NotEnoughItems/src/main/java/codechicken/nei/NEIChestGuiHandler.java

package codechicken.nei;

import codechicken.nei.api.INEIGuiAdapter;
import codechicken.nei.api.TaggedInventoryArea;
import java.util.Collections;
import java.util.List;
import net.minecraft.client.gui.inventory.GuiChest;
import net.minecraft.client.gui.inventory.GuiContainer;
import net.minecraft.inventory.ContainerChest;
import net.minecraft.item.ItemStack;

public class NEIChestGuiHandler extends INEIGuiAdapter {
    public int chestSize(GuiContainer gui) {
        return ((ContainerChest) gui.inventorySlots).getLowerChestInventory().getSizeInventory();
    }

    @Override
    public Iterable<Integer> getItemSpawnSlots(GuiContainer gui, ItemStack item) {
        return gui instanceof GuiChest ? NEIServerUtils.getRange(0, chestSize(gui)) : Collections.emptyList();
    }

    @Override
    public List<TaggedInventoryArea> getInventoryAreas(GuiContainer gui) {
        return gui instanceof GuiChest
                ? Collections.singletonList(new TaggedInventoryArea("Chest", 0, chestSize(gui), gui.inventorySlots))
                : null;
    }
}