From 730241b0858ff7118862440345c2d9b041ebd82a Mon Sep 17 00:00:00 2001
From: Jason Rohrer <jasonrohrer@fastmail.fm>
Date: Tue, 15 Aug 2023 11:36:10 -0400
Subject: [PATCH] Fixed to send an intermediary PU message whenver a MOVE chain
 takes the player more than 16 tiles away from where their last PU message
 occured.  This prevents out-of-date player status (like what they are
 holding/riding/wearing) from being presented to other players when they move
 back into range using a long move chain after being out of range, when their
 status changed while they were out of range.  Before, no PU message would be
 sent until the very end of a long move chain.  No more players zipping onto
 the screen and suddenly having their delivery truck appear around them.  No
 more players squeaking into view with a hand cart that they are no longer
 actually holding, and then suddenly seeing the hand cart disappear when they
 stop moving.  This still might be an issue on modded clients with a zoomed
 out view, because the threshold is only 16 tiles, but it seems to work fine
 in all cases on the official client.  Fixes #906

---
 server/server.cpp | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/server/server.cpp b/server/server.cpp
index 7a373eb5..0d1f1710 100644
--- a/server/server.cpp
+++ b/server/server.cpp
@@ -764,6 +764,25 @@ typedef struct LiveObject {
 
         char newMove;
         
+        // Absolute position used when generating last PU sent out about this
+        // player.
+        // If they are making a very long chained move, and their status
+        // isn't changing, they might not generate a PU message for a very
+        // long time.  This becomes a problem when them move out/in range
+        // of another player.  If their status (held item, etc) has changed
+        // while they are out of range, the other player won't see that
+        // status change when they come back in range (because the PU
+        // happened when they were out of range) and the long chained move
+        // isn't generating any PU messages now that they are back in range.
+        // Since modded clients might make very long MOVEs for each part
+        // of a MOVE chain (since they are zoomed out), we can't just count
+        // MOVE messages sent since the las PU message went out.
+        // We use this position to determine how far they've moved away
+        // from their last PU position, and send an intermediary PU if
+        // they get too far away
+        GridPos lastPlayerUpdateAbsolutePos;
+        
+
         // heat map that player carries around with them
         // every time they stop moving, it is updated to compute
         // their local temp
@@ -6307,6 +6326,9 @@ static UpdateRecord getUpdateRecord(
                                  inPlayer->posForced );
         r.absolutePosX = x;
         r.absolutePosY = y;
+
+        inPlayer->lastPlayerUpdateAbsolutePos.x = x;
+        inPlayer->lastPlayerUpdateAbsolutePos.y = y;
         }
     
     SimpleVector<char> clothingListBuffer;
@@ -8145,6 +8167,10 @@ int processLoggedInPlayer( char inAllowReconnect,
     newObject.deathLogged = false;
     newObject.newMove = false;
     
+    newObject.lastPlayerUpdateAbsolutePos.x = 0;
+    newObject.lastPlayerUpdateAbsolutePos.y = 0;
+    
+
     newObject.posForced = false;
     newObject.waitingForForceResponse = false;
     
@@ -15939,6 +15965,19 @@ int main() {
                         nextPlayer->xd = m.extraPos[ m.numExtraPos - 1].x;
                         nextPlayer->yd = m.extraPos[ m.numExtraPos - 1].y;
                         
+
+                        if( distance( nextPlayer->lastPlayerUpdateAbsolutePos,
+                                      m.extraPos[ m.numExtraPos - 1] ) 
+                            > 
+                            getMaxChunkDimension() / 2 ) {
+                            // they have moved a long way since their
+                            // last PU was sent
+                            // Send one now, mid-move
+                            
+                            playerIndicesToSendUpdatesAbout.push_back( i );
+                            }
+                        
+
                         
                         if( nextPlayer->xd == nextPlayer->xs &&
                             nextPlayer->yd == nextPlayer->ys ) {