vs-manual-cartography/ManualCartography/Items/ItemCompass.cs

using System;
using Vintagestory.API.Client;
using Vintagestory.API.Common;

namespace ManualCartography.Items;

public class ItemCompass : Item
{
    public override void OnHeldInteractStart(
        ItemSlot slot,
        EntityAgent byEntity,
        BlockSelection blockSel,
        EntitySelection entitySel,
        bool firstEvent,
        ref EnumHandHandling handling
    )
    {
        (api as ICoreClientAPI)?.TriggerChatMessage("Yaw: " + (byEntity.Pos.Yaw * 180 / Math.PI));
    }
}