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:0.6.39:dev")
-    implementation("com.github.GTNewHorizons:NotEnoughItems:2.7.84-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

@@ -39,9 +39,33 @@ remoteMappings = https\://raw.githubusercontent.com/MinecraftForge/FML/1.7.10/co
 # `./gradlew runClient --username=AnotherPlayer`, or configuring this command in your IDE.
 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!
@@ -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 '1.0.42'
+    id 'com.gtnewhorizons.gtnhsettingsconvention' version '2.0.24'
 }
 
 

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/gui/GuiScreenConfigureChannels.java

@@ -164,40 +164,17 @@ public class GuiScreenConfigureChannels extends GuiContainer implements IGuiScre
         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(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("item.structurelib.constructableTrigger.gui.info"))
-                                .spliterator(),
+                        Splitter.on("\\n").split(StatCollector.translateToLocal(I18N_PREFIX + "info")).spliterator(),
                         false)
-                .flatMap(line -> fontRendererObj.listFormattedStringToWidth(line, width * 3 / 5).stream())
+                .flatMap(line -> fontRendererObj.listFormattedStringToWidth(line, width * 1 / 3).stream())
                 .collect(Collectors.toList());
     }
 
@@ -241,8 +218,7 @@ public class GuiScreenConfigureChannels extends GuiContainer implements IGuiScre
         actionPerformed(but);
     }
 
-    @SuppressWarnings("unchecked")
-    private List<GuiButton> getButtonList() {
+    public List<GuiButton> getButtonList() {
         return buttonList;
     }
 
@@ -285,6 +261,11 @@ public class GuiScreenConfigureChannels extends GuiContainer implements IGuiScre
         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 {
@@ -322,11 +303,10 @@ public class GuiScreenConfigureChannels extends GuiContainer implements IGuiScre
                 }
                 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);
     }
 
@@ -337,7 +317,8 @@ public class GuiScreenConfigureChannels extends GuiContainer implements IGuiScre
         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());
 
@@ -397,22 +378,10 @@ public class GuiScreenConfigureChannels extends GuiContainer implements IGuiScre
         int topLeftY = (this.height - this.getYSize()) / 2;
         drawTexturedModalRect(topLeftX, topLeftY, 0, 0, getXSize(), getYSize());
         list.drawScreen(mX, mY, partialTick);
-        fontRendererObj.drawString(
-                I18n.format("item.structurelib.constructableTrigger.gui.title"),
-                guiLeft + 12,
-                guiTop + 9,
-                0);
-        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();
     }
 
@@ -455,7 +424,7 @@ public class GuiScreenConfigureChannels extends GuiContainer implements IGuiScre
             tooltip.addAll(
                     fontRendererObj.listFormattedStringToWidth(
                             StatCollector.translateToLocalFormatted(
-                                    "item.structurelib.constructableTrigger.gui.channels.from",
+                                    I18N_PREFIX + "channels.from",
                                     Loader.instance().getIndexedModList().get(e.getKey()).getName()),
                             maxLine));
             tooltip.addAll(

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

@@ -29,9 +29,10 @@ public class ItemConstructableTrigger extends Item {
     @Override
     public ItemStack onItemRightClick(ItemStack stack, World world, EntityPlayer player) {
         if (getMovingObjectPositionFromPlayer(world, player, true) == null) {
-            if (!world.isRemote) {
+            // 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 (player.isSneaking()) {
+            } else if (world.isRemote && player.isSneaking()) {
                 StructureLib.instance().proxy().displayConfigGUI("registries");
             }
         }

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.
      *

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))
@@ -706,6 +707,29 @@ public class StructureUtility {
     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);
@@ -767,7 +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);
@@ -784,6 +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;
+            }
+
         };
     }
 
@@ -1407,10 +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);
@@ -1439,6 +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");
+                }
             };
         }
     }
@@ -1481,6 +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>() {
@@ -1513,6 +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");
+                }
             };
         }
     }
@@ -1776,6 +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;
+            }
         };
     }
 
@@ -1832,6 +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);
+            }
         };
     }
 
@@ -1840,11 +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);
     }
 
     /**
@@ -1901,6 +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);
+            }
         };
     }
 
@@ -1913,10 +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.
@@ -1998,6 +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
@@ -2835,6 +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/resources/assets/structurelib/lang/en_US.lang

@@ -34,11 +34,11 @@ 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.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 its structure and use sub channels to indicate which variant to use.\n Sub channels are has a sequence of lower case characters as key and a positive integer as value. Most known sub channels should be available as typeahead completions.\nYou can also drag and drop items from NEI to set the corresponding sub channel value. These items all have a tooltip of §oIndicates value X for sub channel Y§r.
+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
 
@@ -51,6 +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