Xin chào các bạn, bài viết hôm nay mình tiếp tục hướng dẫn các bạn cách xoay màn hình trên máy tính Windows bằng ngôn ngữ lập trình C#, Winform.

[C#] How to Rotate and Flip Screen Monitor in PC

Giao diện demo ứng dụng:

Khi các bạn có hai màn hình để sử dụng, thường các anh coder sử dụng rất nhiều màn hình.

Và các bạn muốn màn hình khác xoay lại 180 độ chẳn hạn như hình bên dưới:

Thì bài viết này sẽ giúp bạn dễ dàng xoay màn hình để sử dụng.

Đầu tiên, các bạn tạo cho mình một class DisplayHelper.cs với nội dung bên dưới:

using System;
using System.Runtime.InteropServices;

public class DisplayHelper
{
    public enum Orientations
    {
        DEGREES_CW_0 = 0,
        DEGREES_CW_90 = 3,
        DEGREES_CW_180 = 2,
        DEGREES_CW_270 = 1
    }

    public static bool Rotate(uint DisplayNumber, Orientations Orientation)
    {
        if (DisplayNumber == 0)
            throw new ArgumentOutOfRangeException("DisplayNumber", DisplayNumber, "First display is 1.");

        bool result = false;

        DISPLAY_DEVICE d = new DISPLAY_DEVICE();
        d.cb = Marshal.SizeOf(d);

        DEVMODE dm = new DEVMODE();

        if (!NativeMethods.EnumDisplayDevices(null, DisplayNumber - 1, ref d, 0))
            throw new ArgumentOutOfRangeException("DisplayNumber", DisplayNumber, "Number is greater than connected displays.");

        if (0 != NativeMethods.EnumDisplaySettings(
            d.DeviceName, NativeMethods.ENUM_CURRENT_SETTINGS, ref dm))
        {
            if ((dm.dmDisplayOrientation + (int)Orientation) % 2 == 1) // Need to swap height and width?
            {
                int temp = dm.dmPelsHeight;
                dm.dmPelsHeight = dm.dmPelsWidth;
                dm.dmPelsWidth = temp;
            }

            switch (Orientation)
            {
                case Orientations.DEGREES_CW_90:
                    dm.dmDisplayOrientation = NativeMethods.DMDO_270;
                    break;
                case Orientations.DEGREES_CW_180:
                    dm.dmDisplayOrientation = NativeMethods.DMDO_180;
                    break;
                case Orientations.DEGREES_CW_270:
                    dm.dmDisplayOrientation = NativeMethods.DMDO_90;
                    break;
                case Orientations.DEGREES_CW_0:
                    dm.dmDisplayOrientation = NativeMethods.DMDO_DEFAULT;
                    break;
                default:
                    break;
            }

            DISP_CHANGE ret = NativeMethods.ChangeDisplaySettingsEx(
                d.DeviceName, ref dm, IntPtr.Zero,
                DisplaySettingsFlags.CDS_UPDATEREGISTRY, IntPtr.Zero);

            result = ret == 0;
        }

        return result;
    }

    public static void ResetAllRotations()
    {
        try
        {
            uint i = 0;
            while (++i <= 64)
            {
                Rotate(i, Orientations.DEGREES_CW_0);
            }
        }
        catch (ArgumentOutOfRangeException ex)
        {
            // Everything is fine, just reached the last display
        }
    }
}

internal class NativeMethods
{
    [DllImport("user32.dll")]
    internal static extern DISP_CHANGE ChangeDisplaySettingsEx(
        string lpszDeviceName, ref DEVMODE lpDevMode, IntPtr hwnd,
        DisplaySettingsFlags dwflags, IntPtr lParam);

    [DllImport("user32.dll")]
    internal static extern bool EnumDisplayDevices(
        string lpDevice, uint iDevNum, ref DISPLAY_DEVICE lpDisplayDevice,
        uint dwFlags);

    [DllImport("user32.dll", CharSet = CharSet.Ansi)]
    internal static extern int EnumDisplaySettings(
        string lpszDeviceName, int iModeNum, ref DEVMODE lpDevMode);

    public const int DMDO_DEFAULT = 0;
    public const int DMDO_90 = 1;
    public const int DMDO_180 = 2;
    public const int DMDO_270 = 3;

    public const int ENUM_CURRENT_SETTINGS = -1;

}

// See: https://msdn.microsoft.com/en-us/library/windows/desktop/dd183565(v=vs.85).aspx
[StructLayout(LayoutKind.Explicit, CharSet = CharSet.Ansi)]
internal struct DEVMODE
{
    public const int CCHDEVICENAME = 32;
    public const int CCHFORMNAME = 32;

    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = CCHDEVICENAME)]
    [System.Runtime.InteropServices.FieldOffset(0)]
    public string dmDeviceName;
    [System.Runtime.InteropServices.FieldOffset(32)]
    public Int16 dmSpecVersion;
    [System.Runtime.InteropServices.FieldOffset(34)]
    public Int16 dmDriverVersion;
    [System.Runtime.InteropServices.FieldOffset(36)]
    public Int16 dmSize;
    [System.Runtime.InteropServices.FieldOffset(38)]
    public Int16 dmDriverExtra;
    [System.Runtime.InteropServices.FieldOffset(40)]
    public DM dmFields;

    [System.Runtime.InteropServices.FieldOffset(44)]
    Int16 dmOrientation;
    [System.Runtime.InteropServices.FieldOffset(46)]
    Int16 dmPaperSize;
    [System.Runtime.InteropServices.FieldOffset(48)]
    Int16 dmPaperLength;
    [System.Runtime.InteropServices.FieldOffset(50)]
    Int16 dmPaperWidth;
    [System.Runtime.InteropServices.FieldOffset(52)]
    Int16 dmScale;
    [System.Runtime.InteropServices.FieldOffset(54)]
    Int16 dmCopies;
    [System.Runtime.InteropServices.FieldOffset(56)]
    Int16 dmDefaultSource;
    [System.Runtime.InteropServices.FieldOffset(58)]
    Int16 dmPrintQuality;

    [System.Runtime.InteropServices.FieldOffset(44)]
    public POINTL dmPosition;
    [System.Runtime.InteropServices.FieldOffset(52)]
    public Int32 dmDisplayOrientation;
    [System.Runtime.InteropServices.FieldOffset(56)]
    public Int32 dmDisplayFixedOutput;

    [System.Runtime.InteropServices.FieldOffset(60)]
    public short dmColor;
    [System.Runtime.InteropServices.FieldOffset(62)]
    public short dmDuplex;
    [System.Runtime.InteropServices.FieldOffset(64)]
    public short dmYResolution;
    [System.Runtime.InteropServices.FieldOffset(66)]
    public short dmTTOption;
    [System.Runtime.InteropServices.FieldOffset(68)]
    public short dmCollate;
    [System.Runtime.InteropServices.FieldOffset(72)]
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = CCHFORMNAME)]
    public string dmFormName;
    [System.Runtime.InteropServices.FieldOffset(102)]
    public Int16 dmLogPixels;
    [System.Runtime.InteropServices.FieldOffset(104)]
    public Int32 dmBitsPerPel;
    [System.Runtime.InteropServices.FieldOffset(108)]
    public Int32 dmPelsWidth;
    [System.Runtime.InteropServices.FieldOffset(112)]
    public Int32 dmPelsHeight;
    [System.Runtime.InteropServices.FieldOffset(116)]
    public Int32 dmDisplayFlags;
    [System.Runtime.InteropServices.FieldOffset(116)]
    public Int32 dmNup;
    [System.Runtime.InteropServices.FieldOffset(120)]
    public Int32 dmDisplayFrequency;
}

// See: https://msdn.microsoft.com/en-us/library/windows/desktop/dd183569(v=vs.85).aspx
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
internal struct DISPLAY_DEVICE
{
    [MarshalAs(UnmanagedType.U4)]
    public int cb;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
    public string DeviceName;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
    public string DeviceString;
    [MarshalAs(UnmanagedType.U4)]
    public DisplayDeviceStateFlags StateFlags;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
    public string DeviceID;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
    public string DeviceKey;
}

// See: https://msdn.microsoft.com/de-de/library/windows/desktop/dd162807(v=vs.85).aspx
[StructLayout(LayoutKind.Sequential)]
internal struct POINTL
{
    long x;
    long y;
}



internal enum DISP_CHANGE : int
{
    Successful = 0,
    Restart = 1,
    Failed = -1,
    BadMode = -2,
    NotUpdated = -3,
    BadFlags = -4,
    BadParam = -5,
    BadDualView = -6
}

// http://www.pinvoke.net/default.aspx/Enums/DisplayDeviceStateFlags.html
[Flags()]
internal enum DisplayDeviceStateFlags : int
{
    /// <summary>The device is part of the desktop.</summary>
    AttachedToDesktop = 0x1,
    MultiDriver = 0x2,
    /// <summary>The device is part of the desktop.</summary>
    PrimaryDevice = 0x4,
    /// <summary>Represents a pseudo device used to mirror application drawing for remoting or other purposes.</summary>
    MirroringDriver = 0x8,
    /// <summary>The device is VGA compatible.</summary>
    VGACompatible = 0x10,
    /// <summary>The device is removable; it cannot be the primary display.</summary>
    Removable = 0x20,
    /// <summary>The device has more display modes than its output devices support.</summary>
    ModesPruned = 0x8000000,
    Remote = 0x4000000,
    Disconnect = 0x2000000
}

// http://www.pinvoke.net/default.aspx/user32/ChangeDisplaySettingsFlags.html
[Flags()]
internal enum DisplaySettingsFlags : int
{
    CDS_NONE = 0,
    CDS_UPDATEREGISTRY = 0x00000001,
    CDS_TEST = 0x00000002,
    CDS_FULLSCREEN = 0x00000004,
    CDS_GLOBAL = 0x00000008,
    CDS_SET_PRIMARY = 0x00000010,
    CDS_VIDEOPARAMETERS = 0x00000020,
    CDS_ENABLE_UNSAFE_MODES = 0x00000100,
    CDS_DISABLE_UNSAFE_MODES = 0x00000200,
    CDS_RESET = 0x40000000,
    CDS_RESET_EX = 0x20000000,
    CDS_NORESET = 0x10000000
}

[Flags()]
internal enum DM : int
{
    Orientation = 0x00000001,
    PaperSize = 0x00000002,
    PaperLength = 0x00000004,
    PaperWidth = 0x00000008,
    Scale = 0x00000010,
    Position = 0x00000020,
    NUP = 0x00000040,
    DisplayOrientation = 0x00000080,
    Copies = 0x00000100,
    DefaultSource = 0x00000200,
    PrintQuality = 0x00000400,
    Color = 0x00000800,
    Duplex = 0x00001000,
    YResolution = 0x00002000,
    TTOption = 0x00004000,
    Collate = 0x00008000,
    FormName = 0x00010000,
    LogPixels = 0x00020000,
    BitsPerPixel = 0x00040000,
    PelsWidth = 0x00080000,
    PelsHeight = 0x00100000,
    DisplayFlags = 0x00200000,
    DisplayFrequency = 0x00400000,
    ICMMethod = 0x00800000,
    ICMIntent = 0x01000000,
    MediaType = 0x02000000,
    DitherType = 0x04000000,
    PanningWidth = 0x08000000,
    PanningHeight = 0x10000000,
    DisplayFixedOutput = 0x20000000
}

Cách sử dụng:

DisplayHelper.Rotate(1, DisplayHelper.Orientations.DEGREES_CW_270);

Tham số 1: chính là màn hình thứ nhất, nếu muốn xoay màn hình khác thì bạn truyền vào số 2, 3... 

Và khi bấm nút sử dụng chúng ta sẽ gọi hàm sau trên form 1 điều khiển: (nhấn Ctrl + K) => trả về mặc định

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;

namespace RotateScreen
{
    public partial class Form1 : Form
    {
        [System.Runtime.InteropServices.DllImport("user32.dll")]
        private static extern bool RegisterHotKey(IntPtr hWnd, int id, int fsModifiers, int vk);
        [System.Runtime.InteropServices.DllImport("user32.dll")]
        private static extern bool UnregisterHotKey(IntPtr hWnd, int id);

        enum KeyModifier
        {
            None = 0,
            Alt = 1,
            Control = 2,
            Shift = 4,
            WinKey = 8
        }
        public Form1()
        {
            InitializeComponent();
            this.FormClosing += Form1_FormClosing;
            int id = 0;    
            RegisterHotKey(this.Handle, id, (int)KeyModifier.Control, Keys.K.GetHashCode());
        }
        protected override void WndProc(ref Message m)
        {
            base.WndProc(ref m);

            if (m.Msg == 0x0312)
            {
                

                Keys key = (Keys)(((int)m.LParam >> 16) & 0xFFFF);                  
                KeyModifier modifier = (KeyModifier)((int)m.LParam & 0xFFFF);       
                int id = m.WParam.ToInt32();

                DisplayHelper.Rotate(1, DisplayHelper.Orientations.DEGREES_CW_0);

            }
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            DisplayHelper.Rotate(1, DisplayHelper.Orientations.DEGREES_CW_0);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            DisplayHelper.Rotate(1, DisplayHelper.Orientations.DEGREES_CW_0);
        }

        private void button3_Click(object sender, EventArgs e)
        {
            DisplayHelper.Rotate(1, DisplayHelper.Orientations.DEGREES_CW_180);
        }

        private void button2_Click(object sender, EventArgs e)
        {
            DisplayHelper.Rotate(1, DisplayHelper.Orientations.DEGREES_CW_90);
        }

        private void button4_Click(object sender, EventArgs e)
        {
            DisplayHelper.Rotate(1, DisplayHelper.Orientations.DEGREES_CW_270);
        }
    }
}

Thanks for watching!

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