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Posted 22 Jun 2000

FaderWnd - a Window Fader for Windows 2000

, 28 Jun 2000
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An MFC class to fade any window with only one line of code.
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    One of the attractive new features of Windows 2000 is the menu and other selections that fade away instead of just disappearing. To see this in operation you need to select "Use transition effects for menus and tooltips" on the "Effects" tab of the Display Properties dialog and then select "Fade effect" in the combo box.

    In this article I present a simple MFC class that allows you to apply a similar fading effect to any window you choose - with only one line of code! Don't just close a window - have it fade away! The effect is most appropriate to small windows; I use it most often for splash windows, about boxes and other small dialogs.

    To use the code you just add the FaderWnd source and header files to your MFC project, include the header in the relevant source file and construct a CFaderWnd when you want your window to fade. The CFaderWnd object itself takes care of fading your window and then destroying and deleting itself.

    The only code you need to write is new CFaderWnd(this). Once the CFaderWnd is constructed you can destroy or hide your window, or call EndDialog if the window is a modal dialog.

    For example, a modeless dialog (or it could be any child window):
    void CFadeTestDlg::OnClose() 
    	new CFaderWnd(this);
    or a modal dialog:
    void CFadeTestDlg::OnOK() 
    	if (UpdateData)
    		new CFaderWnd(this);
    void CFadeTestDlg::OnCancel() 
    	new CFaderWnd(this);

    How it works

    The CFaderWnd uses the new layered windows feature and the UpdateLayeredWindow API function. The constructor creates a new topmost window with the WS_EX_LAYERED style (among others) and with the same size and position as the source window (the window to be faded). It then uses UpdateLayeredWindow to fill the new window with a bitmap that is an exact copy of the source window. It also sets up a timer. When the constructor returns the source window can be destroyed (or hidden) and the new window remains visible.

    On each timer message CFaderWnd calls UpdateLayeredWindow again with a smaller value of alpha. Reducing the alpha value makes the window increasingly translucent. When alpha is at or very near zero CFaderWnd destroys the window and PostNcDestroy deletes the CFaderWnd object.

    The CFaderWnd constructor takes three parameters; it looks like this:

    CFaderWnd(CWnd *pWndToFade, UINT nFadeTime = 2000, BYTE byAlpha = 255);

    The second and third parameters are optional; the examples above all use the default values for these parameters. For obvious reasons (and if they're not obvious you shouldn't be reading this) the first parameter, which specifies the window to fade, must be supplied.

    CWnd *pWndToFade This is a pointer to the source window (the window to be faded).
    UINT nFadeTime This is a number of milliseconds for the whole duration of the fade. The default value gives a 2 second fade.
    BYTE byAlpha This is the alpha value at which to start the fade. The default value of 255 represents starting with a fully opaque window. You might choose to start at 127, for example, so that the window immediately becomes semi-transparent and then fades from there.

    UpdateLayeredWindow is only available on Windows 2000, so if the code were to call that function directly any program using the CFaderWnd class would fail to run on any other platform. I usually want my programs to run on any Win32 platform but to use the new features when they're available. Therefore the code does not call UpdateLayeredWindow directly. Instead it uses GetProcAddress to find out whether the function is available and calls it through the returned pointer when it is. If the function is not available CFaderWnd quietly deletes itself so it behaves as a no-op on older platforms. Thus you can use CFaderWnd in all your programs without compromising their ability to run on all Win32 platforms.


    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

    P J Pearson
    United Kingdom United Kingdom
    No Biography provided

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    Comments and Discussions

    GeneralFader on Vista... Pin
    Paul Runner22-Dec-08 14:02
    memberPaul Runner22-Dec-08 14:02 
    GeneralRe: Fader on Vista... Pin
    Andrew Kulikov9-Feb-09 11:26
    memberAndrew Kulikov9-Feb-09 11:26 
    GeneralFading out a Splash Screen. Pin
    Nick Thomas21-Jul-06 2:45
    memberNick Thomas21-Jul-06 2:45 
    GeneralRe: Fading out a Splash Screen. Pin
    Phil J Pearson21-Jul-06 10:01
    memberPhil J Pearson21-Jul-06 10:01 
    QuestionUpdateLayeredWindow on extended desktops? Pin
    lamagaaya8-Mar-06 7:35
    memberlamagaaya8-Mar-06 7:35 
    AnswerRe: UpdateLayeredWindow on extended desktops? Pin
    b@andreasen8.org25-Sep-06 9:32
    memberb@andreasen8.org25-Sep-06 9:32 
    GeneralRe: UpdateLayeredWindow on extended desktops? Pin
    lamagaaya26-Sep-06 17:11
    memberlamagaaya26-Sep-06 17:11 
    GeneralInvalid access to memory location. Pin
    iampams1-Nov-05 20:12
    memberiampams1-Nov-05 20:12 
    AnswerRe: Invalid access to memory location. Pin
    Phil J Pearson2-Nov-05 9:59
    memberPhil J Pearson2-Nov-05 9:59 
    GeneralLayered Windows API Pin
    Zero DeHero14-May-03 1:08
    memberZero DeHero14-May-03 1:08 
    QuestionDivide by zero? Pin
    msvcpp17-Mar-03 2:21
    membermsvcpp17-Mar-03 2:21 
    GeneralSmall memory leak Pin
    Corey A16-Jan-03 5:36
    memberCorey A16-Jan-03 5:36 
    Generallayerd window on 9x Pin
    kuzi6-Mar-02 6:46
    memberkuzi6-Mar-02 6:46 
    GeneralRe: layerd window on 9x Pin
    Phil J Pearson6-Mar-02 11:04
    memberPhil J Pearson6-Mar-02 11:04 
    QuestionHelp with Alpha Blending? Pin
    swinefeaster30-Jan-02 11:41
    memberswinefeaster30-Jan-02 11:41 
    GeneralA question of "FaderWnd"Class from China. Pin
    Sailing11-Oct-01 4:43
    memberSailing11-Oct-01 4:43 
    GeneralDoes'nt work with maximized windows Pin
    Anonymous6-Sep-01 3:33
    memberAnonymous6-Sep-01 3:33 
    GeneralGreat + Small Suggestion Pin
    DanG21-Aug-01 0:13
    memberDanG21-Aug-01 0:13 
    Questionhow can i use on winnt?? are you know it? Pin
    what?26-Jul-00 22:07
    susswhat?26-Jul-00 22:07 
    AnswerRe: how can i use on winnt?? are you know it? Pin
    ChangYoung Jung16-Sep-00 19:28
    sussChangYoung Jung16-Sep-00 19:28 
    GeneralExplain of code in lame Pin
    Adun13-Jul-00 11:35
    sussAdun13-Jul-00 11:35 
    Here is an explain of the FaderWnd.cpp in lame terms -

    Basicly, it simply takes the Window/Dialog propties by using various functions,
    (GetWindowRect) and then he uses the retrived propeties to create a duplicate of the
    Wnd/Dialog and then he destroyes the original.
    After that and by using the given value which is set in the UINT nFadeTime var
    this value is used in the AlphaBend and it specify the time of the fade,
    after creating the transperency, it reduces the AlphaBend until 0 and then there is total
    tranperency and then we Destroy the WND/Dialog.

    *Function Explain:

    CFaderWnd - This is the main fucntion which the Dialog/WND calls as this is
    the function that 'do' it all and by calling her we call the entire FaderWND.CPP.

    GetWindowRect - Gets the (left, top, right, bottom) rect strcutre of the specified wnd.

    CreateEx - This function creats the duplicated Window/Dlg.

    UpdateLayeredWindow- The UpdateLayeredWindow function updates the position, size, shape, content,
    and translucency of a layered window.
    Mean - Every time we reduce the Alpha (SourceConstantAlpha )
    value (the transp level) it updated the Window
    with it. the function includes as a parameter a pointer into a Blend functions strcutre.

    AlphaBend-(BLENDFUNCTION_) - This is a function that sets the transp of a WND/Dialog it has a value (SourceConstantAlpha ) that specified the transp level and we reduce
    it as the time pass by making it equal to the time value var of as ->
    SourceConstantAlpha = UINT nFadeTime = nElapse = byAlpha = ALPHA_STEP
    and this is the deal as we reduce the nElapse in the Timer we also reduce the ALPHA_STEP
    which reduce the SourceConstantAlpha.
    GeneralRe: Explain of code in lame Pin
    Romout8-Sep-01 3:10
    memberRomout8-Sep-01 3:10 
    GeneralRe: Explain of code in lame Pin
    Romout8-Sep-01 3:10
    memberRomout8-Sep-01 3:10 
    GeneralRe: Explain of code in lame Pin
    Phil J Pearson10-Sep-01 11:52
    memberPhil J Pearson10-Sep-01 11:52 
    GeneralComments Pin
    Rui Lopes24-Jun-00 1:51
    sussRui Lopes24-Jun-00 1:51 

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