preventing growth outside of pixel block borders

src/main/java/eu/mhsl/minecraft/pixelblocks/Main.java

@@ -73,7 +73,8 @@ public final class Main extends JavaPlugin {
             new PreventPistonsListener(),
             new PreventEntityPlacementListener(),
             new DiscoverRecipesListener(),
-            new QuitWhileInPixelBlockListener()
+            new QuitWhileInPixelBlockListener(),
+            new PreventGrowthListener()
         };
 
         for (Listener listener : listeners) {

src/main/java/eu/mhsl/minecraft/pixelblocks/listeners/PreventGrowthListener.java

@@ -0,0 +1,23 @@
+package eu.mhsl.minecraft.pixelblocks.listeners;
+
+import eu.mhsl.minecraft.pixelblocks.pixelblock.PixelBlock;
+import eu.mhsl.minecraft.pixelblocks.pixelblock.PixelBlockWorld;
+import org.bukkit.Material;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.block.BlockFertilizeEvent;
+
+import java.util.Objects;
+
+public class PreventGrowthListener implements Listener {
+    @EventHandler
+    public void inBoneMeal(BlockFertilizeEvent event) {
+        if(!PixelBlockWorld.isPixelWorld(event.getBlock().getWorld())) return;
+        PixelBlock pixelBlock = PixelBlock.getPixelBlockFromBlockWorld(event.getBlock().getWorld());
+        Objects.requireNonNull(pixelBlock);
+
+        event.getBlocks().stream()
+            .filter(blockState -> !pixelBlock.getPixelWorld().allowPlacements(blockState.getBlock().getLocation()))
+            .forEach(blockState -> blockState.setType(Material.AIR));
+    }
+}