Add Drag-And-Drop support for digital tank (#1333)

* Add Drag-And-Drop support for digital tank

* lockedFluidName is null in old save

12 files changed, 237 insertions, 84 deletions

diff --git a/src/main/java/gregtech/api/gui/GT_Container_BasicMachine.java b/src/main/java/gregtech/api/gui/GT_Container_BasicMachine.java
index fc0b3270d2..590d406ca4 100644
--- a/src/main/java/gregtech/api/gui/GT_Container_BasicMachine.java
+++ b/src/main/java/gregtech/api/gui/GT_Container_BasicMachine.java
@@ -4,6 +4,7 @@ import static gregtech.api.metatileentity.implementations.GT_MetaTileEntity_Basi
 
 import cpw.mods.fml.relauncher.Side;
 import cpw.mods.fml.relauncher.SideOnly;
+import gregtech.api.interfaces.IFluidAccess;
 import gregtech.api.interfaces.tileentity.IGregTechTileEntity;
 import gregtech.api.metatileentity.implementations.GT_MetaTileEntity_BasicMachine;
 import gregtech.api.metatileentity.implementations.GT_MetaTileEntity_BasicTank;
@@ -221,7 +222,7 @@ public class GT_Container_BasicMachine extends GT_Container_BasicTank {
                         tTank.setFillableStack(GT_Utility.getFluidFromDisplayStack(tTank.getStackInSlot(2)));
                     }
                     GT_MetaTileEntity_BasicTank tTank = (GT_MetaTileEntity_BasicTank) mTileEntity.getMetaTileEntity();
-                    BasicTankFluidAccess tFillableAccess = BasicTankFluidAccess.from(tTank, true);
+                    IFluidAccess tFillableAccess = constructFluidAccess(tTank, true);
                     GT_Recipe_Map recipes = machine.getRecipeList();
                     // If the  machine has recipes but no fluid inputs, disallow filling this slot with fluids.
                     ItemStack tToken = handleFluidSlotClick(
diff --git a/src/main/java/gregtech/api/gui/GT_Container_BasicTank.java b/src/main/java/gregtech/api/gui/GT_Container_BasicTank.java
index 8d8d018cdc..27138511f0 100644
--- a/src/main/java/gregtech/api/gui/GT_Container_BasicTank.java
+++ b/src/main/java/gregtech/api/gui/GT_Container_BasicTank.java
@@ -54,7 +54,7 @@ public class GT_Container_BasicTank extends GT_ContainerMetaTile_Machine {
                 tTank.setDrainableStack(GT_Utility.getFluidFromDisplayStack(tTank.getStackInSlot(2)));
             }
             GT_MetaTileEntity_BasicTank tTank = (GT_MetaTileEntity_BasicTank) mTileEntity.getMetaTileEntity();
-            BasicTankFluidAccess tDrainableAccess = BasicTankFluidAccess.from(tTank, false);
+            IFluidAccess tDrainableAccess = constructFluidAccess(tTank, false);
             return handleFluidSlotClick(
                     tDrainableAccess, aPlayer, aMouseclick == 0, true, !tTank.isDrainableStackSeparate());
         }
@@ -106,9 +106,13 @@ public class GT_Container_BasicTank extends GT_ContainerMetaTile_Machine {
         return 1;
     }
 
+    protected IFluidAccess constructFluidAccess(GT_MetaTileEntity_BasicTank aTank, boolean aIsFillableStack) {
+        return new BasicTankFluidAccess(aTank, aIsFillableStack);
+    }
+
     static class BasicTankFluidAccess implements IFluidAccess {
-        private final GT_MetaTileEntity_BasicTank mTank;
-        private final boolean mIsFillableStack;
+        protected final GT_MetaTileEntity_BasicTank mTank;
+        protected final boolean mIsFillableStack;
 
         public BasicTankFluidAccess(GT_MetaTileEntity_BasicTank aTank, boolean aIsFillableStack) {
             this.mTank = aTank;
@@ -132,22 +136,5 @@ public class GT_Container_BasicTank extends GT_ContainerMetaTile_Machine {
         public int getCapacity() {
             return mTank.getCapacity();
         }
-
-        @Override
-        public int getRealCapacity() {
-            if (mTank instanceof GT_MetaTileEntity_DigitalTankBase) {
-                return ((GT_MetaTileEntity_DigitalTankBase) mTank).getRealCapacity();
-            }
-            return IFluidAccess.super.getRealCapacity();
-        }
-
-        static BasicTankFluidAccess from(GT_MetaTileEntity_BasicTank aTank, boolean aIsFillableStack) {
-            return new BasicTankFluidAccess(aTank, aIsFillableStack);
-        }
-
-        @Override
-        public void verifyFluidStack() {
-            if (!(mTank instanceof GT_MetaTileEntity_DigitalTankBase) && get() != null && get().amount <= 0) set(null);
-        }
     }
 }
diff --git a/src/main/java/gregtech/api/gui/GT_Container_DigitalTank.java b/src/main/java/gregtech/api/gui/GT_Container_DigitalTank.java
index bdc2b32c80..b4cdf698dc 100644
--- a/src/main/java/gregtech/api/gui/GT_Container_DigitalTank.java
+++ b/src/main/java/gregtech/api/gui/GT_Container_DigitalTank.java
@@ -2,7 +2,9 @@ package gregtech.api.gui;
 
 import cpw.mods.fml.relauncher.Side;
 import cpw.mods.fml.relauncher.SideOnly;
+import gregtech.api.interfaces.IFluidAccess;
 import gregtech.api.interfaces.tileentity.IGregTechTileEntity;
+import gregtech.api.metatileentity.implementations.GT_MetaTileEntity_BasicTank;
 import gregtech.api.util.GT_Utility;
 import gregtech.common.tileentities.storage.GT_MetaTileEntity_DigitalTankBase;
 import net.minecraft.entity.player.EntityPlayer;
@@ -53,15 +55,16 @@ public class GT_Container_DigitalTank extends GT_Container_BasicTank {
             mte.mLockFluid = !mte.mLockFluid;
             if (mte.mLockFluid) {
                 if (mte.mFluid == null) {
-                    mte.lockedFluidName = null;
+                    mte.setLockedFluidName(null);
                     inBrackets = GT_Utility.trans("264", "currently none, will be locked to the next that is put in");
                 } else {
-                    mte.lockedFluidName = mte.getDrainableStack().getUnlocalizedName();
+                    mte.setLockedFluidName(mte.getDrainableStack().getFluid().getName());
                     inBrackets = mte.getDrainableStack().getLocalizedName();
                 }
                 GT_Utility.sendChatToPlayer(
                         aPlayer, String.format("%s (%s)", GT_Utility.trans("265", "1 specific Fluid"), inBrackets));
             } else {
+                mte.setLockedFluidName(null);
                 GT_Utility.sendChatToPlayer(aPlayer, GT_Utility.trans("266", "Lock Fluid Mode Disabled"));
             }
             return null;
@@ -152,4 +155,24 @@ public class GT_Container_DigitalTank extends GT_Container_BasicTank {
                 break;
         }
     }
+
+    @Override
+    protected IFluidAccess constructFluidAccess(GT_MetaTileEntity_BasicTank aTank, boolean aIsFillableStack) {
+        return new DigitalTankFluidAccess(aTank, aIsFillableStack);
+    }
+
+    static class DigitalTankFluidAccess extends BasicTankFluidAccess {
+
+        public DigitalTankFluidAccess(GT_MetaTileEntity_BasicTank aTank, boolean aIsFillableStack) {
+            super(aTank, aIsFillableStack);
+        }
+
+        @Override
+        public int getRealCapacity() {
+            return ((GT_MetaTileEntity_DigitalTankBase) mTank).getRealCapacity();
+        }
+
+        @Override
+        public void verifyFluidStack() {}
+    }
 }
diff --git a/src/main/java/gregtech/api/gui/GT_GUIContainer_DigitalTank.java b/src/main/java/gregtech/api/gui/GT_GUIContainer_DigitalTank.java
index 5d72c9ff51..c1e90ed68a 100644
--- a/src/main/java/gregtech/api/gui/GT_GUIContainer_DigitalTank.java
+++ b/src/main/java/gregtech/api/gui/GT_GUIContainer_DigitalTank.java
@@ -2,14 +2,21 @@ package gregtech.api.gui;
 
 import static gregtech.api.enums.GT_Values.RES_PATH_GUI;
 
+import gregtech.api.enums.GT_Values;
+import gregtech.api.interfaces.IDragAndDropSupport;
 import gregtech.api.interfaces.tileentity.IGregTechTileEntity;
+import gregtech.api.net.GT_Packet_SetLockedFluid;
 import gregtech.api.util.GT_Utility;
+import gregtech.common.tileentities.storage.GT_MetaTileEntity_DigitalTankBase;
 import java.util.ArrayList;
 import java.util.List;
+import net.minecraft.client.gui.inventory.GuiContainer;
 import net.minecraft.entity.player.InventoryPlayer;
+import net.minecraft.item.ItemStack;
 import net.minecraft.util.StatCollector;
+import net.minecraftforge.fluids.FluidStack;
 
-public class GT_GUIContainer_DigitalTank extends GT_GUIContainerMetaTile_Machine {
+public class GT_GUIContainer_DigitalTank extends GT_GUIContainerMetaTile_Machine implements IDragAndDropSupport {
 
     private final String mName;
     private final int textColor = this.getTextColorOrDefault("text", 0xFAFAFF),
@@ -94,4 +101,23 @@ public class GT_GUIContainer_DigitalTank extends GT_GUIContainerMetaTile_Machine
             }
         }
     }
+
+    @Override
+    public boolean handleDragAndDropGT(
+            GuiContainer gui, int mousex, int mousey, ItemStack draggedStack, int button, boolean isGhost) {
+        if (!(gui instanceof GT_GUIContainer_DigitalTank)
+                || !((GT_GUIContainer_DigitalTank) gui).isMouseOverSlot(2, mousex, mousey)
+                || !isGhost) return false;
+        FluidStack fluidStack = GT_Utility.getFluidFromContainerOrFluidDisplay(draggedStack);
+        if (fluidStack == null) return false;
+        IGregTechTileEntity te = ((GT_GUIContainer_DigitalTank) gui).mContainer.mTileEntity;
+        GT_MetaTileEntity_DigitalTankBase mte = (GT_MetaTileEntity_DigitalTankBase) te.getMetaTileEntity();
+        if (mte == null || !mte.allowChangingLockedFluid(fluidStack.getFluid().getName())) return false;
+
+        GT_Values.NW.sendToServer(new GT_Packet_SetLockedFluid(te, fluidStack));
+        draggedStack.stackSize = 0;
+        // propagate to client too
+        mte.setLockedFluidName(fluidStack.getFluid().getName());
+        return true;
+    }
 }
diff --git a/src/main/java/gregtech/api/interfaces/IDragAndDropSupport.java b/src/main/java/gregtech/api/interfaces/IDragAndDropSupport.java
new file mode 100644
index 0000000000..53b3a2b059
--- /dev/null
+++ b/src/main/java/gregtech/api/interfaces/IDragAndDropSupport.java
@@ -0,0 +1,53 @@
+package gregtech.api.interfaces;
+
+import codechicken.nei.NEIClientUtils;
+import codechicken.nei.VisiblityData;
+import codechicken.nei.api.INEIGuiHandler;
+import codechicken.nei.api.TaggedInventoryArea;
+import cpw.mods.fml.common.Optional;
+import java.util.Collections;
+import java.util.List;
+import net.minecraft.client.gui.inventory.GuiContainer;
+import net.minecraft.item.ItemStack;
+
+/**
+ * Implement this interface if your GuiContainer supports Drag-And-Drop behavior on NEI.
+ */
+@Optional.Interface(modid = "NotEnoughItems", iface = "codechicken.nei.api.INEIGuiHandler")
+public interface IDragAndDropSupport extends INEIGuiHandler {
+
+    /**
+     * Implement this to handle Drag-And-Drop behavior.
+     * This may be invoked on normal click too ({@code isGhost==false}), so be careful
+     * if your slot supports both Drag-And-Drop and other behaviors e.g. fluid I/O with FluidDisplay click
+     * @param gui Current gui instance. Make sure to check if it is an instance of your GuiContainer.
+     * @param mousex X position of the mouse
+     * @param mousey Y position of the mouse
+     * @param draggedStack ItemStack user is holding on cursor
+     * @param button 0 = left click, 1 = right click
+     * @param isGhost Whether {@code draggedStack} is dragged from ItemPanel/BookmarkPanel, or actual item player holds
+     * @return True if success
+     */
+    boolean handleDragAndDropGT(
+            GuiContainer gui, int mousex, int mousey, ItemStack draggedStack, int button, boolean isGhost);
+
+    default boolean handleDragNDrop(GuiContainer gui, int mousex, int mousey, ItemStack draggedStack, int button) {
+        return handleDragAndDropGT(gui, mousex, mousey, draggedStack, button, NEIClientUtils.getHeldItem() == null);
+    }
+
+    default VisiblityData modifyVisiblity(GuiContainer gui, VisiblityData currentVisibility) {
+        return currentVisibility;
+    }
+
+    default Iterable<Integer> getItemSpawnSlots(GuiContainer gui, ItemStack item) {
+        return Collections.emptyList();
+    }
+
+    default List<TaggedInventoryArea> getInventoryAreas(GuiContainer gui) {
+        return null;
+    }
+
+    default boolean hideItemPanelSlot(GuiContainer gui, int x, int y, int w, int h) {
+        return false;
+    }
+}
diff --git a/src/main/java/gregtech/api/interfaces/metatileentity/IFluidLockable.java b/src/main/java/gregtech/api/interfaces/metatileentity/IFluidLockable.java
new file mode 100644
index 0000000000..688a85b521
--- /dev/null
+++ b/src/main/java/gregtech/api/interfaces/metatileentity/IFluidLockable.java
@@ -0,0 +1,29 @@
+package gregtech.api.interfaces.metatileentity;
+
+import net.minecraftforge.fluids.Fluid;
+
+/**
+ * Implement this interface if your MetaTileEntity supports fluid lock mechanism.
+ */
+@SuppressWarnings({"BooleanMethodIsAlwaysInverted", "unused"})
+public interface IFluidLockable {
+
+    /**
+     * Use {@link Fluid#getName()} instead of {@link Fluid#getUnlocalizedName()} for fluid name
+     */
+    void setLockedFluidName(String name);
+
+    String getLockedFluidName();
+
+    /**
+     * Set fluid lock state.
+     * Would be useful when you don't necessarily want to change mode when locked fluid is changed.
+     */
+    void lockFluid(boolean lock);
+
+    boolean isFluidLocked();
+
+    boolean allowChangingLockedFluid(String name);
+
+    default void onFluidLockPacketReceived(String name) {}
+}
diff --git a/src/main/java/gregtech/api/metatileentity/implementations/GT_MetaTileEntity_Hatch_Output.java b/src/main/java/gregtech/api/metatileentity/implementations/GT_MetaTileEntity_Hatch_Output.java
index 9e949220f7..55ca9f9605 100644
--- a/src/main/java/gregtech/api/metatileentity/implementations/GT_MetaTileEntity_Hatch_Output.java
+++ b/src/main/java/gregtech/api/metatileentity/implementations/GT_MetaTileEntity_Hatch_Output.java
@@ -5,6 +5,7 @@ import static gregtech.api.enums.Textures.BlockIcons.OVERLAY_PIPE_OUT;
 
 import gregtech.GT_Mod;
 import gregtech.api.interfaces.ITexture;
+import gregtech.api.interfaces.metatileentity.IFluidLockable;
 import gregtech.api.interfaces.tileentity.IGregTechTileEntity;
 import gregtech.api.metatileentity.MetaTileEntity;
 import gregtech.api.render.TextureFactory;
@@ -22,7 +23,7 @@ import net.minecraft.util.StatCollector;
 import net.minecraftforge.common.util.ForgeDirection;
 import net.minecraftforge.fluids.*;
 
-public class GT_MetaTileEntity_Hatch_Output extends GT_MetaTileEntity_Hatch {
+public class GT_MetaTileEntity_Hatch_Output extends GT_MetaTileEntity_Hatch implements IFluidLockable {
     private String lockedFluidName = null;
     private WeakReference<EntityPlayer> playerThatLockedfluid = null;
     public byte mMode = 0;
@@ -368,18 +369,31 @@ public class GT_MetaTileEntity_Hatch_Output extends GT_MetaTileEntity_Hatch {
         return mMode % 4 < 2 && mMode != 9;
     }
 
-    public boolean isFluidLocked() {
-        return mMode == 8 || mMode == 9;
-    }
-
+    @Override
     public String getLockedFluidName() {
         return lockedFluidName;
     }
 
+    @Override
     public void setLockedFluidName(String lockedFluidName) {
         this.lockedFluidName = lockedFluidName;
     }
 
+    @Override
+    public void lockFluid(boolean lock) {
+        this.mMode = (byte) (lock ? 9 : 0);
+    }
+
+    @Override
+    public boolean isFluidLocked() {
+        return mMode == 8 || mMode == 9;
+    }
+
+    @Override
+    public boolean allowChangingLockedFluid(String name) {
+        return true;
+    }
+
     public boolean canStoreFluid(Fluid fluid) {
         if (isFluidLocked()) {
             if (lockedFluidName == null) return true;
@@ -403,7 +417,7 @@ public class GT_MetaTileEntity_Hatch_Output extends GT_MetaTileEntity_Hatch {
             GT_Utility.sendChatToPlayer(
                     player,
                     String.format(
-                            GT_Utility.trans("151.4", "Sucessfully locked Fluid to %s"), mFluid.getLocalizedName()));
+                            GT_Utility.trans("151.4", "Successfully locked Fluid to %s"), mFluid.getLocalizedName()));
             playerThatLockedfluid = null;
         }
     }
diff --git a/src/main/java/gregtech/api/net/GT_Packet_SetLockedFluid.java b/src/main/java/gregtech/api/net/GT_Packet_SetLockedFluid.java
index d100dd6055..d3f6d9ae4d 100644
--- a/src/main/java/gregtech/api/net/GT_Packet_SetLockedFluid.java
+++ b/src/main/java/gregtech/api/net/GT_Packet_SetLockedFluid.java
@@ -1,9 +1,9 @@
 package gregtech.api.net;
 
 import com.google.common.io.ByteArrayDataInput;
+import gregtech.api.interfaces.metatileentity.IFluidLockable;
 import gregtech.api.interfaces.metatileentity.IMetaTileEntity;
 import gregtech.api.interfaces.tileentity.IGregTechTileEntity;
-import gregtech.api.metatileentity.implementations.GT_MetaTileEntity_Hatch_Output;
 import gregtech.api.util.GT_LanguageManager;
 import gregtech.api.util.GT_Utility;
 import io.netty.buffer.ByteBuf;
@@ -77,17 +77,20 @@ public class GT_Packet_SetLockedFluid extends GT_Packet_New {
         TileEntity tile = world.getTileEntity(mX, mY, mZ);
         if (!(tile instanceof IGregTechTileEntity) || ((IGregTechTileEntity) tile).isDead()) return;
         IMetaTileEntity mte = ((IGregTechTileEntity) tile).getMetaTileEntity();
-        if (!(mte instanceof GT_MetaTileEntity_Hatch_Output)) return;
+        if (!(mte instanceof IFluidLockable)) return;
         Fluid tFluid = FluidRegistry.getFluid(mFluidID);
         if (tFluid == null) return;
-        GT_MetaTileEntity_Hatch_Output hatch = (GT_MetaTileEntity_Hatch_Output) mte;
-        hatch.setLockedFluidName(tFluid.getName());
-        hatch.mMode = 9;
+        IFluidLockable mteToLock = (IFluidLockable) mte;
+        if (!mteToLock.allowChangingLockedFluid(tFluid.getName())) return;
+
+        mteToLock.setLockedFluidName(tFluid.getName());
         GT_Utility.sendChatToPlayer(
                 mPlayer,
                 String.format(
                         GT_LanguageManager.addStringLocalization(
-                                "Interaction_DESCRIPTION_Index_151.4", "Sucessfully locked Fluid to %s", false),
+                                "Interaction_DESCRIPTION_Index_151.4", "Successfully locked Fluid to %s", false),
                         new FluidStack(tFluid, 1).getLocalizedName()));
+
+        mteToLock.onFluidLockPacketReceived(tFluid.getName());
     }
 }
diff --git a/src/main/java/gregtech/api/util/GT_Utility.java b/src/main/java/gregtech/api/util/GT_Utility.java
index b35b703ab9..abc6366cf3 100644
--- a/src/main/java/gregtech/api/util/GT_Utility.java
+++ b/src/main/java/gregtech/api/util/GT_Utility.java
@@ -2019,6 +2019,14 @@ public class GT_Utility {
         return null;
     }
 
+    public static FluidStack getFluidFromContainerOrFluidDisplay(ItemStack stack) {
+        FluidStack fluidStack = GT_Utility.getFluidForFilledItem(stack, true);
+        if (fluidStack == null) {
+            fluidStack = GT_Utility.getFluidFromDisplayStack(stack);
+        }
+        return fluidStack;
+    }
+
     public static synchronized boolean removeIC2BottleRecipe(
             ItemStack aContainer,
             ItemStack aInput,
diff --git a/src/main/java/gregtech/common/gui/GT_Container_OutputHatch.java b/src/main/java/gregtech/common/gui/GT_Container_OutputHatch.java
index 954b8ab61b..135c20dafe 100644
--- a/src/main/java/gregtech/common/gui/GT_Container_OutputHatch.java
+++ b/src/main/java/gregtech/common/gui/GT_Container_OutputHatch.java
@@ -37,15 +37,15 @@ public class GT_Container_OutputHatch extends GT_Container_BasicTank {
                     || (tMode >= 8 && tReadyLockFluid.getFluid().getName().equals(tHatch.getLockedFluidName()))) {
                 tHatch.setLockedFluidName(null);
                 GT_Utility.sendChatToPlayer(aPlayer, GT_Utility.trans("300", "Fluid Lock Cleared."));
-                tHatch.mMode = 0;
+                tHatch.lockFluid(false);
             } else {
                 tHatch.setLockedFluidName(tReadyLockFluid.getFluid().getName());
                 GT_Utility.sendChatToPlayer(
                         aPlayer,
                         String.format(
-                                GT_Utility.trans("151.4", "Sucessfully locked Fluid to %s"),
+                                GT_Utility.trans("151.4", "Successfully locked Fluid to %s"),
                                 tReadyLockFluid.getLocalizedName()));
-                tHatch.mMode = 9;
+                tHatch.lockFluid(true);
             }
         }
         return super.slotClick(aSlotIndex, aMouseclick, aShifthold, aPlayer);
diff --git a/src/main/java/gregtech/common/gui/GT_GUIContainer_OutputHatch.java b/src/main/java/gregtech/common/gui/GT_GUIContainer_OutputHatch.java
index 605fb5a463..7e27a7409a 100644
--- a/src/main/java/gregtech/common/gui/GT_GUIContainer_OutputHatch.java
+++ b/src/main/java/gregtech/common/gui/GT_GUIContainer_OutputHatch.java
@@ -2,25 +2,19 @@ package gregtech.common.gui;
 
 import static gregtech.api.enums.GT_Values.RES_PATH_GUI;
 
-import codechicken.nei.VisiblityData;
-import codechicken.nei.api.INEIGuiHandler;
-import codechicken.nei.api.TaggedInventoryArea;
-import cpw.mods.fml.common.Optional;
 import gregtech.api.enums.GT_Values;
 import gregtech.api.gui.GT_GUIContainerMetaTile_Machine;
+import gregtech.api.interfaces.IDragAndDropSupport;
 import gregtech.api.interfaces.tileentity.IGregTechTileEntity;
 import gregtech.api.net.GT_Packet_SetLockedFluid;
 import gregtech.api.util.GT_Utility;
-import java.util.Collections;
-import java.util.List;
 import net.minecraft.client.gui.inventory.GuiContainer;
 import net.minecraft.entity.player.InventoryPlayer;
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.StatCollector;
 import net.minecraftforge.fluids.FluidStack;
 
-@Optional.Interface(modid = "NotEnoughItems", iface = "codechicken.nei.api.INEIGuiHandler")
-public class GT_GUIContainer_OutputHatch extends GT_GUIContainerMetaTile_Machine implements INEIGuiHandler {
+public class GT_GUIContainer_OutputHatch extends GT_GUIContainerMetaTile_Machine implements IDragAndDropSupport {
 
     private final String mName;
     private final int textColor = this.getTextColorOrDefault("text", 0xFAFAFF),
@@ -62,31 +56,12 @@ public class GT_GUIContainer_OutputHatch extends GT_GUIContainerMetaTile_Machine
     }
 
     @Override
-    @Optional.Method(modid = "NotEnoughItems")
-    public VisiblityData modifyVisiblity(GuiContainer gui, VisiblityData currentVisibility) {
-        return currentVisibility;
-    }
-
-    @Override
-    public Iterable<Integer> getItemSpawnSlots(GuiContainer gui, ItemStack item) {
-        return Collections.emptyList();
-    }
-
-    @Override
-    public List<TaggedInventoryArea> getInventoryAreas(GuiContainer gui) {
-        return null;
-    }
-
-    @Override
-    public boolean handleDragNDrop(GuiContainer gui, int mousex, int mousey, ItemStack draggedStack, int button) {
+    public boolean handleDragAndDropGT(
+            GuiContainer gui, int mousex, int mousey, ItemStack draggedStack, int button, boolean isGhost) {
         if (gui instanceof GT_GUIContainer_OutputHatch
                 && ((GT_GUIContainer_OutputHatch) gui).isMouseOverSlot(3, mousex, mousey)) {
             // the instanceof check should be unnecessary, but we will do it regardless, just in case.
-            FluidStack tFluidStack;
-            tFluidStack = GT_Utility.getFluidForFilledItem(draggedStack, true);
-            if (tFluidStack == null) {
-                tFluidStack = GT_Utility.getFluidFromDisplayStack(draggedStack);
-            }
+            FluidStack tFluidStack = GT_Utility.getFluidFromContainerOrFluidDisplay(draggedStack);
             if (tFluidStack != null) {
                 GT_Values.NW.sendToServer(new GT_Packet_SetLockedFluid(
                         ((GT_GUIContainer_OutputHatch) gui).mContainer.mTileEntity, tFluidStack));
@@ -96,9 +71,4 @@ public class GT_GUIContainer_OutputHatch extends GT_GUIContainerMetaTile_Machine
         }
         return false;
     }
-
-    @Override
-    public boolean hideItemPanelSlot(GuiContainer gui, int x, int y, int w, int h) {
-        return false;
-    }
 }
diff --git a/src/main/java/gregtech/common/tileentities/storage/GT_MetaTileEntity_DigitalTankBase.java b/src/main/java/gregtech/common/tileentities/storage/GT_MetaTileEntity_DigitalTankBase.java
index 765597283a..9a7c75cb83 100644
--- a/src/main/java/gregtech/common/tileentities/storage/GT_MetaTileEntity_DigitalTankBase.java
+++ b/src/main/java/gregtech/common/tileentities/storage/GT_MetaTileEntity_DigitalTankBase.java
@@ -5,6 +5,7 @@ import static gregtech.api.enums.Textures.BlockIcons.*;
 import gregtech.api.gui.GT_Container_DigitalTank;
 import gregtech.api.gui.GT_GUIContainer_DigitalTank;
 import gregtech.api.interfaces.ITexture;
+import gregtech.api.interfaces.metatileentity.IFluidLockable;
 import gregtech.api.interfaces.tileentity.IGregTechTileEntity;
 import gregtech.api.metatileentity.implementations.GT_MetaTileEntity_BasicTank;
 import gregtech.api.render.TextureFactory;
@@ -15,13 +16,15 @@ import net.minecraft.item.ItemStack;
 import net.minecraft.nbt.NBTTagCompound;
 import net.minecraft.util.StatCollector;
 import net.minecraftforge.common.util.ForgeDirection;
+import net.minecraftforge.fluids.Fluid;
+import net.minecraftforge.fluids.FluidRegistry;
 import net.minecraftforge.fluids.FluidStack;
 import net.minecraftforge.fluids.FluidTankInfo;
 import net.minecraftforge.fluids.IFluidHandler;
 
-public abstract class GT_MetaTileEntity_DigitalTankBase extends GT_MetaTileEntity_BasicTank {
+public abstract class GT_MetaTileEntity_DigitalTankBase extends GT_MetaTileEntity_BasicTank implements IFluidLockable {
     public boolean mOutputFluid = false, mVoidFluidPart = false, mVoidFluidFull = false, mLockFluid = false;
-    public String lockedFluidName = null;
+    protected String lockedFluidName = null;
     private boolean voidBreak;
     public boolean mAllowInputFromOutputSide = false;
 
@@ -77,15 +80,14 @@ public abstract class GT_MetaTileEntity_DigitalTankBase extends GT_MetaTileEntit
     @Override
     public void setItemNBT(NBTTagCompound aNBT) {
         if (!voidBreak) {
-            if (mFluid != null && mFluid.amount > 0) {
+            if (mFluid != null && mFluid.amount >= 0) {
                 aNBT.setTag("mFluid", mFluid.writeToNBT(new NBTTagCompound()));
             }
             aNBT.setBoolean("mOutputFluid", this.mOutputFluid);
             aNBT.setBoolean("mVoidOverflow", this.mVoidFluidPart);
             aNBT.setBoolean("mVoidFluidFull", this.mVoidFluidFull);
             aNBT.setBoolean("mLockFluid", mLockFluid);
-            if (lockedFluidName != null && lockedFluidName.length() != 0)
-                aNBT.setString("lockedFluidName", lockedFluidName);
+            if (GT_Utility.isStringValid(lockedFluidName)) aNBT.setString("lockedFluidName", lockedFluidName);
             else aNBT.removeTag("lockedFluidName");
             aNBT.setBoolean("mAllowInputFromOutputSide", this.mAllowInputFromOutputSide);
         }
@@ -99,8 +101,7 @@ public abstract class GT_MetaTileEntity_DigitalTankBase extends GT_MetaTileEntit
         aNBT.setBoolean("mVoidOverflow", this.mVoidFluidPart);
         aNBT.setBoolean("mVoidFluidFull", this.mVoidFluidFull);
         aNBT.setBoolean("mLockFluid", mLockFluid);
-        if (lockedFluidName != null && lockedFluidName.length() != 0)
-            aNBT.setString("lockedFluidName", lockedFluidName);
+        if (GT_Utility.isStringValid(lockedFluidName)) aNBT.setString("lockedFluidName", lockedFluidName);
         else aNBT.removeTag("lockedFluidName");
         aNBT.setBoolean("mAllowInputFromOutputSide", this.mAllowInputFromOutputSide);
     }
@@ -113,13 +114,15 @@ public abstract class GT_MetaTileEntity_DigitalTankBase extends GT_MetaTileEntit
         mVoidFluidFull = aNBT.getBoolean("mVoidFluidFull");
         mLockFluid = aNBT.getBoolean("mLockFluid");
         lockedFluidName = aNBT.getString("lockedFluidName");
-        lockedFluidName = lockedFluidName.length() == 0 ? null : lockedFluidName;
+        lockedFluidName = GT_Utility.isStringInvalid(lockedFluidName) ? null : lockedFluidName;
         mAllowInputFromOutputSide = aNBT.getBoolean("mAllowInputFromOutputSide");
     }
 
     @Override
     public boolean isFluidInputAllowed(FluidStack aFluid) {
-        return !mLockFluid || lockedFluidName == null || lockedFluidName.equals(aFluid.getUnlocalizedName());
+        return !mLockFluid
+                || lockedFluidName == null
+                || lockedFluidName.equals(aFluid.getFluid().getName());
     }
 
     @Override
@@ -130,7 +133,7 @@ public abstract class GT_MetaTileEntity_DigitalTankBase extends GT_MetaTileEntit
     @Override
     public void onEmptyingContainerWhenEmpty() {
         if (this.lockedFluidName == null && this.mFluid != null) {
-            this.lockedFluidName = this.mFluid.getUnlocalizedName();
+            this.lockedFluidName = this.mFluid.getFluid().getName();
         }
     }
 
@@ -170,6 +173,42 @@ public abstract class GT_MetaTileEntity_DigitalTankBase extends GT_MetaTileEntit
     }
 
     @Override
+    public void setLockedFluidName(String lockedFluidName) {
+        this.lockedFluidName = lockedFluidName;
+        if (lockedFluidName != null) {
+            Fluid fluid = FluidRegistry.getFluid(lockedFluidName);
+            if (fluid != null) {
+                // create new FluidStack, otherwise existing 0-amount FluidStack will
+                // prevent new fluid from being locked
+                setFillableStack(new FluidStack(fluid, getFluidAmount()));
+                mLockFluid = true;
+            }
+        }
+        // Don't unlock if lockedFluidName == null,
+        // as player might explicitly enable fluid locking with no fluid contained
+    }
+
+    @Override
+    public String getLockedFluidName() {
+        return this.lockedFluidName;
+    }
+
+    @Override
+    public void lockFluid(boolean lock) {
+        this.mLockFluid = lock;
+    }
+
+    @Override
+    public boolean isFluidLocked() {
+        return this.mLockFluid;
+    }
+
+    @Override
+    public boolean allowChangingLockedFluid(String name) {
+        return getFluidAmount() == 0;
+    }
+
+    @Override
     public ITexture[] getTexture(
             IGregTechTileEntity aBaseMetaTileEntity,
             byte aSide,