Implement addBiome, hopefully. Pushes biome list to the WorldType field. Sorry Bioxx.

fml/patches/minecraft_server/net/minecraft/server/MinecraftServer.java.patch

@@ -25,21 +25,19 @@
          this.field_6033_f = new ServerConfigurationManager(this);
          this.field_6028_k[0] = new EntityTracker(this, 0);
          this.field_6028_k[1] = new EntityTracker(this, -1);
-@@ -444,6 +448,8 @@
+@@ -370,6 +374,7 @@
+                         var7 = 0L;
+                     }
  
-     private void func_6018_h()
-     {
-+        FMLServerHandler.instance().onPreTick();
-+        
-         long var1 = System.nanoTime();
-         ArrayList var3 = new ArrayList();
-         Iterator var4 = field_6037_b.keySet().iterator();
-@@ -533,6 +539,8 @@
-         this.field_48076_G = Packet.field_48101_l;
-         this.field_48082_x[this.field_9014_h % 100] = Packet.field_48102_m - this.field_48077_H;
-         this.field_48077_H = Packet.field_48102_m;
-+
-+        FMLServerHandler.instance().onPostTick();
-     }
++                    FMLServerHandler.instance().onPreTick();
+                     var3 += var7;
+                     var1 = var5;
  
-     public void func_6010_a(String p_6010_1_, ICommandListener p_6010_2_)
+@@ -386,6 +391,7 @@
+                             this.func_6018_h();
+                         }
+                     }
++                    FMLServerHandler.instance().onPostTick();
+                 }
+             }
+             else

fml/patches/minecraft_server/net/minecraft/src/GenLayerBiome.java.patch

@@ -0,0 +1,17 @@
+--- ../src-base/minecraft_server/net/minecraft/src/GenLayerBiome.java	0000-00-00 00:00:00.000000000 -0000
++++ ../src-work/minecraft_server/net/minecraft/src/GenLayerBiome.java	0000-00-00 00:00:00.000000000 -0000
+@@ -7,13 +7,8 @@
+     public GenLayerBiome(long p_i1078_1_, GenLayer p_i1078_3_, WorldType p_i1078_4_)
+     {
+         super(p_i1078_1_);
+-        this.field_35029_b = new BiomeGenBase[] {BiomeGenBase.field_4293_h, BiomeGenBase.field_4297_d, BiomeGenBase.field_35518_e, BiomeGenBase.field_4299_b, BiomeGenBase.field_35520_c, BiomeGenBase.field_4294_g, BiomeGenBase.field_48443_w};
++        this.field_35029_b = p_i1078_4_.getBiomesForWorldType();
+         this.field_35023_a = p_i1078_3_;
+-
+-        if (p_i1078_4_ == WorldType.field_48456_d)
+-        {
+-            this.field_35029_b = new BiomeGenBase[] {BiomeGenBase.field_4293_h, BiomeGenBase.field_4297_d, BiomeGenBase.field_35518_e, BiomeGenBase.field_4299_b, BiomeGenBase.field_35520_c, BiomeGenBase.field_4294_g};
+-        }
+     }
+ 
+     public int[] func_35018_a(int p_35018_1_, int p_35018_2_, int p_35018_3_, int p_35018_4_)

fml/patches/minecraft_server/net/minecraft/src/WorldType.java.patch

@@ -0,0 +1,47 @@
+--- ../src-base/minecraft_server/net/minecraft/src/WorldType.java	0000-00-00 00:00:00.000000000 -0000
++++ ../src-work/minecraft_server/net/minecraft/src/WorldType.java	0000-00-00 00:00:00.000000000 -0000
+@@ -1,5 +1,8 @@
+ package net.minecraft.src;
+ 
++import java.util.Arrays;
++import java.util.List;
++
+ public class WorldType
+ {
+     public static final WorldType[] field_48459_a = new WorldType[16];
+@@ -11,9 +14,20 @@
+     private boolean field_48455_g;
+     private boolean field_48460_h;
+ 
++    private BiomeGenBase[] biomesForWorldType;
++    
+     private WorldType(int p_i1025_1_, String p_i1025_2_)
+     {
+         this(p_i1025_1_, p_i1025_2_, 0);
++        switch (p_i1025_1_) {
++            case 8:
++                biomesForWorldType = new BiomeGenBase[] { BiomeGenBase.field_4293_h, BiomeGenBase.field_4297_d, BiomeGenBase.field_35518_e,
++                        BiomeGenBase.field_4299_b, BiomeGenBase.field_35520_c, BiomeGenBase.field_4294_g };
++                break;
++            default:
++                biomesForWorldType = new BiomeGenBase[] { BiomeGenBase.field_4293_h, BiomeGenBase.field_4297_d, BiomeGenBase.field_35518_e,
++                        BiomeGenBase.field_4299_b, BiomeGenBase.field_35520_c, BiomeGenBase.field_4294_g, BiomeGenBase.field_48443_w };
++    }            
+     }
+ 
+     private WorldType(int p_i1026_1_, String p_i1026_2_, int p_i1026_3_)
+@@ -68,4 +82,14 @@
+ 
+         return null;
+     }
++    
++    public BiomeGenBase[] getBiomesForWorldType() {
++        return biomesForWorldType;
++    }
++    
++    public void addNewBiome(BiomeGenBase biome) {
++        List<BiomeGenBase> biomes=Arrays.asList(biomesForWorldType);
++        biomes.add(biome);
++        biomesForWorldType=biomes.toArray(new BiomeGenBase[0]);
++    }
+ }

fml/server/cpw/mods/fml/server/FMLServerHandler.java

@@ -36,6 +36,7 @@ import net.minecraft.src.Packet250CustomPayload;
 import net.minecraft.src.Packet3Chat;
 import net.minecraft.src.ServerRegistry;
 import net.minecraft.src.World;
+import net.minecraft.src.WorldType;
 import cpw.mods.fml.common.FMLCommonHandler;
 import cpw.mods.fml.common.IFMLSidedHandler;
 import cpw.mods.fml.common.Loader;
@@ -537,4 +538,12 @@ public class FMLServerHandler implements IFMLSidedHandler
             }
         }
     }
+
+    /**
+     * @param biome
+     */
+    public void addBiomeToDefaultWorldGenerator(BiomeGenBase biome)
+    {
+        WorldType.field_48457_b.addNewBiome(biome);
+    }
 }

fml/server/net/minecraft/src/ModLoader.java

@@ -33,6 +33,7 @@ public class ModLoader
      */
     public static void addAchievementDesc(Achievement achievement, String name, String description)
     {
+        
     }
 
     /**
@@ -62,13 +63,13 @@ public class ModLoader
     }
 
     /**
-     * This method does not work. Creation of a BiomeGenBase is sufficient to populate this array. Using this method will likely corrupt worlds.
+     * This method adds the supplied biome to the set of candidate biomes for the default world generator type.
      *
      * @param biome
      */
-    @Deprecated
     public static void addBiome(BiomeGenBase biome)
     {
+        FMLServerHandler.instance().addBiomeToDefaultWorldGenerator(biome);
     }
 
     /**