[1.15.x] Add horizon hook (#7528)

* Redirect getHorizonHeight to extension interface

* Add getHorizonHeight method

patches/minecraft/net/minecraft/client/world/ClientWorld.java.patch

@@ -69,3 +69,12 @@
        if (p_217384_1_ == this.field_73037_M.field_71439_g) {
           this.field_73037_M.func_147118_V().func_147682_a(new EntityTickableSound(p_217384_3_, p_217384_4_, p_217384_2_));
        }
+@@ -689,7 +706,7 @@
+    }
+ 
+    public double func_228331_m_() {
+-      return this.field_72986_A.func_76067_t() == WorldType.field_77138_c ? 0.0D : 63.0D;
++      return this.field_73011_w.getHorizonHeight();
+    }
+ 
+    public int func_228332_n_() {

src/main/java/net/minecraftforge/common/extensions/IForgeDimension.java

@@ -26,9 +26,8 @@ import net.minecraft.client.renderer.Vector3f;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.entity.player.ServerPlayerEntity;
 import net.minecraft.util.math.BlockPos;
-import net.minecraft.util.math.Vec3d;
 import net.minecraft.world.World;
-import net.minecraft.world.biome.Biome;
+import net.minecraft.world.WorldType;
 import net.minecraft.world.biome.Biomes;
 import net.minecraft.world.chunk.Chunk;
 import net.minecraft.world.dimension.Dimension;
@@ -239,6 +238,11 @@ public interface IForgeDimension
         return 63;
     }
 
+    default double getHorizonHeight()
+    {
+        return getWorld().getWorldInfo().getGenerator() == WorldType.FLAT ? 0.0D : 63.0D;
+    }
+
     /**
      * Determine if the cursor on the map should 'spin' when rendered, like it does for the player in the nether.
      *