Glamourer/Glamourer/Interop/VisorService.cs

using Dalamud.Hooking;
using Dalamud.Plugin.Services;
using FFXIVClientStructs.FFXIV.Client.Graphics.Scene;
using Glamourer.Events;
using Penumbra.GameData.Enums;
using Penumbra.GameData.Interop;

namespace Glamourer.Interop;

public class VisorService : IDisposable
{
    private readonly PenumbraReloaded      _penumbra;
    private readonly IGameInteropProvider  _interop;
    public readonly  VisorStateChanged     Event;

    public VisorService(VisorStateChanged visorStateChanged, IGameInteropProvider interop, PenumbraReloaded penumbra)
    {
        _interop        = interop;
        _penumbra       = penumbra;
        Event           = visorStateChanged;
        _setupVisorHook = Create();
        _penumbra.Subscribe(Restore, PenumbraReloaded.Priority.VisorService);
    }

    public void Dispose()
    {
        _setupVisorHook.Dispose();
        _penumbra.Unsubscribe(Restore);
    }

    /// <summary> Obtain the current state of the Visor for the given draw object (true: toggled). </summary>
    public static unsafe bool GetVisorState(Model characterBase)
        => characterBase.IsCharacterBase && characterBase.AsCharacterBase->VisorToggled;

    /// <summary> Manually set the state of the Visor for the given draw object. </summary>
    /// <param name="human"> The draw object. </param>
    /// <param name="on"> The desired state (true: toggled). </param>
    /// <returns> Whether the state was changed. </returns>
    public bool SetVisorState(Model human, bool on)
    {
        if (!human.IsHuman)
            return false;

        var oldState = GetVisorState(human);
        Glamourer.Log.Verbose($"[SetVisorState] Invoked manually on 0x{human.Address:X} switching from {oldState} to {on}.");
        if (oldState == on)
            return false;

        SetupVisorDetour(human, human.GetArmor(EquipSlot.Head).Set.Id, on);
        return true;
    }

    private delegate void UpdateVisorDelegateInternal(nint humanPtr, ushort modelId, byte on);

    private Hook<UpdateVisorDelegateInternal> _setupVisorHook;

    private void SetupVisorDetour(nint human, ushort modelId, byte value)
    {
        var originalOn = value != 0;
        var on         = originalOn;
        // Invoke an event that can change the requested value
        // and also control whether the function should be called at all.
        Event.Invoke(human, false, ref on);

        Glamourer.Log.Verbose(
            $"[SetVisorState] Invoked from game on 0x{human:X} switching to {on} (original {originalOn} from {value} with {modelId}).");

        SetupVisorDetour(human, modelId, on);
    }

    /// <summary>
    /// The SetupVisor function does not set the visor state for the draw object itself,
    /// it only sets the "visor is changing" state to false.
    /// So we wrap a manual change of that flag with the function call.
    /// </summary>
    [MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
    private unsafe void SetupVisorDetour(Model human, ushort modelId, bool on)
    {
        human.AsCharacterBase->VisorToggled = on;
        _setupVisorHook.Original(human.Address, modelId, on ? (byte)1 : (byte)0);
    }

    private unsafe Hook<UpdateVisorDelegateInternal> Create()
    {
        var hook = _interop.HookFromAddress<UpdateVisorDelegateInternal>((nint)Human.MemberFunctionPointers.SetupVisor, SetupVisorDetour);
        hook.Enable();
        return hook;
    }

    private void Restore()
    {
        _setupVisorHook.Dispose();
        _setupVisorHook = Create();
    }
}