Try harder to prevent desynch on player leaving.

There seem to be way too many ways that a player can leave, disconnect, drop, be
kicked, leave (again), be destroyed and/or be cleared.

During a game, NET_PLAYER_DROPPED must not be sent, since it is executed at a random
game time, and GAME_PLAYER_LEFT must be sent instead. Independently of whether the
player left, disconnected, dropped, was kicked, left, was destroyed, was eaten by a
grue, or was cleared.

lib/netplay/netplay.cpp

@@ -452,9 +452,12 @@ static void NETplayerClientDisconnect(uint32_t index)
 		NETlogEntry("Player has left unexpectedly.", SYNC_FLAG, index);
 		// Announce to the world. This was really icky, because we may have been calling the send
 		// function recursively. We really ought to have had a send queue, and now we finally do...
-		NETbeginEncode(NETbroadcastQueue(), NET_PLAYER_DROPPED);
-			NETuint32_t(&index);
-		NETend();
+		if (ingame.localJoiningInProgress)  // Only if game hasn't actually started yet.
+		{
+			NETbeginEncode(NETbroadcastQueue(), NET_PLAYER_DROPPED);
+				NETuint32_t(&index);
+			NETend();
+		}
 	}
 	else
 	{
@@ -485,7 +488,10 @@ static void NETplayerLeaving(UDWORD index)
 	}
 	sync_counter.left++;
 	MultiPlayerLeave(index);		// more cleanup
-	NET_DestroyPlayer(index);		// sets index player's array to false
+	if (ingame.localJoiningInProgress)  // Only if game hasn't actually started yet.
+	{
+		NET_DestroyPlayer(index);       // sets index player's array to false
+	}
 }
 
 /**
@@ -503,14 +509,17 @@ static void NETplayerDropped(UDWORD index)
 		return;
 	}
 
-	// Send message type specifically for dropped / disconnects
-	NETbeginEncode(NETbroadcastQueue(), NET_PLAYER_DROPPED);
-		NETuint32_t(&id);
-	NETend();
-	debug(LOG_INFO, "sending NET_PLAYER_DROPPED for player %d", id);
 	sync_counter.drops++;
-	NET_DestroyPlayer(id);		// just clears array
 	MultiPlayerLeave(id);			// more cleanup
+	if (ingame.localJoiningInProgress)  // Only if game hasn't actually started yet.
+	{
+		// Send message type specifically for dropped / disconnects
+		NETbeginEncode(NETbroadcastQueue(), NET_PLAYER_DROPPED);
+			NETuint32_t(&id);
+		NETend();
+		debug(LOG_INFO, "sending NET_PLAYER_DROPPED for player %d", id);
+		NET_DestroyPlayer(id);          // just clears array
+	}
 
 	NETsetPlayerConnectionStatus(CONNECTIONSTATUS_PLAYER_DROPPED, id);
 }

src/loop.cpp

@@ -426,7 +426,14 @@ static void gameStateUpdate()
 	// Can't dump isHumanPlayer, since it causes spurious desynch dumps when players leave.
 	// TODO isHumanPlayer should probably be synchronised, since the game state seems to depend on it, so there might also be a risk of real desynchs when players leave.
 	//syncDebug("map = \"%s\", humanPlayers = %d %d %d %d %d %d %d %d", game.map, isHumanPlayer(0), isHumanPlayer(1), isHumanPlayer(2), isHumanPlayer(3), isHumanPlayer(4), isHumanPlayer(5), isHumanPlayer(6), isHumanPlayer(7));
-	syncDebug("map = \"%s\", pseudorandom 32-bit integer = 0x%08X", game.map, gameRandU32());
+	syncDebug("map = \"%s\", pseudorandom 32-bit integer = 0x%08X, allocated = %d %d %d %d %d %d %d %d %d %d, position = %d %d %d %d %d %d %d %d %d %d", game.map, gameRandU32(),
+	          NetPlay.players[0].allocated, NetPlay.players[1].allocated, NetPlay.players[2].allocated, NetPlay.players[3].allocated, NetPlay.players[4].allocated, NetPlay.players[5].allocated, NetPlay.players[6].allocated, NetPlay.players[7].allocated, NetPlay.players[8].allocated, NetPlay.players[9].allocated,
+	          NetPlay.players[0].position, NetPlay.players[1].position, NetPlay.players[2].position, NetPlay.players[3].position, NetPlay.players[4].position, NetPlay.players[5].position, NetPlay.players[6].position, NetPlay.players[7].position, NetPlay.players[8].position, NetPlay.players[9].position
+	         );
+	for (unsigned n = 0; n < MAX_PLAYERS; ++n)
+	{
+		syncDebug("Player %d = \"%s\"", n, NetPlay.players[n].name);
+	}
 
 	// Actually send pending droid orders.
 	sendQueuedDroidInfo();

src/multijoin.cpp

@@ -239,14 +239,17 @@ void recvPlayerLeft(NETQUEUE queue)
 	NETbeginDecode(queue, GAME_PLAYER_LEFT);
 		NETuint32_t(&playerIndex);
 	NETend();
-	if (queue.index == NET_HOST_ONLY || queue.index == playerIndex)
+	if (queue.index != NET_HOST_ONLY && queue.index != playerIndex)
 	{
 		return;
 	}
 
 	turnOffMultiMsg(true);
 	clearPlayer(playerIndex, false);  // don't do it quietly
 	turnOffMultiMsg(false);
+	NetPlay.players[playerIndex].allocated = false;
+
+	debug(LOG_INFO, "** player %u has dropped, in-game!", playerIndex);
 }
 
 // ////////////////////////////////////////////////////////////////////////////