VB.net Click through form - vb.net

Question

I'm trying to make a program for my late night star gazing, I need my laptop screen to be only red, so I want to make a program that acts as a red filter. It would cover the whole screen and be transparent + red. The user can click through it, it would be just like putting a piece of transparent red plastic in-front of the screen.
So far I have a form that sizes itself to what ever your screen size is, and moves itself to the upper left corner. It is slightly transparent and red.
I need to make all clicks on the form pass through, as I will eventually make the form transparent and red, but I don't want the user to be able to interact with it.
Program is called "Red_Filter"
Public Class Form1
Dim Screens As Array
Dim TotalWidth As Integer
Dim TotalHeight As Integer
Dim Heights As List(Of Integer) = New List(Of Integer)
'Load / Close
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Screens = Screen.AllScreens
For I As Integer = 0 To UBound(Screens)
TotalWidth += Screens(I).Bounds.Width
Heights.Add(Screens(I).Bounds.Height)
Next
TotalHeight = Heights.Max()
Me.Width = TotalWidth
Me.Height = TotalWidth
Me.Location = New Point(0, 0)
Me.BackColor = Color.Red
Me.Opacity = 0.5
Me.TopMost = True
'Make it click through
SetWindowLong(Me.Handle, GWL_EXSTYLE, WS_EX_TRANSPARENT)
End Sub
'Click Through Functionality
Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Const GWL_EXSTYLE = -20
Const WS_EX_TRANSPARENT = &H20
End Class
This is what I have so far, the part after "'Click Through Functionality" I found online, however, it gives me this error:
A call to PInvoke function 'Red Filter!Red_Filter.Form1::SetWindowLong' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.
I do not know how the code I found online works, but the error happens in the last line of the form's load event.
Does anyone know how to make a form click-through?

Answer 1

I ripped code from this codeproject post: http://www.codeproject.com/Articles/12877/Transparent-Click-Through-Forms
Here's a complex version with all the comment-ey goodness:
Imports System.Runtime.InteropServices
Public Class Form1
Private InitialStyle As Integer
Dim PercentVisible As Decimal
Private Sub Form_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
' Grab the Extended Style information
' for this window and store it.
InitialStyle = GetWindowLong(Me.Handle, GWL.ExStyle)
PercentVisible = 0.8
' Set this window to Transparent
' (to the mouse that is!)
' This creates a new Extended Style
' for our window, which takes effect
' immediately upon being set, that
' combines the initial style of our window
' (saved in Form.Load) and adds the ability
' to be Transparent to the mouse.
' Both Layered and Transparent must be
' turned on for this to work AND have
' the window render properly!
SetWindowLong(Me.Handle, GWL.ExStyle, InitialStyle Or WS_EX.Layered Or WS_EX.Transparent)
' Don't forget to set the Alpha
' for the window or else you won't be able
' to see the window! Possible values
' are 0 (visibly transparent)
' to 255 (visibly opaque). I'll set
' it to 70% visible here for show.
' The second parameter is 0, because
' we're not using a ColorKey!
SetLayeredWindowAttributes(Me.Handle, 0, 255 * PercentVisible, LWA.Alpha)
' Just for giggles, set this window
' to stay on top of all others so we
' can see what's happening.
Me.TopMost = True
Me.BackColor = Color.Red
End Sub
Public Enum GWL As Integer
ExStyle = -20
End Enum
Public Enum WS_EX As Integer
Transparent = &H20
Layered = &H80000
End Enum
Public Enum LWA As Integer
ColorKey = &H1
Alpha = &H2
End Enum
<DllImport("user32.dll", EntryPoint:="GetWindowLong")> _
Public Shared Function GetWindowLong( _
ByVal hWnd As IntPtr, _
ByVal nIndex As GWL _
) As Integer
End Function
<DllImport("user32.dll", EntryPoint:="SetWindowLong")> _
Public Shared Function SetWindowLong( _
ByVal hWnd As IntPtr, _
ByVal nIndex As GWL, _
ByVal dwNewLong As WS_EX _
) As Integer
End Function
<DllImport("user32.dll", _
EntryPoint:="SetLayeredWindowAttributes")> _
Public Shared Function SetLayeredWindowAttributes( _
ByVal hWnd As IntPtr, _
ByVal crKey As Integer, _
ByVal alpha As Byte, _
ByVal dwFlags As LWA _
) As Boolean
End Function
End Class
And here's the simplified version I'm using that makes more sense to me:
Imports System.Runtime.InteropServices
Public Class Form1
Private InitialStyle As Integer
Dim PercentVisible As Decimal
Private Sub Form_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
InitialStyle = GetWindowLong(Me.Handle, -20)
PercentVisible = 0.8
SetWindowLong(Me.Handle, -20, InitialStyle Or &H80000 Or &H20)
SetLayeredWindowAttributes(Me.Handle, 0, 255 * PercentVisible, &H2)
Me.BackColor = Color.Red
Me.TopMost = True
End Sub
<DllImport("user32.dll", EntryPoint:="GetWindowLong")> Public Shared Function GetWindowLong(ByVal hWnd As IntPtr, ByVal nIndex As Integer) As Integer
End Function
<DllImport("user32.dll", EntryPoint:="SetWindowLong")> Public Shared Function SetWindowLong(ByVal hWnd As IntPtr, ByVal nIndex As Integer, ByVal dwNewLong As Integer) As Integer
End Function
<DllImport("user32.dll", EntryPoint:="SetLayeredWindowAttributes")> Public Shared Function SetLayeredWindowAttributes(ByVal hWnd As IntPtr, ByVal crKey As Integer, ByVal alpha As Byte, ByVal dwFlags As Integer) As Boolean
End Function
End Class

Answer 2

Try this:
Protected Overrides ReadOnly Property CreateParams() As CreateParams
Get
Const WS_EX_TRANSPARENT As Integer = &H20 'Check if it can
Dim params As CreateParams = MyBase.CreateParams
params.ExStyle = params.ExStyle Or WS_EX_TRANSPARENT
Return params 'return
End Get
End Property

Answer 3

Using VS 2012, I created a simple program without your Screens object, like this:
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Me.BackColor = Color.Red
Me.Opacity = 0.5
Me.TopMost = True
SetWindowLong(Me.Handle.ToInt64(), GWL_EXSTYLE, WS_EX_TRANSPARENT)
End Sub
Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Const GWL_EXSTYLE = -20
Const WS_EX_TRANSPARENT = &H20
End Class
Note the call to SetWindowLong:
SetWindowLong(Me.Handle.ToInt64(), GWL_EXSTYLE, WS_EX_TRANSPARENT)
Here's a screen shot of the program running:
EDITED TO ADD
Note that you can get this same effect without calling SetWindowLong.

Answer 4

Add this after Class:
Private Const WS_EX_TRANSPARENT As Integer = &H20
Protected Overrides ReadOnly Property CreateParams() As System.Windows.Forms.CreateParams
Get
Dim cp As CreateParams = MyBase.CreateParams
cp.ExStyle = cp.ExStyle Or WS_EX_TRANSPARENT
Return cp
End Get
End Property
Then run it. It should work. Also it dose not work on non-transparent forms from what i know.

Answer 5

A little variant for a ghost form (You can see through it and click through it!), with the most recent Declare syntax. Thanx to Postman for the useful post.
Imports System.Runtime.InteropServices
Public Class GhostForm
Private InitialStyle As Integer
Private PercentVisible As Decimal
Declare Function GetWindowLong Lib "user32.dll" Alias "GetWindowLongA" (ByVal hwnd As System.IntPtr, ByVal nIndex As Integer) As Integer
Declare Function SetWindowLong Lib "user32.dll" Alias "SetWindowLongA" (ByVal hwnd As System.IntPtr, ByVal nIndex As Integer, ByVal dwNewLong As Integer) As Integer
Declare Function SetLayeredWindowAttributes Lib "user32.dll" (ByVal hWnd As IntPtr, ByVal crKey As Integer, ByVal alpha As Byte, ByVal dwFlags As Integer) As Boolean
Private Sub Form_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
InitialStyle = GetWindowLong(Me.Handle, -20)
PercentVisible = 0.5
SetWindowLong(Me.Handle, -20, InitialStyle Or &H80000 Or &H20)
SetLayeredWindowAttributes(Me.Handle, 0, 255 * PercentVisible, &H2)
Me.BackColor = Color.Green
Me.TopMost = True
End Sub
End Class