Add a harvestblock event, to allow mods to intercept and change the drops for blocks. Don't abuse this, or we'll have to take safety measures.

Fires for both silktouch and non-silktouch harvesting, and provides the player. Note, you may need to
change your break overrides to pass on the player for best results.

common/net/minecraftforge/event/world/BlockEvent.java

@@ -0,0 +1,46 @@
+package net.minecraftforge.event.world;
+
+import java.util.ArrayList;
+
+import net.minecraft.block.Block;
+import net.minecraft.entity.player.EntityPlayer;
+import net.minecraft.item.ItemStack;
+import net.minecraft.world.World;
+import net.minecraftforge.event.Event;
+
+public class BlockEvent extends Event {
+    public final int x;
+    public final int y;
+    public final int z;
+    public final World world;
+    public final Block block;
+    public final int blockMetadata;
+    public BlockEvent(int x, int y, int z, World world, Block block, int blockMetadata)
+    {
+        this.x = x;
+        this.y = y;
+        this.z = z;
+        this.world = world;
+        this.block = block;
+        this.blockMetadata = blockMetadata;
+    }
+    
+    public static class HarvestDropsEvent extends BlockEvent {
+        public final int fortuneLevel;
+        public final ArrayList<ItemStack> drops;
+        public final boolean isSilkTouching;
+        public float dropChance; // Change to e.g. 1.0f, if you manipulate the list and want to guarantee it always drops
+        public final EntityPlayer harvester; // May be null for non-player harvesting such as explosions or machines
+
+        public HarvestDropsEvent(int x, int y, int z, World world, Block block, int blockMetadata, int fortuneLevel, float dropChance, ArrayList<ItemStack> drops, EntityPlayer harvester, boolean isSilkTouching)
+        {
+            super(x, y, z, world, block, blockMetadata);
+            this.fortuneLevel = fortuneLevel;
+            this.dropChance = dropChance;
+            this.drops = drops;
+            this.isSilkTouching = isSilkTouching;
+            this.harvester = harvester;
+        }
+    }
+
+}

patches/minecraft/net/minecraft/block/Block.java.patch

@@ -36,7 +36,7 @@
  import net.minecraft.util.Icon;
  import net.minecraft.util.MovingObjectPosition;
  import net.minecraft.util.StatCollector;
-@@ -35,9 +44,19 @@
+@@ -35,9 +44,21 @@
  import net.minecraft.world.Explosion;
  import net.minecraft.world.IBlockAccess;
  import net.minecraft.world.World;
@@ -45,7 +45,9 @@
 +import net.minecraftforge.common.ForgeDirection;
 +import net.minecraftforge.common.ForgeHooks;
 +import net.minecraftforge.common.IPlantable;
++import net.minecraftforge.common.MinecraftForge;
 +import net.minecraftforge.common.RotationHelper;
++import net.minecraftforge.event.world.BlockEvent;
 +import cpw.mods.fml.relauncher.Side;
 +import cpw.mods.fml.relauncher.SideOnly;
  
@@ -56,7 +58,7 @@
      /**
       * used as foreach item, if item.tab = current tab, display it on the screen
       */
-@@ -460,9 +479,10 @@
+@@ -460,9 +481,10 @@
          return this.needsRandomTick;
      }
  
@@ -68,7 +70,7 @@
      }
  
      /**
-@@ -485,7 +505,7 @@
+@@ -485,7 +507,7 @@
       */
      public float getBlockBrightness(IBlockAccess par1IBlockAccess, int par2, int par3, int par4)
      {
@@ -77,7 +79,7 @@
      }
  
      @SideOnly(Side.CLIENT)
-@@ -495,7 +515,7 @@
+@@ -495,7 +517,7 @@
       */
      public int getMixedBrightnessForBlock(IBlockAccess par1IBlockAccess, int par2, int par3, int par4)
      {
@@ -86,7 +88,7 @@
      }
  
      @SideOnly(Side.CLIENT)
-@@ -648,7 +668,13 @@
+@@ -648,7 +670,13 @@
       * different metadata value, but before the new metadata value is set. Args: World, x, y, z, old block ID, old
       * metadata
       */
@@ -101,7 +103,7 @@
  
      /**
       * Returns the quantity of items to drop on block destruction.
-@@ -673,7 +699,7 @@
+@@ -673,7 +701,7 @@
      public float getPlayerRelativeBlockHardness(EntityPlayer par1EntityPlayer, World par2World, int par3, int par4, int par5)
      {
          float f = this.getBlockHardness(par2World, par3, par4, par5);
@@ -110,30 +112,41 @@
      }
  
      /**
-@@ -691,18 +717,13 @@
+@@ -681,7 +709,7 @@
+      */
+     public final void dropBlockAsItem(World par1World, int par2, int par3, int par4, int par5, int par6)
      {
-         if (!par1World.isRemote)
+-        this.dropBlockAsItemWithChance(par1World, par2, par3, par4, par5, 1.0F, par6);
++        dropBlockAsItem(par1World, par2, par3, par4, par5, par6, null);
+     }
+ 
+     /**
+@@ -689,23 +717,7 @@
+      */
+     public void dropBlockAsItemWithChance(World par1World, int par2, int par3, int par4, int par5, float par6, int par7)
      {
+-        if (!par1World.isRemote)
+-        {
 -            int j1 = this.quantityDroppedWithBonus(par7, par1World.rand);
 -
 -            for (int k1 = 0; k1 < j1; ++k1)
-+            ArrayList<ItemStack> items = getBlockDropped(par1World, par2, par3, par4, par5, par7);
+-            {
-+
+-                if (par1World.rand.nextFloat() <= par6)
-+            for (ItemStack item : items)
+-                {
-             {
-                 if (par1World.rand.nextFloat() <= par6)
-                 {
 -                    int l1 = this.idDropped(par5, par1World.rand, par7);
 -
 -                    if (l1 > 0)
 -                    {
 -                        this.dropBlockAsItem_do(par1World, par2, par3, par4, new ItemStack(l1, 1, this.damageDropped(par5)));
 -                    }
-+                    this.dropBlockAsItem_do(par1World, par2, par3, par4, item);
+-                }
+-            }
+-        }
++        dropBlockAsItemWithChance(par1World, par2, par3, par4, par5, par6, par7, null);
      }
-             }
+ 
-         }
+     /**
-@@ -935,7 +956,8 @@
+@@ -935,7 +947,8 @@
      public boolean canPlaceBlockAt(World par1World, int par2, int par3, int par4)
      {
          int l = par1World.getBlockId(par2, par3, par4);
@@ -143,7 +156,7 @@
      }
  
      /**
-@@ -1095,7 +1117,7 @@
+@@ -1095,28 +1108,38 @@
          par2EntityPlayer.addStat(StatList.mineBlockStatArray[this.blockID], 1);
          par2EntityPlayer.addExhaustion(0.025F);
  
@@ -151,11 +164,35 @@
 +        if (this.canSilkHarvest(par1World, par2EntityPlayer, par3, par4, par5, par6) && EnchantmentHelper.getSilkTouchModifier(par2EntityPlayer))
          {
              ItemStack itemstack = this.createStackedBlock(par6);
- 
+-
-@@ -1111,12 +1133,13 @@
+-            if (itemstack != null)
++            ArrayList<ItemStack> results = new ArrayList<ItemStack>();
++            if (itemstack!=null)
+             {
+-                this.dropBlockAsItem_do(par1World, par3, par4, par5, itemstack);
++                results.add(itemstack);
              }
++
++            MinecraftForge.EVENT_BUS.post(new BlockEvent.HarvestDropsEvent(par3, par4, par5, par1World, this, par6, 0, 1.0f, results, par2EntityPlayer, true));
++            if (itemstack != null && !results.isEmpty())
++            {
++                for (ItemStack is : results)
++                {
++                    this.dropBlockAsItem_do(par1World, par3, par4, par5, is);
++                }
++            }
          }
- 
+         else
+         {
+             int i1 = EnchantmentHelper.getFortuneModifier(par2EntityPlayer);
+-            this.dropBlockAsItem(par1World, par3, par4, par5, par6, i1);
+-        }
+-    }
+-
++            this.dropBlockAsItem(par1World, par3, par4, par5, par6, i1, par2EntityPlayer);
++        }
++    }
++
 +    private int silk_check_meta = -1; //Dirty hack to stop us from needing to special case the silk check hook.
      /**
       * Return true if a player with Silk Touch can harvest this block directly, and not its normal drops.
@@ -167,7 +204,7 @@
      }
  
      /**
-@@ -1457,4 +1480,979 @@
+@@ -1457,4 +1480,1000 @@
          canBlockGrass[0] = true;
          StatList.initBreakableStats();
      }
@@ -536,6 +573,27 @@
 +        return ret;
 +    }
 +
++    public final void dropBlockAsItem(World par1World, int par2, int par3, int par4, int par5, int par6, EntityPlayer player)
++    {
++        this.dropBlockAsItemWithChance(par1World, par2, par3, par4, par5, 1.0F, par6, player);
++    }
++
++    public void dropBlockAsItemWithChance(World world, int x, int y, int z, int metadata, float dropChance, int fortune, EntityPlayer player)
++    {
++        if (!world.isRemote)
++        {
++            ArrayList<ItemStack> items = getBlockDropped(world, x, y, z, metadata, fortune);
++            MinecraftForge.EVENT_BUS.post(new BlockEvent.HarvestDropsEvent(x, y, z, world, this, metadata, fortune, dropChance, items, player, false));
++            for (ItemStack item : items)
++            {
++                if (world.rand.nextFloat() <= dropChance)
++                {
++                    this.dropBlockAsItem_do(world, x, y, z, item);
++                }
++            }
++        }
++    }
++
 +    /**
 +     * Determines if a specified mob type can spawn on this block, returning false will
 +     * prevent any mob from spawning on the block.

patches/minecraft/net/minecraft/block/BlockCocoa.java.patch

@@ -1,6 +1,6 @@
 --- ../src_base/minecraft/net/minecraft/block/BlockCocoa.java
 +++ ../src_work/minecraft/net/minecraft/block/BlockCocoa.java
-@@ -2,6 +2,8 @@
+@@ -2,10 +2,13 @@
  
  import cpw.mods.fml.relauncher.Side;
  import cpw.mods.fml.relauncher.SideOnly;
@@ -9,12 +9,21 @@
  import java.util.Random;
  import net.minecraft.block.material.Material;
  import net.minecraft.client.renderer.texture.IconRegister;
-@@ -201,7 +203,14 @@
+ import net.minecraft.entity.EntityLivingBase;
++import net.minecraft.entity.player.EntityPlayer;
+ import net.minecraft.item.Item;
+ import net.minecraft.item.ItemStack;
+ import net.minecraft.util.AxisAlignedBB;
+@@ -199,9 +202,16 @@
+     /**
+      * Drops the block items with a specified chance of dropping the specified items
       */
-     public void dropBlockAsItemWithChance(World par1World, int par2, int par3, int par4, int par5, float par6, int par7)
+-    public void dropBlockAsItemWithChance(World par1World, int par2, int par3, int par4, int par5, float par6, int par7)
-     {
+-    {
 -        int j1 = func_72219_c(par5);
-+        super.dropBlockAsItemWithChance(par1World, par2, par3, par4, par5, par6, 0);
++    public void dropBlockAsItemWithChance(World par1World, int par2, int par3, int par4, int par5, float par6, int par7, EntityPlayer player)
++    {
++        super.dropBlockAsItemWithChance(par1World, par2, par3, par4, par5, par6, 0, player);
 +    }
 +
 +    @Override
@@ -25,7 +34,7 @@
          byte b0 = 1;
  
          if (j1 >= 2)
-@@ -211,8 +220,9 @@
+@@ -211,8 +221,9 @@
  
          for (int k1 = 0; k1 < b0; ++k1)
          {
@@ -37,7 +46,7 @@
      }
  
      @SideOnly(Side.CLIENT)
-@@ -248,4 +258,10 @@
+@@ -248,4 +259,10 @@
              this.iconArray[i] = par1IconRegister.registerIcon(this.getTextureName() + "_stage_" + i);
          }
      }

patches/minecraft/net/minecraft/block/BlockCrops.java.patch

@@ -1,6 +1,6 @@
 --- ../src_base/minecraft/net/minecraft/block/BlockCrops.java
 +++ ../src_work/minecraft/net/minecraft/block/BlockCrops.java
-@@ -2,6 +2,7 @@
+@@ -2,14 +2,17 @@
  
  import cpw.mods.fml.relauncher.Side;
  import cpw.mods.fml.relauncher.SideOnly;
@@ -8,7 +8,9 @@
  import java.util.Random;
  import net.minecraft.client.renderer.texture.IconRegister;
  import net.minecraft.creativetab.CreativeTabs;
-@@ -10,6 +11,7 @@
++import net.minecraft.entity.player.EntityPlayer;
+ import net.minecraft.item.Item;
+ import net.minecraft.item.ItemStack;
  import net.minecraft.util.Icon;
  import net.minecraft.util.MathHelper;
  import net.minecraft.world.World;
@@ -16,7 +18,7 @@
  
  public class BlockCrops extends BlockFlower
  {
-@@ -103,11 +105,11 @@
+@@ -103,11 +106,11 @@
                  int j3 = par1World.getBlockId(l2, par3 - 1, i3);
                  float f1 = 0.0F;
  
@@ -30,14 +32,20 @@
                      {
                          f1 = 3.0F;
                      }
-@@ -175,22 +177,25 @@
+@@ -172,25 +175,28 @@
-     public void dropBlockAsItemWithChance(World par1World, int par2, int par3, int par4, int par5, float par6, int par7)
+     /**
-     {
+      * Drops the block items with a specified chance of dropping the specified items
-         super.dropBlockAsItemWithChance(par1World, par2, par3, par4, par5, par6, 0);
+      */
+-    public void dropBlockAsItemWithChance(World par1World, int par2, int par3, int par4, int par5, float par6, int par7)
+-    {
+-        super.dropBlockAsItemWithChance(par1World, par2, par3, par4, par5, par6, 0);
 -
 -        if (!par1World.isRemote)
 -        {
 -            if (par5 >= 7)
++    public void dropBlockAsItemWithChance(World par1World, int par2, int par3, int par4, int par5, float par6, int par7, EntityPlayer player)
++    {
++        super.dropBlockAsItemWithChance(par1World, par2, par3, par4, par5, par6, 0, player);
 +    }
 +
 +    @Override 

patches/minecraft/net/minecraft/block/BlockMobSpawner.java.patch

@@ -0,0 +1,22 @@
+--- ../src_base/minecraft/net/minecraft/block/BlockMobSpawner.java
++++ ../src_work/minecraft/net/minecraft/block/BlockMobSpawner.java
+@@ -4,6 +4,7 @@
+ import cpw.mods.fml.relauncher.SideOnly;
+ import java.util.Random;
+ import net.minecraft.block.material.Material;
++import net.minecraft.entity.player.EntityPlayer;
+ import net.minecraft.tileentity.TileEntity;
+ import net.minecraft.tileentity.TileEntityMobSpawner;
+ import net.minecraft.world.World;
+@@ -42,9 +43,9 @@
+     /**
+      * Drops the block items with a specified chance of dropping the specified items
+      */
+-    public void dropBlockAsItemWithChance(World par1World, int par2, int par3, int par4, int par5, float par6, int par7)
++    public void dropBlockAsItemWithChance(World par1World, int par2, int par3, int par4, int par5, float par6, int par7, EntityPlayer player)
+     {
+-        super.dropBlockAsItemWithChance(par1World, par2, par3, par4, par5, par6, par7);
++        super.dropBlockAsItemWithChance(par1World, par2, par3, par4, par5, par6, par7, player);
+         int j1 = 15 + par1World.rand.nextInt(15) + par1World.rand.nextInt(15);
+         this.dropXpOnBlockBreak(par1World, par2, par3, par4, j1);
+     }

patches/minecraft/net/minecraft/block/BlockOre.java.patch

@@ -0,0 +1,22 @@
+--- ../src_base/minecraft/net/minecraft/block/BlockOre.java
++++ ../src_work/minecraft/net/minecraft/block/BlockOre.java
+@@ -3,6 +3,7 @@
+ import java.util.Random;
+ import net.minecraft.block.material.Material;
+ import net.minecraft.creativetab.CreativeTabs;
++import net.minecraft.entity.player.EntityPlayer;
+ import net.minecraft.item.Item;
+ import net.minecraft.util.MathHelper;
+ import net.minecraft.world.World;
+@@ -56,9 +57,9 @@
+     /**
+      * Drops the block items with a specified chance of dropping the specified items
+      */
+-    public void dropBlockAsItemWithChance(World par1World, int par2, int par3, int par4, int par5, float par6, int par7)
++    public void dropBlockAsItemWithChance(World par1World, int par2, int par3, int par4, int par5, float par6, int par7, EntityPlayer player)
+     {
+-        super.dropBlockAsItemWithChance(par1World, par2, par3, par4, par5, par6, par7);
++        super.dropBlockAsItemWithChance(par1World, par2, par3, par4, par5, par6, par7, player);
+ 
+         if (this.idDropped(par5, par1World.rand, par7) != this.blockID)
+         {