How to use WPF Mouse.OverrideCursor in a VB.NET application

Question

I tried a sample WPF code, that Kareninstructor recommended to me, from https://github.com/karenpayneoregon/visual-basic-getting-started/tree/master/ChangeCursor to test the usage of Mouse.OverrideCursor - this worked beautifully. However, it is a WPF standalone application, and I have not been able to find a way of incorporating the Mouse.OverrideCursor in my VB.NET code (I am writing in Visual Basic using VS 2019).

I need to force my mouse pointer to a custom cursor image when I am performing a drag and drop operation. Mouse.OverrideCursor is the required instruction but I have not been able to get it to work in VB. Any clues or pointers would be more than welcome.

HotIndigo

Answer

I update CursorExample code as below:

Public Function CreateCursor() As Cursor  
        Dim brush As SolidColorBrush = Brushes.Gold  
        Dim rx As Double = 50  
        Dim ry As Double = 50  
        Dim vis = New DrawingVisual()  
  
  
        Using dc = vis.RenderOpen()  
            dc.DrawRectangle(brush, New Pen(Brushes.Black, 0.1), New Rect(0, 0, rx, ry))  
            dc.Close()  
        End Using  
  
        Dim rtb = New RenderTargetBitmap(64, 64, 96, 96, PixelFormats.Pbgra32)  
        rtb.Render(vis)  
  
        Using ms1 = New MemoryStream()  
            Dim penc = New PngBitmapEncoder()  
            penc.Frames.Add(BitmapFrame.Create(rtb))  
            penc.Save(ms1)  
            Dim pngBytes = ms1.ToArray()  
            Dim size = pngBytes.GetLength(0)  
  
            Using ms = New MemoryStream()  
  
                If True Then  
                    ms.Write(BitConverter.GetBytes(CType(0, Int16)), 0, 2)  
                    ms.Write(BitConverter.GetBytes(CType(2, Int16)), 0, 2)  
                    ms.Write(BitConverter.GetBytes(CType(1, Int16)), 0, 2)  
                End If  
  
                If True Then  
                    ms.WriteByte(32)  
                    ms.WriteByte(32)  
                    ms.WriteByte(0)  
                    ms.WriteByte(0)  
                    ms.Write(BitConverter.GetBytes(CType((rx / 2.0), Int16)), 0, 2)  
                    ms.Write(BitConverter.GetBytes(CType((ry / 2.0), Int16)), 0, 2)  
                    ms.Write(BitConverter.GetBytes(size), 0, 4)  
                    ms.Write(BitConverter.GetBytes(CType(22, Int32)), 0, 4)  
                End If  
  
                ms.Write(pngBytes, 0, size)  
                ms.Seek(0, SeekOrigin.Begin)  
                Return New Cursor(ms)  
            End Using  
        End Using  
    End Function

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Answer

Hello,

I added to my repository a code sample where in this case I loaded the image from disk, there are of course other ways to load e.g. from resources.

Full source

Cursor class

(has two methods, one to use a bitmap, one for text)

Option Infer On  
  
Imports System.Drawing  
Imports System.Globalization  
Imports System.IO  
Imports System.Runtime.InteropServices  
Imports System.Security.Permissions  
Imports System.Windows.Interop  
Imports Microsoft.Win32.SafeHandles  
  
Public Class CursorHelper  
    Private NotInheritable Class NativeMethods  
        Public Structure IconInfo  
            Public fIcon As Boolean  
            Public xHotspot As Integer  
            Public yHotspot As Integer  
            Public hbmMask As IntPtr  
            Public hbmColor As IntPtr  
        End Structure  
  
        Private Sub New()  
        End Sub  
  
  
          
        Public Shared Function CreateIconIndirect(ByRef icon As IconInfo) As SafeIconHandle  
        End Function  
  
          
        Public Shared Function DestroyIcon(hIcon As IntPtr) As Boolean  
        End Function  
  
          
        Public Shared Function GetIconInfo(  
           hIcon As IntPtr,  
           ByRef pIconInfo As IconInfo) As  Boolean  
        End Function  
    End Class  
  
      
    Private Class SafeIconHandle  
        Inherits SafeHandleZeroOrMinusOneIsInvalid  
  
        Public Sub New()  
            MyBase.New(True)  
        End Sub  
  
        Protected Overrides Function ReleaseHandle() As Boolean  
            Return NativeMethods.DestroyIcon(handle)  
        End Function  
  
    End Class  
  
    Private Shared Function InternalCreateCursor(bmp As Bitmap) As Cursor  
  
        Dim iconInfo = New NativeMethods.IconInfo()  
        NativeMethods.GetIconInfo(bmp.GetHicon(), iconInfo)  
  
        iconInfo.xHotspot = 0  
        iconInfo.yHotspot = 0  
        iconInfo.fIcon = False  
  
        Dim cursorHandle As SafeIconHandle = NativeMethods.CreateIconIndirect(iconInfo)  
  
        Return CursorInteropHelper.Create(cursorHandle)  
  
    End Function  
    Public Shared Function CreateCursorFromImage(  
         bmpName As String,  
         Optional xHotSpot As Integer = 0,  
         Optional yHotSpot As Integer = 0) As Cursor  
  
        Dim bitmapImage = New BitmapImage()  
  
        Using stream = New FileStream(bmpName, FileMode.Open)  
            bitmapImage.BeginInit()  
            bitmapImage.CacheOption = BitmapCacheOption.OnLoad  
            bitmapImage.StreamSource = stream  
            bitmapImage.EndInit()  
            bitmapImage.Freeze()  
        End Using  
  
        Dim bitMap = BitmapImage2Bitmap(bitmapImage)  
  
        Dim iconInfo As New NativeMethods.IconInfo()  
        NativeMethods.GetIconInfo(bitMap.GetHicon(), iconInfo)  
  
        iconInfo.xHotspot = 0  
        iconInfo.yHotspot = 0  
        iconInfo.fIcon = False  
  
        Dim cursorHandle As SafeIconHandle = NativeMethods.CreateIconIndirect(iconInfo)  
  
        Return CursorInteropHelper.Create(cursorHandle)  
  
  
    End Function  
    Private Shared Function BitmapImage2Bitmap(bitmapImage As BitmapImage) As Bitmap  
  
        Using outStream As New MemoryStream()  
            Dim enc As BitmapEncoder = New BmpBitmapEncoder()  
            enc.Frames.Add(BitmapFrame.Create(bitmapImage))  
            enc.Save(outStream)  
            Dim bitmap As New Bitmap(outStream)  
  
            Return New Bitmap(bitmap)  
  
        End Using  
    End Function  
    Public Shared Function CreateCursor(cursorText As String) As Cursor  
  
  
        Dim formattedText As New FormattedText(  
            cursorText,  
            New CultureInfo("en-us"), FlowDirection.LeftToRight,  
            New Typeface(New Media.FontFamily("Arial"), FontStyles.Normal,  
                         FontWeights.Normal,  
                         New FontStretch()), 12.0, Media.Brushes.Black)  
  
  
        Dim drawingVisual As New DrawingVisual()  
        Dim drawingContext As DrawingContext = drawingVisual.RenderOpen()  
        drawingContext.DrawText(formattedText, New Windows.Point())  
        drawingContext.Close()  
  
  
        Dim rtb As New RenderTargetBitmap(  
            CInt(drawingVisual.ContentBounds.Width),  
            CInt(drawingVisual.ContentBounds.Height), 96, 96, PixelFormats.Pbgra32)  
  
        rtb.Render(drawingVisual)  
  
        Dim encoder As New PngBitmapEncoder()  
        encoder.Frames.Add(BitmapFrame.Create(rtb))  
  
        Using ms = New MemoryStream()  
  
            encoder.Save(ms)  
  
            Using bmp = New Bitmap(ms)  
                Return InternalCreateCursor(bmp)  
            End Using  
  
        End Using  
    End Function  
  
End Class

Code behind

Class MainWindow  
    Private Sub Label_MouseLeftButtonDown(sender As Object, e As MouseButtonEventArgs)  
  
        Dim data As New DataObject(DataFormats.Text, CType(e.Source, Label).Content)  
  
        DragDrop.DoDragDrop(CType(e.Source, DependencyObject), data, DragDropEffects.Copy)  
  
    End Sub  
  
    Private Sub Label_Drop(sender As Object, e As DragEventArgs)  
  
        CType(e.Source, Label).Content = CStr(e.Data.GetData(DataFormats.Text))  
        MessageBox.Show("Dropped")  
  
    End Sub  
  
    Private _customCursor As Cursor = Nothing  
  
    Private Sub Label_GiveFeedback(sender As Object, e As GiveFeedbackEventArgs)  
  
        If e.Effects = DragDropEffects.Copy Then  
            If _customCursor Is Nothing Then  
                _customCursor = CursorHelper.CreateCursorFromImage("Dynamic.bmp")  
            End If  
  
            If _customCursor IsNot Nothing Then  
                e.UseDefaultCursors = False  
                Mouse.SetCursor(_customCursor)  
            End If  
        Else  
            e.UseDefaultCursors = True  
        End If  
  
        e.Handled = True  
  
    End Sub  
  
End Class

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How to use WPF Mouse.OverrideCursor in a VB.NET application

3 answers

Cursor class

Code behind

XAML

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