copy to the current good spot
-	cl.snap = newSnap;
-	cl.snap.ping = 999;
-	// calculate ping time
-	for ( i = 0 ; i < PACKET_BACKUP ; i++ ) {
-		packetNum = ( clc.netchan.outgoingSequence - 1 - i ) & PACKET_MASK;
-		if ( cl.snap.ps.commandTime >= cl.outPackets[ packetNum ].p_serverTime ) {
-			cl.snap.ping = cls.realtime - cl.outPackets[ packetNum ].p_realtime;
-			break;
+	{
+		int oldSnapFlags = cl.snap.snapFlags;
+
+		// copy to the current good spot
+		cl.snap = newSnap;
+		cl.snap.ping = 999;
+		// calculate ping time
+		for ( i = 0 ; i < PACKET_BACKUP ; i++ ) {
+			packetNum = ( clc.netchan.outgoingSequence - 1 - i ) & PACKET_MASK;
+			if ( cl.snap.ps.commandTime >= cl.outPackets[ packetNum ].p_serverTime ) {
+				cl.snap.ping = cls.realtime - cl.outPackets[ packetNum ].p_realtime;
+				break;
+			}
+		}
+		// if server count changed (map_restart or demo unpause), force-reset
+		// the time delta so the client doesn't slowly drift back to sync
+		if ( ( oldSnapFlags ^ newSnap.snapFlags ) & SNAPFLAG_SERVERCOUNT ) {
+			cl.serverTimeDelta = cl.snap.serverTime - cls.realtime;
+			cl.oldServerTime = cl.snap.serverTime;
+			cl.serverTime = cl.snap.serverTime;
 		}
 	}
+
 	// save the frame off in the backup array for later delta comparisons
 	cl.snapshots[cl.snap.messageNum & PACKET_MASK] = cl.snap;
 
diff --git a/code/server/sv_netdemo.c b/code/server/sv_netdemo.c
index 1ef536f..143a856 100644
--- a/code/server/sv_netdemo.c
+++ b/code/server/sv_netdemo.c
@@ -994,6 +994,14 @@ void SVD_Pause_f( void ) {
 		return;
 	}
 	demo.paused = !demo.paused;
+	if ( !demo.paused ) {
+		// resuming — reset entities so client doesn't interpolate
+		// from frozen positions to post-pause positions.
+		// also toggle SERVERCOUNT to reset client snapshot timing
+		// (drifted during pause from identical serverTimes).
+		svs.snapFlagServerBit |= SNAPFLAG_RESET_ENTITIES;
+		svs.snapFlagServerBit ^= SNAPFLAG_SERVERCOUNT;
+	}
 	Com_Printf( "Demo playback %s.\n", demo.paused ? "paused" : "resumed" );
 }