Try get stuff working

build.gradle

@@ -22,6 +22,10 @@ repositories {
     // Loom adds the essential maven repositories to download Minecraft and libraries from automatically.
     // See https://docs.gradle.org/current/userguide/declaring_repositories.html
     // for more information about repositories.
+
+    flatDir {
+        dir "libs"
+    }
 }
 
 loom {
@@ -32,6 +36,8 @@ dependencies {
     minecraft "net.minecraft:minecraft:$project.minecraft_version"
     mappings loom.officialMojangMappings()
     neoForge "net.neoforged:neoforge:$project.neoforge_version"
+
+    modImplementation "libs:l2backpack:3.0.10"
 }
 
 processResources {

gradle.properties

@@ -3,7 +3,7 @@ org.gradle.jvmargs=-Xmx1G
 loom.platform = neoforge
 
 # Mod properties
-mod_version = 0.1.0
+mod_version = 0.1.1
 maven_group = org.teacon
 archives_name = gimmeman
 

src/main/java/org/teacon/gimmeman/GiveMeMan.java

@@ -0,0 +1,18 @@
+package org.teacon.gimmeman;
+
+import net.minecraft.resources.ResourceLocation;
+import net.neoforged.bus.api.IEventBus;
+import net.neoforged.fml.common.Mod;
+
+@Mod(GiveMeMan.MOD_ID)
+public final class GiveMeMan {
+    public static final String MOD_ID = "gimmeman";
+
+    public GiveMeMan(IEventBus eventBus) {
+
+    }
+
+    public static ResourceLocation id(String path) {
+        return ResourceLocation.fromNamespaceAndPath(MOD_ID, path);
+    }
+}

src/main/java/org/teacon/gimmeman/mixin/L2BackpackMixin.java

@@ -0,0 +1,34 @@
+package org.teacon.gimmeman.mixin;
+
+import dev.xkmc.l2backpack.events.StartUpGiveItemEvents;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.level.storage.loot.LootParams;
+import net.minecraft.world.level.storage.loot.LootTable;
+import net.minecraft.world.level.storage.loot.parameters.LootContextParamSet;
+import net.neoforged.neoforge.event.tick.PlayerTickEvent;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+import org.teacon.gimmeman.GiveMeMan;
+
+@Mixin(StartUpGiveItemEvents.class)
+public class L2BackpackMixin {
+
+    @Inject(method = "onPlayerTick", at = @At(value = "INVOKE", target = "Lnet/minecraft/world/entity/player/Inventory;placeItemBackInInventory(Lnet/minecraft/world/item/ItemStack;)V", shift = At.Shift.AFTER))
+    private static void afterBackpackGiven(PlayerTickEvent.Post event, CallbackInfo ci) {
+        if (!(event.getEntity() instanceof ServerPlayer player)) return;
+        LootTable lootTable = player.server.reloadableRegistries().getLootTable(
+                ResourceKey.create(Registries.LOOT_TABLE, GiveMeMan.id("startup_items")));
+        LootParams lootParams = (new LootParams.Builder(player.serverLevel()))
+                .withLuck(player.getLuck())
+                .create(LootContextParamSet.builder().build());
+        lootTable.getRandomItems(lootParams).forEach(itemStack -> {
+            if (!player.getInventory().add(itemStack)) {
+                player.drop(itemStack, false);
+            }
+        });
+    }
+}

src/main/java/org/teacon/gimmeman/mixin/MixinClientAdvancements.java

@@ -0,0 +1,20 @@
+package org.teacon.gimmeman.mixin;
+
+import net.minecraft.client.Minecraft;
+import net.minecraft.client.gui.components.toasts.Toast;
+import net.minecraft.client.gui.components.toasts.ToastComponent;
+import net.minecraft.client.multiplayer.ClientAdvancements;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+@Mixin(ClientAdvancements.class)
+public class MixinClientAdvancements {
+
+    @Redirect(method = "update",at = @At(value = "INVOKE", target = "Lnet/minecraft/client/gui/components/toasts/ToastComponent;addToast(Lnet/minecraft/client/gui/components/toasts/Toast;)V"))
+    public void onAddToast(ToastComponent instance, Toast arg){
+        assert Minecraft.getInstance().player != null;
+        if (Minecraft.getInstance().player.tickCount < 100) return;
+        instance.addToast(arg);
+    }
+}

src/main/java/org/teacon/gimmeman/mixin/MixinPlayerAdvancements.java

@@ -0,0 +1,25 @@
+package org.teacon.gimmeman.mixin;
+
+import net.minecraft.advancements.DisplayInfo;
+import net.minecraft.server.PlayerAdvancements;
+import net.minecraft.server.level.ServerPlayer;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+import java.util.Optional;
+import java.util.function.Consumer;
+
+@Mixin(PlayerAdvancements.class)
+public class MixinPlayerAdvancements {
+
+    @Shadow private ServerPlayer player;
+
+    @SuppressWarnings("OptionalUsedAsFieldOrParameterType")
+    @Redirect(method = "award", at = @At(value = "INVOKE", target = "Ljava/util/Optional;ifPresent(Ljava/util/function/Consumer;)V"))
+    public void onBoardCastMessage(Optional<DisplayInfo> instance, Consumer<DisplayInfo> action){
+        if (player.tickCount < 100) return;
+        instance.ifPresent(action);
+    }
+}

src/main/resources/gimmeman.mixins.json

@@ -4,11 +4,11 @@
   "compatibilityLevel": "JAVA_21",
   "minVersion": "0.8",
   "client": [
+    "MixinClientAdvancements"
   ],
   "mixins": [
-    "AdvancementManagerMixin",
-    "AdvancementRewardsMixin",
-    "DisplayInfoMixin"
+    "L2BackpackMixin",
+    "MixinPlayerAdvancements"
   ],
   "injectors": {
     "defaultRequire": 1