HiddenForm.cs

// Hidden form logic
using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace KidTimerLock
{
    public partial class HiddenForm : Form
    {

        [DllImport("user32.dll")]
        private static extern bool RegisterHotKey(IntPtr hWnd, int id, int fsModifiers, int vk);
        private const int MOD_ALT = 0x1;
        private const int MOD_CONTROL = 0x2;

        public HiddenForm()
        {
            InitializeComponent();
            this.WindowState = FormWindowState.Minimized;
            this.ShowInTaskbar = false;
            this.Load += HiddenForm_Load;
        }

        private void HiddenForm_Load(object sender, EventArgs e)
        {
            // Register global hotkey CTRL + ALT + L
            RegisterHotKey(this.Handle, 1, MOD_CONTROL | MOD_ALT, (int)Keys.L);
            // When triggered, show TimerForm
            


            var timerForm = new TimerForm();
            timerForm.Show();
            
            
        }

        protected override void WndProc(ref Message m)
        {
            const int WM_HOTKEY = 0x0312;
            if (m.Msg == WM_HOTKEY)
            {
                int id = m.WParam.ToInt32();
                if (id == 1) // Our hotkey ID
                {
                    ShowTimerForm(); // Reshow the main dialog
                    
                }
            }
            base.WndProc(ref m);
        }

        private void ShowTimerForm()
        {

            if (Application.OpenForms["TimerForm"] is TimerForm timerForm)
            {
                
                timerForm.Show();
                timerForm.buttonStartAccept();
                timerForm.WindowState = FormWindowState.Normal;
                timerForm.BringToFront();
                timerForm.Activate();                             // Set focus to it
                timerForm.Focus();                                // Just to make sure
                timerForm.FocusMinutesInput(); // set focus to minutes input field to avoid a mouse click
                

            }
        }
    }

}