Use 3 priorities.

src/Chunk.cpp

@@ -1742,7 +1742,7 @@ void cChunk::SetAreaBiome(int a_MinRelX, int a_MaxRelX, int a_MinRelZ, int a_Max
 	// Re-send the chunk to all clients:
 	for (cClientHandleList::iterator itr = m_LoadedByClient.begin(); itr != m_LoadedByClient.end(); ++itr)
 	{
-		m_World->ForceSendChunkTo(m_PosX, m_PosZ, cChunkSender::E_CHUNK_PRIORITY_HIGH, (*itr));
+		m_World->ForceSendChunkTo(m_PosX, m_PosZ, cChunkSender::E_CHUNK_PRIORITY_MEDIUM, (*itr));
 	}  // for itr - m_LoadedByClient[]
 }
 

src/ChunkSender.cpp

@@ -100,6 +100,7 @@ void cChunkSender::QueueSendChunkTo(int a_ChunkX, int a_ChunkZ, eChunkPriority a
 		cCSLock Lock(m_CS);
 		if (
 			std::find(m_SendChunksLowPriority.begin(), m_SendChunksLowPriority.end(), Chunk) != m_SendChunksLowPriority.end() ||
+			std::find(m_SendChunksMediumPriority.begin(), m_SendChunksMediumPriority.end(), Chunk) != m_SendChunksMediumPriority.end() ||
 			std::find(m_SendChunksHighPriority.begin(), m_SendChunksHighPriority.end(), Chunk) != m_SendChunksHighPriority.end()
 		)
 		{
@@ -107,10 +108,27 @@ void cChunkSender::QueueSendChunkTo(int a_ChunkX, int a_ChunkZ, eChunkPriority a
 			return;
 		}
 
-		if (a_Priority == E_CHUNK_PRIORITY_LOW) {
+		switch (a_Priority)
+		{
+			case E_CHUNK_PRIORITY_LOW:
+			{
 				m_SendChunksLowPriority.push_back(Chunk);
-		} else if (a_Priority == E_CHUNK_PRIORITY_HIGH) {
+				break;
+			}
+			case E_CHUNK_PRIORITY_MEDIUM:
+			{
+				m_SendChunksMediumPriority.push_back(Chunk);
+				break;
+			}
+			case E_CHUNK_PRIORITY_HIGH:
+			{
 				m_SendChunksHighPriority.push_back(Chunk);
+				break;
+			}
+			default:
+			{
+				ASSERT(!"Unknown chunk priority!");
+			}
 		}
 	}
 	m_evtQueue.Set();
@@ -133,6 +151,15 @@ void cChunkSender::RemoveClient(cClientHandle * a_Client)
 			}
 			++itr;
 		}  // for itr - m_SendChunksLowPriority[]
+		for (sSendChunkList::iterator itr = m_SendChunksMediumPriority.begin(); itr != m_SendChunksMediumPriority.end();)
+		{
+			if (itr->m_Client == a_Client)
+			{
+				itr = m_SendChunksMediumPriority.erase(itr);
+				continue;
+			}
+			++itr;
+		}  // for itr - m_SendChunksMediumPriority[]
 		for (sSendChunkList::iterator itr = m_SendChunksHighPriority.begin(); itr != m_SendChunksHighPriority.end();)
 		{
 			if (itr->m_Client == a_Client)
@@ -191,6 +218,15 @@ void cChunkSender::Execute(void)
 			
 			SendChunk(Coords.m_ChunkX, Coords.m_ChunkZ, nullptr);
 		}
+		else if (!m_SendChunksMediumPriority.empty())
+		{
+			// Take one from the queue:
+			sSendChunk Chunk(m_SendChunksMediumPriority.front());
+			m_SendChunksMediumPriority.pop_front();
+			Lock.Unlock();
+
+			SendChunk(Chunk.m_ChunkX, Chunk.m_ChunkZ, Chunk.m_Client);
+		}
 		else
 		{
 			// Take one from the queue:

src/ChunkSender.h

@@ -79,7 +79,8 @@ public:
 	enum eChunkPriority
 	{
 		E_CHUNK_PRIORITY_HIGH   = 0,
-		E_CHUNK_PRIORITY_LOW    = 1,
+		E_CHUNK_PRIORITY_MEDIUM = 1,
+		E_CHUNK_PRIORITY_LOW    = 2,
 	};
 	
 	bool Start(cWorld * a_World);
@@ -143,6 +144,7 @@ protected:
 	cCriticalSection  m_CS;
 	cChunkCoordsList  m_ChunksReady;
 	sSendChunkList    m_SendChunksLowPriority;
+	sSendChunkList    m_SendChunksMediumPriority;
 	sSendChunkList    m_SendChunksHighPriority;
 	cEvent            m_evtQueue;  // Set when anything is added to m_ChunksReady
 	cEvent            m_evtRemoved;  // Set when removed clients are safe to be deleted

src/ClientHandle.cpp

@@ -463,7 +463,7 @@ bool cClientHandle::StreamNextChunk(void)
 
 				// Unloaded chunk found -> Send it to the client.
 				Lock.Unlock();
-				StreamChunk(ChunkX, ChunkZ, cChunkSender::E_CHUNK_PRIORITY_HIGH);
+				StreamChunk(ChunkX, ChunkZ, ((Range <= 2) ? cChunkSender::E_CHUNK_PRIORITY_HIGH : cChunkSender::E_CHUNK_PRIORITY_MEDIUM));
 				return false;
 			}
 		}