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Posted 20 Feb 2001

Win2K transparent dialogs

, 20 Feb 2001
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How to make your windows transparent in Win2K without downloading the Platform SDK
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This article shows how you can make your apps transparent using the new functions provided with Win2K. If you download the Platform SDK from Microsoft then these functions will be available, but those of you without fast Internet connections this article could be useful.

This is a mix of stuff I found on the net so if anyone feels that I have stolen something and should get the credit, sorry...

The functions you want are included in the USER32.DLL in Win2K, but the SDK provides the header files and the source code in libraries. But to use the functions one could just import the functions from the USER32.DLL. So here it goes...

First some constants must be declared:

#define WS_EX_LAYERED           0x00080000
#define LWA_COLORKEY            0x00000001
#define LWA_ALPHA               0x00000002
#endif // ndef WS_EX_LAYERED

Then some declarations in the header-file:

// Preparation for the function we want to import from USER32.DLL
typedef BOOL (WINAPI *lpfnSetLayeredWindowAttributes)(HWND hWnd, 
                                  COLORREF crKey, BYTE bAlpha, DWORD dwFlags);

lpfnSetLayeredWindowAttributes m_pSetLayeredWindowAttributes

That is all for the header file, now to the implementation!

// Here we import the function from USER32.DLL
HMODULE hUser32 = GetModuleHandle(_T("USER32.DLL"));
m_pSetLayeredWindowAttributes = 

// If the import did not succeed, make sure your app can handle it!
if (NULL == m_pSetLayeredWindowAttributes)
	return FALSE; //Bail out!!!

If the function was imported correctly we must set the dialog we want to make transparent into "transparent-mode". E.G. Set the style for the dialog so that it can be transparent, and that is done with the flag WS_EX_LAYERED defined earlier.

// Check the current state of the dialog, and then add the 
// WS_EX_LAYERED attribute
SetWindowLong(m_hWnd, GWL_EXSTYLE, GetWindowLong(m_hWnd, GWL_EXSTYLE) 
              | WS_EX_LAYERED);

Now when that is done its time to describe the function we imported, and to tell you the truth I'm not 100% sure about all of the parameters...

hwnd [in] Handle to the layered window.

crKey [in] Pointer to a COLORREF value that specifies the transparency color key to be used. (When making a certain color transparent...)

bAlpha [in] Alpha value used to describe the opacity of the layered window. 0 = Invisible, 255 = Fully visible

dwFlags [in] Specifies an action to take. This parameter can be LWA_COLORKEY (When making a certain color transparent...) or LWA_ALPHA.

// Sets the window to 70% visibility.
m_pSetLayeredWindowAttributes(m_hWnd, 0, (255 / 70) * 100, LWA_ALPHA);

One thing you must make sure of is to disable this function if the app is running under any OS other then Win2K. And there is probably some very easy way to do that, but here is how I did it:

OSVERSIONINFO os = { sizeof(os) };
// use m_bWin2k before any call to the
// m_pSetLayeredWindowAttributes to make sure we are runninng Win2K
BOOL m_bWin2K = ( VER_PLATFORM_WIN32_NT == os.dwPlatformId && 
                  os.dwMajorVersion >= 5 ); 

That's about it!


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


About the Author

Per-Erik Nordlund
United States United States
No Biography provided

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Comments and Discussions

GeneralAnother problem with OpenGL Pin
zergus26-Sep-04 0:24
memberzergus26-Sep-04 0:24 
GeneralRe: Another problem with OpenGL Pin
Dennis Radon18-Jun-05 1:37
sussDennis Radon18-Jun-05 1:37 
GeneralRe: Another problem with OpenGL Pin
Dennis Radon18-Jun-05 1:57
sussDennis Radon18-Jun-05 1:57 
GeneralTransparency with OpenGL.. Pin
S.L20-Jun-04 21:24
memberS.L20-Jun-04 21:24 
GeneralRe: Transparency with OpenGL.. Pin
zergus26-Sep-04 0:08
memberzergus26-Sep-04 0:08 
GeneralRe: Transparency with OpenGL.. Pin
twxs25611-May-06 12:30
membertwxs25611-May-06 12:30 
Generala new problem Pin
beavis2-Nov-03 17:31
memberbeavis2-Nov-03 17:31 
GeneralRe: a new problem Pin
Anonymous29-Jun-04 4:55
sussAnonymous29-Jun-04 4:55 
GeneralCool .... But Pin
Powerpeeltz2-Jul-03 7:03
memberPowerpeeltz2-Jul-03 7:03 
GeneralCheck your math ! Pin
Kochise2-Oct-03 1:07
memberKochise2-Oct-03 1:07 
QuestionHow transparecy works? Pin
Lucidity3-May-02 20:17
memberLucidity3-May-02 20:17 
GeneralGetModuleHandle or LoadLibrary Pin
Anonymous1-Mar-02 2:25
memberAnonymous1-Mar-02 2:25 
GeneralRe: GetModuleHandle or LoadLibrary Pin
Tim Smith1-Mar-02 3:12
memberTim Smith1-Mar-02 3:12 
GeneralRe: GetModuleHandle or LoadLibrary Pin
happycujo12-Aug-03 4:50
memberhappycujo12-Aug-03 4:50 
GeneralOrignial state Pin
Anonymous21-Feb-02 9:02
memberAnonymous21-Feb-02 9:02 

I use

SetWindowLong(hWnd, GWL_EXSTYLE, GetWindowLong(hWnd, GWL_EXSTYLE) | WS_EX_LAYERED);

and m_pSetLayeredWindowAttributes(hWnd, 0, 255 * 0.5, LWA_ALPHA);

to make a window transparent. But when I set

m_pSetLayeredWindowAttributes(hWnd, 0, 255, LWA_ALPHA);

to remove the transparancy, the drawing of the window is very slow... is there a there way to set the original state of the window ? or to remove the WS_EX_LAYERED style (I tried SetWindowLong(hWnd, GWL_EXSTYLE, GetWindowLong(hWnd, GWL_EXSTYLE) | ~WS_EX_LAYERED); but it didn't work).

Thanks for help !
GeneralRe: Orignial state Pin
Anonymous25-Feb-02 7:31
memberAnonymous25-Feb-02 7:31 
GeneralRe: Setting window orignial WS_EX_LAYERED state not working Pin
mediamaster409-Sep-03 8:32
membermediamaster409-Sep-03 8:32 
Generalproblem Pin
woodey30-Jan-02 22:44
memberwoodey30-Jan-02 22:44 
GeneralJust realized what I was reading in your status window. Pin
Mike Whitenton2-Jul-01 23:51
memberMike Whitenton2-Jul-01 23:51 
GeneralRe: Just realized what I was reading in your status window. Pin
Steve McLenithan30-Nov-02 17:37
memberSteve McLenithan30-Nov-02 17:37 
GeneralTransparency vs. Windows Media Player Pin
Mac21-May-01 8:51
memberMac21-May-01 8:51 
GeneralRe: Transparency vs. Windows Media Player Pin
Per-Erik Nordlund21-May-01 21:28
memberPer-Erik Nordlund21-May-01 21:28 
GeneralRe: Transparency vs. Windows Media Player Pin
Mac22-May-01 5:12
memberMac22-May-01 5:12 
GeneralRe: Transparency vs. Windows Media Player Pin
Per-Erik Nordlund24-May-01 12:07
memberPer-Erik Nordlund24-May-01 12:07 
GeneralRe: Transparency vs. Windows Media Player Pin
Till Toenshoff17-Dec-01 9:55
memberTill Toenshoff17-Dec-01 9:55 

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