Macro-Deck/MacroDeck/WindowFocus/WindowFocusDetection.cs

using System.Diagnostics;
using System.Runtime.InteropServices;
using SuchByte.MacroDeck.Variables;

namespace SuchByte.MacroDeck.WindowsFocus;

public class WindowFocusDetection
{
    delegate void WinEventDelegate(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime);

    [DllImport("user32.dll")]
    static extern IntPtr SetWinEventHook(uint eventMin, uint eventMax, IntPtr hmodWinEventProc, WinEventDelegate lpfnWinEventProc, uint idProcess, uint idThread, uint dwFlags);

    private const uint WINEVENT_OUTOFCONTEXT = 0;
    private const uint EVENT_SYSTEM_FOREGROUND = 3;

    [DllImport("user32.dll", SetLastError = true)]
    static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint processId);


    public event EventHandler<WindowChangedEventArgs>? OnWindowFocusChanged;
    private string _focusedApplication = "";

    static WinEventDelegate dele;

    public WindowFocusDetection()
    {
        dele = WinEventProc;
        var m_hhook = SetWinEventHook(EVENT_SYSTEM_FOREGROUND, EVENT_SYSTEM_FOREGROUND, IntPtr.Zero, dele, 0, 0, WINEVENT_OUTOFCONTEXT);

    }

    private uint GetActiveWindowProcessId(IntPtr hwnd)
    {
        uint processId = 0;
        var handle = IntPtr.Zero;

        if (GetWindowThreadProcessId(hwnd, out processId) > 0)
        {
            return processId;
        }

        return 0;
    }

    public void WinEventProc(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime)
    {
        try
        {
            var processId = GetActiveWindowProcessId(hwnd);
            using var process = Process.GetProcessById((int)processId);
            if (process.ProcessName == _focusedApplication)
            {
                return;
            }

            var windowChangedEventArgs = new WindowChangedEventArgs
            {
                NewProcess = process.ProcessName,
                PreviousProcess = _focusedApplication
            };
            
            OnWindowFocusChanged?.Invoke(_focusedApplication, windowChangedEventArgs);
            _focusedApplication = process.ProcessName;
            VariableManager.SetValue("previous_focused_application", windowChangedEventArgs.PreviousProcess, VariableType.String, "Macro Deck");
            VariableManager.SetValue("focused_application", process.ProcessName, VariableType.String, "Macro Deck");
        }
        catch { }
    }
}