added player_picks_up_item and better docs on events.

src/main/java/carpet/mixins/PlayerInventory_scarpetEventMixin.java

@@ -0,0 +1,41 @@
+package carpet.mixins;
+
+import net.minecraft.entity.player.PlayerEntity;
+import net.minecraft.entity.player.PlayerInventory;
+import net.minecraft.item.Item;
+import net.minecraft.item.ItemStack;
+import net.minecraft.server.network.ServerPlayerEntity;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+import static carpet.script.CarpetEventServer.Event.PLAYER_PICKS_UP_ITEM;
+
+@Mixin(PlayerInventory.class)
+public abstract class PlayerInventory_scarpetEventMixin
+{
+    @Shadow @Final public PlayerEntity player;
+
+    @Redirect(method = "insertStack(Lnet/minecraft/item/ItemStack;)Z", at = @At(
+            value = "INVOKE",
+            target = "Lnet/minecraft/entity/player/PlayerInventory;insertStack(ILnet/minecraft/item/ItemStack;)Z"
+    ))
+    private boolean onItemAcquired(PlayerInventory playerInventory, int slot, ItemStack stack)
+    {
+        if (!PLAYER_PICKS_UP_ITEM.isNeeded() || !(player instanceof ServerPlayerEntity))
+            return playerInventory.insertStack(-1, stack);
+        Item item = stack.getItem();
+        int count = stack.getCount();
+        boolean res = playerInventory.insertStack(-1, stack);
+        if (res)
+        {
+            ItemStack diffStack = new ItemStack(item, count - stack.getCount());
+            diffStack.setTag(stack.getTag());
+            PLAYER_PICKS_UP_ITEM.onItemAction((ServerPlayerEntity) player, null, diffStack);
+        }
+        return res;
+    }
+
+}