禁用屏幕拷贝调用派生的析构函数

原文出处：Disabling Print Screen, Calling Derived Destructors, and More


我正在开发一个显示图形的程序，该图形具有知识产权，有没有什么办法禁用屏幕拷贝功能（Print Screen）以防止用户将图像拷贝到剪贴板上？

CWindowDC dc(NULL);   // 用 NULL 获取整个屏幕
            CDC memdc;
            ... // 创建, 初始化 memdc
            memdc.BitBlt(..., &dc); // 拷贝屏幕内容

// 热键的处理方法

            // MainFrame.h
            #include "FolderFrame.h"
            #include "resource.h"
            ////////////////
            // Typical MFC Main frame window, override to disable PrintScreen.
            //
            class CMainFrame : public CFrameWnd {
            protected:
            ...
            afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
            // disable PrintScreen
            afx_msg void OnActivate(UINT nState, CWnd* pWndOther, BOOL bMinimized);
            afx_msg LRESULT OnHotKey(WPARAM wp, LPARAM lp);
            afx_msg void OnDestroy();
            DECLARE_MESSAGE_MAP()
            };
            MainFrame.cpp
            #include "StdAfx.h"
            #include "MainFrm.h"
            #include "View.h"
            IMPLEMENT_DYNCREATE(CMainFrame, CFrameWnd)
            BEGIN_MESSAGE_MAP(CMainFrame, CFrameWnd)
            ...
            // disable PrintScreen:
            ON_WM_CREATE()
            ON_WM_DESTROY()
            ON_WM_ACTIVATE()
            ON_MESSAGE(WM_HOTKEY, OnHotKey)
            END_MESSAGE_MAP()
            ...
            int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
            {
            ...
            RegisterHotKey(m_hWnd, IDHOT_SNAPDESKTOP, 0, VK_SNAPSHOT);
            return 0;
            }
            void CMainFrame::OnDestroy()
            {
            UnregisterHotKey(m_hWnd, IDHOT_SNAPDESKTOP);
            }
            //////////////////
            // Handle hotkey: should be PrintScreen or Alt-PrintScreen.
            // Do nothing (bypass Windows screen capture)
            //
            LRESULT CMainFrame::OnHotKey(WPARAM wp, LPARAM)
            {
            UNREFERENCED_PARAMETER(wp);
            return 0; // ignore
            }
            //////////////////
            // When window is activated/deactivated, disable/enable Alt-PrintScreen.
            // (IDHOT_SNAPWINDOW)
            //
            void CMainFrame::OnActivate(UINT nState, CWnd* pWndOther,
            BOOL bMinimized)
            {
            CFrameWnd::OnActivate(nState, pWndOther, bMinimized);
            if (nState)
            RegisterHotKey(m_hWnd, IDHOT_SNAPWINDOW, MOD_ALT, VK_SNAPSHOT);
            else
            UnregisterHotKey(m_hWnd, IDHOT_SNAPWINDOW);
            }      

在 2004 年 11 月的专栏中，你谈到了在托管和非托管代码中调用虚拟函数的问题，参见“调用虚拟函数，持续化视图状态，POD 类型概念”。在 C++ 里，如果我想让派生类的析构函数在释放内存时被调用，我得在基类中将其声明为虚拟函数。那么在 Visual Studio 2005 中，对于某个派生类来说，即使它在基类中未被声明为虚拟的，其析构也会被调用吗？

ctor: CBase
            ctor: CDerived
            dtor: CDerived
            dtor: CBase