[1.21.1] Allow mods to add custom FeatureFlags

patches/net/minecraft/client/gui/screens/worldselection/ExperimentsScreen.java.patch

@@ -0,0 +1,14 @@
+--- a/net/minecraft/client/gui/screens/worldselection/ExperimentsScreen.java
++++ b/net/minecraft/client/gui/screens/worldselection/ExperimentsScreen.java
+@@ -50,6 +_,11 @@
+
+     @Override
+     protected void init() {
++        if (net.minecraft.world.flag.FeatureFlags.REGISTRY.hasAnyModdedFlags()) {
++            this.minecraft.setScreen(new net.neoforged.neoforge.client.gui.ScrollableExperimentsScreen(this.parent, this.packRepository, this.output));
++            return;
++        }
++
+         this.layout.addTitleHeader(TITLE, this.font);
+         LinearLayout linearlayout = this.layout.addToContents(LinearLayout.vertical());
+         linearlayout.addChild(new MultiLineTextWidget(INFO, this.font).setMaxWidth(310), p_293611_ -> p_293611_.paddingBottom(15));

patches/net/minecraft/world/flag/FeatureFlag.java.patch

@@ -0,0 +1,28 @@
+--- a/net/minecraft/world/flag/FeatureFlag.java
++++ b/net/minecraft/world/flag/FeatureFlag.java
+@@ -3,9 +_,25 @@
+ public class FeatureFlag {
+     final FeatureFlagUniverse universe;
+     final long mask;
++    final int offset;
++    final boolean modded;
+
++    /**
++     * @deprecated Neo: use {@link #FeatureFlag(FeatureFlagUniverse, int, int, boolean)} instead
++     */
++    @Deprecated
+     FeatureFlag(FeatureFlagUniverse p_249115_, int p_251067_) {
++        this(p_249115_, p_251067_, 0, false);
++    }
++
++    FeatureFlag(FeatureFlagUniverse p_249115_, int p_251067_, int offset, boolean modded) {
+         this.universe = p_249115_;
+         this.mask = 1L << p_251067_;
++        this.offset = offset;
++        this.modded = modded;
++    }
++
++    public boolean isModded() {
++        return modded;
+     }
+ }

patches/net/minecraft/world/flag/FeatureFlagRegistry.java.patch

@@ -0,0 +1,44 @@
+--- a/net/minecraft/world/flag/FeatureFlagRegistry.java
++++ b/net/minecraft/world/flag/FeatureFlagRegistry.java
+@@ -75,6 +_,18 @@
+         }, p_249796_ -> List.copyOf(this.toNames(p_249796_)));
+     }
+
++    public FeatureFlag getFlag(ResourceLocation name) {
++        return com.google.common.base.Preconditions.checkNotNull(this.names.get(name), "Flag %s was not registered", name);
++    }
++
++    public Map<ResourceLocation, FeatureFlag> getAllFlags() {
++        return this.names;
++    }
++
++    public boolean hasAnyModdedFlags() {
++        return this.names.values().stream().anyMatch(FeatureFlag::isModded);
++    }
++
+     public static class Builder {
+         private final FeatureFlagUniverse universe;
+         private int id;
+@@ -88,11 +_,20 @@
+             return this.create(ResourceLocation.withDefaultNamespace(p_251782_));
+         }
+
++        /**
++         * @deprecated Neo: use {@link #create(ResourceLocation, boolean)} instead
++         */
++        @Deprecated
+         public FeatureFlag create(ResourceLocation p_250098_) {
+-            if (this.id >= 64) {
++            return create(p_250098_, false);
++        }
++
++        public FeatureFlag create(ResourceLocation p_250098_, boolean modded) {
++            if (this.id >= 64 && false) {
+                 throw new IllegalStateException("Too many feature flags");
+             } else {
+-                FeatureFlag featureflag = new FeatureFlag(this.universe, this.id++);
++                FeatureFlag featureflag = new FeatureFlag(this.universe, this.id % FeatureFlagSet.MAX_CONTAINER_SIZE, this.id / FeatureFlagSet.MAX_CONTAINER_SIZE, modded);
++                this.id++;
+                 FeatureFlag featureflag1 = this.flags.put(p_250098_, featureflag);
+                 if (featureflag1 != null) {
+                     throw new IllegalStateException("Duplicate feature flag " + p_250098_);

patches/net/minecraft/world/flag/FeatureFlagSet.java.patch

@@ -0,0 +1,188 @@
+--- a/net/minecraft/world/flag/FeatureFlagSet.java
++++ b/net/minecraft/world/flag/FeatureFlagSet.java
+@@ -7,14 +_,21 @@
+
+ public final class FeatureFlagSet {
+     private static final FeatureFlagSet EMPTY = new FeatureFlagSet(null, 0L);
++    private static final long[] EMPTY_EXT_MASK = new long[0];
+     public static final int MAX_CONTAINER_SIZE = 64;
+     @Nullable
+     private final FeatureFlagUniverse universe;
+     private final long mask;
++    private final long[] extendedMask;
+
+     private FeatureFlagSet(@Nullable FeatureFlagUniverse p_250433_, long p_251523_) {
++        this(p_250433_, p_251523_, EMPTY_EXT_MASK);
++    }
++
++    private FeatureFlagSet(@Nullable FeatureFlagUniverse p_250433_, long p_251523_, long[] extendedMask) {
+         this.universe = p_250433_;
+         this.mask = p_251523_;
++        this.extendedMask = extendedMask;
+     }
+
+     static FeatureFlagSet create(FeatureFlagUniverse p_251573_, Collection<FeatureFlag> p_251037_) {
+@@ -22,7 +_,8 @@
+             return EMPTY;
+         } else {
+             long i = computeMask(p_251573_, 0L, p_251037_);
+-            return new FeatureFlagSet(p_251573_, i);
++            long[] extMask = computeExtendedMask(p_251573_, 0, 0L, p_251037_);
++            return new FeatureFlagSet(p_251573_, i, extMask);
+         }
+     }
+
+@@ -31,16 +_,19 @@
+     }
+
+     public static FeatureFlagSet of(FeatureFlag p_252331_) {
+-        return new FeatureFlagSet(p_252331_.universe, p_252331_.mask);
++        long[] extMask = computeExtendedMask(p_252331_.universe, p_252331_.offset, p_252331_.mask, java.util.List.of());
++        return new FeatureFlagSet(p_252331_.universe, p_252331_.offset > 0 ? 0L : p_252331_.mask, extMask);
+     }
+
+     public static FeatureFlagSet of(FeatureFlag p_251008_, FeatureFlag... p_249805_) {
+-        long i = p_249805_.length == 0 ? p_251008_.mask : computeMask(p_251008_.universe, p_251008_.mask, Arrays.asList(p_249805_));
+-        return new FeatureFlagSet(p_251008_.universe, i);
++        long i = p_249805_.length == 0 ? (p_251008_.offset > 0 ? 0L : p_251008_.mask) : computeMask(p_251008_.universe, p_251008_.offset > 0 ? 0L : p_251008_.mask, Arrays.asList(p_249805_));
++        long[] extMask = computeExtendedMask(p_251008_.universe, p_251008_.offset, p_251008_.mask, p_249805_.length == 0 ? java.util.List.of() : Arrays.asList(p_249805_));
++        return new FeatureFlagSet(p_251008_.universe, i, extMask);
+     }
+
+     private static long computeMask(FeatureFlagUniverse p_249684_, long p_250982_, Iterable<FeatureFlag> p_251734_) {
+         for (FeatureFlag featureflag : p_251734_) {
++            if (featureflag.offset > 0) continue;
+             if (p_249684_ != featureflag.universe) {
+                 throw new IllegalStateException("Mismatched feature universe, expected '" + p_249684_ + "', but got '" + featureflag.universe + "'");
+             }
+@@ -51,8 +_,36 @@
+         return p_250982_;
+     }
+
++    private static long[] computeExtendedMask(FeatureFlagUniverse universe, int firstOffset, long firstMask, Iterable<FeatureFlag> otherFlags) {
++        long[] extMask = EMPTY_EXT_MASK;
++        if (firstOffset > 0) {
++            extMask = new long[firstOffset + 1];
++            extMask[firstOffset] |= firstMask;
++        }
++        for (FeatureFlag flag : otherFlags) {
++            if (flag.offset == 0) continue;
++            if (universe != flag.universe) {
++                throw new IllegalStateException("Mismatched feature universe, expected '" + universe + "', but got '" + flag.universe + "'");
++            }
++            if (flag.offset >= extMask.length) {
++                extMask = Arrays.copyOfRange(extMask, 0, flag.offset + 1);
++            }
++            extMask[flag.offset] |= flag.mask;
++        }
++        return extMask;
++    }
++
+     public boolean contains(FeatureFlag p_249521_) {
+-        return this.universe != p_249521_.universe ? false : (this.mask & p_249521_.mask) != 0L;
++        if (this.universe != p_249521_.universe) {
++            return false;
++        }
++        if (p_249521_.offset == 0) {
++            return (this.mask & p_249521_.mask) != 0L;
++        }
++        if (this.extendedMask.length > p_249521_.offset) {
++            return (this.extendedMask[p_249521_.offset] & p_249521_.mask) != 0L;
++        }
++        return false;
+     }
+
+     public boolean isEmpty() {
+@@ -62,13 +_,33 @@
+     public boolean isSubsetOf(FeatureFlagSet p_249164_) {
+         if (this.universe == null) {
+             return true;
+-        } else {
+-            return this.universe != p_249164_.universe ? false : (this.mask & ~p_249164_.mask) == 0L;
++        } else if (this.universe == p_249164_.universe) {
++            int len = Math.max(this.extendedMask.length, p_249164_.extendedMask.length);
++            for (int i = 0; i < len; i++) {
++                long thisMask = i < this.extendedMask.length ? this.extendedMask[i] : 0L;
++                long otherMask = i < p_249164_.extendedMask.length ? p_249164_.extendedMask[i] : 0L;
++                if ((thisMask & ~otherMask) != 0L) {
++                    return false;
++                }
++            }
++            return (this.mask & ~p_249164_.mask) == 0L;
+         }
++        return false;
+     }
+
+     public boolean intersects(FeatureFlagSet p_341635_) {
+-        return this.universe != null && p_341635_.universe != null && this.universe == p_341635_.universe ? (this.mask & p_341635_.mask) != 0L : false;
++        if (this.universe == null || p_341635_.universe == null || this.universe != p_341635_.universe) {
++            return false;
++        }
++        int len = Math.min(this.extendedMask.length, p_341635_.extendedMask.length);
++        for (int i = 0; i < len; i++) {
++            long thisMask = this.extendedMask[i];
++            long otherMask = p_341635_.extendedMask[i];
++            if ((thisMask & otherMask) != 0L) {
++                return true;
++            }
++        }
++        return (this.mask & p_341635_.mask) != 0L;
+     }
+
+     public FeatureFlagSet join(FeatureFlagSet p_251527_) {
+@@ -79,7 +_,16 @@
+         } else if (this.universe != p_251527_.universe) {
+             throw new IllegalArgumentException("Mismatched set elements: '" + this.universe + "' != '" + p_251527_.universe + "'");
+         } else {
+-            return new FeatureFlagSet(this.universe, this.mask | p_251527_.mask);
++            long[] extMask = EMPTY_EXT_MASK;
++            if (this.extendedMask.length > 0 || p_251527_.extendedMask.length > 0) {
++                extMask = new long[Math.max(this.extendedMask.length, p_251527_.extendedMask.length)];
++                for (int i = 0; i < extMask.length; i++) {
++                    long thisMask = i < this.extendedMask.length ? this.extendedMask[i] : 0L;
++                    long otherMask = i < p_251527_.extendedMask.length ? p_251527_.extendedMask[i] : 0L;
++                    extMask[i] = thisMask | otherMask;
++                }
++            }
++            return new FeatureFlagSet(this.universe, this.mask | p_251527_.mask, extMask);
+         }
+     }
+
+@@ -90,7 +_,15 @@
+             throw new IllegalArgumentException("Mismatched set elements: '" + this.universe + "' != '" + p_341688_.universe + "'");
+         } else {
+             long i = this.mask & ~p_341688_.mask;
+-            return i == 0L ? EMPTY : new FeatureFlagSet(this.universe, i);
++            long[] extMask = EMPTY_EXT_MASK;
++            if (this.extendedMask.length > 0 || p_341688_.extendedMask.length > 0) {
++                extMask = new long[this.extendedMask.length];
++                for (int idx = 0; idx < extMask.length; idx++) {
++                    long otherMask = idx < p_341688_.extendedMask.length ? p_341688_.extendedMask[idx] : 0L;
++                    extMask[idx] = this.extendedMask[idx] & ~otherMask;
++                }
++            }
++            return i == 0L && extMask.length == 0 ? EMPTY : new FeatureFlagSet(this.universe, i, extMask);
+         }
+     }
+
+@@ -99,7 +_,7 @@
+         if (this == p_248691_) {
+             return true;
+         } else {
+-            if (p_248691_ instanceof FeatureFlagSet featureflagset && this.universe == featureflagset.universe && this.mask == featureflagset.mask) {
++            if (p_248691_ instanceof FeatureFlagSet featureflagset && this.universe == featureflagset.universe && this.mask == featureflagset.mask && Arrays.equals(this.extendedMask, featureflagset.extendedMask)) {
+                 return true;
+             }
+
+@@ -109,6 +_,10 @@
+
+     @Override
+     public int hashCode() {
+-        return (int)HashCommon.mix(this.mask);
++        int hash = (int)HashCommon.mix(this.mask);
++        for (long extMask : this.extendedMask) {
++            hash = 13 * hash + (int) HashCommon.mix(extMask);
++        }
++        return hash;
+     }
+ }

patches/net/minecraft/world/flag/FeatureFlags.java.patch

@@ -0,0 +1,10 @@
+--- a/net/minecraft/world/flag/FeatureFlags.java
++++ b/net/minecraft/world/flag/FeatureFlags.java
+@@ -33,6 +_,7 @@
+         VANILLA = featureflagregistry$builder.createVanilla("vanilla");
+         BUNDLE = featureflagregistry$builder.createVanilla("bundle");
+         TRADE_REBALANCE = featureflagregistry$builder.createVanilla("trade_rebalance");
++        net.neoforged.neoforge.common.util.flag.FeatureFlagLoader.loadModdedFlags(featureflagregistry$builder);
+         REGISTRY = featureflagregistry$builder.build();
+         CODEC = REGISTRY.codec();
+         VANILLA_SET = FeatureFlagSet.of(VANILLA);