mfc-dimmer

/**********************************************************************************************

    MFC screen dim test
        :: oystein          :: November 2010

    Creates a simple window - click it to toggle whether a translucent black "dimmer" window
    is shown. The dimmer-window covers the entire screen, but the taskbar ("superbar" in
    Windows 7) will jump on top of it if clicked - it seems. Simple suggestions to fix that
    are welcome.

    Should work on Windows 2000 and later.

    Disclaimer: This is my first MFC program ever, so if anything seems wrong, it probably is.
    I have previously only coded with pure Win32 API, and hacked this together using online
    tutorials. Code provided "as-is" with no guarantees - I can not be held responsible for
    anything bad that happens if you run this program.

***********************************************************************************************/

#include "stdafx.h"

#undef WINVER
#define WINVER 0x500 // Windows 2000 & above, because of layered windows


// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
//
//                       Black window used to dim everything else
//
class CDimWnd : public CFrameWnd
{
public:
    CDimWnd()
    {
        // Get screen res into rect
        RECT rc;
        GetDesktopWindow()->GetWindowRect(&rc);

        CreateEx(WS_EX_LAYERED |        // Layered window for translucency
                 WS_EX_TRANSPARENT |    // Click through
                 WS_EX_TOPMOST |        // Always on top
                 WS_EX_TOOLWINDOW,      // Do not appear in taskbar & similar
                 NULL, TEXT(""),
                 WS_POPUP,              // No frame/borders - though there is
                                        // still some border left - we'll remove
                                        // it with regions

                 0, 0, rc.right + 10, rc.bottom + 10, // Make the window 10px larger
                                                      // than screen resolution in both
                                                      // directions - it is still positioned
                                                      // at 0,0
                 NULL, NULL);

        // Grab a part of the window the size of the desktop - but 5px into it
        // Because the window is larger than the desktop res, the borders are removed
        CRgn rgn;
        rgn.CreateRectRgn(rc.left + 5, rc.top + 5, rc.right + 5, rc.bottom + 5);
        SetWindowRgn((HRGN)rgn, FALSE);
        rgn.Detach();

        // We have to reposition window - (0,0) of window has not changed
        SetWindowPos(NULL, -5, -5, 0, 0, SWP_NOSIZE | SWP_NOZORDER);

        // This is where we set the opacity of the window: 0-255
        SetLayeredWindowAttributes(RGB(0,0,0), 150, LWA_ALPHA);
    }
    void Close()
    {
        CFrameWnd::OnClose();
    }
    BOOL CDimWnd::OnEraseBkgnd(CDC* pDC); // Set BKG color
    DECLARE_MESSAGE_MAP()
};

BOOL CDimWnd::OnEraseBkgnd(CDC* pDC)
{
    // Set brush to desired background color
    CBrush backBrush(RGB(0, 0, 0));

    // Save old brush
    CBrush* pOldBrush = pDC->SelectObject(&backBrush);

    CRect rect;
    pDC->GetClipBox(&rect);     // Erase the area needed

    pDC->PatBlt(rect.left, rect.top, rect.Width(), rect.Height(), PATCOPY);
    pDC->SelectObject(pOldBrush);
    return TRUE;
}

BEGIN_MESSAGE_MAP(CDimWnd, CFrameWnd)
    ON_WM_ERASEBKGND()
END_MESSAGE_MAP()

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


// Global variable - is screen dimmed?
bool g_bIsDimmed = false;


// The main window
class CMainWnd : public CFrameWnd
{
    // Contains a CDimWnd - I'm not sure if this is the "MFC way" of doing things
    CDimWnd dimmer;

public:
    CMainWnd()
    {
        Create(NULL, TEXT("Screen dimmer - Press left mouse button on window to toggle"),
            WS_OVERLAPPEDWINDOW, CRect(50, 50, 400, 250));
    }
    // Left mouse button toggles dimming
    afx_msg void OnLButtonDown(UINT Flags, CPoint Point)
    {
        if(!g_bIsDimmed)
        {
            dimmer.ShowWindow(SW_SHOW);
            dimmer.BringWindowToTop();
            g_bIsDimmed = true;
        }
        else
        {
            dimmer.ShowWindow(SW_HIDE);
            g_bIsDimmed = false;
        }
    }
    DECLARE_MESSAGE_MAP()
};

BEGIN_MESSAGE_MAP(CMainWnd, CFrameWnd)
    ON_WM_LBUTTONDOWN()
END_MESSAGE_MAP()


// The app
class CApp : public CWinApp
{
public:
    virtual BOOL InitInstance();
};

BOOL CApp::InitInstance()
{
    m_pMainWnd = new CMainWnd();
    m_pMainWnd->ShowWindow(m_nCmdShow);
    m_pMainWnd->UpdateWindow();
    return TRUE;
}

CApp HelloApp;