Library code snippets
Making Windows Transparent
By Yew Chin Sing, published on 26 Jan 2004
Here's some code demonstrating how to make a form in VB transparent!
Option Explicit
Private Declare Function SendMessage Lib "User32" Alias "SendMessageA" _
(ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, _
lParam As Any) As Long
Private Declare Sub ReleaseCapture Lib "User32" ()
Private Declare Function GetWindowLong Lib "User32" Alias _
"GetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long) As Long
Private Declare Function SetWindowLong Lib "User32" Alias _
"SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, _
ByVal dwNewLong As Long) As Long
Private Declare Function SetLayeredWindowAttributes Lib "User32" _
(ByVal hWnd As Long, ByVal crKey As Long, ByVal bAlpha As Byte, _
ByVal dwFlags As Long) As Long
Const WM_NCLBUTTONDOWN = &HA1
Const HTCAPTION = 2
Const WS_EX_LAYERED = &H80000
Const GWL_EXSTYLE = (-20)
Const LWA_ALPHA = &H2
Const LWA_COLORKEY = &H1
Private Sub Form_Load()
DarkMe
End sub
Public Function DarkMe()
Dim rtn As Long
rtn = GetWindowLong(hWnd, GWL_EXSTYLE)
rtn = rtn Or WS_EX_LAYERED
SetWindowLong hWnd, GWL_EXSTYLE, rtn
SetLayeredWindowAttributes hWnd, 0, 200, LWA_ALPHA
End Function
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As you will see, if you change the window style in the form load event, then the bitblting becomes very choppy. If you wait and change the window style in the form unload event, just before the fade out effect, then you will see an ugly flicker.
====================================================================
The only solution I find is capture the image of the window to the clipboard, and load a wide form with BorderStyle = 0 and put the image of the main form, unload the main form, and do the effect of transparency with this form, the capturewindow image code is how this:
Option Explicit
Public Type RECT_Type
left As Long
top As Long
right As Long
bottom As Long
End Type
'The following Public Declare statements are case sensitive.
Public Declare Function GetActiveWindow Lib "User32" () As Long
Public Declare Function GetDesktopWindow Lib "User32" () As Long
Public Declare Sub GetWindowRect Lib "User32" (ByVal Hwnd As Long, _
lpRect As RECT_Type)
Public Declare Function GetDC Lib "User32" (ByVal Hwnd As Long) As Long
Public Declare Function CreateCompatibleDC Lib "Gdi32" (ByVal hdc As Long) _
As Long
Public Declare Function CreateCompatibleBitmap Lib "Gdi32" (ByVal hdc _
As Long, ByVal nWidth As Long, _
ByVal nHeight As Long) As Long
Public Declare Function SelectObject Lib "Gdi32" (ByVal hdc As Long, _
ByVal hObject As Long) As Long
Public 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
Public Declare Function OpenClipboard Lib "User32" (ByVal Hwnd As Long) As Long
Public Declare Function EmptyClipboard Lib "User32" () As Long
Public Declare Function SetClipboardData Lib "User32" (ByVal wFormat As Long, _
ByVal hMem As Long) As Long
Public Declare Function CloseClipboard Lib "User32" () As Long
Public Declare Function ReleaseDC Lib "User32" (ByVal Hwnd As Long, _
ByVal hdc As Long) As Long
Public Declare Function DeleteDC Lib "Gdi32" (ByVal hdc As Long) As Long
Global Const SRCCOPY = &HCC0020
Global Const CF_BITMAP = 2
Public Function CaptureWindowArea(AccessHwnd As Long)
Dim DeskHwnd As Long
Dim hdc As Long
Dim hdcMem As Long
Dim rect As RECT_Type
Dim junk As Long
Dim fwidth As Long, fheight As Long
Dim hBitmap As Long
'DoCmd.Hourglass True
'---------------------------------------------------
' Get window handle to Windows and Microsoft Access
'---------------------------------------------------
DeskHwnd = GetDesktopWindow()
AccessHwnd = GetActiveWindow()
'---------------------------------------------------
' Get screen coordinates of Microsoft Access
'---------------------------------------------------
Call GetWindowRect(AccessHwnd, rect)
fwidth = rect.right - rect.left
fheight = rect.bottom - rect.top
'---------------------------------------------------
' Get the device context of Desktop and allocate memory
'---------------------------------------------------
hdc = GetDC(DeskHwnd)
hdcMem = CreateCompatibleDC(hdc)
hBitmap = CreateCompatibleBitmap(hdc, fwidth, fheight)
If hBitmap <> 0 Then
junk = SelectObject(hdcMem, hBitmap)
'---------------------------------------------
' Copy the Desktop bitmap to memory location
' based on Microsoft Access coordinates.
'---------------------------------------------
junk = BitBlt(hdcMem, 0, 0, fwidth, fheight, hdc, rect.left, _
rect.top, SRCCOPY)
'---------------------------------------------
' Set up the Clipboard and copy bitmap
'---------------------------------------------
junk = OpenClipboard(DeskHwnd)
junk = EmptyClipboard()
junk = SetClipboardData(CF_BITMAP, hBitmap)
junk = CloseClipboard()
End If
'---------------------------------------------
' Clean up handles
'---------------------------------------------
junk = DeleteDC(hdcMem)
junk = ReleaseDC(DeskHwnd, hdc)
'DoCmd.Hourglass False
End Function
Thanks for the code. Works a treat, but the form is not entirely transparent - just semi-transparent
Yes, thanks for the help. The following code is an example of the problem:
Option Explicit
Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _
(ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Function SetLayeredWindowAttributes Lib "user32.dll" (ByVal _
hwnd As Long, ByValcrKey As Long, ByVal bAlpha As Byte, ByVal dwFlags As Long) As Boolean
Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" _
(ByVal hwnd As Long, ByVal nIndex 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 Const SRCCOPY = &HCC0020
Private Const LWAALPHA = 2
Private Const GWLEXSTYLE = (-20)
Private Const WSEXLAYERED = &H80000
Dim iLeft As Integer
Private Sub FormLoad()
'Change window style to layered
'Comment out the code for smooth scrolling (disables fade effect)
SetWindowLong Form1.hwnd, GWLEXSTYLE, GetWindowLong(Form1.hwnd, _
GWLEXSTYLE) Or WSEXLAYERED
SetLayeredWindowAttributes Form1.hwnd, 0, 255, LWAALPHA
End Sub
Private Sub FormUnload(Cancel As Integer)
'Can't change the window style here, because it creates flicker
'Cut and paste the FormLoad code here to see
'Fade effect
Timer1.Enabled = False
Dim i As Integer
For i = 255 To 0 Step -5
SetLayeredWindowAttributes Me.hwnd, 0, i, LWA_ALPHA
DoEvents
Next
End Sub
Private Sub Timer1_Timer()
'BitBLT scrolling
iLeft = iLeft + 1
If iLeft = ((Form1.Width + Picture1.Width) / Screen.TwipsPerPixelX) Then _
iLeft = 0
BitBlt Picture1.hDC, 0, 0, Picture1.Width, Picture1.Height, Form1.hDC, _
iLeft, 0, SRCCOPY
End Sub
To use the code, add a small picture box to your form and add a timer (enable it, and set the interval to 1). Then load a large picture into the form (the form1.picture property)
As you will see, if you change the window style in the form load event, then the bitblting becomes very choppy. If you wait and change the window style in the form unload event, just before the fade out effect, then you will see an ugly flicker.
I would like to change the window style to layered, only when i need it at form unload, but would like to avoid the flicker problem.
Thanks for the help,
-Joe
if possible, can u send the code to me? maybe i wil help u to solve the problem
again, when u use the code, it wil slow ur application down.
The problem with the putting the code in the form_load event is that the form will be significantly slowed down. Since my application uses many bitblt's to the form, setting the form to a layered, but 255 opacity, destroyed the bitblting effects entirely.
So now, i change the form to a layered in the form unload event, but I still have the associated flicker of changing the window style outside of the form_load event.
Any ideas?
I really want to thank you for sharing your code for making a form true transparent. your the best.
thank you
put the code in Form_Load event
SetWindowLong Me.hwnd, GWL_EXSTYLE, GetWindowLong(Me.hwnd, GWL_EXSTYLE) Or WS_EX_LAYERED
SetLayeredWindowAttributes Me.hwnd, 0, 255, LWA_ALPHA 'make it not transparent
and no need to resize it
and set the transparency when you want in the code
for instance at the unload
Private Sub Form_Unload(Cancel As Integer)
Dim i As Integer
For i = 255 To 0 Step -20
SetLayeredWindowAttributes Me.hwnd, 0, i, LWA_ALPHA
DoEvents
Next
End Sub
flicker free
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