Problem confining pointer to Form

Hi Guys,

I am trying to confine the mouse pointer to the form in a little test app.

So far, I am able to trap all the buttons and wheel action, but when I attempt to limit the pointer movement to the active form, I am encountering an error.

The Error I am getting is " Value does not fall within the expected range. The error occurs on line 122 of my code.
I did have to convert some of the snippets from VB6 code so that is where I may have messed up, but I cannot figure out my mistake.

Code:

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Imports System.Deployment.Application
Imports System.Reflection.Emit
Imports System.Windows.Forms.VisualStyles.VisualStyleElement

Public Class Form1
    Dim lTwipsX As Long
    Dim lTwipsY As Long
    Structure RECT
        Public left As Long
        Public top As Long
        Public right As Long
        Public bottom As Long
    End Structure
    Dim RectArea As RECT
    Structure POINT
        Public x As Long
        Public y As Long
    End Structure

    'Private Declare Function ClipCursor Lib "user32" (lpRect As Any) As Long
    Private Declare Function ClipCursor Lib "user32" (lpRect) As Long
    Private Declare Function GetClientRect Lib "user32" (ByVal hwnd As Long, lpRect As RECT) As Long
    Private Declare Function ClientToScreen Lib "user32" (ByVal hwnd As Long, lpPoint As POINT) As Long
    Private Declare Function OffsetRect Lib "user32" (lpRect As RECT, ByVal x As Long, ByVal y As Long) As Long
    Private Declare Function GetAsyncKeyState Lib "user32" (ByVal vKey As Long) As Integer
    Private Const VK_LBUTTON = &H1
    Private Const VK_RBUTTON = &H2
    Dim RightClicked As Integer

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        lTwipsX = My.Computer.Screen.Bounds.Width / 15 ' TwipsPerPixelX
        lTwipsY = My.Computer.Screen.Bounds.Height / 15 ' TwipsPerPixelY
        For Each c As Control In Controls
            AddHandler c.MouseClick, AddressOf ClickHandler
        Next
    End Sub

    Private Sub Form1_MouseEnter(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.MouseEnter
        TextBox1.Text = " Mouse Entered "
        'displaying "mouse entered" when the mouse pointer enters the form
    End Sub

    Private Sub Form1_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseDown
        If e.Button = MouseButtons.Left Then
            TextBox2.Text = " Mouse Left click at " + CStr(e.X) + " :" + CStr(e.Y)
        ElseIf e.Button = MouseButtons.Right Then
            TextBox2.Text = " Mouse Right click at " + CStr(e.X) + " :" + CStr(e.Y)
        ElseIf e.Button = MouseButtons.Middle Then
            TextBox2.Text = " Mouse Middle click at " + CStr(e.X) + " :" + CStr(e.Y)
        Else
            'displaying the coordinates when the mouse is pressed on the form
        End If
    End Sub

    Private Sub Form1_MouseLeave(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.MouseLeave
        TextBox1.Text = " Mouse Exited "
        'displaying "mouse exited" when the mouse pointer leaves the form
    End Sub

    Private Sub Form1_MouseClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseClick
        If e.Button = MouseButtons.Right Then
            RightClicked += CStr(e.Clicks)
            TextBox3.Text = " Mouse Right click " + RightClicked.ToString + " times."
            'Displaying number of times the mouse right button is pressed and released.
        End If
    End Sub

    Private Sub Form1_MouseWheel(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseWheel
        If e.Delta > 0 Then
            TextBox2.Text = " Mouse Wheel Scrolled UP "
            Label1.Text = "Wheel UP"
        Else
            TextBox2.Text = " Mouse Wheel Scrolled DOWN "
            Label1.Text = "Wheel Down"
        End If

        'If MouseWheel.scrollup Then
        '        UserZoom = UserZoom + 0.05
        'Me.Refresh()
        'End If

    End Sub

    ' Source - https://stackoverflow.com/a/37639493
    ' Posted by Apachi, modified by community. See post 'Timeline' for change history
    ' Retrieved 2026-03-30, License - CC BY-SA 3.0

    Public Sub ClickHandler(sender As Object, e As MouseEventArgs) Handles Me.MouseClick, PictureBox1.MouseClick, Label1.MouseClick, Button1.MouseClick
        Label1.Text = String.Format("Clicked ""{0}"" with the {1} mouse button.", sender.name, e.Button.ToString.ToLower)

        Select Case e.Button
            Case MouseButtons.Left, Label1.Text = "Left"
            Case MouseButtons.Right, Label1.Text = "Right"
            Case MouseButtons.Middle, Label1.Text = "Middle"
            Case Else
                Label1.Text = "Some other button"
        End Select
    End Sub

    Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
        If GetAsyncKeyState(VK_LBUTTON) Then
            Label2.Text = "Left Click"
        ElseIf GetAsyncKeyState(VK_RBUTTON) Then
            Label2.Text = "Right Click"
        Else
            Label2.Text = ""
        End If
    End Sub

    Private Sub CmdTrap_Click(sender As Object, e As EventArgs) Handles CmdTrap.Click

        If CmdTrap.Text = "Trap Cursor" Then
            'MsgBox("Cursor Clipped to the Form")

            With RectArea
                .left = .left / lTwipsX
                .top = .top / lTwipsY
                .right = .left + Me.Width / lTwipsX
                .bottom = .top + Me.Height / lTwipsY
            End With

            Call ClipCursor(RectArea)
            CmdTrap.Text = "Release Cursor"
        Else
            'MsgBox("Cursor Released")

            With RectArea
                .left = 0
                .top = 0
                .right = My.Computer.Screen.Bounds.Width / lTwipsX
                .bottom = My.Computer.Screen.Bounds.Height / lTwipsY
            End With
            Call ClipCursor(RectArea)
            CmdTrap.Text = "Trap Cursor"
        End If
    End Sub
End Class

---

Regards,
Antony.

You can restrict your cursor with the Cursor.Clip property…

https://learn.microsoft.com/en-us/do...wsdesktop-10.0

As a clue why your API functions aren’t working, you’re using legacy declarations. VB.Net uses 32 bit variables. What was Short is now Integer, what was Long is now Integer. When a Long would’ve been used for a handle, that’s now IntPtr

Code:

---

Private Declare Function ClipCursor Lib "user32" (lpRect As RECT) As Integer
Private Declare Function GetClientRect Lib "user32" (ByVal hwnd As IntPtr, lpRect As RECT) As Integer
Private Declare Function ClientToScreen Lib "user32" (ByVal hwnd As IntPtr, lpPoint As POINT) As Integer
Private Declare Function OffsetRect Lib "user32" (lpRect As RECT, ByVal x As Integer, ByVal y As Integer) As Integer
Private Declare Function GetAsyncKeyState Lib "user32" (ByVal vKey As Integer) As Integer
Private Const VK_LBUTTON As Integer = &H1
Private Const VK_RBUTTON As Integer = &H2
Dim RightClicked As Boolean

---

Thanks Paul.

Your guidance helped me sort out the clip.cursor function and now it works.

Cheers.

Quote:

---

Originally Posted by .paul.

You can restrict your cursor with the Cursor.Clip property…

https://learn.microsoft.com/en-us/do...wsdesktop-10.0

As a clue why your API functions aren’t working, you’re using legacy declarations. VB.Net uses 32 bit variables. What was Short is now Integer, what was Long is now Integer. When a Long would’ve been used for a handle, that’s now IntPtr

Code:

---

Private Declare Function ClipCursor Lib "user32" (lpRect As RECT) As Integer
Private Declare Function GetClientRect Lib "user32" (ByVal hwnd As IntPtr, lpRect As RECT) As Integer
Private Declare Function ClientToScreen Lib "user32" (ByVal hwnd As IntPtr, lpPoint As POINT) As Integer
Private Declare Function OffsetRect Lib "user32" (lpRect As RECT, ByVal x As Integer, ByVal y As Integer) As Integer
Private Declare Function GetAsyncKeyState Lib "user32" (ByVal vKey As Integer) As Integer
Private Const VK_LBUTTON As Integer = &H1
Private Const VK_RBUTTON As Integer = &H2
Dim RightClicked As Boolean

---

---

Ok… I can see problems there. To clarify…

Short or Int16 is 16 bit
Integer or Int32 is 32 bit
Long or Int64 is 64 bit

IntPtr represents a signed integer where the bit-width is the same as a pointer.

I was originally encountering problems but I understood what was going on and was able to adjust to get it working.
The only difference was in the last line, I couldn't use the Boolean response so I changed it to an integer and was able to get the test to work.

I am now trying to get the clip rect to go back to full screen (I.E. turn clip.cursor on and off as needed.
I can change the dimensions of rect but cannot seem to define coord 0,0, screen height, screen width in pixels or in twips as the acceptable input is only size (width, height) and it assumes that 0,0 is form top left.

Wish it was as simple as define rect(top,left,bottom,right), then clip.cursor.enable or clip.cursor.disable but alas, it is not

Regards,
Antony.

Code:

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Cursor.Clip = Me.ClientRectangle

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To reset…

Code:

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Cursor.Clip = Nothing

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RightClicked += CStr(e.Clicks)???

Not sure what you’re doing there? If it’s an Integer, why CStr?

Or save the clip value to a variable before changing it, then you can easily reset it after

Thanks Paul.

It's embarrassing when the fix is so simple.
I have the values in a string and can now toggle it on and off as needed.
Threw away thirtyfive lines of useless code that I created and replaced it with three.
This is a clear case of Nothing being so much more than a stack of code doing nothing.

Thanks again.

You should turn Option Strict on for all of your projects.
To set Option Strict in this dialog box, on the Tools menu, click Options. In the Options dialog box, expand Projects and Solutions, and then click VB Defaults. The initial default setting in VB Defaults is Off.
You’ll find it won’t let you set an Integer with a String. Also, if you have a Rectangle, use a variable of type Rectangle instead of a String…