using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace AntiAgeScreen
{
    public partial class Form1: Form
    {
        [DllImport("User32.dll")]
        public static extern IntPtr GetDC(IntPtr hwnd);
        [DllImport("User32.dll")]
        public static extern void ReleaseDC(IntPtr hwnd, IntPtr dc);
        
        [DllImport("gdi32.dll", CharSet = CharSet.Auto, EntryPoint = "GetCurrentObject", ExactSpelling = true, SetLastError = true)]
        public static extern IntPtr IntGetCurrentObject(HandleRef hDC, int uObjectType);

        [DllImport("gdi32.dll")]
        public static extern UInt32 SetPixel(IntPtr hdc, int X, int Y, UInt32 crColor);

        public Form1()
        {
            InitializeComponent();
            timer1.Start();
        }

        bool InTimer = false;
        private void timer1_Tick(object sender, EventArgs e)
        {
            if (InTimer) return; else InTimer = true;

            try
            {
                IntPtr desktopPtr = GetDC(IntPtr.Zero);

                UInt32 clr = ((uint)Color.Yellow.R) | ( ((uint)Color.Yellow.G) << 8)
                    | ((uint)(Color.Yellow.B)<<16);

                Graphics g = Graphics.FromHdc(desktopPtr);
                IntPtr hdc = g.GetHdc();
                IntPtr hbitmap = IntGetCurrentObject(new HandleRef(null, hdc), 7 /*OBJ_BITMAP*/);
                Bitmap bitmap = Image.FromHbitmap(hbitmap);
                g.ReleaseHdc(hdc);

                for (int y = 0; y < bitmap.Height - 1; y += 40)
                {
                    for (int x = 0; x < bitmap.Width - 1; x += 40)
                    {
                        SetPixel(desktopPtr, x, y, clr);
                        SetPixel(desktopPtr, x + 1, y, clr);
                        SetPixel(desktopPtr, x, y + 1, clr);
                        SetPixel(desktopPtr, x + 1, y + 1, clr);
                    }
                }
                g.Dispose();
                ReleaseDC(IntPtr.Zero, desktopPtr);
            }
            catch { }

            InTimer = false;
        }
    }
}