Add an easier way for MTEs to be added to creative tabs

src/main/java/gregtech/api/metatileentity/MetaTileEntity.java

@@ -100,13 +100,15 @@
 import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
 import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
 import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
+import it.unimi.dsi.fastutil.objects.ObjectArraySet;
 import org.apache.commons.lang3.ArrayUtils;
 import org.apache.commons.lang3.tuple.Pair;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.EnumMap;
 import java.util.List;
 import java.util.Map;
@@ -166,6 +168,13 @@ public abstract class MetaTileEntity implements ISyncedTileEntity, CoverHolder,
     @Nullable
     private UUID owner = null;
 
+    private final Set<CreativeTabs> creativeTabs = new ObjectArraySet<>();
+
+    {
+        creativeTabs.add(CreativeTabs.SEARCH);
+        creativeTabs.add(GTCreativeTabs.TAB_GREGTECH_MACHINES);
+    }
+
     protected MetaTileEntity(@NotNull ResourceLocation metaTileEntityId) {
         this.metaTileEntityId = metaTileEntityId;
         this.registry = GregTechAPI.mteManager.getRegistry(metaTileEntityId.getNamespace());
@@ -362,7 +371,7 @@ public void getSubItems(CreativeTabs creativeTab, NonNullList<ItemStack> subItem
      *      MachineItemBlock#addCreativeTab(CreativeTabs)
      */
     public boolean isInCreativeTab(CreativeTabs creativeTab) {
-        return creativeTab == CreativeTabs.SEARCH || creativeTab == GTCreativeTabs.TAB_GREGTECH_MACHINES;
+        return creativeTabs.contains(creativeTab);
     }
 
     public String getItemSubTypeId(ItemStack itemStack) {
@@ -1661,4 +1670,45 @@ public AENetworkProxy getProxy() {
 
     @Method(modid = Mods.Names.APPLIED_ENERGISTICS2)
     public void gridChanged() {}
+
+    /**
+     * Add MTE to a creative tab. Ensure that the creative tab has been registered via
+     * {@link gregtech.api.block.machines.MachineItemBlock#addCreativeTab(CreativeTabs)
+     * MachineItemBlock#addCreativeTab(CreativeTabs)} beforehand.
+     */
+    public void addAdditionalCreativeTabs(CreativeTabs creativeTab) {
+        Preconditions.checkNotNull(creativeTab, "creativeTab");
+        if (creativeTabs.contains(creativeTab)) {
+            GTLog.logger.error("{} is already in the creative tab {}.", this, creativeTab.tabLabel,
+                    new IllegalArgumentException());
+            return;
+        }
+
+        creativeTabs.add(creativeTab);
+    }
+
+    public void removeFromCreativeTab(CreativeTabs creativeTab) {
+        Preconditions.checkNotNull(creativeTab, "creativeTab");
+        if (creativeTab == CreativeTabs.SEARCH) {
+            GTLog.logger.error("Cannot remove MTEs from the creative search tab.",
+                    new IllegalArgumentException());
+            return;
+        }
+        if (creativeTab == GTCreativeTabs.TAB_GREGTECH_MACHINES &&
+                metaTileEntityId.getNamespace().equals(GTValues.MODID)) {
+            GTLog.logger.error("Cannot remove GT MTEs from the GT machines tab.", new IllegalArgumentException());
+            return;
+        }
+        if (!creativeTabs.contains(creativeTab)) {
+            GTLog.logger.error("{} is not in the creative tab {}.", this, creativeTab.tabLabel,
+                    new IllegalArgumentException());
+            return;
+        }
+
+        creativeTabs.remove(creativeTab);
+    }
+
+    public Set<CreativeTabs> getCreativeTabs() {
+        return Collections.unmodifiableSet(creativeTabs);
+    }
 }