From 16a239a7a3fe88568efba55f267052c76faa7b64 Mon Sep 17 00:00:00 2001
From: Tom Anderson <tom@squeat.com>
Date: Wed, 19 Feb 2025 17:54:28 -0700
Subject: [PATCH] more fixes to auto-LT

the biggest problem was that it would use the local player's latencyTolerance
setting as the max value instead of what the server sent over.  This
could result in weird stuff happening when the LT started changing.
Also, a value of 0 or less is ignored in case somebody unknowingly
tries to force it to go faster than it can.
---
 src/game/CNetManager.cpp | 28 ++++++++++++++++++----------
 src/game/CNetManager.h   |  1 +
 src/gui/Preferences.h    |  2 +-
 3 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/src/game/CNetManager.cpp b/src/game/CNetManager.cpp
index 4b296bd7..4b4680ad 100644
--- a/src/game/CNetManager.cpp
+++ b/src/game/CNetManager.cpp
@@ -815,16 +815,18 @@ void CNetManager::AutoLatencyControl(FrameNumber frameNumber, Boolean didWait) {
 
                 // Usually maxFrameLatency is determined primarily by maxRoundTripLatency...
                 // but addOneLatency helps account for deficiencies in the calculation by measuring how often clients had to wait too long for packets to arrive
-                short maxFrameLatency = addOneLatency + itsGame->RoundTripToFrameLatency(maxRoundTripLatency);
+                short newFrameLatency = addOneLatency + itsGame->RoundTripToFrameLatency(maxRoundTripLatency);
 
-                // treat kLatencyToleranceTag as upper limit when in AutoLT mode
-                maxFrameLatency = std::min<short>(maxFrameLatency, gApplication->Get<double>(kLatencyToleranceTag)/itsGame->fpsScale);
+                // limit LT unless it's set to zero
+                if (maxAutoLatency > 0) {
+                    newFrameLatency = std::min<short>(newFrameLatency, maxAutoLatency);
+                }
 
                 DBG_Log("lt", "  fn=%d RTT=%d, Classic LT=%.2lf, add=%lf --> FL=%d\n",
                         frameNumber, maxRoundTripLatency,
-                        (maxRoundTripLatency) / (2.0*CLASSICFRAMETIME), addOneLatency*itsGame->fpsScale, maxFrameLatency);
+                        (maxRoundTripLatency) / (2.0*CLASSICFRAMETIME), addOneLatency*itsGame->fpsScale, newFrameLatency);
 
-                itsGame->SetFrameLatency(maxFrameLatency, 2, maxPlayer);
+                itsGame->SetFrameLatency(newFrameLatency, 2, maxPlayer);
             }
 
             ResetLatencyVote();
@@ -1298,8 +1300,17 @@ void CNetManager::DoConfig(short senderSlot) {
     if (PermissionQuery(kAllowLatencyBit, 0) || !(activePlayersDistribution & kdServerOnly) || senderSlot == 0) {
         // transmitting latencyTolerance in terms of frameLatency to keep it as a short value on transmission
         itsGame->SetFrameTime(theConfig->frameTime);
-        itsGame->SetFrameLatency(theConfig->frameLatency, -1);
-        SDL_Log("DoConfig LT = %lf\n", itsGame->latencyTolerance);
+        maxAutoLatency = theConfig->frameLatency;
+        short initFrameLatency = theConfig->frameLatency;
+        if (IsAutoLatencyEnabled()) {
+            // try setting initial FL from max local RTT value, maybe need the server to send this?  we'll see
+            initFrameLatency = itsGame->RoundTripToFrameLatency(itsCommManager->GetMaxRoundTrip(AlivePlayersDistribution()));
+            if (maxAutoLatency > 0) {
+                initFrameLatency = std::min<short>(initFrameLatency, maxAutoLatency);
+            }
+        }
+        itsGame->SetFrameLatency(initFrameLatency, -1);
+        SDL_Log("DoConfig LT = %lf, FL = %d\n", itsGame->latencyTolerance, maxAutoLatency);
         itsGame->SetSpawnOrder((SpawnOrder)theConfig->spawnOrder);
         latencyVoteFrame = itsGame->NextFrameForPeriod(AUTOLATENCYPERIOD);
     }
@@ -1310,9 +1321,6 @@ void CNetManager::UpdateLocalConfig() {
 
     config.frameLatency = gApplication
         ? gApplication->Get<float>(kLatencyToleranceTag) / itsGame->fpsScale : 0;
-    if (IsAutoLatencyEnabled()) {
-        config.frameLatency = std::min<short>(config.frameLatency, itsGame->initialFrameLatency);
-    }
     config.frameTime = itsGame->frameTime;
     config.spawnOrder = gApplication ? gApplication->Get<short>(kSpawnOrder) : ksHybrid;
     config.hullType = gApplication ? gApplication->Number(kHullTypeTag) : 0;
diff --git a/src/game/CNetManager.h b/src/game/CNetManager.h
index d5165ad1..63cc07f8 100644
--- a/src/game/CNetManager.h
+++ b/src/game/CNetManager.h
@@ -96,6 +96,7 @@ class CNetManager : public CDirectObject {
 
     short serverOptions;
     short loaderSlot;
+    short maxAutoLatency;  // max frame latency for auto-LT
 
     PlayerConfigRecord config {};
 
diff --git a/src/gui/Preferences.h b/src/gui/Preferences.h
index 7e0c8c94..f9c487de 100755
--- a/src/gui/Preferences.h
+++ b/src/gui/Preferences.h
@@ -105,7 +105,7 @@ static json defaultPrefs = {
     // {kJoystickModeTag, false},
     {kInvertYAxisTag, false},
     {kMouseSensitivityTag, 0},
-    {kLatencyToleranceTag, 1.0},
+    {kLatencyToleranceTag, 2.5},  // 2.5 = max for auto latency
     {kHullTypeTag, 0}, // 0 = light, 1 = medium, 2 = heavy
     {kServerOptionsTag, 129}, // 1 = allow load, 128 = auto latency
     {kDefaultUDPPort, 19567},