Add reject_continue to PlaceResult and make SKIP short-circuit in ofChain (#63)

ofChain survival placement had a bug where SKIP (returned when a block
already exists) would not stop the chain, causing fallback alternatives
to replace already valid blocks , for example:
<img width="436" height="477" alt="image"
src="https://github.com/user-attachments/assets/7ff3d6fa-de98-4716-823f-3ad2abab7394"
/>

SKIP now short-circuits the chain, remaining alternatives are skipped
because the position is already valid.
To keep correct behavior for elements without autobuild (which
previously returned SKIP as a "no implementation" signal), a new
REJECT_CONTINUE value is added, which: continues silently like SKIP (no
error, not counted) in the walker and in the chain tries the next
alternative like REJECT
Default survivalPlaceBlock and IStructureElementCheckOnly now return
REJECT_CONTINUE instead of SKIP for unhandled paths.

Tested this with the example above, and fixed the issue:
<img width="435" height="498" alt="image"
src="https://github.com/user-attachments/assets/d92bce4d-b5ad-4051-af79-ffd8c819f9f7"
/>
survival placement also still works:
<img width="1234" height="916" alt="image"
src="https://github.com/user-attachments/assets/632d5556-524d-4dc5-a7f5-75c859cb6b70"
/>

this should ideally merged before
https://github.com/GTNewHorizons/GT5-Unofficial/pull/6922 , to fix this
underlying bug, but if possible not be tagged without the other PR,
which would cause all NEI previews of multis with water to not show any
water anymore

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

.github/workflows/optimize-images.yml

@@ -0,0 +1,17 @@
+name: Optimize images
+
+on:
+  pull_request:
+    branches: [ master, main, release/** ]
+    paths:
+      - "**/*.png"
+
+  push:
+    branches: [ master, main, release/** ]
+    paths:
+      - "**/*.png"
+
+jobs:
+  optimize-images:
+    uses: GTNewHorizons/GTNH-Actions-Workflows/.github/workflows/optimize-images.yml@master
+    secrets: inherit

dependencies.gradle

@@ -1,9 +1,10 @@
 // Add your dependencies here
 
 dependencies {
-    api("com.github.GTNewHorizons:GTNHLib:0.6.13:dev")
-    runtimeOnly("com.github.GTNewHorizons:NotEnoughItems:2.7.29-GTNH:dev")
+    api("com.github.GTNewHorizons:GTNHLib:0.9.47:dev")
+    implementation("com.github.GTNewHorizons:NotEnoughItems:2.8.84-GTNH:dev")
 
     testImplementation(platform('org.junit:junit-bom:5.9.2'))
     testImplementation('org.junit.jupiter:junit-jupiter')
+	testRuntimeOnly ('org.junit.platform:junit-platform-launcher')
 }

gradle.properties

@@ -14,7 +14,7 @@ modId = structurelib
 modGroup = com.gtnewhorizon.structurelib
 
 # Whether to use modGroup as the maven publishing group.
-# Due to a history of using JitPack, the default is com.github.GTNewHorizons for all mods.
+# When false, com.github.GTNewHorizons is used.
 useModGroupForPublishing = false
 
 # Updates your build.gradle and settings.gradle automatically whenever an update is available.
@@ -37,11 +37,35 @@ remoteMappings = https\://raw.githubusercontent.com/MinecraftForge/FML/1.7.10/co
 
 # Select a default username for testing your mod. You can always override this per-run by running
 # `./gradlew runClient --username=AnotherPlayer`, or configuring this command in your IDE.
-developmentEnvironmentUserName = "Developer"
+developmentEnvironmentUserName = Developer
 
-# Enables using modern Java syntax (up to version 17) via Jabel, while still targeting JVM 8.
-# See https://github.com/bsideup/jabel for details on how this works.
-enableModernJavaSyntax = true
+# Enables modern Java syntax support. Valid values:
+# - false: No modern syntax, Java 8 only
+# - jabel: Jabel syntax-only support, compiles to J8 bytecode
+# - jvmDowngrader: Full modern Java via JVM Downgrader (syntax + stdlib APIs)
+# - modern: Native modern Java bytecode, no downgrading
+enableModernJavaSyntax = jabel
+
+# If set, ignores the above setting and compiles with the given toolchain. This may cause unexpected issues,
+# and should *not* be used in most situations. -1 disables this.
+# forceToolchainVersion = -1
+
+# Target JVM version for JVM Downgrader bytecode downgrading.
+# Only used when enableModernJavaSyntax = jvmDowngrader
+# downgradeTargetVersion = 8
+
+# Comma-separated list of Java versions for multi-release jar support (JVM Downgrader only).
+# Classes will be available in META-INF/versions/N/ for each version N in this list.
+# Default: "21,25" (J25+ gets native classes, J21-24 gets partial downgrade, J8-20 gets full downgrade).
+# jvmDowngraderMultiReleaseVersions = 21,25
+
+# Specifies how JVM Downgrader API stubs are provided. Options:
+# - shade: Shade minimized stubs into the jar
+# - gtnhlib: GTNHLib provides stubs at runtime (adds version constraint)
+# - external: Another dependency provides stubs (no constraint, no warning)
+# - (empty): Warning reminding you to configure stubs
+# Note: 'shade' option requires you to verify license compliance, see: https://github.com/unimined/JvmDowngrader/blob/main/LICENSE.md
+# jvmDowngraderStubsProvider =
 
 # Enables injecting missing generics into the decompiled source code for a better coding experience.
 # Turns most publicly visible List, Map, etc. into proper List<E>, Map<K, V> types.
@@ -96,7 +120,9 @@ usesMixinDebug = false
 # Specify the location of your implementation of IMixinConfigPlugin. Leave it empty otherwise.
 mixinPlugin =
 
-# Specify the package that contains all of your Mixins. You may only place Mixins in this package or the build will fail!
+# Specify the package that contains all of your Mixins. The package must exist or
+# the build will fail. If you have a package property defined in your mixins.<modid>.json,
+# it must match with this or the build will fail.
 mixinsPackage = mixins
 
 # Specify the core mod entry class if you use a core mod. This class must implement IFMLLoadingPlugin!
@@ -151,7 +177,7 @@ modrinthProjectId =
 #       type can be one of [project, version],
 #       and the name is the Modrinth project or version slug/id of the other mod.
 # Example: required-project:fplib;optional-project:gasstation;incompatible-project:gregtech
-# Note: GTNH Mixins is automatically set as a required dependency if usesMixins = true
+# Note: UniMixins is automatically set as a required dependency if usesMixins = true.
 modrinthRelations =
 
 # Publishing to CurseForge requires you to set the CURSEFORGE_TOKEN environment variable to one of your CurseForge API tokens.
@@ -172,6 +198,12 @@ curseForgeRelations =
 # projects. New projects should not use this parameter.
 # customArchiveBaseName =
 
+# Optional parameter to customize the default working directory used by the runClient* tasks. Relative to the project directory.
+# runClientWorkingDirectory = run/client
+
+# Optional parameter to customize the default working directory used by the runServer* tasks. Relative to the project directory.
+# runServerWorkingDirectory = run/server
+
 # Optional parameter to have the build automatically fail if an illegal version is used.
 # This can be useful if you e.g. only want to allow versions in the form of '1.1.xxx'.
 # The check is ONLY performed if the version is a git tag.
@@ -201,3 +233,6 @@ curseForgeRelations =
 # This is meant to be set in $HOME/.gradle/gradle.properties.
 # ideaCheckSpotlessOnBuild = true
 
+# Non-GTNH properties
+org.gradle.configuration-cache = true
+org.gradle.parallel = true

gradle/gradle-daemon-jvm.properties

@@ -0,0 +1,12 @@
+#This file is generated by updateDaemonJvm
+toolchainUrl.FREE_BSD.AARCH64=https\://api.foojay.io/disco/v3.0/ids/1630f7ebef05444cb27a2709ea0249b3/redirect
+toolchainUrl.FREE_BSD.X86_64=https\://api.foojay.io/disco/v3.0/ids/cd495626d2ee49a75447e3fdc6afb287/redirect
+toolchainUrl.LINUX.AARCH64=https\://api.foojay.io/disco/v3.0/ids/1630f7ebef05444cb27a2709ea0249b3/redirect
+toolchainUrl.LINUX.X86_64=https\://api.foojay.io/disco/v3.0/ids/cd495626d2ee49a75447e3fdc6afb287/redirect
+toolchainUrl.MAC_OS.AARCH64=https\://api.foojay.io/disco/v3.0/ids/d4fd992c9557644e637ebe98263e0ae7/redirect
+toolchainUrl.MAC_OS.X86_64=https\://api.foojay.io/disco/v3.0/ids/faa12903720d410b387cc69ccafb1a74/redirect
+toolchainUrl.UNIX.AARCH64=https\://api.foojay.io/disco/v3.0/ids/1630f7ebef05444cb27a2709ea0249b3/redirect
+toolchainUrl.UNIX.X86_64=https\://api.foojay.io/disco/v3.0/ids/cd495626d2ee49a75447e3fdc6afb287/redirect
+toolchainUrl.WINDOWS.AARCH64=https\://api.foojay.io/disco/v3.0/ids/a4c09dd2e2d7079373d30e524bbc2829/redirect
+toolchainUrl.WINDOWS.X86_64=https\://api.foojay.io/disco/v3.0/ids/8e1d9ee5d0f13e442218f6884a306da1/redirect
+toolchainVersion=25

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.13-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.4.0-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME

gradlew

@@ -1,7 +1,7 @@
 #!/bin/sh
 
 #
-# Copyright © 2015-2021 the original authors.
+# Copyright © 2015 the original authors.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -57,7 +57,7 @@
 #       Darwin, MinGW, and NonStop.
 #
 #   (3) This script is generated from the Groovy template
-#       https://github.com/gradle/gradle/blob/HEAD/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       https://github.com/gradle/gradle/blob/b631911858264c0b6e4d6603d677ff5218766cee/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
 #       within the Gradle project.
 #
 #       You can find Gradle at https://github.com/gradle/gradle/.
@@ -114,7 +114,6 @@ case "$( uname )" in                #(
   NONSTOP* )        nonstop=true ;;
 esac
 
-CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
 
 
 # Determine the Java command to use to start the JVM.
@@ -172,7 +171,6 @@ fi
 # For Cygwin or MSYS, switch paths to Windows format before running java
 if "$cygwin" || "$msys" ; then
     APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
-    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
 
     JAVACMD=$( cygpath --unix "$JAVACMD" )
 
@@ -212,8 +210,7 @@ DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \
-        -classpath "$CLASSPATH" \
-        org.gradle.wrapper.GradleWrapperMain \
+        -jar "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" \
         "$@"
 
 # Stop when "xargs" is not available.

gradlew.bat

@@ -70,11 +70,10 @@ goto fail
 :execute
 @rem Setup the command line
 
-set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
 
 
 @rem Execute Gradle
-"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %*
 
 :end
 @rem End local scope for the variables with windows NT shell

settings.gradle

@@ -17,7 +17,7 @@ pluginManagement {
 }
 
 plugins {
-    id 'com.gtnewhorizons.gtnhsettingsconvention' version '1.0.37'
+    id 'com.gtnewhorizons.gtnhsettingsconvention' version '2.0.24'
 }
 
 

src/main/java/com/gtnewhorizon/structurelib/ChannelDescription.java

@@ -0,0 +1,94 @@
+package com.gtnewhorizon.structurelib;
+
+import java.util.AbstractMap;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import net.minecraft.item.ItemStack;
+
+import com.gtnewhorizon.gtnhlib.util.map.ItemStackMap;
+
+import cpw.mods.fml.common.Loader;
+
+// this is not an API! go check StructureLibAPI instead!
+public class ChannelDescription {
+
+    private static final ItemStackMap<Set<ChannelDescription>> itemToChannels = new ItemStackMap<>(true);
+    private static final Map<String, ChannelDescription> registry = new HashMap<>();
+    private final String channel;
+    private final Map<String, String> descriptions = new HashMap<>();
+    private final ItemStackMap<Integer> items = new ItemStackMap<>(true);
+
+    public static ChannelDescription get(final String channel) {
+        if (StructureLibAPI.isDebugEnabled() && !channel.toLowerCase(Locale.ROOT).equals(channel))
+            throw new IllegalArgumentException("Channel name can be lower case ONLY");
+        return registry.computeIfAbsent(channel, ChannelDescription::new);
+    }
+
+    public static boolean has(final String channel) {
+        if (StructureLibAPI.isDebugEnabled() && !channel.toLowerCase(Locale.ROOT).equals(channel))
+            throw new IllegalArgumentException("Channel name can be lower case ONLY");
+        return registry.containsKey(channel);
+    }
+
+    public static Collection<Map.Entry<String, Integer>> iterate(final ItemStack block) {
+        Set<ChannelDescription> channels = itemToChannels.get(block);
+        if (channels == null) return Collections.emptySet();
+        return channels.stream().map(d -> new AbstractMap.SimpleImmutableEntry<>(d.channel, d.items.get(block)))
+                .collect(Collectors.toList());
+    }
+
+    public static void set(final String channel, final String modid, final String description) {
+        if (StructureLibAPI.isDebugEnabled() && !channel.toLowerCase(Locale.ROOT).equals(channel))
+            throw new IllegalArgumentException("Channel name can be lower case ONLY");
+        registry.computeIfAbsent(channel, ChannelDescription::new).add(modid, description);
+    }
+
+    public static void item(final String channel, int channelValue, ItemStack stack) {
+        if (StructureLibAPI.isDebugEnabled()) {
+            if (!channel.toLowerCase(Locale.ROOT).equals(channel)) {
+                throw new IllegalArgumentException("Channel name can be lower case ONLY");
+            }
+            if (channelValue <= 0) {
+                throw new IllegalArgumentException("Channel value must be greater than 0");
+            }
+        }
+        ChannelDescription inst = registry.computeIfAbsent(channel, ChannelDescription::new);
+        inst.items.put(stack, channelValue);
+        itemToChannels.computeIfAbsent(stack, s -> new HashSet<>()).add(inst);
+    }
+
+    public static Map<String, ChannelDescription> getAll() {
+        return Collections.unmodifiableMap(registry);
+    }
+
+    private ChannelDescription(String channel) {
+        this.channel = channel;
+    }
+
+    public String getChannel() {
+        return channel;
+    }
+
+    public ChannelDescription add(String modid, String description) {
+        if (Loader.instance().getIndexedModList().get(modid) == null) {
+            throw new IllegalArgumentException("Mod not found: " + modid);
+        }
+        descriptions.put(modid, description);
+        return this;
+    }
+
+    public Map<String, String> getDescriptions() {
+        return Collections.unmodifiableMap(descriptions);
+    }
+
+    public Map<ItemStack, Integer> getItems() {
+        return Collections.unmodifiableMap(items);
+    }
+}

src/main/java/com/gtnewhorizon/structurelib/DevelopHelper.java

@@ -0,0 +1,48 @@
+package com.gtnewhorizon.structurelib;
+
+import net.minecraft.init.Blocks;
+import net.minecraft.item.ItemStack;
+import net.minecraft.nbt.NBTTagCompound;
+import net.minecraft.nbt.NBTTagList;
+
+import cpw.mods.fml.common.event.FMLInterModComms;
+
+public class DevelopHelper {
+
+    private static final boolean DEBUG = Boolean.getBoolean("structurelib.develop_helper");
+
+    public static void onPreInit() {
+        if (!DEBUG) return;
+        StructureLib.LOGGER.info("Running develop helper");
+        StructureLibAPI.registerChannelDescription("sandstone", StructureLibAPI.MOD_ID, "variants of Sandstone");
+        StructureLibAPI.registerChannelItem("sandstone", StructureLibAPI.MOD_ID, 1, new ItemStack(Blocks.sandstone));
+        StructureLibAPI
+                .registerChannelItem("sandstone", StructureLibAPI.MOD_ID, 2, new ItemStack(Blocks.sandstone, 1, 1));
+        StructureLibAPI
+                .registerChannelItem("sandstone", StructureLibAPI.MOD_ID, 3, new ItemStack(Blocks.sandstone, 1, 2));
+        StructureLibAPI.registerChannelDescription("sandbricks", StructureLibAPI.MOD_ID, "variants of Sandbricks");
+        StructureLibAPI.registerChannelDescription("apple", StructureLibAPI.MOD_ID, "apple");
+        StructureLibAPI.registerChannelDescription("bright", StructureLibAPI.MOD_ID, "bright");
+        StructureLibAPI.registerChannelDescription("apple_blight", StructureLibAPI.MOD_ID, "apple_blight");
+        StructureLibAPI.registerChannelDescription("app_eagle", StructureLibAPI.MOD_ID, "app_eagle");
+    }
+
+    public void x() {
+        NBTTagCompound command = new NBTTagCompound();
+        NBTTagList items = new NBTTagList();
+        int[] metas = { 0, 1, 2 };
+        for (int meta : metas) {
+            NBTTagCompound tag = new NBTTagCompound();
+            tag.setTag("Item", new ItemStack(Blocks.sandstone, 1, meta).writeToNBT(new NBTTagCompound()));
+            NBTTagList channels = new NBTTagList();
+            NBTTagCompound channel = new NBTTagCompound();
+            channel.setString("Channel", "sandstone");
+            channel.setInteger("Value", meta + 1);
+            channels.appendTag(channel);
+            tag.setTag("Channels", channels);
+            items.appendTag(tag);
+        }
+        command.setTag("Items", items);
+        FMLInterModComms.sendMessage("structurelib", "register_channel_item", command);
+    }
+}

src/main/java/com/gtnewhorizon/structurelib/GuiHandler.java

@@ -3,6 +3,7 @@ package com.gtnewhorizon.structurelib;
 import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.world.World;
 
+import com.gtnewhorizon.structurelib.gui.EmptyContainer;
 import com.gtnewhorizon.structurelib.gui.GuiScreenConfigureChannels;
 
 import cpw.mods.fml.common.network.IGuiHandler;
@@ -11,14 +12,19 @@ public class GuiHandler implements IGuiHandler {
 
     @Override
     public Object getServerGuiElement(int ID, EntityPlayer player, World world, int x, int y, int z) {
-        return null;
+        switch (ID) {
+            case 0:
+                return new EmptyContainer(player);
+            default:
+                return null;
+        }
     }
 
     @Override
     public Object getClientGuiElement(int ID, EntityPlayer player, World world, int x, int y, int z) {
         switch (ID) {
             case 0:
-                return new GuiScreenConfigureChannels(player.inventory.getStackInSlot(x));
+                return new GuiScreenConfigureChannels(new EmptyContainer(player), player.inventory.getStackInSlot(x));
             default:
                 return null;
         }

src/main/java/com/gtnewhorizon/structurelib/StructureLib.java

@@ -1,11 +1,18 @@
 package com.gtnewhorizon.structurelib;
 
+import static com.gtnewhorizon.structurelib.StructureLibAPI.CHANNEL_SHOW_ERROR;
+import static com.gtnewhorizon.structurelib.StructureLibAPI.MOD_ID;
+
 import net.minecraft.block.Block;
 import net.minecraft.creativetab.CreativeTabs;
 import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemBlock;
+import net.minecraft.item.ItemStack;
 import net.minecraft.launchwrapper.Launch;
+import net.minecraft.nbt.NBTTagCompound;
+import net.minecraft.nbt.NBTTagList;
+import net.minecraftforge.common.util.Constants;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -24,9 +31,9 @@ import com.gtnewhorizon.structurelib.net.UpdateHintParticleMessage;
 import com.gtnewhorizon.structurelib.util.InventoryUtility;
 import com.gtnewhorizon.structurelib.util.XSTR;
 
-import cpw.mods.fml.common.Loader;
 import cpw.mods.fml.common.Mod;
 import cpw.mods.fml.common.SidedProxy;
+import cpw.mods.fml.common.event.FMLInterModComms;
 import cpw.mods.fml.common.event.FMLLoadCompleteEvent;
 import cpw.mods.fml.common.event.FMLPreInitializationEvent;
 import cpw.mods.fml.common.event.FMLServerStartingEvent;
@@ -40,7 +47,7 @@ import cpw.mods.fml.relauncher.SideOnly;
  * This class does not contain a stable API. Refrain from using this class.
  */
 @Mod(
-        modid = StructureLibAPI.MOD_ID,
+        modid = MOD_ID,
         name = "StructureLib",
         version = Tags.VERSION,
         acceptableRemoteVersions = "*",
@@ -57,7 +64,7 @@ public class StructureLib {
             clientSide = "com.gtnewhorizon.structurelib.ClientProxy")
     static CommonProxy proxy;
 
-    static final SimpleNetworkWrapper net = NetworkRegistry.INSTANCE.newSimpleChannel(StructureLibAPI.MOD_ID);
+    static final SimpleNetworkWrapper net = NetworkRegistry.INSTANCE.newSimpleChannel(MOD_ID);
 
     static {
         net.registerMessage(
@@ -84,7 +91,7 @@ public class StructureLib {
 
     @Mod.Instance
     static StructureLib INSTANCE;
-
+    @Mod.Instance(STRUCTURECOMPAT_MODID)
     static Object COMPAT;
 
     static Block blockHint;
@@ -100,8 +107,6 @@ public class StructureLib {
         }
     };
 
-    public static boolean isGTLoaded;
-
     @Mod.EventHandler
     public void preInit(FMLPreInitializationEvent e) {
         ConfigurationHandler.INSTANCE.init(e.getSuggestedConfigurationFile());
@@ -117,11 +122,10 @@ public class StructureLib {
         NetworkRegistry.INSTANCE.registerGuiHandler(instance(), new GuiHandler());
 
         InventoryUtility.init();
-        if (Loader.isModLoaded(STRUCTURECOMPAT_MODID)) {
-            COMPAT = Loader.instance().getIndexedModList().get(STRUCTURECOMPAT_MODID).getMod();
-        }
 
-        isGTLoaded = Loader.isModLoaded("gregtech");
+        ChannelDescription.set(CHANNEL_SHOW_ERROR, MOD_ID, "channels.structurelib.show_errors");
+
+        DevelopHelper.onPreInit();
     }
 
     @Mod.EventHandler
@@ -135,6 +139,48 @@ public class StructureLib {
         e.registerServerCommand(new CommandRegistryDebug());
     }
 
+    @Mod.EventHandler
+    public void handleIMC(FMLInterModComms.IMCEvent event) {
+        for (FMLInterModComms.IMCMessage message : event.getMessages()) {
+            switch (message.key) {
+                case "register_channel":
+                    processRegisterChannel(message);
+                    break;
+                case "register_channel_item":
+                    processRegisterChannelItem(message);
+                    break;
+            }
+        }
+    }
+
+    private void processRegisterChannel(FMLInterModComms.IMCMessage message) {
+        NBTTagList tags = message.getNBTValue().getTagList("Channels", Constants.NBT.TAG_COMPOUND);
+        for (int i = 0; i < tags.tagCount(); i++) {
+            NBTTagCompound tag = tags.getCompoundTagAt(i);
+            StructureLibAPI.registerChannelDescription(
+                    tag.getString("Channel"),
+                    message.getSender(),
+                    tag.getString("Description"));
+        }
+    }
+
+    private void processRegisterChannelItem(FMLInterModComms.IMCMessage message) {
+        NBTTagList items = message.getNBTValue().getTagList("Items", Constants.NBT.TAG_COMPOUND);
+        for (int i = 0; i < items.tagCount(); i++) {
+            NBTTagCompound itemTag = items.getCompoundTagAt(i);
+            ItemStack item = ItemStack.loadItemStackFromNBT(itemTag.getCompoundTag("Item"));
+            NBTTagList tags = itemTag.getTagList("Channels", Constants.NBT.TAG_COMPOUND);
+            for (int j = 0; j < tags.tagCount(); j++) {
+                NBTTagCompound tag = tags.getCompoundTagAt(j);
+                StructureLibAPI.registerChannelItem(
+                        tag.getString("Channel"),
+                        message.getSender(),
+                        tag.getInteger("Value"),
+                        item);
+            }
+        }
+    }
+
     public static void addClientSideChatMessages(String... messages) {
         proxy.addClientSideChatMessages(messages);
     }

src/main/java/com/gtnewhorizon/structurelib/StructureLibAPI.java

@@ -11,6 +11,7 @@ import net.minecraft.util.IChatComponent;
 import net.minecraft.util.IIcon;
 import net.minecraft.world.World;
 
+import com.gtnewhorizon.gtnhlib.util.AnimatedTooltipHandler;
 import com.gtnewhorizon.structurelib.alignment.IAlignment;
 import com.gtnewhorizon.structurelib.alignment.IAlignmentProvider;
 import com.gtnewhorizon.structurelib.alignment.enumerable.ExtendedFacing;
@@ -43,6 +44,7 @@ public class StructureLibAPI {
     public static final int HINT_BLOCK_META_AIR = 13;
     public static final int HINT_BLOCK_META_NOT_AIR = 14;
     public static final int HINT_BLOCK_META_ERROR = 15;
+    public static final String CHANNEL_SHOW_ERROR = "show_error";
     static final ThreadLocal<Object> instrument = new ThreadLocal<>();
 
     /**
@@ -350,4 +352,37 @@ public class StructureLibAPI {
             short intervalRequired, boolean forceUpdateLastSend) {
         proxy.addThrottledChat(throttleKey, player, text, intervalRequired, forceUpdateLastSend);
     }
+
+    /**
+     * Register a channel description here. The description should describe how a channel will be used inside your mod.
+     *
+     * @param channel     channel key
+     * @param modid       your modid
+     * @param description localization key for your description
+     */
+    public static void registerChannelDescription(final String channel, final String modid, final String description) {
+        ChannelDescription.set(channel, modid, description);
+    }
+
+    /**
+     * Register an item stack as an indicator for a (channel, value) pair.
+     *
+     * @param channel      channel key
+     * @param modid        your modid
+     * @param channelValue value
+     * @param stack        item stack. having a metadata of
+     *                     {@link net.minecraftforge.oredict.OreDictionary#WILDCARD_VALUE} will match without comparing
+     *                     NBT or metadata value. having a tag with {@code tag.getBoolean("*") == true} will match
+     *                     without comparing NBT.
+     */
+    public static void registerChannelItem(final String channel, final String modid, final int channelValue,
+            final ItemStack stack) {
+        ChannelDescription.item(channel, channelValue, stack);
+        AnimatedTooltipHandler.addItemTooltip(
+                stack,
+                AnimatedTooltipHandler.translatedText("structurelib.tooltip.channelvalue", channelValue, channel));
+        AnimatedTooltipHandler.addItemTooltip(
+                stack,
+                AnimatedTooltipHandler.translatedText("structurelib.tooltip.indicator_dnd", channelValue, channel));
+    }
 }

src/main/java/com/gtnewhorizon/structurelib/alignment/IAlignmentLimits.java

@@ -14,8 +14,28 @@ import com.gtnewhorizon.structurelib.alignment.enumerable.Rotation;
 
 public interface IAlignmentLimits {
 
+    /**
+     * Can be placed in any orientation.
+     */
     IAlignmentLimits UNLIMITED = (direction, rotation, flip) -> true;
 
+    /**
+     * Must be standing upright; i.e., top side of the block facing up.
+     */
+    IAlignmentLimits UPRIGHT = (direction, rotation, flip) -> direction.offsetY == 0
+            && (flip.isVerticallyFliped() ? rotation.isUpsideDown() : rotation.isNotRotated());
+
+    /**
+     * Can be in any orientation except upside down; i.e., top side of the block facing down.
+     */
+    IAlignmentLimits NOT_UPSIDE_DOWN = (direction, rotation, flip) -> direction.offsetY != 0
+            || (flip.isVerticallyFliped() ? !rotation.isNotRotated() : !rotation.isUpsideDown());
+
+    /**
+     * Front side of the block must be facing up.
+     */
+    IAlignmentLimits FACING_UP = (direction, rotation, flip) -> direction == ForgeDirection.UP;
+
     boolean isNewExtendedFacingValid(ForgeDirection direction, Rotation rotation, Flip flip);
 
     default boolean isNewExtendedFacingValid(ExtendedFacing alignment) {

src/main/java/com/gtnewhorizon/structurelib/block/BlockHint.java

@@ -50,6 +50,10 @@ public class BlockHint extends Block {
 
     @Override
     public IIcon getIcon(int aSide, int aMeta) {
+        // For numbered hints, top and bottom are blank
+        if (aSide <= 1 && aMeta <= 11) {
+            return hint[13];
+        }
         return hint[aMeta];
     }
 

src/main/java/com/gtnewhorizon/structurelib/core/StructureLibCore.java

@@ -1,34 +1,20 @@
 package com.gtnewhorizon.structurelib.core;
 
+import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
-import org.apache.logging.log4j.LogManager;
-import org.apache.logging.log4j.Logger;
-
 import com.gtnewhorizon.gtnhmixins.IEarlyMixinLoader;
-import com.gtnewhorizon.structurelib.mixins.Mixins;
 
 import cpw.mods.fml.relauncher.IFMLLoadingPlugin;
 
+@IFMLLoadingPlugin.MCVersion("1.7.10")
 public class StructureLibCore implements IFMLLoadingPlugin, IEarlyMixinLoader {
 
-    public static final Logger log = LogManager.getLogger("StructureLibCore");
-
-    @Override
-    public String getMixinConfig() {
-        return "mixins.structurelib.early.json";
-    }
-
-    @Override
-    public List<String> getMixins(Set<String> loadedCoreMods) {
-        return Mixins.getEarlyMixins(loadedCoreMods);
-    }
-
     @Override
     public String[] getASMTransformerClass() {
-        return new String[0];
+        return null;
     }
 
     @Override
@@ -50,4 +36,14 @@ public class StructureLibCore implements IFMLLoadingPlugin, IEarlyMixinLoader {
     public String getAccessTransformerClass() {
         return null;
     }
+
+    @Override
+    public String getMixinConfig() {
+        return "mixins.structurelib.early.json";
+    }
+
+    @Override
+    public List<String> getMixins(Set<String> loadedCoreMods) {
+        return Arrays.asList("blockChangeNotifier.MixinForgeHooks", "blockChangeNotifier.MixinWorld");
+    }
 }

src/main/java/com/gtnewhorizon/structurelib/gui/EmptyContainer.java

@@ -0,0 +1,18 @@
+package com.gtnewhorizon.structurelib.gui;
+
+import net.minecraft.entity.player.EntityPlayer;
+import net.minecraft.inventory.Container;
+
+public class EmptyContainer extends Container {
+
+    private final EntityPlayer player;
+
+    public EmptyContainer(EntityPlayer player) {
+        this.player = player;
+    }
+
+    @Override
+    public boolean canInteractWith(EntityPlayer player) {
+        return player == this.player;
+    }
+}

src/main/java/com/gtnewhorizon/structurelib/gui/GuiScreenConfigureChannels.java

@@ -1,56 +1,82 @@
 package com.gtnewhorizon.structurelib.gui;
 
+import java.util.AbstractMap;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
+import java.util.Map;
 import java.util.Map.Entry;
+import java.util.Set;
 import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
 
 import net.minecraft.client.gui.GuiButton;
-import net.minecraft.client.gui.GuiScreen;
 import net.minecraft.client.gui.GuiTextField;
+import net.minecraft.client.gui.inventory.GuiContainer;
 import net.minecraft.client.renderer.Tessellator;
 import net.minecraft.client.resources.I18n;
+import net.minecraft.inventory.Container;
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.EnumChatFormatting;
 import net.minecraft.util.ResourceLocation;
+import net.minecraft.util.StatCollector;
 
 import org.apache.commons.lang3.StringUtils;
 import org.lwjgl.input.Keyboard;
 import org.lwjgl.input.Mouse;
 import org.lwjgl.opengl.GL11;
 
+import com.google.common.base.Splitter;
+import com.gtnewhorizon.structurelib.ChannelDescription;
 import com.gtnewhorizon.structurelib.StructureLib;
 import com.gtnewhorizon.structurelib.alignment.constructable.ChannelDataAccessor;
 import com.gtnewhorizon.structurelib.gui.GuiScrollableList.IGuiScreen;
 
-public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen {
+import codechicken.nei.VisiblityData;
+import codechicken.nei.api.INEIGuiHandler;
+import codechicken.nei.api.TaggedInventoryArea;
+import cpw.mods.fml.common.Loader;
+import cpw.mods.fml.common.Optional;
+import gnu.trove.map.TIntObjectMap;
+import gnu.trove.map.hash.TIntObjectHashMap;
+
+@Optional.Interface(iface = "codechicken.nei.api.INEIGuiHandler", modid = "NotEnoughItems")
+public class GuiScreenConfigureChannels extends GuiContainer implements IGuiScreen, INEIGuiHandler {
 
     private static final String I18N_PREFIX = "item.structurelib.constructableTrigger.gui.";
 
     private static final int ADD_BTN = 0;
     private static final int UNSET_BTN = 1;
     private static final int WIPE_BTN = 2;
-    private static final int SHOW_ERROR_BTN = 3;
-    private static final int GT_NO_HATCH_BTN = 4;
-
-    private static final String SHOW_ERROR_CHANNEL = "show_error";
-    private static final String GT_NO_HATCH_CHANNEL = "gt_no_hatch";
 
     private static final int KEY_MAX_WIDTH = 50;
+    private static final int INFO_BOX_SIZE = 11;
     private final ItemStack trigger;
     private final GuiChannelsList list;
+    private final GuiAutoCompleteList autoCompleteList;
+    private final Map<String, List<String>> tooltipSplitCache = new HashMap<>();
+    private final TIntObjectMap<Map<String, String>> trimCache = new TIntObjectHashMap<>();
     private GuiTextField key, value;
     protected int guiTop, guiLeft;
+    private List<String> info;
+
+    public GuiScreenConfigureChannels(Container container, ItemStack trigger) {
+        super(container);
 
-    public GuiScreenConfigureChannels(ItemStack trigger) {
         this.trigger = trigger;
-        list = new GuiChannelsList(152, 100, 12, 12, 14);
+        list = new GuiChannelsList(152, 91, 12, 21, 14);
         list.addSelectionListener((list, selectedIndex) -> {
             Entry<String, Integer> e = list.getElementAt(selectedIndex);
             key.setText(e.getKey());
             value.setText(e.getValue().toString());
             updateButtons();
         });
+        autoCompleteList = new GuiAutoCompleteList(151 + 12 - 45 - 2, 50, 45, 119 + 12, 14);
     }
 
     @Override
@@ -136,47 +162,20 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
         };
 
         list.onGuiInit(this);
+        autoCompleteList.onGuiInit(this);
 
-        addButton(
-                new GuiButton(
-                        ADD_BTN,
-                        guiLeft + 12,
-                        guiTop + 157,
-                        47,
-                        20,
-                        I18n.format("item.structurelib.constructableTrigger.gui.add")));
-        addButton(
-                new GuiButton(
-                        UNSET_BTN,
-                        guiLeft + 65,
-                        guiTop + 157,
-                        47,
-                        20,
-                        I18n.format("item.structurelib.constructableTrigger.gui.unset")));
-        addButton(
-                new GuiButton(
-                        WIPE_BTN,
-                        guiLeft + 118,
-                        guiTop + 157,
-                        47,
-                        20,
-                        I18n.format("item.structurelib.constructableTrigger.gui.wipe")));
-
-        addButton(
-                new GuiButton(
-                        SHOW_ERROR_BTN,
-                        StructureLib.isGTLoaded ? guiLeft + 12 : guiLeft + 52,
-                        guiTop + 180,
-                        73,
-                        20,
-                        ""));
-
-        // only show GT hatch button if GT is loaded
-        if (StructureLib.isGTLoaded) {
-            addButton(new GuiButton(GT_NO_HATCH_BTN, guiLeft + 92, guiTop + 180, 73, 20, ""));
-        }
+        addButton(new GuiButton(ADD_BTN, guiLeft + 12, guiTop + 157, 47, 20, I18n.format(I18N_PREFIX + "add")));
+        addButton(new GuiButton(UNSET_BTN, guiLeft + 65, guiTop + 157, 47, 20, I18n.format(I18N_PREFIX + "unset")));
+        addButton(new GuiButton(WIPE_BTN, guiLeft + 118, guiTop + 157, 47, 20, I18n.format(I18N_PREFIX + "wipe")));
 
         updateButtons();
+        tooltipSplitCache.clear();
+        info = StreamSupport
+                .stream(
+                        Splitter.on("\\n").split(StatCollector.translateToLocal(I18N_PREFIX + "info")).spliterator(),
+                        false)
+                .flatMap(line -> fontRendererObj.listFormattedStringToWidth(line, width * 1 / 3).stream())
+                .collect(Collectors.toList());
     }
 
     @Override
@@ -196,7 +195,7 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
 
     @Override
     public int getYSize() {
-        return 211;
+        return 188;
     }
 
     @Override
@@ -219,8 +218,7 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
         actionPerformed(but);
     }
 
-    @SuppressWarnings("unchecked")
-    private List<GuiButton> getButtonList() {
+    public List<GuiButton> getButtonList() {
         return buttonList;
     }
 
@@ -252,16 +250,22 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
 
     @Override
     protected void mouseClicked(int mX, int mY, int button) {
+        super.mouseClicked(mX, mY, button);
         key.mouseClicked(mX, mY, button);
         value.mouseClicked(mX, mY, button);
-        super.mouseClicked(mX, mY, button);
     }
 
     @Override
     protected void keyTyped(char aChar, int aKey) {
+        GuiScrollableList<?> l = key.isFocused() ? autoCompleteList : list;
         switch (aKey) {
             case Keyboard.KEY_TAB:
                 if (key.isFocused()) {
+                    if (autoCompleteList.getSelectedElement() != null) {
+                        key.setText(autoCompleteList.getSelectedElement());
+                        return;
+                    }
+
                     key.setFocused(false);
                     value.setFocused(true);
                 } else {
@@ -271,21 +275,38 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
                 return;
             case Keyboard.KEY_RETURN:
             case Keyboard.KEY_NUMPADENTER:
-                GuiButton add = getButtonList().get(0);
+                if (key.isFocused() && autoCompleteList.getSelectedElement() != null) {
+                    key.setText(autoCompleteList.getSelectedElement());
+                    key.setFocused(false);
+                    value.setFocused(true);
+                    value.setText("1");
+                    value.setSelectionPos(0);
+                    return;
+                }
+                GuiButton add = getButtonList().get(ADD_BTN);
                 if (add.enabled) doActionPerformed(add);
                 return;
             case Keyboard.KEY_UP:
-                if (list.selectedIndex > 0) list.setSelection(list.selectedIndex - 1);
+                if (l.selectedIndex > 0) l.setSelection(l.selectedIndex - 1);
                 return;
             case Keyboard.KEY_DOWN:
-                if (list.selectedIndex < list.getNumElements() - 1) list.setSelection(list.selectedIndex + 1);
+                if (l.selectedIndex < l.getNumElements() - 1) l.setSelection(l.selectedIndex + 1);
                 return;
+            case Keyboard.KEY_ESCAPE:
+                if (key.isFocused()) {
+                    if (autoCompleteList.getSelectedElement() != null) {
+                        autoCompleteList.reset();
+                    } else {
+                        key.setFocused(false);
+                    }
+                    return;
+                }
+                break;
         }
-        if (key.textboxKeyTyped(aChar, aKey)) {
+        if (key.textboxKeyTyped(aChar, aKey) || value.textboxKeyTyped(aChar, aKey)) {
             updateButtons();
             return;
         }
-        if (value.textboxKeyTyped(aChar, aKey)) return;
         super.keyTyped(aChar, aKey);
     }
 
@@ -296,24 +317,12 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
         boolean existing = !StringUtils.isEmpty(keyText) && ChannelDataAccessor.hasSubChannel(trigger, keyText);
         getButtonList().get(ADD_BTN).displayString = existing ? I18n.format(I18N_PREFIX + "set")
                 : I18n.format(I18N_PREFIX + "add");
-        getButtonList().get(ADD_BTN).enabled = !StringUtils.isBlank(value.getText())
+        getButtonList().get(ADD_BTN).enabled = !StringUtils.isBlank(key.getText())
+                && !StringUtils.isBlank(value.getText())
                 && Integer.parseInt(value.getText()) > 0;
         getButtonList().get(UNSET_BTN).enabled = existing && !StringUtils.isBlank(value.getText());
 
-        if (ChannelDataAccessor.hasSubChannel(trigger, SHOW_ERROR_CHANNEL)) {
-            getButtonList().get(SHOW_ERROR_BTN).displayString = I18n.format(I18N_PREFIX + "error.hide");
-        } else {
-            getButtonList().get(SHOW_ERROR_BTN).displayString = I18n.format(I18N_PREFIX + "error.show");
-        }
-
-        // this button only exists if GT is loaded.
-        if (StructureLib.isGTLoaded) {
-            if (ChannelDataAccessor.hasSubChannel(trigger, GT_NO_HATCH_CHANNEL)) {
-                getButtonList().get(GT_NO_HATCH_BTN).displayString = I18n.format(I18N_PREFIX + "gt_no_hatch.disable");
-            } else {
-                getButtonList().get(GT_NO_HATCH_BTN).displayString = I18n.format(I18N_PREFIX + "gt_no_hatch.enable");
-            }
-        }
+        autoCompleteList.reset();
     }
 
     private int getValue() {
@@ -338,20 +347,8 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
                 break;
             case WIPE_BTN:
                 ChannelDataAccessor.wipeChannelData(trigger);
-                break;
-            case SHOW_ERROR_BTN:
-                if (ChannelDataAccessor.hasSubChannel(trigger, SHOW_ERROR_CHANNEL)) {
-                    ChannelDataAccessor.unsetChannelData(trigger, SHOW_ERROR_CHANNEL);
-                } else {
-                    ChannelDataAccessor.setChannelData(trigger, SHOW_ERROR_CHANNEL, 1);
-                }
-                break;
-            case GT_NO_HATCH_BTN:
-                if (ChannelDataAccessor.hasSubChannel(trigger, GT_NO_HATCH_CHANNEL)) {
-                    ChannelDataAccessor.unsetChannelData(trigger, GT_NO_HATCH_CHANNEL);
-                } else {
-                    ChannelDataAccessor.setChannelData(trigger, GT_NO_HATCH_CHANNEL, 1);
-                }
+                key.setText("");
+                this.value.setText("");
                 break;
         }
 
@@ -375,32 +372,234 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
     }
 
     @Override
-    public boolean doesGuiPauseGame() {
-        return false;
-    }
-
-    @Override
-    public void drawScreen(int mX, int mY, float partialTick) {
+    public void drawGuiContainerBackgroundLayer(float partialTick, int mX, int mY) {
         mc.renderEngine.bindTexture(new ResourceLocation("structurelib", "textures/gui/channels.png"));
         int topLeftX = (this.width - this.getXSize()) / 2;
         int topLeftY = (this.height - this.getYSize()) / 2;
         drawTexturedModalRect(topLeftX, topLeftY, 0, 0, getXSize(), getYSize());
-        super.drawScreen(mX, mY, partialTick);
         list.drawScreen(mX, mY, partialTick);
-        fontRendererObj.drawString(
-                I18n.format("item.structurelib.constructableTrigger.gui.key"),
-                guiLeft + 12,
-                guiTop + 122,
-                0);
+        fontRendererObj.drawString(I18n.format(I18N_PREFIX + "title"), guiLeft + 12, guiTop + 9, 0);
+        fontRendererObj.drawString(I18n.format(I18N_PREFIX + "key"), guiLeft + 12, guiTop + 122, 0);
         key.drawTextBox();
-        fontRendererObj.drawString(
-                I18n.format("item.structurelib.constructableTrigger.gui.value"),
-                guiLeft + 12,
-                guiTop + 142,
-                0);
+        fontRendererObj.drawString(I18n.format(I18N_PREFIX + "value"), guiLeft + 12, guiTop + 142, 0);
         value.drawTextBox();
     }
 
+    @Override
+    protected void drawGuiContainerForegroundLayer(int mouseX, int mouseY) {
+        if (key.isFocused() && autoCompleteList.getNumElements() > 0) {
+            autoCompleteList.drawScreen(mouseX, mouseY, 0);
+        }
+    }
+
+    @Override
+    public void drawScreen(int mouseX, int mouseY, float partialTicks) {
+        super.drawScreen(mouseX, mouseY, partialTicks);
+        String highlight = null;
+        if (key.isFocused() && autoCompleteList.getNumElements() > 0) {
+            highlight = autoCompleteList.getSelectedElement();
+        }
+        if (highlight == null && ChannelDescription.has(key.getText())) {
+            highlight = key.getText();
+        }
+        if (highlight != null) {
+            drawChannelDescriptionTooltip(highlight);
+        }
+        if (mouseX > xSize + guiLeft - INFO_BOX_SIZE - 12 && mouseX < xSize + guiLeft - 12
+                && mouseY > guiTop + 7
+                && mouseY < guiTop + INFO_BOX_SIZE + 7) {
+            drawHoveringText(info, mouseX, mouseY, fontRendererObj);
+        }
+    }
+
+    private void drawChannelDescriptionTooltip(String candidate) {
+        List<String> tooltip = tooltipSplitCache.computeIfAbsent(candidate, this::getChannelDescriptionTooltip);
+        drawHoveringText(tooltip, guiLeft + 151 + 12, guiTop + 122, fontRendererObj);
+    }
+
+    private List<String> getChannelDescriptionTooltip(String candidate) {
+        List<String> tooltip = new ArrayList<>();
+        int maxLine = width - (guiLeft + 151 + 12) - 12;
+        for (Entry<String, String> e : ChannelDescription.get(candidate).getDescriptions().entrySet()) {
+            tooltip.addAll(
+                    fontRendererObj.listFormattedStringToWidth(
+                            StatCollector.translateToLocalFormatted(
+                                    I18N_PREFIX + "channels.from",
+                                    Loader.instance().getIndexedModList().get(e.getKey()).getName()),
+                            maxLine));
+            tooltip.addAll(
+                    fontRendererObj.listFormattedStringToWidth(StatCollector.translateToLocal(e.getValue()), maxLine));
+        }
+        return tooltip;
+    }
+
+    public String trim(String str, int keyMaxWidth) {
+        Map<String, String> cache = trimCache.get(keyMaxWidth);
+        if (cache == null) {
+            trimCache.put(keyMaxWidth, cache = new HashMap<>());
+        }
+        return cache.computeIfAbsent(str, e -> {
+            String s = fontRendererObj.trimStringToWidth(e, keyMaxWidth);
+            if (s.length() != e.length()) {
+                StringBuilder buffer = new StringBuilder(s).deleteCharAt(s.length() - 1).append("...");
+                while ((s = fontRendererObj.trimStringToWidth(buffer.toString(), keyMaxWidth)).length()
+                        != buffer.length())
+                    // drop last original char
+                    buffer.deleteCharAt(s.length() - 4);
+                do {
+                    buffer.append('.');
+                } while (fontRendererObj.getStringWidth(buffer.toString()) <= keyMaxWidth);
+                s = buffer.deleteCharAt(s.length() - 1).insert(s.length() - 3, EnumChatFormatting.GRAY).toString();
+            }
+            return s;
+        });
+    }
+
+    @Override
+    @Optional.Method(modid = "NotEnoughItems")
+    public VisiblityData modifyVisiblity(GuiContainer gui, VisiblityData currentVisibility) {
+        return null;
+    }
+
+    @Override
+    public Iterable<Integer> getItemSpawnSlots(GuiContainer gui, ItemStack item) {
+        return Collections.emptyList();
+    }
+
+    @Override
+    public List<TaggedInventoryArea> getInventoryAreas(GuiContainer gui) {
+        return Collections.emptyList();
+    }
+
+    @Override
+    public boolean handleDragNDrop(GuiContainer gui, int mousex, int mousey, ItemStack draggedStack, int button) {
+        if (button != 0 || mousex <= guiLeft
+                || mousey <= guiTop
+                || mousex >= guiLeft + getXSize()
+                || mousey >= guiTop + getYSize()) {
+            return false;
+        }
+        Collection<Entry<String, Integer>> channels = ChannelDescription.iterate(draggedStack);
+        switch (channels.size()) {
+            case 0:
+                return false;
+            case 1:
+            default: // TODO implement a GUI to select which pair to use, instead of blindly using the first
+                Entry<String, Integer> e = channels.iterator().next();
+                ChannelDataAccessor.setChannelData(trigger, e.getKey(), e.getValue());
+                key.setText(e.getKey());
+                value.setText(e.getValue().toString());
+                draggedStack.stackSize = 0;
+                return true;
+        }
+    }
+
+    @Override
+    public boolean hideItemPanelSlot(GuiContainer gui, int x, int y, int w, int h) {
+        return false;
+    }
+
+    private class GuiAutoCompleteList extends GuiScrollableList<String> {
+
+        private List<Entry<String, String>> cache; // <key, display string>
+
+        public GuiAutoCompleteList(int width, int height, int originX, int originY, int slotHeight) {
+            super(width, height, originX, originY, slotHeight);
+            margin = 2;
+        }
+
+        private List<Entry<String, String>> getOptions() {
+            if (cache == null) {
+                cache = search();
+            }
+            return cache;
+        }
+
+        private List<Entry<String, String>> search() {
+            List<Entry<String, String>> cache = new ArrayList<>();
+            Set<String> added = new HashSet<>();
+            String term = key.getText();
+            String[] subjects = ChannelDescription.getAll().keySet().toArray(new String[0]);
+            Arrays.sort(subjects);
+            if (StringUtils.isBlank(term)) {
+                // nothing. just gives out everything
+                for (String subject : subjects) {
+                    cache.add(new AbstractMap.SimpleImmutableEntry<>(subject, EnumChatFormatting.GRAY + subject));
+                }
+                return cache;
+            }
+            // prefix match
+            for (String s : subjects) {
+                if (s.startsWith(term)) {
+                    cache.add(
+                            new AbstractMap.SimpleImmutableEntry<>(
+                                    s,
+                                    term + EnumChatFormatting.GRAY + s.substring(term.length())));
+                    added.add(s);
+                }
+            }
+            // subsequence match
+            for (String subject : subjects) {
+                if (!added.contains(subject) && subject.length() > term.length()) {
+                    int i = 0, j = 0;
+                    StringBuilder sb = new StringBuilder();
+                    boolean mode = true;
+                    sb.append(EnumChatFormatting.WHITE);
+                    while (i < term.length() && j < subject.length()) {
+                        if (term.codePointAt(i) == subject.codePointAt(j)) {
+                            if (!mode) {
+                                sb.append(EnumChatFormatting.WHITE);
+                                mode = true;
+                            }
+                            sb.appendCodePoint(term.codePointAt(i));
+                            i++;
+                            j++;
+                        } else {
+                            if (mode) {
+                                sb.append(EnumChatFormatting.GRAY);
+                                mode = false;
+                            }
+                            sb.appendCodePoint(subject.codePointAt(j));
+                            j++;
+                        }
+                    }
+                    if (i == term.length()) {
+                        if (j < subject.length()) {
+                            sb.append(EnumChatFormatting.GRAY);
+                            sb.append(subject, j, subject.length());
+                        }
+                        cache.add(new AbstractMap.SimpleImmutableEntry<>(subject, sb.toString()));
+                        added.add(subject);
+                    }
+                }
+            }
+            return cache;
+        }
+
+        public void reset() {
+            cache = search();
+            selectedIndex = cache.isEmpty() ? -1 : 0;
+            resetScroll();
+        }
+
+        @Override
+        public String getElementAt(int index) {
+            return index >= 0 && index < cache.size() ? getOptions().get(index).getKey() : null;
+        }
+
+        @Override
+        public int getNumElements() {
+            return getOptions().size();
+        }
+
+        @Override
+        protected void drawElement(int elementIndex, int x, int y, int height, Tessellator tessellator,
+                boolean isHovering) {
+            int color = elementIndex == selectedIndex ? 0xffffff : 0xcccccc;
+            fontRendererObj.drawString(getOptions().get(elementIndex).getValue(), x + margin, y + margin / 2, color);
+        }
+    }
+
     private class GuiChannelsList extends GuiScrollableList<Entry<String, Integer>> {
 
         private List<Entry<String, Integer>> cache;
@@ -468,22 +667,5 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
             // args x1, y1, y2, color
             drawVerticalLine(minX + margin + margin / 2 + KEY_MAX_WIDTH * 2, minY + 1, maxY - 1, 0xffaaaaaa);
         }
-
-        public String trim(String e, int keyMaxWidth) {
-            // TODO optimize this to not create a billion string, or maybe cache this
-            String s = fontRendererObj.trimStringToWidth(e, keyMaxWidth);
-            if (s.length() != e.length()) {
-                StringBuilder buffer = new StringBuilder(s).deleteCharAt(s.length() - 1).append("...");
-                while ((s = fontRendererObj.trimStringToWidth(buffer.toString(), keyMaxWidth)).length()
-                        != buffer.length())
-                    // drop last original char
-                    buffer.deleteCharAt(s.length() - 4);
-                do {
-                    buffer.append('.');
-                } while (fontRendererObj.getStringWidth(buffer.toString()) <= keyMaxWidth);
-                s = buffer.deleteCharAt(s.length() - 1).insert(s.length() - 3, EnumChatFormatting.GRAY).toString();
-            }
-            return s;
-        }
     }
 }

src/main/java/com/gtnewhorizon/structurelib/gui/GuiScrollableList.java

@@ -16,7 +16,7 @@ import org.lwjgl.opengl.GL11;
  * <p>
  * As the code has been released into public domain, it is now LGPL as part of this library as a whole. You can go to
  * EnderCore's repository to obtain a public domain copy though
- *
+ * <p>
  * Major edits
  * <ul>
  * <li>Separate dwheel handling to handleDWheel. The next event calls often cause the mouse click event to not fire on
@@ -167,10 +167,17 @@ public abstract class GuiScrollableList<T> {
         }
     }
 
+    protected void resetScroll() {
+        amountScrolled = 0;
+    }
+
     /**
      * draws the slot to the screen, pass in mouse's current x and y and partial ticks
      */
     public void drawScreen(int mX, int mY, float partialTick) {
+        GL11.glPushMatrix();
+        GL11.glLoadIdentity();
+        GL11.glTranslatef(0.0F, 0.0F, -2000.0F);
         this.mouseX = mX;
         this.mouseY = mY;
 
@@ -199,13 +206,26 @@ public abstract class GuiScrollableList<T> {
         int contentYOffset = this.minY + margin - amountScrolled;
 
         boolean hoveringPrecondition = mX >= minX && mX <= maxX && mY >= minY && mY <= maxY;
+        int slotHeight = this.slotHeight - margin;
+
+        if (selectedIndex != -1) {
+            int elementY = contentYOffset + selectedIndex * this.slotHeight;
+            if (elementY + slotHeight > maxY) {
+                this.amountScrolled = (selectedIndex + 1) * this.slotHeight - this.height + margin;
+                amountScrolled = (int) this.amountScrolled;
+                contentYOffset = this.minY + margin - amountScrolled;
+            } else if (elementY < minY) {
+                this.amountScrolled = selectedIndex * this.slotHeight;
+                amountScrolled = (int) this.amountScrolled;
+                contentYOffset = this.minY + margin - amountScrolled;
+            }
+        }
 
         prepareDrawElements();
 
         for (int i = 0; i < getNumElements(); ++i) {
 
             int elementY = contentYOffset + i * this.slotHeight;
-            int slotHeight = this.slotHeight - margin;
 
             if (elementY <= maxY && elementY + slotHeight >= minY) {
 
@@ -264,6 +284,7 @@ public abstract class GuiScrollableList<T> {
         GL11.glShadeModel(GL11.GL_FLAT);
         GL11.glEnable(GL11.GL_ALPHA_TEST);
         GL11.glDisable(GL11.GL_BLEND);
+        GL11.glPopMatrix();
     }
 
     protected void prepareDrawElements() {}
@@ -412,7 +433,7 @@ public abstract class GuiScrollableList<T> {
         GL11.glColor4f(1.0F, 1.0F, 1.0F, 1.0F);
         GL11.glDisable(GL11.GL_TEXTURE_2D);
         tess.startDrawingQuads();
-        tess.setColorOpaque_I(2105376);
+        tess.setColorOpaque_I(0x202020);
         tess.addVertex(minX, maxY, 0.0D);
         tess.addVertex(maxX, maxY, 0.0D);
         tess.addVertex(maxX, minY, 0.0D);

src/main/java/com/gtnewhorizon/structurelib/item/ItemConstructableTrigger.java

@@ -17,9 +17,6 @@ import org.lwjgl.input.Keyboard;
 import com.gtnewhorizon.structurelib.StructureLib;
 import com.gtnewhorizon.structurelib.alignment.constructable.ChannelDataAccessor;
 import com.gtnewhorizon.structurelib.alignment.constructable.ConstructableUtility;
-import com.gtnewhorizon.structurelib.gui.GuiScreenConfigureChannels;
-
-import cpw.mods.fml.common.FMLCommonHandler;
 
 public class ItemConstructableTrigger extends Item {
 
@@ -31,11 +28,12 @@ public class ItemConstructableTrigger extends Item {
 
     @Override
     public ItemStack onItemRightClick(ItemStack stack, World world, EntityPlayer player) {
-        if (world.isRemote && getMovingObjectPositionFromPlayer(world, player, true) == null) {
-            if (player.isSneaking()) {
+        if (getMovingObjectPositionFromPlayer(world, player, true) == null) {
+            // channel gui is opened from server and config gui from client
+            if (!world.isRemote && !player.isSneaking()) {
+                player.openGui(StructureLib.instance(), 0, world, player.inventory.currentItem, 0, 0);
+            } else if (world.isRemote && player.isSneaking()) {
                 StructureLib.instance().proxy().displayConfigGUI("registries");
-            } else {
-                FMLCommonHandler.instance().showGuiScreen(new GuiScreenConfigureChannels(stack));
             }
         }
         return super.onItemRightClick(stack, world, player);

src/main/java/com/gtnewhorizon/structurelib/mixins/Mixins.java

@@ -1,188 +0,0 @@
-package com.gtnewhorizon.structurelib.mixins;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
-import java.util.Set;
-import java.util.function.Supplier;
-
-import com.gtnewhorizon.structurelib.core.StructureLibCore;
-
-import cpw.mods.fml.relauncher.FMLLaunchHandler;
-
-public enum Mixins {
-
-    BLOCK_CHANGE_NOTIFIER(new Builder("Block Change Notifier").setPhase(Phase.EARLY)
-            .addMixinClasses("blockChangeNotifier.MixinForgeHooks", "blockChangeNotifier.MixinWorld")
-            .addTargetedMod(TargetedMod.VANILLA).setSide(Side.BOTH).setApplyIf(() -> true));
-
-    private final List<String> mixinClasses;
-    private final List<TargetedMod> targetedMods;
-    private final List<TargetedMod> excludedMods;
-    private final Supplier<Boolean> applyIf;
-    private final Phase phase;
-    private final Side side;
-
-    Mixins(Builder builder) {
-        this.mixinClasses = builder.mixinClasses;
-        this.targetedMods = builder.targetedMods;
-        this.excludedMods = builder.excludedMods;
-        this.applyIf = builder.applyIf;
-        this.phase = builder.phase;
-        this.side = builder.side;
-        if (this.mixinClasses.isEmpty()) {
-            throw new RuntimeException("No mixin class specified for Mixin : " + this.name());
-        }
-        if (this.targetedMods.isEmpty()) {
-            throw new RuntimeException("No targeted mods specified for Mixin : " + this.name());
-        }
-        if (this.applyIf == null) {
-            throw new RuntimeException("No ApplyIf function specified for Mixin : " + this.name());
-        }
-        if (this.phase == null) {
-            throw new RuntimeException("No Phase specified for Mixin : " + this.name());
-        }
-        if (this.side == null) {
-            throw new RuntimeException("No Side function specified for Mixin : " + this.name());
-        }
-    }
-
-    public static List<String> getEarlyMixins(Set<String> loadedCoreMods) {
-        final List<String> mixins = new ArrayList<>();
-        final List<String> notLoading = new ArrayList<>();
-        for (Mixins mixin : Mixins.values()) {
-            if (mixin.phase == Phase.EARLY) {
-                if (mixin.shouldLoad(loadedCoreMods, Collections.emptySet())) {
-                    mixins.addAll(mixin.mixinClasses);
-                } else {
-                    notLoading.addAll(mixin.mixinClasses);
-                }
-            }
-        }
-        StructureLibCore.log.info("Not loading the following EARLY mixins: {}", notLoading.toString());
-        return mixins;
-    }
-
-    public static List<String> getLateMixins(Set<String> loadedMods) {
-        // NOTE: Any targetmod here needs a modid, not a coremod id
-        final List<String> mixins = new ArrayList<>();
-        final List<String> notLoading = new ArrayList<>();
-        for (Mixins mixin : Mixins.values()) {
-            if (mixin.phase == Phase.LATE) {
-                if (mixin.shouldLoad(Collections.emptySet(), loadedMods)) {
-                    mixins.addAll(mixin.mixinClasses);
-                } else {
-                    notLoading.addAll(mixin.mixinClasses);
-                }
-            }
-        }
-        StructureLibCore.log.info("Not loading the following LATE mixins: {}", notLoading.toString());
-        return mixins;
-    }
-
-    private boolean shouldLoadSide() {
-        return side == Side.BOTH || (side == Side.SERVER && FMLLaunchHandler.side().isServer())
-                || (side == Side.CLIENT && FMLLaunchHandler.side().isClient());
-    }
-
-    private boolean allModsLoaded(List<TargetedMod> targetedMods, Set<String> loadedCoreMods, Set<String> loadedMods) {
-        if (targetedMods.isEmpty()) return false;
-
-        for (TargetedMod target : targetedMods) {
-            if (target == TargetedMod.VANILLA) continue;
-
-            // Check coremod first
-            if (!loadedCoreMods.isEmpty() && target.coreModClass != null
-                    && !loadedCoreMods.contains(target.coreModClass))
-                return false;
-            else if (!loadedMods.isEmpty() && target.modId != null && !loadedMods.contains(target.modId)) return false;
-        }
-
-        return true;
-    }
-
-    private boolean noModsLoaded(List<TargetedMod> targetedMods, Set<String> loadedCoreMods, Set<String> loadedMods) {
-        if (targetedMods.isEmpty()) return true;
-
-        for (TargetedMod target : targetedMods) {
-            if (target == TargetedMod.VANILLA) continue;
-
-            // Check coremod first
-            if (!loadedCoreMods.isEmpty() && target.coreModClass != null
-                    && loadedCoreMods.contains(target.coreModClass))
-                return false;
-            else if (!loadedMods.isEmpty() && target.modId != null && loadedMods.contains(target.modId)) return false;
-        }
-
-        return true;
-    }
-
-    private boolean shouldLoad(Set<String> loadedCoreMods, Set<String> loadedMods) {
-        return (shouldLoadSide() && applyIf.get()
-                && allModsLoaded(targetedMods, loadedCoreMods, loadedMods)
-                && noModsLoaded(excludedMods, loadedCoreMods, loadedMods));
-    }
-
-    private static class Builder {
-
-        private final String name;
-        private final List<String> mixinClasses = new ArrayList<>();
-        private final List<TargetedMod> targetedMods = new ArrayList<>();
-        private final List<TargetedMod> excludedMods = new ArrayList<>();
-        private Supplier<Boolean> applyIf = null;
-        private Phase phase = null;
-        private Side side = null;
-
-        public Builder(String name) {
-            this.name = name;
-        }
-
-        public Builder addMixinClasses(String... mixinClasses) {
-            this.mixinClasses.addAll(Arrays.asList(mixinClasses));
-            return this;
-        }
-
-        public Builder setPhase(Phase phase) {
-            if (this.phase != null) {
-                throw new RuntimeException("Trying to define Phase twice for " + this.name);
-            }
-            this.phase = phase;
-            return this;
-        }
-
-        public Builder setSide(Side side) {
-            if (this.side != null) {
-                throw new RuntimeException("Trying to define Side twice for " + this.name);
-            }
-            this.side = side;
-            return this;
-        }
-
-        public Builder setApplyIf(Supplier<Boolean> applyIf) {
-            this.applyIf = applyIf;
-            return this;
-        }
-
-        public Builder addTargetedMod(TargetedMod mod) {
-            this.targetedMods.add(mod);
-            return this;
-        }
-
-        public Builder addExcludedMod(TargetedMod mod) {
-            this.excludedMods.add(mod);
-            return this;
-        }
-    }
-
-    private enum Side {
-        BOTH,
-        CLIENT,
-        SERVER
-    }
-
-    private enum Phase {
-        EARLY,
-        LATE,
-    }
-}

src/main/java/com/gtnewhorizon/structurelib/structure/IStructureDefinition.java

@@ -319,6 +319,22 @@ public interface IStructureDefinition<T> {
         return walker.getBuilt();
     }
 
+    default void iterate(String piece, World world, ExtendedFacing extendedFacing, int basePositionX, int basePositionY,
+            int basePositionZ, int basePositionA, int basePositionB, int basePositionC, IStructureWalker<T> predicate) {
+        StructureUtility.iterateV2(
+                getStructureFor(piece),
+                world,
+                extendedFacing,
+                basePositionX,
+                basePositionY,
+                basePositionZ,
+                basePositionA,
+                basePositionB,
+                basePositionC,
+                predicate,
+                "customIterate");
+    }
+
     /**
      * Low level utility.
      *
@@ -395,7 +411,7 @@ public interface IStructureDefinition<T> {
                         basePositionC,
                         ignoreBlockUnloaded((e, w, x, y, z, a, b, c) -> {
                             e.spawnHint(object, world, x, y, z, trigger);
-                            if (ChannelDataAccessor.hasSubChannel(trigger, "show_error")
+                            if (ChannelDataAccessor.hasSubChannel(trigger, StructureLibAPI.CHANNEL_SHOW_ERROR)
                                     && !e.couldBeValid(object, world, x, y, z, trigger)) {
                                 StructureLibAPI.markHintParticleError(StructureLib.getCurrentPlayer(), world, x, y, z);
                             }

src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElement.java

@@ -5,6 +5,7 @@ import static com.gtnewhorizon.structurelib.StructureLib.PANIC_MODE;
 
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.List;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 
@@ -42,6 +43,30 @@ public interface IStructureElement<T> {
         return true;
     }
 
+    /**
+     * Returns a human-readable description of what block(s) this element accepts. Used for diagnostic messages when
+     * structure checks fail (e.g. "expected Input Bus at (1, 2, 3)").
+     * <p>
+     * Unlike {@link #getBlocksToPlace}, which returns the full set of concrete block variants for autoplacing (e.g.
+     * every tier of Input Bus), this method returns <b>category-level</b> descriptions suitable for display to the
+     * player (e.g. just "Input Bus"). It also requires no parameters, no world, trigger item, or environment, making it
+     * usable in contexts where those are unavailable.
+     * <p>
+     * Implementations should return <b>lang keys</b> (e.g. {@code "tile.blockGlass.name"}) rather than pre-translated
+     * display names. The caller is responsible for translating these keys on the client side via
+     * {@code StatCollector.translateToLocal()}. If a key has no matching translation, {@code translateToLocal} returns
+     * the input string unchanged, so pre-translated fallback strings also work.
+     *
+     * @param context the context object (e.g. the multiblock controller), used to determine state-dependent
+     *                descriptions
+     * @return a list of accepted block descriptions as lang keys (or display names as fallback), or null if no
+     *         description is available
+     */
+    @Nullable
+    default List<String> getDescription(T context) {
+        return null;
+    }
+
     boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger);
 
     boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger);
@@ -71,7 +96,7 @@ public interface IStructureElement<T> {
                 "Default implementation of survivalPlaceBlock hit! Things aren't going to work well! IStructureElement class: {}",
                 getClass().getName());
         if (!StructureLibAPI.isBlockTriviallyReplaceable(world, x, y, z, actor)) return PlaceResult.REJECT;
-        return PlaceResult.SKIP;
+        return PlaceResult.REJECT_CONTINUE;
     }
 
     /**
@@ -181,7 +206,7 @@ public interface IStructureElement<T> {
         if (StructureLibAPI.isDebugEnabled()) LOGGER.info(
                 "Fallback shim code of survivalPlaceBlock hit! Things aren't going to work well! IStructureElement class: {}",
                 getClass().getName());
-        return PlaceResult.SKIP;
+        return PlaceResult.REJECT_CONTINUE;
     }
 
     /**
@@ -204,6 +229,12 @@ public interface IStructureElement<T> {
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 return IStructureElement.this.spawnHint(t, world, x, y, z, trigger);
             }
+
+            @Nullable
+            @Override
+            public List<String> getDescription(T context) {
+                return IStructureElement.this.getDescription(context);
+            }
         };
     }
 
@@ -237,16 +268,21 @@ public interface IStructureElement<T> {
 
     enum PlaceResult {
         /**
-         * This element either exists already, or does not yet have an implementation for survivalPlaceBlock, or some
-         * other unforeseen situations. TODO this definition doesn't seem right. Should we separate SKIP from EXISTS, or
-         * SKIP from ERROR?
+         * The element's check passed, the position is already valid. No placement is needed. In the walker: continue
+         * iteration (no error, not counted as placed). In ofChain: short-circuits, remaining alternatives are skipped.
          */
         SKIP,
         /**
-         * This element's space is occupied by other stuff and require player attention, or player missing required
-         * resource, or the block cannot be placed due to obscure mechanisms, or some other unforeseen situations.
+         * The element cannot handle this position (occupied, missing resources, etc.). In the walker: stop iteration
+         * with error particles. In ofChain: try next alternative.
          */
         REJECT,
+        /**
+         * This element has no survivalPlaceBlock implementation (default fallback), or otherwise cannot place but is
+         * not an error condition. In the walker: continue iteration silently (like SKIP). In ofChain: try next
+         * alternative (like REJECT), so a better-suited element can handle it.
+         */
+        REJECT_CONTINUE,
         /**
          * Autoplace cannot proceed within this tick. To proceed further would require stopping the placement and wait
          * for next round.

src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElementChain.java

@@ -1,7 +1,9 @@
 package com.gtnewhorizon.structurelib.structure;
 
 import java.util.ArrayList;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Set;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 
@@ -61,6 +63,19 @@ public interface IStructureElementChain<T> extends IStructureElement<T> {
         return false;
     }
 
+    @Nullable
+    @Override
+    default List<String> getDescription(T context) {
+        Set<String> descriptions = new LinkedHashSet<>();
+        for (IStructureElement<T> fallback : fallbacks()) {
+            List<String> desc = fallback.getDescription(context);
+            if (desc != null) {
+                descriptions.addAll(desc);
+            }
+        }
+        return descriptions.isEmpty() ? null : new ArrayList<>(descriptions);
+    }
+
     @Nullable
     @Override
     default BlocksToPlace getBlocksToPlace(T t, World world, int x, int y, int z, ItemStack trigger,
@@ -82,47 +97,51 @@ public interface IStructureElementChain<T> extends IStructureElement<T> {
     @Override
     default PlaceResult survivalPlaceBlock(T t, World world, int x, int y, int z, ItemStack trigger, IItemSource s,
             EntityPlayerMP actor, Consumer<IChatComponent> chatter) {
-        boolean haveSkip = false;
+        boolean allContinue = true;
         List<IChatComponent> bufferedNoise = new ArrayList<>();
         for (IStructureElement<T> fallback : fallbacks()) {
             PlaceResult result = fallback.survivalPlaceBlock(t, world, x, y, z, trigger, s, actor, bufferedNoise::add);
             switch (result) {
+                case REJECT_CONTINUE:
+                    break;
                 case REJECT:
+                    allContinue = false;
                     break;
                 case SKIP:
-                    haveSkip = true;
-                    break;
+                    bufferedNoise.forEach(chatter);
+                    return PlaceResult.SKIP;
                 default:
                     return result;
             }
         }
         // dump all that noise back into upstream
         bufferedNoise.forEach(chatter);
-        // TODO need reconsider to ensure this is the right course of action
-        return haveSkip ? PlaceResult.SKIP : PlaceResult.REJECT;
+        return allContinue ? PlaceResult.REJECT_CONTINUE : PlaceResult.REJECT;
     }
 
     @Override
     default PlaceResult survivalPlaceBlock(T t, World world, int x, int y, int z, ItemStack trigger,
             AutoPlaceEnvironment env) {
-        boolean haveSkip = false;
+        boolean allContinue = true;
         List<IChatComponent> bufferedNoise = new ArrayList<>();
         for (IStructureElement<T> fallback : fallbacks()) {
             PlaceResult result = fallback
                     .survivalPlaceBlock(t, world, x, y, z, trigger, env.withChatter(bufferedNoise::add));
             switch (result) {
+                case REJECT_CONTINUE:
+                    break;
                 case REJECT:
+                    allContinue = false;
                     break;
                 case SKIP:
-                    haveSkip = true;
-                    break;
+                    bufferedNoise.forEach(env.getChatter());
+                    return PlaceResult.SKIP;
                 default:
                     return result;
             }
         }
         // dump all that noise back into upstream
         bufferedNoise.forEach(env.getChatter());
-        // TODO need reconsider to ensure this is the right course of action
-        return haveSkip ? PlaceResult.SKIP : PlaceResult.REJECT;
+        return allContinue ? PlaceResult.REJECT_CONTINUE : PlaceResult.REJECT;
     }
 }

src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElementCheckOnly.java

@@ -27,12 +27,12 @@ public interface IStructureElementCheckOnly<T> extends IStructureElement<T> {
     @Override
     default PlaceResult survivalPlaceBlock(T t, World world, int x, int y, int z, ItemStack trigger, IItemSource s,
             EntityPlayerMP actor, Consumer<IChatComponent> chatter) {
-        return PlaceResult.SKIP;
+        return PlaceResult.REJECT_CONTINUE;
     }
 
     @Override
     default PlaceResult survivalPlaceBlock(T t, World world, int x, int y, int z, ItemStack trigger,
             AutoPlaceEnvironment env) {
-        return PlaceResult.SKIP;
+        return PlaceResult.REJECT_CONTINUE;
     }
 }

src/main/java/com/gtnewhorizon/structurelib/structure/IStructureWalker.java

@@ -2,8 +2,25 @@ package com.gtnewhorizon.structurelib.structure;
 
 import net.minecraft.world.World;
 
-interface IStructureWalker<T> {
+/**
+ * A functional interface that is used to iterate over an arbitrary structure.
+ */
+@FunctionalInterface
+public interface IStructureWalker<T> {
 
+    /**
+     * Called once per structure element.
+     *
+     * @param element The current element
+     * @param world   The current world
+     * @param x       The absolute X position of the element in world coordinates
+     * @param y       The absolute Y position of the element in world coordinates
+     * @param z       The absolute Z position of the element in world coordinates
+     * @param a       The relative A position of the element in structure-local coordinates (pre transform)
+     * @param b       The relative B position of the element in structure-local coordinates (pre transform)
+     * @param c       The relative C position of the element in structure-local coordinates (pre transform)
+     * @return False to stop iterating, true to continue.
+     */
     boolean visit(IStructureElement<T> element, World world, int x, int y, int z, int a, int b, int c);
 
     default boolean blockNotLoaded(IStructureElement<T> element, World world, int x, int y, int z, int a, int b,

src/main/java/com/gtnewhorizon/structurelib/structure/LazyStructureElement.java

@@ -1,5 +1,6 @@
 package com.gtnewhorizon.structurelib.structure;
 
+import java.util.List;
 import java.util.function.Consumer;
 import java.util.function.Function;
 
@@ -65,4 +66,10 @@ class LazyStructureElement<T> implements IStructureElementDeferred<T> {
             AutoPlaceEnvironment env) {
         return get(t).survivalPlaceBlock(t, world, x, y, z, trigger, env);
     }
+
+    @Nullable
+    @Override
+    public List<String> getDescription(T context) {
+        return elem != null ? elem.getDescription(context) : null;
+    }
 }

src/main/java/com/gtnewhorizon/structurelib/structure/StructureDefinition.java

@@ -148,15 +148,32 @@ public class StructureDefinition<T> implements IStructureDefinition<T> {
 
             occupiedSpaces.put(name, occupiedSpace);
 
-            String built = builder.toString().replaceAll("[\\uA000\\uB000\\uC000]", "");
+            boolean hasPlus = false;
+            boolean hasMinus = false;
 
-            if (built.contains("+")) {
+            int write = 0;
+            for (int read = 0; read < builder.length(); read++) {
+                char ch = builder.charAt(read);
+                if (ch == A || ch == B || ch == C) {
+                    continue;
+                }
+                if (ch == '+') {
+                    hasPlus = true;
+                } else if (ch == '-') {
+                    hasMinus = true;
+                }
+                if (read != write) builder.setCharAt(write, ch);
+                write++;
+            }
+            builder.setLength(write);
+
+            if (hasPlus) {
                 addElement('+', notAir());
             }
-            if (built.contains("-")) {
+            if (hasMinus) {
                 addElement('-', isAir());
             }
-            shapes.put(name, built);
+            shapes.put(name, builder.toString());
             return this;
         }
 

src/main/java/com/gtnewhorizon/structurelib/structure/StructureUtility.java

@@ -36,7 +36,10 @@ import net.minecraft.item.ItemBlock;
 import net.minecraft.item.ItemStack;
 import net.minecraft.nbt.NBTTagCompound;
 import net.minecraft.tileentity.TileEntity;
+import net.minecraft.util.ChatComponentText;
 import net.minecraft.util.ChatComponentTranslation;
+import net.minecraft.util.ChatStyle;
+import net.minecraft.util.EnumChatFormatting;
 import net.minecraft.util.IChatComponent;
 import net.minecraft.util.IIcon;
 import net.minecraft.world.World;
@@ -338,9 +341,7 @@ public class StructureUtility {
         ItemStack stack = new ItemStack(itemBlock, 1, itemMeta);
         if (!s.takeOne(stack, true)) {
             if (chatter != null) chatter.accept(
-                    new ChatComponentTranslation(
-                            "structurelib.autoplace.error.no_simple_block",
-                            stack.func_151000_E()));
+                    new ChatComponentTranslation("structurelib.autoplace.missing_block", stack.func_151000_E()));
             return PlaceResult.REJECT;
         }
         if (block instanceof ICustomBlockSetting) {
@@ -447,7 +448,7 @@ public class StructureUtility {
         if (!StructureLibAPI.isBlockTriviallyReplaceable(world, x, y, z, actor)) return PlaceResult.REJECT;
         if (!assumeStackPresent && !s.takeOne(stack, true)) {
             if (chatter != null) chatter.accept(
-                    new ChatComponentTranslation("structurelib.autoplace.error.no_item_stack", stack.func_151000_E()));
+                    new ChatComponentTranslation("structurelib.autoplace.missing_block", stack.func_151000_E()));
             return PlaceResult.REJECT;
         }
         if (!stack.copy().tryPlaceItemIntoWorld(actor, world, x, y, z, ForgeDirection.UP.ordinal(), 0.5f, 0.5f, 0.5f))
@@ -614,35 +615,35 @@ public class StructureUtility {
 
     /**
      * Element representing a component with different tiers. Your multi will accept any of them (as long as player does
-     * not mix them (*)), but would like to know which is used. Player can use more blueprint to get hints denoting more
+     * not mix tier (*)), but would like to know which is used. Player can use more blueprint to get hints denoting more
      * advanced components.
      * <p>
-     * (*): Implementation wise, this structure element will only accept a block if its tier is the same as existing
-     * tier or if existing tier is unset (i.e. value of third argument)
-     * <p>
-     * Above all else, you need to decide what tier you are going to use. For simpler cases, Integer is a good choice.
-     * You can also use an existing Enum. Tier can never be null though. It can also be a String or a
+     * Above all else, you need to decide what type of tier you are going to use. For simpler cases, Integer is a good
+     * choice. You can also use an existing Enum. It can also be a String or a
      * {@link net.minecraft.util.ResourceLocation}, or basically anything. It doesn't even have to implement
      * {@link Comparable}.
      * <p>
-     * This assumes you will reset the backing storage, and on the first occurrence getter would return notSet. You can
-     * also make getter to return other value to forcefully select a certain tier, but you're probably better off using
-     * block adders or {@link #ofBlock(Block, int, Block, int)} and its overloads
+     * If your tier extractor function returns null on any (Block, meta) pair, then it means this block is rejected.
+     * This also implies null can never be a valid tier.
      * <p>
-     * Implementation wise, this allows a block only when we don't yet have a tier, or the block at that location has
-     * the same tier as we already have.
-     * <p>
-     * Notice that if your tier extractor function returns null on any (Block, meta) pair, then it means this block is
-     * rejected, since null can never be a valid tier.
+     * This structure element require you will reset the backing storage of getter in your own code, such that in every
+     * round of structure checking, the first call to getter would always return notSet. You can also make getter to
+     * return other value on that occasion to forcefully select a certain tier, but then you'd probably be better off
+     * using block adders or {@link #ofBlock(Block, int, Block, int)} and its overloads
      * <p>
      * There is yet no TileEntity counterpart of this utility. Feel free to submit a PR to add it.
      * <p>
-     * For most typical use cases, you will NOT want to return notSet from your tierExtractor. If you do so, we will
-     * have this kind of chain of events:
+     * (*): Implementation wise, this structure element will only accept a block if its tier is the same as existing
+     * tier or if existing tier is unset (i.e. value of third argument). If there are multiple (block, tier) tuple for a
+     * given tier, then player will be allowed to use multiple kinds of blocks, but their tier is guaranteed to be the
+     * same.
+     * <p>
+     * <h3>WARNING</h3> <b>You SHOULD NOT return notSet from your tierExtractor.</b> If you do so, we will have this
+     * chain of events:
      * <ul>
      * <li>at check start, tier is reset to notSet
-     * <li>at first occurrence, ofBlocksTiered finds your current tier is notSet, and the block's tier is notSet, so
-     * it's accepted
+     * <li>the tier extractor returns notSet for first block, so since ofBlocksTiered finds your current tier is notSet,
+     * and the new block's tier is the same as that, so it's accepted
      * <li>at 2nd, 3rd..., same thing in 2 happens
      * <li>at last occurrence, player placed a valid block with a tier not notSet. ofBlocksTiered now sets your current
      * tier to this tier, and accept the block
@@ -650,10 +651,10 @@ public class StructureUtility {
      * doing its business
      * <li>Player enjoy a (probably) hilariously shaped multi and (probably) reduced build cost.
      * </ul>
+     * <h3>Example Implementation</h3>
      * <p>
-     * <b>Example:</b>
-     * <p>
-     * Assume you have 16 tier, each map to one block's 16 different meta. You will usually want something like this
+     * Assume you have 16 tier, each map to one particular block's 16 different meta. You will usually want something
+     * like this
      *
      * <pre>
      * public class Tile extends TileEntity {
@@ -677,6 +678,18 @@ public class StructureUtility {
      * }
      * </pre>
      *
+     * Important bits of this example implementation:
+     * <ul>
+     * <li>The supplied ITierConverter returns null for an invalid block</li>
+     * <li>Possible tier returned by ITierConverter is Integer object 0 to 15.</li>
+     * <li>notSet is set to -1. tier got reset to this value by caller before calling into
+     * {@link IStructureDefinition#check(Object, String, World, ExtendedFacing, int, int, int, int, int, int, boolean)}</li>
+     * <li>notSet is never a tier returned by ITierConverter.</li>
+     * </ul>
+     * <p>
+     * As a friendly reminder, the above characteristics are only for this simply demo, not as a general restriction
+     * imposed by ofBlocksTiered.
+     *
      * @param tierExtractor a function to extract tier info from a block. This function can return null and will never
      *                      be passed a null block or an invalid block meta. If this function returns null, then the
      *                      block would be considered invalid.
@@ -686,14 +699,37 @@ public class StructureUtility {
      *                      construction time, use {@link #lazy(Supplier)} or its overloads to delay a bit. This list is
      *                      only for hint particle spawning and survival build. The hint/autoplace code will choose 1st
      *                      pair to spawn/place if trigger item has master channel data of 1, 2nd pair if 2, and so on.
-     * @param notSet        The value returned from {@code getter} when there were no tier info found in T yet. Can be
-     *                      null.
+     * @param notSet        The value returned from {@code getter} when there were no tier info found in T yet. Cannot
+     *                      be null.
      * @param getter        a function to retrieve the current tier from context object
      * @param setter        a function to set the current tier into context object
      */
     public static <T, TIER> IStructureElement<T> ofBlocksTiered(ITierConverter<TIER> tierExtractor,
             @Nullable List<Pair<Block, Integer>> allKnownTiers, @Nullable TIER notSet, BiConsumer<T, TIER> setter,
             Function<T, TIER> getter) {
+        List<String> descriptions = null;
+        if (allKnownTiers != null) {
+            descriptions = new java.util.ArrayList<>();
+            for (Pair<Block, Integer> tier : allKnownTiers) {
+                Item item = Item.getItemFromBlock(tier.getLeft());
+                if (item != null) {
+                    descriptions.add(new ItemStack(item, 1, tier.getRight()).getUnlocalizedName() + ".name");
+                }
+            }
+        }
+        return ofBlocksTiered(tierExtractor, allKnownTiers, notSet, setter, getter, descriptions);
+    }
+
+    /**
+     * Like {@link #ofBlocksTiered(ITierConverter, List, Object, BiConsumer, Function)}, but with an explicit
+     * description that will be returned by {@link IStructureElement#getDescription(Object)}.
+     *
+     * @param description the description lang keys to attach to this element, or null for no description
+     * @see #ofBlocksTiered(ITierConverter, List, Object, BiConsumer, Function)
+     */
+    public static <T, TIER> IStructureElement<T> ofBlocksTiered(ITierConverter<TIER> tierExtractor,
+            @Nullable List<Pair<Block, Integer>> allKnownTiers, @Nullable TIER notSet, BiConsumer<T, TIER> setter,
+            Function<T, TIER> getter, @Nullable List<String> description) {
         List<Pair<Block, Integer>> hints = allKnownTiers == null ? Collections.emptyList() : allKnownTiers;
         if (hints.stream().anyMatch(Objects::isNull)) throw new IllegalArgumentException();
         IStructureElementCheckOnly<T> check = ofBlocksTiered(tierExtractor, notSet, setter, getter);
@@ -755,7 +791,7 @@ public class StructureUtility {
             public PlaceResult survivalPlaceBlock(T t, World world, int x, int y, int z, ItemStack trigger,
                     AutoPlaceEnvironment env) {
                 Pair<Block, Integer> hint = getHint(trigger);
-                if (hint == null) return PlaceResult.REJECT; // TODO or SKIP?
+                if (hint == null) return PlaceResult.REJECT;
                 Block block = world.getBlock(x, y, z);
                 int meta = world.getBlockMetadata(x, y, z);
                 TIER tier = tierExtractor.convert(block, meta);
@@ -772,6 +808,24 @@ public class StructureUtility {
                         env.getActor(),
                         env.getChatter());
             }
+
+            @Nullable
+            @Override
+            public List<String> getDescription(T context) {
+                TIER currentTier = getter.apply(context);
+                if (Objects.equals(currentTier, notSet)) return description;
+
+                for (Pair<Block, Integer> pair : hints) {
+                    TIER pairTier = tierExtractor.convert(pair.getKey(), pair.getValue());
+                    if (!Objects.equals(pairTier, currentTier)) continue;
+                    Item item = Item.getItemFromBlock(pair.getKey());
+                    if (item == null) continue;
+                    return Collections
+                            .singletonList(new ItemStack(item, 1, pair.getValue()).getUnlocalizedName() + ".name");
+                }
+                return description;
+            }
+
         };
     }
 
@@ -1395,10 +1449,65 @@ public class StructureUtility {
                         AutoPlaceEnvironment env) {
                     return BlocksToPlace.create(block, meta);
                 }
+
+                @Nullable
+                @Override
+                public List<String> getDescription(T context) {
+                    Item item = Item.getItemFromBlock(block);
+                    if (item == null) return null;
+                    return Collections.singletonList(new ItemStack(item, 1, meta).getUnlocalizedName() + ".name");
+                }
             };
         } else {
             return new IStructureElement<T>() {
 
+                @Override
+                public PlaceResult survivalPlaceBlock(T t, World world, int x, int y, int z, ItemStack trigger,
+                        AutoPlaceEnvironment env) {
+                    BlocksToPlace e = getBlocksToPlace(t, world, x, y, z, trigger, env);
+                    IItemSource source = env.getSource();
+                    EntityPlayer actor = env.getActor();
+                    Consumer<IChatComponent> chatter = env.getChatter();
+                    if (check(t, world, x, y, z)) return PlaceResult.SKIP;
+                    if (e.getStacks() == null) {
+                        ItemStack taken = source.takeOne(e.getPredicate(), true);
+                        return StructureUtility.survivalPlaceBlock(
+                                taken,
+                                NBTMode.EXACT,
+                                taken.stackTagCompound,
+                                false,
+                                world,
+                                x,
+                                y,
+                                z,
+                                source,
+                                actor,
+                                chatter);
+                    }
+                    for (ItemStack stack : e.getStacks()) {
+                        if (!source.takeOne(stack, true)) {
+                            IChatComponent name = new ChatComponentText(stack.getDisplayName());
+                            name.setChatStyle(new ChatStyle().setColor(EnumChatFormatting.YELLOW));
+                            env.getChatter()
+                                    .accept(new ChatComponentTranslation("structurelib.autoplace.missing_block", name));
+                            continue;
+                        }
+                        return StructureUtility.survivalPlaceBlock(
+                                stack,
+                                NBTMode.EXACT,
+                                stack.stackTagCompound,
+                                false,
+                                world,
+                                x,
+                                y,
+                                z,
+                                source,
+                                actor,
+                                chatter);
+                    }
+                    return PlaceResult.REJECT;
+                }
+
                 @Override
                 public boolean check(T t, World world, int x, int y, int z) {
                     Block worldBlock = world.getBlock(x, y, z);
@@ -1427,6 +1536,14 @@ public class StructureUtility {
                         AutoPlaceEnvironment env) {
                     return BlocksToPlace.create(block, meta);
                 }
+
+                @Nullable
+                @Override
+                public List<String> getDescription(T context) {
+                    Item item = Item.getItemFromBlock(block);
+                    if (item == null) return null;
+                    return Collections.singletonList(new ItemStack(item, 1, meta).getUnlocalizedName() + ".name");
+                }
             };
         }
     }
@@ -1469,6 +1586,14 @@ public class StructureUtility {
                     // there is getSubItems on ItemBlock, but it's client only
                     return BlocksToPlace.create(defaultBlock, defaultMeta);
                 }
+
+                @Nullable
+                @Override
+                public List<String> getDescription(T context) {
+                    Item item = Item.getItemFromBlock(block);
+                    if (item == null) return null;
+                    return Collections.singletonList(new ItemStack(item, 1, 0).getUnlocalizedName() + ".name");
+                }
             };
         } else {
             return new IStructureElement<T>() {
@@ -1501,6 +1626,14 @@ public class StructureUtility {
                     // there is getSubItems on ItemBlock, but it's client only
                     return BlocksToPlace.create(defaultBlock, defaultMeta);
                 }
+
+                @Nullable
+                @Override
+                public List<String> getDescription(T context) {
+                    Item item = Item.getItemFromBlock(block);
+                    if (item == null) return null;
+                    return Collections.singletonList(new ItemStack(item, 1, 0).getUnlocalizedName() + ".name");
+                }
             };
         }
     }
@@ -1764,6 +1897,71 @@ public class StructureUtility {
                     AutoPlaceEnvironment env) {
                 return element.survivalPlaceBlock(t, world, x, y, z, trigger, env);
             }
+
+            @Nullable
+            @Override
+            public List<String> getDescription(T context) {
+                return element.getDescription(context);
+            }
+        };
+    }
+
+    /**
+     * Wraps an element and overrides its description. Useful for providing human-readable names to elements whose
+     * underlying implementation doesn't provide a description (e.g. tiered block elements).
+     *
+     * @param description the description to use, or null to clear any existing description
+     * @param element     the element to wrap
+     */
+    public static <B extends IStructureElement<T>, T> IStructureElement<T> withDescription(
+            @Nullable List<String> description, B element) {
+        return new IStructureElement<T>() {
+
+            @Override
+            public boolean check(T t, World world, int x, int y, int z) {
+                return element.check(t, world, x, y, z);
+            }
+
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return element.couldBeValid(t, world, x, y, z, trigger);
+            }
+
+            @Override
+            public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return element.placeBlock(t, world, x, y, z, trigger);
+            }
+
+            @Override
+            public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return element.spawnHint(t, world, x, y, z, trigger);
+            }
+
+            @Nullable
+            @Override
+            public BlocksToPlace getBlocksToPlace(T t, World world, int x, int y, int z, ItemStack trigger,
+                    AutoPlaceEnvironment env) {
+                return element.getBlocksToPlace(t, world, x, y, z, trigger, env);
+            }
+
+            @Override
+            @Deprecated
+            public PlaceResult survivalPlaceBlock(T t, World world, int x, int y, int z, ItemStack trigger,
+                    IItemSource s, EntityPlayerMP actor, Consumer<IChatComponent> chatter) {
+                return element.survivalPlaceBlock(t, world, x, y, z, trigger, s, actor, chatter);
+            }
+
+            @Override
+            public PlaceResult survivalPlaceBlock(T t, World world, int x, int y, int z, ItemStack trigger,
+                    AutoPlaceEnvironment env) {
+                return element.survivalPlaceBlock(t, world, x, y, z, trigger, env);
+            }
+
+            @Nullable
+            @Override
+            public List<String> getDescription(T context) {
+                return description;
+            }
         };
     }
 
@@ -1820,6 +2018,12 @@ public class StructureUtility {
                     AutoPlaceEnvironment env) {
                 return element.survivalPlaceBlock(t, world, x, y, z, trigger, env);
             }
+
+            @Nullable
+            @Override
+            public List<String> getDescription(T context) {
+                return element.getDescription(context);
+            }
         };
     }
 
@@ -1828,11 +2032,11 @@ public class StructureUtility {
     /**
      * Enable this structure element only if given predicate returns true.
      * <p>
-     * Return SKIP when survival auto place if given predicate returns false.
+     * Return REJECT_CONTINUE when survival auto place if given predicate returns false.
      */
     public static <T> IStructureElement<T> onlyIf(Predicate<? super T> predicate,
             IStructureElement<? super T> downstream) {
-        return onlyIf(predicate, downstream, PlaceResult.SKIP);
+        return onlyIf(predicate, downstream, PlaceResult.REJECT_CONTINUE);
     }
 
     /**
@@ -1889,6 +2093,12 @@ public class StructureUtility {
                 if (predicate.test(t)) return downstream.survivalPlaceBlock(t, world, x, y, z, trigger, env);
                 return placeResultWhenDisabled;
             }
+
+            @Nullable
+            @Override
+            public List<String> getDescription(T context) {
+                return downstream.getDescription(context);
+            }
         };
     }
 
@@ -1901,10 +2111,10 @@ public class StructureUtility {
      * using {@link #isAir()}. It will not attempt to capture any errors though, so next one will not be tried if
      * previous one would crash.
      * <p>
-     * (*): For survival auto place, it will * REJECT, if all structure element REJECT * SKIP, if 1 or more structure
-     * element SKIP and the rest structure element (0 or more) REJECT * any other result, **immediately** upon any
-     * structure element returns these other results. This behavior is not 100% fixed and might change later on, but we
-     * will send the notice on a best effort basis.
+     * (*): For survival auto place, it will: REJECT, if any structure element returns REJECT (and none returned ACCEPT,
+     * STOP, ACCEPT_STOP, or SKIP); REJECT_CONTINUE, if all structure elements return REJECT_CONTINUE (none returned
+     * REJECT); SKIP, as soon as any structure element returns SKIP; any other result, immediately upon any structure
+     * element returning those.
      * <p>
      * Take care while chaining, as it will try to call every structure element until it returns true. If none does it
      * will finally return false.
@@ -1986,6 +2196,12 @@ public class StructureUtility {
                     AutoPlaceEnvironment env) {
                 return elem.survivalPlaceBlock(t.getCurrentContext(), world, x, y, z, trigger, env);
             }
+
+            @Nullable
+            @Override
+            public List<String> getDescription(T context) {
+                return elem.getDescription(context.getCurrentContext());
+            }
         };
     }
     // endregion
@@ -2823,6 +3039,12 @@ public class StructureUtility {
                     warnNoExplicitSubChannel(env.getActor());
                 return backing.survivalPlaceBlock(t, world, x, y, z, newTrigger, env);
             }
+
+            @Nullable
+            @Override
+            public List<String> getDescription(T context) {
+                return backing.getDescription(context);
+            }
         };
     }
     // endregion

src/main/java/com/gtnewhorizon/structurelib/structure/SurvivalBuildStructureWalker.java

@@ -43,9 +43,10 @@ class SurvivalBuildStructureWalker<T> implements IStructureWalker<T> {
         env.offsetABC[2] = c;
         env.setSource(params.getSource());
         PlaceResult placeResult = element.survivalPlaceBlock(object, world, x, y, z, trigger, env);
-        if (placeResult != PlaceResult.SKIP && built == -1) built = 0;
+        if (placeResult != PlaceResult.SKIP && placeResult != PlaceResult.REJECT_CONTINUE && built == -1) built = 0;
         switch (placeResult) {
             case SKIP:
+            case REJECT_CONTINUE:
                 return true;
             case ACCEPT:
                 if (check) element.check(object, world, x, y, z);

src/main/javadoc/overview.html

@@ -178,6 +178,80 @@ StructureLib API documentation.
 
 Just give me a better name and I'd do the renaming.
 
+<h3>Channel Descriptions</h3>
+<p>
+    Each channel can have one description associated with it per mod.
+    Channel description should briefly describe how a specific channel is used for inside a specific mod.
+    They will be displayed to player in channel editor GUI that comes with StructureLib.
+    The registration process can be done either via direct method call to {@link com.gtnewhorizon.structurelib.StructureLibAPI#registerChannelDescription(String, String, String)},
+    or by sending an IMC message.
+    After registration, the channel will also show up as autocomplete options when players are editing channels.
+</p>
+
+<p>
+    Here is an example of sending an IMC message to register two channels and their description.
+    In this example, we assume your modid is <code>my_mod</code> and your mod will ship with localization entries for
+    localization key <code>channels.my_mod.channel_1</code> and <code>channels.my_mod.channel_2</code>
+</p>
+
+<pre>
+        NBTTagCompound command = new NBTTagCompound();
+        NBTTagList tags = new NBTTagList();
+        String[] channels = {"channel_1", "channel_2"};
+        for (String channel : channels) {
+            NBTTagCompound tag = new NBTTagCompound();
+            tag.setString("Channel", channel);
+            tag.setString("Description", "channels.my_mod." + channel);
+            tags.appendTag(tag);
+        }
+        command.setTag("Channels", tags);
+        FMLInterModComms.sendMessage("structurelib", "register_channel", command);
+</pre>
+
+<p>
+    There is no strict rules over whether you should do direct API method call or send IMC messages.
+    You can choose whichever you prefer.
+</p>
+
+<h3>Channel Indicator Items</h3>
+<p>
+    You can associate an ItemStack with a given (channel, value) pair.
+    It is usually (but not required to be) the ItemBlock for the blocks to be placed by this (channel, value) pair.
+    Player will be able to drag and drop this item to the builtin channel configuration GUI.
+    The registration process can be done either via direct method call to {@link com.gtnewhorizon.structurelib.StructureLibAPI#registerChannelItem(String, String, int, net.minecraft.item.ItemStack)},
+    or by sending an IMC message.
+    After registration, the channel will also show up as autocomplete options when players are editing channels.
+</p>
+
+<p>
+    Here is an example of sending an IMC message to register 3 vanilla sandstone as different indicator for channel "sandstone", with block metadata plus 1 as channel value.
+    In this example, we assume your modid is <code>my_mod</code>.
+</p>
+
+<pre>
+        NBTTagCompound command = new NBTTagCompound();
+        NBTTagList items = new NBTTagList();
+        int[] metas = {0, 1, 2};
+        for (int meta : metas) {
+            NBTTagCompound tag = new NBTTagCompound();
+            tag.setTag("Item", new ItemStack(Blocks.sandstone, 1, meta).writeToNBT(new NBTTagCompound()));
+            NBTTagList channels = new NBTTagList();
+            NBTTagCompound channel = new NBTTagCompound();
+            channel.setString("Channel", "sandstone");
+            channel.setInteger("Value", meta + 1);
+            channels.appendTag(channel);
+            tag.setTag("Channels", channels);
+            items.appendTag(tag);
+        }
+        command.setTag("Items", items);
+        FMLInterModComms.sendMessage("structurelib", "register_channel_item", command);
+</pre>
+
+<p>
+    There is no strict rules over whether you should do direct API method call or send IMC messages.
+    You can choose whichever you prefer.
+</p>
+
 <h3>Examples</h3>
 
 <h4>For Structure Definition Author</h4>

src/main/resources/assets/structurelib/lang/en_US.lang

@@ -30,16 +30,20 @@ item.structurelib.constructableTrigger.desc.4=Quantity of schematics in item sta
 item.structurelib.constructableTrigger.desc.5=Hold §l[LSHIFT]§r to display channel data
 item.structurelib.constructableTrigger.desc.lshift.0=Contain %d sub channel.
 item.structurelib.constructableTrigger.too_fast=Please wait %d milliseconds before another autoplace...
+item.structurelib.constructableTrigger.gui.title=Sub Channels
 item.structurelib.constructableTrigger.gui.key=Key:
 item.structurelib.constructableTrigger.gui.value=Value:
 item.structurelib.constructableTrigger.gui.add=Add
-item.structurelib.constructableTrigger.gui.set=Set
-item.structurelib.constructableTrigger.gui.unset=Unset
-item.structurelib.constructableTrigger.gui.wipe=§4Wipe
-item.structurelib.constructableTrigger.gui.error.show=Show Errors
-item.structurelib.constructableTrigger.gui.error.hide=Hide Errors
-item.structurelib.constructableTrigger.gui.gt_no_hatch.enable=No Hatch
-item.structurelib.constructableTrigger.gui.gt_no_hatch.disable=Hatches
+item.structurelib.constructableTrigger.gui.set=Update
+item.structurelib.constructableTrigger.gui.unset=Remove
+item.structurelib.constructableTrigger.gui.wipe=§4Clear
+item.structurelib.constructableTrigger.gui.channels.from=§rMod: §9§o%s
+item.structurelib.constructableTrigger.gui.info=Many multiblocks support some degree of variation in their structure and a sub channel allows indication of which variant to use.\n All sub channels have a sequence of lowercase characters as key and a positive integer as value. Most known sub channels should be available as typeahead completions.\n You can also drag and drop items from NEI to set the corresponding sub channel value. These items all have a tooltip of "§oIndicates§r §ovalue§r §oX§r §ofor§r §osub§r §ochannel§r §oY§r".
+
+channels.structurelib.show_errors=When set, will highlight parts of the multiblock that is definitely wrong
+
+structurelib.tooltip.channelvalue=§7Indicates value §6%d§r§7 for sub channel §6%s
+structurelib.tooltip.indicator_dnd=Drop into GUI to select this value for this channel
 
 structurelib.autoplace.built_stat=Built %s blocks
 structurelib.autoplace.complete=§aThis multiblock has completed!
@@ -47,6 +51,7 @@ structurelib.autoplace.error.not_enabled=§cThis multiblock does not support aut
 structurelib.autoplace.error.no_simple_block=§cSuggested to place §r%s§c but none was found
 structurelib.autoplace.error.no_item_stack=§cSuggested to place block by using §r%s§c but none was found
 structurelib.autoplace.warning.no_explicit_channel=§6This structure depends on nonexistent sub channel §r%s§6. Using master channel instead.
+structurelib.autoplace.missing_block=§cMissing block: %s
 
 structurelib.blockhint.desc.0=Helps while building
 structurelib.blockhint.0.name=Hint 1 dot

src/main/resources/assets/structurelib/lang/zh_CN.lang

@@ -30,16 +30,20 @@ item.structurelib.constructableTrigger.desc.4=此物品堆叠数量会影响显
 item.structurelib.constructableTrigger.desc.5=按下 §l[左SHIFT]§r 以显示子信道
 item.structurelib.constructableTrigger.desc.lshift.0=包含 %d 个子信道
 item.structurelib.constructableTrigger.too_fast=请在下一次自动搭建前等待 %d 毫秒...
+item.structurelib.constructableTrigger.gui.title=子信道
 item.structurelib.constructableTrigger.gui.key=信道名:
 item.structurelib.constructableTrigger.gui.value=值:
 item.structurelib.constructableTrigger.gui.add=添加
 item.structurelib.constructableTrigger.gui.set=替换
 item.structurelib.constructableTrigger.gui.unset=删除
 item.structurelib.constructableTrigger.gui.wipe=§4全部清空
-item.structurelib.constructableTrigger.gui.error.show=显示结构错误
-item.structurelib.constructableTrigger.gui.error.hide=隐藏结构错误
-item.structurelib.constructableTrigger.gui.gt_no_hatch.enable=跳过舱室
-item.structurelib.constructableTrigger.gui.gt_no_hatch.disable=放置舱室
+item.structurelib.constructableTrigger.gui.channels.from=§r模组: §9§o%s
+item.structurelib.constructableTrigger.gui.info=许多多方块的结构都是可变的，在自动放置时，可以使用子信道来向多方块指明该使用哪一个变体。\n子信道由一个字符串标识、并拥有一个正整数作为值。这个GUI中的信道名支持自动补全到绝大多数已知的子信道。\n你也可以将部分物品从NEI中拖拽至GUI内来设置子信道值为该物品表示的值。这些物品的物品说明中都带有§o表示子信道 X 为 Y§r。
+
+channels.structurelib.show_errors=添加后，在投影时会高亮标出必然错误的部分
+
+structurelib.tooltip.channelvalue=§7表示子信道 §6%2$s§r§7 为 §6%d§r
+structurelib.tooltip.indicator_dnd=拖入GUI中来选择该值
 
 structurelib.autoplace.built_stat=已放置 %s 个方块
 structurelib.autoplace.complete=§a这个多方块结构已经完成自动搭建！