ViaFabricPlus/docs/DEVELOPER_API.md

Developer API

ViaFabricPlus provides various events and APIs for developers to use. This page explains how to use them.

Events

ViaFabricPlus events are using the Fabric Event API. You can register to them like this:

ChangeProtocolVersionCallback.EVENT.register((oldVersion, newVersion) -> {
    System.out.println("Version changed to " + newVersion.getName());
});

ViaFabricPlus has 8 events at the moment

Callback class name	Description
ChangeProtocolVersionCallback	Called when the user changes the target version in the screen, or if you connect to a server for which a specific version has been selected, you disconnect, the event for the actual version is also called.
DisconnectCallback	Called when the user disconnects from a server
LoadCallback	Called at the earliest point ViaFabricPlus is injecting too
LoadClassicProtocolExtensionCallback	Called when the classic server sends the protocol extensions (only in c0.30 CPE)
PostGameLoadCallback	Called when Minecraft is finished with loading all its components
PostViaVersionLoadCallback	Called when ViaVersion is loaded and ready to use
RegisterSettingsCallback	Called after the default setting groups are loaded and before the setting config is loaded
LoadSaveFilesCallback	Called before and after the save files are loaded

Get and set the current protocol version

final VersionEnum version = ProtocolHack.getTargetVersion();
if (version == VersionEnum.r1_8) {
    ProtocolHack.setTargetVersion(VersionEnum.r1_9);
}

Get a Minecraft ClientConnection by channel

final ClientConnection connection = channel.attr(ProtocolHack.CLIENT_CONNECTION_ATTRIBUTE_KEY).get();

Interact with UserConnection objects

// If ViaVersion is translating, this field will return the user connection of the client
final UserConnection userConnection = ProtocolHack.getPlayNetworkUserConnection();

// If you need a dummy user connection for testing, you can use this method
final UserConnection cursedDummy = ProtocolHack.createDummyUserConnection(ProtocolHack.NATIVE_VERSION, VersionEnum.r1_18_2);
// The cursedDummy field now contains all protocols from the native version to 1.18.2

ViaVersion internals

Add CustomPayload channels for versions below 1.13

In order to receive custom payloads with custom channels in versions below 1.13, you need to register them, that's what you do:

Protocol1_13To1_12_2.MAPPINGS.getChannelMappings().put("FML|HS", "fml:hs");

Check if an item exists in a specific version

final VersionRange range = ItemRegistryDiff.ITEM_DIFF.get(Items.WRITABLE_BOOK); // If an item does not appear in the item map, it has always existed

// The Range class then contains all versions in which the item occurs. 
// https://github.com/ViaVersion/ViaLoader
if (ItemRegistryDiff.contains(Items.STONE, VersionRange.andOlder(VersionEnum.r1_8))) {
    // Do something
}

Creating own settings for the settings screen

public class ExampleSettingGroup extends SettingGroup {
    private static final ExampleSettingGroup instance = new ExampleSettingGroup();
    
    public final BooleanSetting test = new BooleanSetting(this, Text.of("Test"), false);
    
    public ExampleSettingGroup() {
        super("Example");
    }
    
    public static ExampleSettingGroup global() {
        return instance;
    }
}

and then you register the setting group in your onLoad method

RegisterSettingsCallback.EVENT.register(state -> {
    if (state == RegisterSettingsCallback.State.POST) {
        ViaFabricPlus.global().getSettingsManager().addGroup(ExampleSettingGroup.INSTANCE);
    }
});