fix player entities desyncing on join sometimes

Author: p2r3

include/packets.h

@@ -21,6 +21,7 @@ int cs_chat (int client_fd);
 int cs_interact (int client_fd);
 int cs_playerInput (int client_fd);
 int cs_playerCommand (int client_fd);
+int cs_playerLoaded (int client_fd);
 
 // Clientbound packets
 int sc_statusResponse (int client_fd);

include/procedures.h

@@ -15,6 +15,7 @@ void resetPlayerData (PlayerData *player);
 int reservePlayerData (int client_fd, uint8_t *uuid, char* name);
 int getPlayerData (int client_fd, PlayerData **output);
 void handlePlayerDisconnect (int client_fd);
+void handlePlayerJoin (PlayerData* player);
 void disconnectClient (int *client_fd, int cause);
 int givePlayerItem (PlayerData *player, uint16_t item, uint8_t count);
 void spawnPlayer (PlayerData *player);

src/main.c

@@ -126,22 +126,13 @@ void handlePacket (int client_fd, int length, int packet_id, int state) {
         // Send full client spawn sequence
         spawnPlayer(player);
 
-        // Prepare join message for broadcast
-        uint8_t player_name_len = strlen(player->name);
-        strcpy((char *)recv_buffer, player->name);
-        strcpy((char *)recv_buffer + player_name_len, " joined the game");
-
-        // Register all existing players and spawn their entities, and broadcast
-        // information about the joining player to all existing players.
+        // Register all existing players and spawn their entities
         for (int i = 0; i < MAX_PLAYERS; i ++) {
           if (player_data[i].client_fd == -1) continue;
-          if (player_data[i].flags & 0x20 && player_data[i].client_fd != client_fd) continue;
+          // Note that this will also filter out the joining player
+          if (player_data[i].flags & 0x20) continue;
           sc_playerInfoUpdateAddPlayer(client_fd, player_data[i]);
-          sc_systemChat(player_data[i].client_fd, (char *)recv_buffer, 16 + player_name_len);
-          if (player_data[i].client_fd == client_fd) continue;
-          sc_playerInfoUpdateAddPlayer(player_data[i].client_fd, *player);
           sc_spawnEntityPlayer(client_fd, player_data[i]);
-          sc_spawnEntityPlayer(player_data[i].client_fd, *player);
         }
 
         // Send information about all other entities (mobs)
@@ -431,14 +422,9 @@ void handlePacket (int client_fd, int length, int packet_id, int state) {
       if (state == STATE_PLAY) cs_playerInput(client_fd);
       break;
 
-    case 0x2B: { // Player Loaded
-      PlayerData *player;
-      if (getPlayerData(client_fd, &player)) break;
-      // Clear "client loading" flag and fallback timer
-      player->flags &= ~0x20;
-      player->flagval_16 = 0;
+    case 0x2B:
+      if (state == STATE_PLAY) cs_playerLoaded(client_fd);
       break;
-    }
 
     case 0x34:
       if (state == STATE_PLAY) cs_setHeldItem(client_fd);

src/packets.c

@@ -1178,6 +1178,18 @@ int sc_pickupItem (int client_fd, int collected, int collector, uint8_t count) {
   return 0;
 }
 
+// C->S Player Loaded
+int cs_playerLoaded (int client_fd) {
+
+  PlayerData *player;
+  if (getPlayerData(client_fd, &player)) return 1;
+
+  // Redirect handling to player join procedure
+  handlePlayerJoin(player);
+
+  return 0;
+}
+
 // S->C Registry Data (multiple packets) and Update Tags (configuration, multiple packets)
 int sc_registries (int client_fd) {
 

src/procedures.c

@@ -146,6 +146,29 @@ void handlePlayerDisconnect (int client_fd) {
   }
 }
 
+// Marks a client as connected and broadcasts their data to other players
+void handlePlayerJoin (PlayerData* player) {
+
+  // Prepare join message for broadcast
+  uint8_t player_name_len = strlen(player->name);
+  strcpy((char *)recv_buffer, player->name);
+  strcpy((char *)recv_buffer + player_name_len, " joined the game");
+
+  // Inform other clients (and the joining client) of the player's name and entity
+  for (int i = 0; i < MAX_PLAYERS; i ++) {
+    sc_systemChat(player_data[i].client_fd, (char *)recv_buffer, 16 + player_name_len);
+    sc_playerInfoUpdateAddPlayer(player_data[i].client_fd, *player);
+    if (player_data[i].client_fd != player->client_fd) {
+      sc_spawnEntityPlayer(player_data[i].client_fd, *player);
+    }
+  }
+
+  // Clear "client loading" flag and fallback timer
+  player->flags &= ~0x20;
+  player->flagval_16 = 0;
+
+}
+
 void disconnectClient (int *client_fd, int cause) {
   if (*client_fd == -1) return;
   client_count --;
@@ -1414,8 +1437,7 @@ void handleServerTick (int64_t time_since_last_tick) {
       // If 3 seconds (60 vanilla ticks) have passed, assume player has loaded
       player->flagval_16 ++;
       if (player->flagval_16 > (uint16_t)(3 * TICKS_PER_SECOND)) {
-        player->flags &= ~0x20;
-        player->flagval_16 = 0;
+        handlePlayerJoin(player);
       } else continue;
     }
     // Reset player attack cooldown