Stop The Cursor From Moving Off Your Form
The ClipCursor API call lets you define a region of
the screen and restrict the cursor to within that region. This lets you prevent
the user from clicking outside of your application's form.
A few words of caution, this doesn't work when running multiple monitiors. Also,
you may experience problems when switching tasks and coming back to the program
and the clipped area may prevent you from reaching certain areas of another
program. Typically, pressing the Windows-Key to display the Start menu should
clear the clip area.
You can solve these problems by subclassing the
form (see my subclassing page) and processing WM_ACTIVATE
to clear and reassign the clip area.
Download Source Code
Add this code to the Declarations Section:
Dim lTwipsX As Long
Dim lTwipsY As Long
Private Type RECT
Left As Long
Top As Long
Right As Long
Bottom As Long
Dim RectArea As RECT
' The ClipCursor function confines the cursor to
' a rectangular area on the screen.
Private Declare Function ClipCursor Lib "user32" (lpRect As Any) As Long
Add this to the form_Load event:
Private Sub Form_Load()
lTwipsX = Screen.TwipsPerPixelX
lTwipsY = Screen.TwipsPerPixelY
Add a button named cmdTrap with this code:
Private Sub cmdTrap_Click()
Form1.Caption = "Cursor Clipped to the Form"
.Left = Form1.Left / lTwipsX
.Top = Form1.Top / lTwipsY
.Right = .Left + Form1.Width / lTwipsX
.Bottom = .Top + Form1.Height / lTwipsY
Add a button named cmdRelease with this code:
Private Sub cmdRelease_Click()
Form1.Caption = "Cursor Released"
.Left = 0
.Top = 0
.Right = Screen.Width / lTwipsX
.Bottom = Screen.Height / lTwipsY
Download the source code. Press F5 to run the program. Move the cursor anywhere
on the screen. Click the Trap button and notice that you cannot move the cursor
outside of the form. Click the Release button to restore normal cursor