just to change from disabling spawn chunks to control over its size. Removes disableSpawnChunks, adds spawnChunksSize. Fixes #192

src/main/java/carpet/mixins/ChunkTicketManager_scarpetMixin.java

@@ -1,15 +1,23 @@
 package carpet.mixins;
 
+import carpet.fakes.ChunkTicketManagerInterface;
 import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
 import net.minecraft.server.world.ChunkTicket;
 import net.minecraft.server.world.ChunkTicketManager;
 import net.minecraft.util.SortedArraySet;
+import org.spongepowered.asm.mixin.Final;
 import org.spongepowered.asm.mixin.Mixin;
-import org.spongepowered.asm.mixin.gen.Accessor;
+import org.spongepowered.asm.mixin.Shadow;
 
 @Mixin(ChunkTicketManager.class)
-public interface ChunkTicketManager_scarpetMixin
+public abstract class ChunkTicketManager_scarpetMixin implements ChunkTicketManagerInterface
 {
-    @Accessor
-    Long2ObjectOpenHashMap<SortedArraySet<ChunkTicket<?>>>  getTicketsByPosition();
+    @Shadow @Final private Long2ObjectOpenHashMap<SortedArraySet<ChunkTicket<?>>> ticketsByPosition;
+
+    @Override
+    public Long2ObjectOpenHashMap<SortedArraySet<ChunkTicket<?>>>  getTicketsByPosition()
+    {
+        return ticketsByPosition;
+    }
+
 }

src/main/java/carpet/mixins/ChunkTicketManager_spawnChunksMixin.java

@@ -0,0 +1,60 @@
+package carpet.mixins;
+
+import carpet.fakes.ChunkTicketManagerInterface;
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
+import net.minecraft.server.world.ChunkTicket;
+import net.minecraft.server.world.ChunkTicketManager;
+import net.minecraft.server.world.ChunkTicketType;
+import net.minecraft.util.SortedArraySet;
+import net.minecraft.util.Unit;
+import net.minecraft.util.math.ChunkPos;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+
+import java.util.Iterator;
+
+@Mixin(ChunkTicketManager.class)
+public abstract class ChunkTicketManager_spawnChunksMixin implements ChunkTicketManagerInterface
+{
+
+    @Shadow protected abstract SortedArraySet<ChunkTicket<?>> getTicketSet(long position);
+
+    @Shadow @Final private Long2ObjectOpenHashMap<SortedArraySet<ChunkTicket<?>>> ticketsByPosition;
+
+    @Shadow public abstract <T> void removeTicket(ChunkTicketType<T> type, ChunkPos pos, int radius, T argument);
+
+    @Shadow protected abstract void removeTicket(long pos, ChunkTicket<?> ticket);
+
+    @Shadow public abstract <T> void addTicket(ChunkTicketType<T> type, ChunkPos pos, int radius, T argument);
+
+    @Override
+    public void changeSpawnChunks(ChunkPos chunkPos,  int distance)
+    {
+        long pos = chunkPos.toLong();
+        SortedArraySet<ChunkTicket<?>> set = ticketsByPosition.get(pos);
+        ChunkTicket existingTicket = null;
+        if (set != null)
+        {
+            Iterator<ChunkTicket<?>> iter = set.iterator();
+            while(iter.hasNext())
+            {
+                ChunkTicket ticket = iter.next();
+                if (ticket.getType() == ChunkTicketType.START)
+                {
+                    existingTicket = ticket;
+                    iter.remove();
+                }
+            }
+            set.add(existingTicket);
+        }
+        // the reason we are removing the ticket this way is that there are sideeffects of removal
+        if (existingTicket != null)
+        {
+            removeTicket(pos, existingTicket);
+        }
+        // set optionally new spawn ticket
+        if (distance > 0)
+            addTicket(ChunkTicketType.START, chunkPos, distance, Unit.INSTANCE);
+    }
+}

src/main/java/carpet/mixins/MinecraftServer_coreMixin.java

@@ -1,8 +1,10 @@
 package carpet.mixins;
 
 import carpet.CarpetServer;
+import carpet.CarpetSettings;
 import com.google.gson.JsonElement;
 import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.WorldGenerationProgressListener;
 import net.minecraft.world.level.LevelGeneratorType;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.injection.At;
@@ -41,4 +43,11 @@ public abstract class MinecraftServer_coreMixin
     {
         CarpetServer.onServerClosed((MinecraftServer) (Object) this);
     }
+
+    @Inject(method = "prepareStartRegion", at = @At("RETURN"))
+    private void afterSpawnCreated(WorldGenerationProgressListener worldGenerationProgressListener, CallbackInfo ci)
+    {
+        if (CarpetSettings.spawnChunksSize != 11)
+            CarpetSettings.ChangeSpawnChunksValidator.changeSpawnSize(CarpetSettings.spawnChunksSize);
+    }
 }

src/main/java/carpet/mixins/ServerChunkManagerMixin.java

@@ -1,8 +1,10 @@
 package carpet.mixins;
 
+import carpet.fakes.ServerChunkManagerInterface;
 import carpet.utils.SpawnReporter;
 import it.unimi.dsi.fastutil.objects.Object2IntMap;
 import net.minecraft.entity.EntityCategory;
+import net.minecraft.server.world.ChunkTicketManager;
 import net.minecraft.server.world.ServerChunkManager;
 import net.minecraft.server.world.ServerWorld;
 import net.minecraft.util.math.BlockPos;
@@ -24,12 +26,20 @@ import java.util.HashMap;
 import java.util.HashSet;
 
 @Mixin(ServerChunkManager.class)
-public abstract class ServerChunkManagerMixin
+public abstract class ServerChunkManagerMixin implements ServerChunkManagerInterface
 {
     @Shadow @Final private ServerWorld world;
 
     @Shadow @Final private static int CHUNKS_ELIGIBLE_FOR_SPAWNING;
 
+    @Shadow @Final private ChunkTicketManager ticketManager;
+
+    @Override // shared between scarpet and spawnChunks setting
+    public ChunkTicketManager getTicketManager()
+    {
+        return ticketManager;
+    }
+
     @Inject(
             method = "tickChunks",
             locals = LocalCapture.CAPTURE_FAILHARD,

src/main/java/carpet/mixins/ServerChunkManager_scarpetMixin.java

@@ -1,13 +0,0 @@
-package carpet.mixins;
-
-import net.minecraft.server.world.ChunkTicketManager;
-import net.minecraft.server.world.ServerChunkManager;
-import org.spongepowered.asm.mixin.Mixin;
-import org.spongepowered.asm.mixin.gen.Accessor;
-
-@Mixin(ServerChunkManager.class)
-public interface ServerChunkManager_scarpetMixin
-{
-    @Accessor
-    ChunkTicketManager getTicketManager();
-}

src/main/java/carpet/mixins/ServerWorld_spawnChunksMixin.java

@@ -0,0 +1,17 @@
+package carpet.mixins;
+
+import carpet.CarpetSettings;
+import net.minecraft.server.world.ServerWorld;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.Constant;
+import org.spongepowered.asm.mixin.injection.ModifyConstant;
+
+@Mixin(ServerWorld.class)
+public class ServerWorld_spawnChunksMixin
+{
+    @ModifyConstant(method = "setSpawnPos", constant = @Constant(intValue = 11), expect = 2)
+    private int pushLimit(int original)
+    {
+        return CarpetSettings.spawnChunksSize;
+    }
+}