C ＃ customize and dynamically switch cursor

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Original author ： Blogs in Tang, song, yuan, Ming and Qing Dynasties

Original address ：https://www.cnblogs.com/kybs0/p/14873136.html

The system has many cursor types ：Cursors class (System.Windows.Input) | Microsoft Docs^[1]

This chapter describes how to customize the cursor 、 And dynamically switch cursor types .

Dynamically switch cursor types

• Take whiteboard writing as an example ：

  • During mouse operation Cursor Red dot ;

  • When touching Cursor It's empty ;

public MainWindow()
    {
        InitializeComponent();
        MouseEnter += (s, e) =>
        {
            ShowMouseCursor(e);
        };
        MouseMove += (s, e) =>
        {
            ShowMouseCursor(e);
        };
        StylusMove += (s, e) =>
        {
            ShowNoneCursor();
        };
    }

• Set the cursor display ;

private void ShowNoneCursor()
  {
      if (Cursor == Cursors.None)
      {
          return;
      }
      Cursor = Cursors.None;
      Mouse.UpdateCursor();
  }
  private void ShowMouseCursor(MouseEventArgs e)
  {
      if (e.StylusDevice != null && e.StylusDevice.Id > -1)
      {
          return;
      }
      if (Cursor == GetFillCursor())
      {
          return;
      }
      Cursor = GetFillCursor();
      Mouse.UpdateCursor();
  }
  private Cursor _fillCursor = null;
  private Cursor GetFillCursor()
  {
      return _fillCursor ?? (_fillCursor = CursorHelper.CreateFillCursor());
  }

When touching writing , There will be a default cursor , So set the cursor blank when touching here Cursors.None;

Mouse.UpdateCursor() The cursor can be forcibly updated . Of course , Without calling this update method, the naked eye can't see anything ...

The cursor switching effect is as above , The first paragraph is written with a mouse , Behind it is touch writing , Cursor type has switching . See the following figure for the red dot cursor customization scheme .

  Custom cursor 1） Customize a solid color Circular cursor ：

public static Cursor CreateFillCursor(int size = 24, Brush fillBrush = null)
    {
        int unitSize = size / 4;
        var bmp = new Bitmap(size, size);
        using (Graphics g = Graphics.FromImage(bmp))
        {
            g.Clip = new Region(new Rectangle(0, 0, size, size));
            g.SmoothingMode = SmoothingMode.HighQuality;
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;
            using (var pen = new Pen(fillBrush ?? Brushes.Red, unitSize))
            {

                g.DrawEllipse(pen, new Rectangle(unitSize, unitSize, unitSize, unitSize));
            }
        }
        return BitmapCursor.CreateBmpCursor(bmp);
    }

2） You can also use image resources BitmapSource To generate the cursor ;

public static Cursor CreateFromBitmapSource(BitmapSource source)
   {
       var bitmap = BitmapSourceToBitmap(source);
       return BitmapCursor.CreateBmpCursor(bitmap);
   }
   private static Bitmap BitmapSourceToBitmap(BitmapSource source)
   {
       using (var stream = new MemoryStream())
       {
           var e = new BmpBitmapEncoder();
           e.Frames.Add(BitmapFrame.Create(source));
           e.Save(stream);

           var bmp = new Bitmap(stream);

           return bmp;
       }
   }

2）BitmapCursor class ;

internal class BitmapCursor : SafeHandle
   {
       public override bool IsInvalid => handle == (IntPtr)(-1);

       public static Cursor CreateBmpCursor(Bitmap cursorBitmap)
       {

           var c = new BitmapCursor(cursorBitmap);

           return CursorInteropHelper.Create(c);
       }
       protected BitmapCursor(Bitmap cursorBitmap)
           : base((IntPtr)(-1), true)
       {
           handle = cursorBitmap.GetHicon();
       }
       protected override bool ReleaseHandle()
       {
           bool result = DestroyIcon(handle);

           handle = (IntPtr)(-1);

           return result;
       }
       [DllImport("user32")]
       private static extern bool DestroyIcon(IntPtr hIcon);
   }

Reference material ：
WPF Custom mouse cursor - DH_ Green leaves - Blog Garden ^[2]
[WPF] Custom mouse pointer - Zhou Yinhui - Blog Garden ^[3]

Reference material

[1]

Cursors class (System.Windows.Input) | Microsoft Docs: https://docs.microsoft.com/zh-cn/dotnet/api/system.windows.input.cursors?view=net-5.0

[2]

WPF Custom mouse cursor - DH_ Green leaves - Blog Garden : https://www.cnblogs.com/dhqy/p/7754176.html

[3]

[WPF] Custom mouse pointer - Zhou Yinhui - Blog Garden : https://www.cnblogs.com/zhouyinhui/archive/2010/05/28/1746502.html