我有一个相当标准的 MFC 应用程序，它包含一个主窗口，偶尔会弹出模式对话框。众所周知，在模式对话框关闭之前，在模式对话框之外什么都做不了。

因此，一个不错的 UI 功能是使对话框后面主窗口的其余部分“变暗”，以直观地指示您在完成模式对话框之前不能使用它。一些网络应用程序和 java/mac 应用程序会这样做，但我从未见过它在传统的 C++/MFC 应用程序中完成。我想试一试，即使这对于平台来说并不常见。

如何做到这一点？我在应用程序中有几个模态对话框，以这种模式使用:

// pMainFrame is available as a pointer to the CWnd of the main window
CMyDialog dialog;
dialog.DoModal(); // invoke modal dialog; returns after dialog closed

有没有一种简单的方法可以让窗口在任何 DoModal() 之前变暗并在之后恢复？我正在使用 Visual Studio 2010，以防更新后的 MFC 具有任何可能有用的功能。

编辑:我已经发布了一个基于 oystein 的回答的解决方案，但我开始悬赏以防任何人可以改进它 - 特别是平滑的淡入/淡出。

最佳答案

您可以在要调暗的窗口之上创建另一个完全黑色的窗口，并使用 SetLayeredWindowAttributes 设置黑色窗口的不透明度。 .当然，它不一定非得是黑色，但我想那是最好的调光颜色。

编辑:我编写了一个示例 - 但请注意，我不是 MFC 开发人员，我通常直接使用 Windows API。不过，它似乎工作正常。 Here是一个pastebin。您可以自己随意添加淡入淡出等。另请注意，这会使整个屏幕变暗，如果您不希望出现这种情况，则必须调整我的调光窗口的大小。请参阅代码注释。

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

    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;

更新:

我为您编写了更多代码来处理褪色。我仍然不是 MFC 开发人员，我让代码处于“粗略”状态(很少有错误处理，不是很健壮)，以便让您也有事可做。 :) 无论如何，这是一种我认为相当干净的方法:

要使用它，请让您的主窗口包含一个调光器窗口

class CMainFrm : public CFrameWnd
{     
    CDimWnd* dimmer; 

public: 
    CMainFrm()
    {
        // constructor code here ...
        dimmer = new CDimWnd();         
    }

// rest of class ...

};  

然后可以使用它，例如像这样:

dimmer->Show();
MessageBox(TEXT("Hello world"));
dimmer->Hide();

或者，我猜你可以将这段代码(Show()/Hide() 调用)放在模态对话框的构造函数和析构函数中，如果你想保留那里的代码。如果你想要一个“范围”-dim，就像你发布的例子一样，这段代码必须进入 CDimWnd 类的构造函数和析构函数，你需要一个静态成员变量之类的东西来确保只有一个调光器是一次运行(除非您想使用全局变量)。

对于调光窗 - 我这样做了:

CDimWnd.h

#define TARGET_OPACITY 70   // Target opacity 0-255 for dimmed window
#define FADE_TIME 20        // Time between each fade step in milliseconds
#define FADE_STEP 5      // How much to add to/remove from opacity each fade step
#define ID_FADE_TIMER 1

// Call Show() and Hide() to fade in/fade out dimmer. 
// Creates the dimmer window in constructor.
class CDimWnd : public CFrameWnd
{         
    bool m_isDimming;       

public: 
    CDimWnd();
    void Show();
    void Hide();            

protected:
    BOOL OnEraseBkgnd(CDC* pDC);
    void OnTimer(UINT_PTR nIDEvent);
    DECLARE_MESSAGE_MAP()
};

CDimWnd.cpp

#include "stdafx.h"
#include "CDimWnd.h"
#include "MainFrm.h"

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

CDimWnd::CDimWnd()
{
    // Get the main frame of the application which we want to dim.
    CMainFrame* pParent = theApp.pMainFrame;

    // Don't do anything if the main frame doesn't appear to be there
    if (pParent != NULL)
    {
        // Get the client area of the window to dim.
        CRect rc;
        pParent->GetClientRect(&rc);
        pParent->ClientToScreen(&rc);       // convert to screen coordinates

        // Do some fudging to fit the client area exactly.
        // Other applications may not need this if the above client area fits already.
        rc.top += GetSystemMetrics(SM_CYFRAME);
        rc.top += GetSystemMetrics(SM_CYCAPTION);           // MFC feature pack seems to include caption in client area
        rc.left -= GetSystemMetrics(SM_CXBORDER);
        rc.right += GetSystemMetrics(SM_CXBORDER) + 1;
        rc.bottom += GetSystemMetrics(SM_CYBORDER) + 1;

        // Create a layered window for transparency, with no caption/border.
        CreateEx(WS_EX_LAYERED | WS_EX_TRANSPARENT | WS_EX_TOOLWINDOW, NULL, TEXT(""), 
            WS_POPUP, rc.left, rc.top, rc.Width(), rc.Height(),
            pParent->GetSafeHwnd(), NULL);
    }
}


void CDimWnd::Show()
{
    // If we are not already dimming, go for it
    if(!m_isDimming)
    {
        // Bring in front of main window.
        BringWindowToTop();

        // Set opacity to 0
        SetLayeredWindowAttributes(RGB(0,0,0), 0, LWA_ALPHA);

        // Show the dimmer window
        ShowWindow(SW_SHOW);

        // Create timer - the rest is handled in OnTimer() function
        SetTimer(ID_FADE_TIMER, FADE_TIME, NULL);
    }
}


void CDimWnd::Hide()
{   
    // If we are dimming, go for it
    if(m_isDimming)
    {
        // Create timer - the rest is handled in OnTimer() function
        SetTimer(ID_FADE_TIMER, FADE_TIME, NULL);
    }
}


void CDimWnd::OnTimer(UINT_PTR nIDEvent)
{
    static int fade = 0;

    if(nIDEvent == ID_FADE_TIMER)
    {
        // We are dimming => we want to fade out
        if(m_isDimming)
        {
            if(fade < 0)
            {
                // Fading finished - hide window completely, update status & destroy timer
                fade = 0;
                ShowWindow(SW_HIDE);
                KillTimer(nIDEvent);
                m_isDimming = false;
            }
            else
            {
                // Set window opacity & update fade counter
                SetLayeredWindowAttributes(RGB(0,0,0), fade, LWA_ALPHA);
                fade -= FADE_STEP;
            }
        }
        else
        // fade in
        {
            if(fade > TARGET_OPACITY)
            {   
                // Fading finished - destroy timer & update status

                fade = TARGET_OPACITY; // but first, let's be accurate.
                SetLayeredWindowAttributes(RGB(0,0,0), fade, LWA_ALPHA);

                KillTimer(nIDEvent);
                m_isDimming = true;             
            }   
            else
            {
                // Set window opacity & update fade counter
                SetLayeredWindowAttributes(RGB(0,0,0), fade, LWA_ALPHA);
                fade += FADE_STEP;
            }
        }
    }
}


BOOL CDimWnd::OnEraseBkgnd(CDC* pDC)
{
    // Fill with black
    CBrush backBrush(RGB(0, 0, 0));
    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;
}

好的。正如我所说，它很快就组合在一起并且处于粗糙状态，但它应该给你一些代码来工作，以及(我认为)如何在 MFC 中使用计时器的一般概念。不过，我绝对不是考虑任何事情的合适人选:)

关于c++ - MFC - 显示模态对话框时主窗口变暗，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/4063547/