Go to sleep! Fade to B/W

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• Download demo source with executable - 56.9 Kb

Introduction

Did you ever notice that when you shutdown Windows/XP there is a fading effect from color to B/W on the desktop? Ok that's the objective of this article, a simple way to capture a given window and fade it in an inactive status.

The main idea to perform this operation is quite simple: the code basically creates a fading-window over the target one. This fading-window has all the needing to make this simple animation and the complete implementation is not long and it's based on 3 parts:

• a snap-shot routine to copy the given window in an in-memory bitmap,
• a function to decolorize the given bitmap,
• the main loop to step the decolorizing.

Notice: this code will work only on 16, 24 or 32 bit display color mode.

Using the code

There are basically 2 modalities to perform the fading process: automatic and controlled.

Automatic - this is the simplest way, and it can be used to put the given window in a "relaxed" mode - when the user will click on the given window, this will return to it's original status - here the simple steps to start with this operation:

1. add the FadeWnd.h and FadeWnd.cpp, to your project,
2. include the FadeWnd.h in the implementation code (.cpp) where you will call the fading effect,
3. simply call the CFadeWnd::AutoFade(CWnd* pWnd) on the window you want to fade.

Controlled - don't worry, this is quite easy too, the difference is that we want to control the moment the fading effect must finish. For this, I have assumed that the fading operation must simply be done before a modal window call - here the steps:

1. as before, add the FadeWnd.h and FadeWnd.cpp, to your project,
2. include the FadeWnd.h in the implementation code (.cpp) where you will call the fading effect,
3. define a CFadeWnd object before a dialog or a message-box modal call, for sample: wndFade,
4. create the fade window, passing as parent the window to fade as shown: wndFade.Create(this).

Difficult?

Let's code!

Remember, first at all, add the FadeWnd.h and FadeWnd.cpp, to your project. To do this, copy these 2 files in the folder of your project, and from the [Project] menu item of the Visual Studio, choose [Add to Project] -> [Files] voice. Select the 2.

Next step, include the FadeWnd.h in the implementation code (.cpp) where you will call the fading effect. If you want to use the CFadeWnd class a bit every where, you can include it in the stdafx.h.

#include "FadeWnd.h"

To use it in a simple way, you can perform the call:

void CMakeInactiveDlg::OnButton1() 
{
    CFadeWnd::AutoFade(this);
}

Fade all the desktop:

void CMakeInactiveDlg::OnButton2() 
{
    CFadeWnd::AutoFade(GetDesktopWindow());
}

Fade the given window for the necessary modal sub-window call:

void CMakeInactiveDlg::OnButton3() 
{
    CFadeWnd wndFade(this);
 
    // modal window call as a DIALOG or a MESSAGEBOX
    AfxMessageBox(
        _T("Disabled until this message will be closed"),
        MB_OK | MB_ICONINFORMATION);
}

Fade using a different gradient color:

void CMakeInactiveDlg::OnButton4() 
{
    CFadeWnd::AutoFade(
        this,                // window to fade
        RGB(255,128, 64),    // light color ref
        RGB( 64, 16,  0));   // dark color ref
}
 
// - or -
 
void CMakeInactiveDlg::OnButton5() 
{
    CFadeWnd wndFade(
        this,                // window to fade
        RGB(255,128, 64),    // light color ref
        RGB( 64, 16,  0));   // dark color ref
 
    // modal window call as a DIALOG or a MESSAGEBOX
    AfxMessageBox(
        _T("Disabled until this message will be closed"),
        MB_OK | MB_ICONINFORMATION);
}

Notices

To permit other programmers to change the behavior of this control, I have added 3 virtual members that can be easily overridden:

• void CreateGradient(...) - this allow to try other fading algorithms
• bool OnLButtonCheck() - this is needed to make security checks directly inside the CFadeWnd during left button mouse clicks
• bool OnRButtonCheck() - same as above, but for right button mouse clicks

Play with the CreateGradient call

I have made virtual the CreateGradien member of the CFadeWnd. This will allow some programmers to play with this call deriving a new class from the CFadeWnd. Let's see a sample of this process.

Create your derived class, for sample:

class CMyGradientFadeWnd : public CFadeWnd
{
public:
    virtual void CreateGradient(
        COLORREF /* clrLight = RGB(255,255,255) */,  // parameters are not 
                                                     // used in this sample
        COLORREF /* clrDark  = RGB(  0,  0,  0) */)
    {
        for(int i=0; i<256; i++)
        {
            m_clrGradient[i] = RGB(i, 255-i, i);
        }
    }
};

Now you have only to use your CMyGradiendFadeWnd in substitution of the CFadeWnd in your application.

Intercepting the left and right mouse button clicks inside the CFadeWnd class using OnLButtonCheck and OnRButtonCheck calls

Of course, this could be done deriving the whole class with CLASSWIZARD, and for more skilled developers, I'll suggest to do it that way - but to allow fast and easy way to inject our own made dialogs directly in the CFadeWnd, I have made the 2 overridden calls.

As for the CreateGradiend saw before, create your derived class, for sample:

class CMyPasswordFadeWnd : public CFadeWnd
{
public:
    virtual bool OnLButtonCheck()
    {
        // add the password check here
        CPasswordDlg dlg; // make your own dialog
        return (dlg.DoModal() == IDOK);
    }
    virtual bool OnRButtonCheck() { return false; } // no response
};

Credits - Special thanks to

Credits are reported inside the source code. The major help come from these articles/posts:

• How to replace a color in a HBITMAP - Dimitri Rochette
• Barry's Screen Capture - Barretto VN
• Creating an application with no taskbar icon - Chris Maunder
• Fade to any gradient array - Mikko Mononen

History

• 10 November 2003 - bug fixes and some new things from the message posts:
  • virtual CreateGradient(...) call to perform a different graying effect
  • virtual OnLButtonChek() and OnRButtonChek() to perform a mouse click security check inside the CFadeWnd class
  • timing calculation to make the fading effect fit in less than 2 seconds
  • region heredity for shaped windows (example skinned windows)
  • disabled the parent window during the fade process, and eliminated the icon on the task-bar
• 3 November 2003 - first public release

// Todo :

• ... and the list is growing

Of course, all suggestions are welcome