I found the coding to display the desktop, but there's an error somewhere?

[Doc Scheinder]

I found the coding to display the desktop, but there's an error somewhere? Can anyone figure out what's wrong

URL:http://support.microsoft.com/support/kb/articles/q140/8/85.asp

Coding:Step-by-Step Example
Start Visual Basic for Windows (VB.EXE). Form1 is created by default.


Add a picture box (Picture1) to Form1.


Set the following properties:
Control Property Value
------------------------------
Picture1 AutoRedraw True
Picture1 Visible False




Add the following code to your .BAS module:
Type lrect
left As Integer
top As Integer
right As Integer
bottom As Integer
End Type

Private Declare Function GetDesktopWindow Lib "user" () As Integer
Private Declare Function GetDC Lib "user" (ByVal hWnd%) As Integer

' Enter the following Declare on one, single line:

Private Declare Function BitBlt Lib "GDI" (ByVal hDestDC%, ByVal X%, ByVal Y%,
ByVal nWidth%, ByVal nHeight%, ByVal hSrcDC%, ByVal XSrc%,
ByVal YSrc%, ByVal dwRop&) As Integer
' Enter the following Declare on one, single line:

Private Declare Function ReleaseDC Lib "User"(ByVal hWnd As Integer, ByVal

hDC As Integer) As Integer

Private Declare Sub GetWindowRect Lib "User" (ByVal hWnd%, lpRect As lrect)
Global TwipsPerPixel As Single



Add the following code to the Form1 Click event procedure:
Private Sub Form_Click ()
Call GrabScreen
End Sub

Public Sub GrabScreen ()

Dim winSize As lrect

' Assign information of the source bitmap.
' Note that BitBlt requires coordinates in pixels.
hwndSrc% = GetDesktopWindow()
hSrcDC% = GetDC(hwndSrc%)
XSrc% = 0: YSrc% = 0
Call GetWindowRect(hwndSrc%, winSize)
nWidth% = winSize.right ' Units in pixels.
nHeight% = winSize.bottom ' Units in pixels.

' Assign informate of the destination bitmap.
hDestDC% = Form1.Picture1.hDC
x% = 0: Y% = 0

' Set global variable TwipsPerPixel and use to set
' picture box to same size as screen being grabbed.
' If picture box not the same size as picture being
' BitBlt'ed to it, it will chop off all that does not
' fit in the picture box.
GetTwipsPerPixel
Form1.Picture1.Top = 0
Form1.Picture1.Left = 0
Form1.Picture1.Width = (nWidth% + 1) * TwipsPerPixel
Form1.Picture1.Height = (nHeight% + 1) * TwipsPerPixel

' Assign the value of the constant SRCOPYY to the Raster operation.
dwRop& = &HCC0020

' NOTE: function call must be on one line:
Suc% = BitBlt(hDestDC%, x%, Y%, nWidth%, nHeight%,
hSrcDC%, XSrc%, YSrc%, dwRop&amp

' Release the DeskTopWindow's hDC to Windows.
' Windows may hang if this is not done.
Dmy% = ReleaseDC(hwndSrc%, hSrcDC%)

'Make the picture box visible.
Form1.Picture1.Visible = True
End Sub

Public Sub GetTwipsPerPixel ()
' Set a global variable with the Twips to Pixel ratio.
Form1.ScaleMode = 3
NumPix = Form1.ScaleHeight
Form1.ScaleMode = 1
TwipsPerPixel = Form1.ScaleHeight / NumPix
End Sub



Run the program. Click Form1.


Using the mouse, change the size of the form to see more of the picture box. With a little work, you can use this as a screen saver program.


OK: When I tried the example I got a whole bunch of undefined variables. When I defined the variables I got an Overflow error Run-time error '6'

Does anyone know what the hell is going on?

[Serge]

By looking at this Microsoft's example I assume you're trying to get an image of the desktop. If that's the case, then it is a lot easier then they're showing. Add a picturebox to the form and copy this code:

Option Explicit
Private Type RECT
        Left As Long
        Top As Long
        Right As Long
        Bottom As Long
End Type
Private Declare Function GetDesktopWindow Lib "user32" () As Long
Private Declare Function GetDC Lib "user32" (ByVal hwnd As Long) As Long
Private Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal dwRop As Long) As Long
Private Declare Function ReleaseDC Lib "user32" (ByVal hwnd As Long, ByVal hdc As Long) As Long
Private Declare Function GetWindowRect Lib "user32" (ByVal hwnd As Long, lpRect As RECT) As Long
Private Const SRCCOPY = &HCC0020

Public Sub GetScreenImage(pPicture As PictureBox)
    Dim recSize As RECT
    Dim lngHwndSource As Long
    Dim lngDCHwnd As Long
    Dim intHeight As Integer
    Dim intWidth As Integer
    Dim intY As Integer
    Dim intX As Integer
    
    pPicture.Visible = False
    
    lngHwndSource = GetDesktopWindow()
    lngDCHwnd = GetDC(lngHwndSource)
    
    Call GetWindowRect(lngHwndSource, recSize)
    intWidth = recSize.Right
    intHeight = recSize.Bottom
    
    pPicture.Top = 0
    pPicture.Left = 0
    pPicture.Width = ScaleWidth
    pPicture.Height = ScaleHeight
    
    Call BitBlt(pPicture.hdc, 0, 0, intWidth, intHeight, lngDCHwnd, 0, 0, SRCCOPY)
    Call ReleaseDC(lngHwndSource, lngDCHwnd)
    pPicture.Visible = True
End Sub

Private Sub Form_Click()
    GetScreenImage Picture1
End Sub

[hitcgar]

Serge is right, but for an explanation -

Your code was old code for 16bit platforms.

- Your Lib "user" etc should be "user32" if your using win 98 and above.

- most of your vars are integers ex. hwndSrc% whereas for this to work they should be declared As Long -
hwnd var types (handles) are always long in win32.

Also:
- If you declare your API functions in a separate module,
as you have, you can only access them from the form's code
if they are declared as Public and not private as in your
code.