正在开发中的游戏有个全屏功能--可以在window桌面背景上运行，就像一些视频播放器在桌面背景上播放一样的，花了个上午整了个Demo放出来留个纪念。

实现功能：显示图标，双击图标执行相应的程序，右击图标弹出该图标对应得菜单，点击非图标区则弹出桌面菜单。需要完整工程可以点此下载：DesktopWindow.rar。程序效果图如下：

 在这个程序里，定义了一个XShellItem的数据结构，保持桌面图标的iten id(ITEMIDLiST)，图标以及文字图标。

    struct XShellItem ...{
        ITEMIDLIST*     itemId;

        int x;
        int y;
        int w;
        int h;

        int nameX;
        int nameY;
        int nameW;
        int nameH;

        BOOL hit;

        CStringW name;
        Bitmap*     icon;
        Bitmap*     nameIcon;

        XShellItem()
        :
        itemId(NULL),
        x(0),
        y(0),
        w(0),
        h(0),
        nameX(0),
        nameY(0),
        nameW(0),
        nameH(0),
        name(L""),
        hit(FALSE),
        icon(NULL),
        nameIcon(NULL) ...{
        }
        ~XShellItem() ...{
        }
    };

然后定义一个数组CAtlArray<XShellItem> itemArray;用来保存所有桌面图标对象，在InitShellFolder()中对它进行初始化：

    // 获取桌面图标的相关数据
    BOOL InitShellFolder()
    ...{
        HRESULT hRslt = SHGetDesktopFolder(&folder);
        if (FAILED(hRslt)) ...{
            return FALSE;
        }

        CComPtr<IEnumIDList> ids;
        hRslt = folder->EnumObjects(0, SHCONTF_FOLDERS | SHCONTF_NONFOLDERS, &ids);
        if (FAILED(hRslt)) ...{
            return FALSE;
        }

        CAtlList<XShellItem> items;
        for (;;) ...{
            ITEMIDLIST*     id = 0;
            ULONG cIds = 0;

            hRslt = ids->Next(1, &id, &cIds);
            if (hRslt != S_OK) ...{
                break;
            }

            CStringW name;
            STRRET str = ...{ 0};
            hRslt = folder->GetDisplayNameOf(id, SHGDN_NORMAL | SHGDN_INFOLDER, &str);
            if (SUCCEEDED(hRslt)) ...{
                LPWSTR pname = 0;
                StrRetToStrW(&str, id, &pname);
                name = pname;
                CoTaskMemFree(pname);
            }

            XShellItem item;

            item.itemId = id;
            item.name = name;
            items.AddTail(item);
        }

        SIZE_T iItem = 0;
        SIZE_T cItems = items.GetCount();

        itemArray.SetCount(cItems);

        POSITION pos = items.GetHeadPosition();
        while (pos != 0) ...{
            XShellItem&     si = items.GetNext(pos);
            itemArray[iItem] = si;
            iItem++;
        }

        HDC hDC = CreateCompatibleDC(0);

        Graphics g(hDC);
        g.Clear(Color(0, 0, 0, 0));

        ICONMETRICS im = ...{ 0};
        im.cbSize = sizeof(im);
        SystemParametersInfo(SPI_GETICONMETRICS, sizeof(im), &im, 0);

        SolidBrush br_t(Color(255, 255, 255));
        Font font_i(hDC, &(im.lfFont));
        float fcy = font_i.GetHeight(&g) * 2 + 2;
        DeleteDC(hDC);

        Gdiplus::StringFormat sf(Gdiplus::StringFormat::GenericTypographic());
        sf.SetAlignment(Gdiplus::StringAlignmentCenter);
        sf.SetTrimming(Gdiplus::StringTrimmingEllipsisWord);

        iconSpacingWidth = im.iHorzSpacing + OFFSET_WIDTH;
        iconSpacingHeight = im.iVertSpacing + OFFSET_HEIGHT;

        int iconWidth = GetSystemMetrics(SM_CXICON);
        int iconHeight = GetSystemMetrics(SM_CYICON);

        for (SIZE_T i = 0; i < cItems; i++) ...{
            XShellItem&     item = itemArray[i];

            // SHGetFileInfo
            HICON hIcon = 0;
            HIMAGELIST hImgList;
            SHFILEINFO stSHFileInfo;
            CImageList cImgList;

            // 获取图标
            hImgList = (HIMAGELIST)::SHGetFileInfo(
                    (LPCWSTR) item.itemId,
                    0,
                    &stSHFileInfo,
                    sizeof(SHFILEINFO),
                    SHGFI_PIDL | SHGFI_ICON | SHGFI_LARGEICON | SHGFI_SYSICONINDEX);

            // DIBSection 8bit
            BITMAPINFO bmi;
            BITMAPINFOHEADER&  bmih = bmi.bmiHeader;
            bmih.biSize = sizeof(bmih);
            bmih.biWidth = ICON_WIDTH;
            bmih.biHeight = -ICON_HEIGHT;    // BMP反转
            bmih.biPlanes = 1;
            bmih.biBitCount = 32;
            bmih.biCompression = BI_RGB;
            bmih.biSizeImage = 0;
            bmih.biXPelsPerMeter = 0;
            bmih.biYPelsPerMeter = 0;
            bmih.biClrUsed = 0;
            bmih.biClrImportant = 0;

            HDC memDC = CreateCompatibleDC(0);
            void*  pDib = 0;
            HBITMAP hBmp = CreateDIBSection(memDC, &bmi, DIB_RGB_COLORS, &pDib, 0, 0);
            GdiFlush();

            HGDIOBJ old = SelectObject(memDC, hBmp);

            // ImageList_Draw WindowsXP
            ImageList_SetBkColor(hImgList, 0x0);
            ImageList_Draw(hImgList, stSHFileInfo.iIcon, memDC, 0, 0, ILD_NORMAL);
            SelectObject(memDC, old);
            DeleteDC(memDC);

            cImgList.Attach(hImgList);
            hIcon = cImgList.ExtractIcon(stSHFileInfo.iIcon);
            cImgList.Detach();

            if (hIcon != 0) ...{

                // Bitmap::FromHICON 0~255
                item.icon = Bitmap::FromHICON(hIcon);
                item.w = iconWidth;
                item.h = iconHeight;

                Gdiplus::RectF rc(float(2), float(2), float(iconSpacingWidth - 4), fcy);

                Gdiplus::Bitmap * nameIcon = new Bitmap(NAME_WIDTH, NAME_HEIGHT, &g);
                Gdiplus::Graphics * g2 = Gdiplus::Graphics::FromImage(nameIcon);
                g2->Clear(Gdiplus::Color(Gdiplus::ARGB(0)));

                g2->DrawString(item.name, item.name.GetLength(), &font_i, rc, &sf, &br_t);

                item.nameIcon = nameIcon;
                item.nameW = NAME_WIDTH;
                item.nameH = NAME_HEIGHT;

                delete g2;
            }

            DestroyIcon(hIcon);
            DeleteObject(hBmp);
            DestroyIcon(stSHFileInfo.hIcon);
        }

        return TRUE;
    }

注意这里面并没有设置图标对象的位置，因为当窗口改变大小的时候，相应地也要调整图标的描绘位置，所以图标位置是在SetShellItemPosition()中动态调整的.

    // 根据窗口大小设置图标位置
    void SetShellItemPosition()
    ...{
        int iconWidth = GetSystemMetrics(SM_CXICON);
        int iconHeight = GetSystemMetrics(SM_CYICON);
        static const int OFFSET_Y = 20;
        int x = 0;
        int y = OFFSET_Y;
        SIZE_T cItems = itemArray.GetCount();
        for (SIZE_T i = 0; i < cItems; i++) ...{
            XShellItem&     item = itemArray[i];
            if (item.icon) ...{
                item.x = x + (iconSpacingWidth - iconWidth) / 2;
                item.y = y;
            }

            if (item.nameIcon) ...{
                item.nameX = x;
                item.nameY = y + iconHeight + 2;
            }

            WTL::CRect rect;
            GetClientRect(&rect);
            y += iconSpacingHeight;
            if (y + iconSpacingHeight >= rect.bottom) ...{
                x += iconSpacingWidth;
                y = OFFSET_Y;
            }
        }
    }

描绘图标就很简单了，呵呵，不贴了，下面来说说弹出图标菜单，执行图标对应的程序以及弹出桌面菜单。

执行图标对应的程序，需要以先前保持的图标itemid作为参数，代码如下：

    void RunShellItem(ITEMIDLIST* pIID)
    ...{
        SHELLEXECUTEINFO info;
        info.cbSize = sizeof(SHELLEXECUTEINFO);
        info.fMask = SEE_MASK_INVOKEIDLIST;
        info.hwnd = m_hWnd;
        info.lpVerb = NULL;
        info.lpFile = NULL;
        info.lpParameters = NULL;
        info.lpDirectory = NULL;
        info.nShow = SW_SHOWNORMAL;
        info.hInstApp = NULL;
        info.lpIDList = pIID;
        ShellExecuteEx(&info);
    }

弹出桌面菜单的代码如下：

    // 桌面菜单
    void DesktopMenu()
    ...{
        HWND program = FindWindowEx(0, 0, _T("Progman"), _T("Program Manager"));
        HWND view = FindWindowEx(program, 0, _T("SHELLDLL_DefView"), 0);

        //HWND list = FindWindowEx(view, 0, _T("SysListView32"), 0);
        ::SetForegroundWindow(view);

        POINT pt;
        GetCursorPos(&pt);

        LPARAM lp = pt.y << 16 | (pt.x - 32);
        ::PostMessage(view, WM_LBUTTONDOWN, 0, lp);
        ::PostMessage(view, WM_RBUTTONUP, 0, lp);
    }

弹出图标菜单的代码如下，这里定义了两个全局的IContextMenu对象：
static IContextMenu2*  g_pIContext2 = NULL;
static IContextMenu3*  g_pIContext3 = NULL;

以便在消息回调函数中使用。具体代码如下：

    // 图标菜单
    void RightMenu(ITEMIDLIST* pIID)
    ...{
        HWND hwnd = m_hWnd;

        LPCONTEXTMENU pContextMenu = NULL;
        LPCONTEXTMENU pCtxMenuTemp = NULL;

        g_pIContext2 = NULL;
        g_pIContext3 = NULL;

        int menuType = 0;

        HRESULT hRslt = folder->GetUIObjectOf(
                hwnd,
                1,
                (LPCITEMIDLIST*) &(pIID),
                IID_IContextMenu,
                0,
                (void**) &pCtxMenuTemp);
        if (FAILED(hRslt)) ...{
            return;
        }

        POINT pt;
        GetCursorPos(&pt);

        if (pCtxMenuTemp->QueryInterface(IID_IContextMenu3, (void**) &pContextMenu) == NOERROR) ...{
            menuType = 3;
        }
        else if (pCtxMenuTemp->QueryInterface(IID_IContextMenu2, (void**) &pContextMenu) == NOERROR) ...{
            menuType = 2;
        }

        if (pContextMenu) ...{
            pCtxMenuTemp->Release();
        }
        else ...{
            pContextMenu = pCtxMenuTemp;
            menuType = 1;
        }

        if (menuType == 0) ...{
            return;
        }

        HMENU hMenu = CreatePopupMenu();
        hRslt = pContextMenu->QueryContextMenu(hMenu, 0, 1, 0x7fff, CMF_NORMAL | CMF_EXPLORE);
        if (FAILED(hRslt)) ...{
            return;
        }

#ifndef _WIN64
    #pragma warning(disable : 4244 4311)
#endif

        // subclass window
        WNDPROC oldWndProc = NULL;
        if (menuType > 1) ...{

            // only subclass if it is IID_IContextMenu2 or IID_IContextMenu3
            oldWndProc = (WNDPROC) SetWindowLongPtr(GWL_WNDPROC, (LONG) HookWndProc);
            if (menuType == 2) ...{
                g_pIContext2 = (LPCONTEXTMENU2) pContextMenu;
            }
            else ...{
                g_pIContext3 = (LPCONTEXTMENU3) pContextMenu;
            }
        }
        else ...{
            oldWndProc = NULL;
        }

        int cmd = ::TrackPopupMenu(
                hMenu,
                TPM_LEFTALIGN | TPM_BOTTOMALIGN | TPM_RETURNCMD | TPM_LEFTBUTTON,
                pt.x,
                pt.y,
                0,
                hwnd,
                0);

        // unsubclass
        if (oldWndProc) ...{
            SetWindowLongPtr(GWL_WNDPROC, (LONG) oldWndProc);
        }

#ifndef _WIN64
    #pragma warning(default : 4244 4311)
#endif
        if (cmd != 0) ...{
            CMINVOKECOMMANDINFO ci = ...{ 0};
            ci.cbSize = sizeof(CMINVOKECOMMANDINFO);
            ci.hwnd = hwnd;
            ci.lpVerb = (LPCSTR) MAKEINTRESOURCE(cmd - 1);
            ci.nShow = SW_SHOWNORMAL;

            pContextMenu->InvokeCommand(&ci);
        }

        pContextMenu->Release();
        g_pIContext2 = NULL;
        g_pIContext3 = NULL;
        ::DestroyMenu(hMenu);
    }

    static LRESULT CALLBACK HookWndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
    ...{
        switch (message) ...{
        case WM_MENUCHAR:    // only supported by IContextMenu3
            if (g_pIContext3) ...{
                LRESULT lResult = 0;
                g_pIContext3->HandleMenuMsg2(message, wParam, lParam, &lResult);
                return(lResult);
            }
            break;
        case WM_DRAWITEM:
        case WM_MEASUREITEM:
            if (wParam) ...{
                break;    // if wParam != 0 then the message is not menu-related
            }

        case WM_INITMENUPOPUP:
            if (g_pIContext2) ...{
                g_pIContext2->HandleMenuMsg(message, wParam, lParam);
            }
            else ...{
                g_pIContext3->HandleMenuMsg(message, wParam, lParam);
            }

            return(message == WM_INITMENUPOPUP ? 0 : TRUE);
            break;
        default:
            break;
        }

        return ::CallWindowProc((WNDPROC) GetProp(hWnd, TEXT("oldWndProc")), hWnd, message, wParam, lParam);
    }

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