C++11?&Win API ドロップされたOLEデータオブジェクトに含まれるShellItemを列挙する

ドロップされたOLEデータオブジェクトに含まれるShellItem（ファイル、フォルダ、特殊フォルダ等）を列挙するサンプルコードです。

#define STRICT
#include <Windows.h>
#include <ShlObj.h>
#include <ShObjIdl.h>

#include <vector>
#include <string>
#include <sstream>
#include <iomanip>

const TCHAR MY_WINDOW_CLASS_NAME[] = TEXT("Project1");
const TCHAR MY_WINDOW_WINDOW_NAME[] = TEXT("Project1");

LRESULT CALLBACK MyWndProc(HWND hWnd, UINT uiMsg, WPARAM wParam, LPARAM lParam);

int WINAPI wWinMain(HINSTANCE, HINSTANCE, LPWSTR, int nCmdShow)
{
    if (FAILED(OleInitialize(nullptr)))
        return -1;

    WNDCLASSEX wce;
    wce.cbSize = sizeof(wce);
    wce.style = 0;
    wce.lpfnWndProc = MyWndProc;
    wce.cbClsExtra = 0;
    wce.cbWndExtra = 0;
    wce.hInstance = nullptr;
    wce.hIcon = LoadIcon(nullptr, IDI_APPLICATION);
    wce.hCursor = LoadCursor(nullptr, IDC_ARROW);
    wce.hbrBackground = (HBRUSH)(COLOR_3DFACE + 1);
    wce.lpszMenuName = nullptr;
    wce.lpszClassName = MY_WINDOW_CLASS_NAME;
    wce.hIconSm = LoadIcon(nullptr, IDI_APPLICATION);
    if (!RegisterClassEx(&wce))
        return 0;

    auto hWnd = CreateWindowEx(
        WS_EX_OVERLAPPEDWINDOW,
        MY_WINDOW_CLASS_NAME,
        MY_WINDOW_WINDOW_NAME,
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT,
        CW_USEDEFAULT, CW_USEDEFAULT,
        nullptr,
        nullptr,
        nullptr,
        nullptr);
    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);

    MSG msg;
    while (GetMessage(&msg, nullptr, 0, 0) > 0)
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    OleUninitialize();

    return msg.wParam;
}

template<size_t INIT = 256, size_t EXPANDING = 256>
std::wstring GetClipboardFormatNameW(CLIPFORMAT cf)
{
    std::vector<WCHAR> buffer(INIT);
    for (;;)
    {
        auto copied = GetClipboardFormatNameW(cf, buffer.data(), buffer.size());
        if (copied != buffer.size() - 1)
        {
            return std::wstring(buffer.data(), copied);
        }
        buffer.resize(buffer.size() + EXPANDING);
    }
}

std::wstring GetShellItemDisplayName(IShellItem *pShellItem, SIGDN sigdnName)
{
    LPWSTR pszName;
    if (SUCCEEDED(pShellItem->GetDisplayName(sigdnName, &pszName)))
    {
        std::wstring s(pszName);
        CoTaskMemFree(pszName);
        return std::move(s);
    }
    return std::wstring();
}

// https://docs.microsoft.com/ja-jp/windows/desktop/api/oleidl/nn-oleidl-idroptarget
class CMyDropTarget : public IDropTarget
{
private:
    ULONG m_ref;
    HWND m_hwndEdit;

    CMyDropTarget() {}

public:
    CMyDropTarget(HWND hwndEdit)
    {
        m_ref = 1;
        m_hwndEdit = hwndEdit;
    }

    HRESULT QueryInterface(
        REFIID riid,
        void **ppvObject)
    {
        if (IsEqualIID(riid, __uuidof(IUnknown)))
        {
            *ppvObject = static_cast<IUnknown*>(this);
        }
        else if (IsEqualIID(riid, __uuidof(IDropTarget)))
        {
            *ppvObject = static_cast<IDropTarget*>(this);
        }
        else
        {
            return E_NOINTERFACE;
        }
        AddRef();
        return S_OK;
    }

    ULONG AddRef()
    {
        return InterlockedIncrement(&m_ref);
    }

    ULONG Release(void)
    {
        if (InterlockedDecrement(&m_ref) == 0)
        {
            delete this;
            return 0;
        }
        return m_ref;
    }

    HRESULT STDMETHODCALLTYPE DragEnter(
        IDataObject *pDataObj,
        DWORD grfKeyState,
        POINTL pt,
        DWORD *pdwEffect)
    {
        *pdwEffect = DROPEFFECT_LINK;
        return S_OK;
    }

    HRESULT DragOver(
        DWORD grfKeyState,
        POINTL pt,
        DWORD *pdwEffect)
    {
        return S_OK;
    }

    HRESULT DragLeave()
    {
        return S_OK;
    }

    HRESULT Drop(
        IDataObject *pDataObj,
        DWORD grfKeyState,
        POINTL pt,
        DWORD *pdwEffect)
    {
        std::vector<CLIPFORMAT> cfs;

        FORMATETC fmtetc = { RegisterClipboardFormat(CFSTR_SHELLIDLIST) };
        if (!pDataObj->QueryGetData(&fmtetc))
            return S_OK;

        IShellItemArray *pShellItems = nullptr;
        if (SUCCEEDED(SHCreateShellItemArrayFromDataObject(pDataObj,
            IID_IShellItemArray, (void**)&pShellItems)))
        {
            DWORD c;
            if (SUCCEEDED(pShellItems->GetCount(&c)))
            {
                std::wstringstream ss;
                // TODO:ここで表示する形式を選択してください。
                ss
                    << "SIGDN_NORMALDISPLAY" << TEXT(", ")
                    << "SIGDN_PARENTRELATIVEPARSING" << TEXT(", ")
                    << "SIGDN_DESKTOPABSOLUTEPARSING" << TEXT(", ")
                    << "SIGDN_PARENTRELATIVEEDITING" << TEXT(", ")
                    << "SIGDN_DESKTOPABSOLUTEEDITING" << TEXT(", ")
                    << "SIGDN_FILESYSPATH" << TEXT(", ")
                    << "SIGDN_URL" << TEXT(", ")
                    << "SIGDN_PARENTRELATIVEFORADDRESSBAR" << TEXT(", ")
                    << "SIGDN_PARENTRELATIVE" << TEXT(", ")
                    << "SIGDN_PARENTRELATIVEFORUI" << TEXT("\r\n");

                for (auto i = 0; i < c; i++)
                {
                    IShellItem *pShellItem = nullptr;
                    if (SUCCEEDED(pShellItems->GetItemAt(i, &pShellItem)))
                    {
                        // TODO:ここで表示する形式を選択してください。
                        ss
                            << GetShellItemDisplayName(pShellItem, SIGDN::SIGDN_NORMALDISPLAY) << TEXT(", ")
                            << GetShellItemDisplayName(pShellItem, SIGDN::SIGDN_PARENTRELATIVEPARSING) << TEXT(", ")
                            << GetShellItemDisplayName(pShellItem, SIGDN::SIGDN_DESKTOPABSOLUTEPARSING) << TEXT(", ")
                            << GetShellItemDisplayName(pShellItem, SIGDN::SIGDN_PARENTRELATIVEEDITING) << TEXT(", ")
                            << GetShellItemDisplayName(pShellItem, SIGDN::SIGDN_DESKTOPABSOLUTEEDITING) << TEXT(", ")
                            << GetShellItemDisplayName(pShellItem, SIGDN::SIGDN_FILESYSPATH) << TEXT(", ")
                            << GetShellItemDisplayName(pShellItem, SIGDN::SIGDN_URL) << TEXT(", ")
                            << GetShellItemDisplayName(pShellItem, SIGDN::SIGDN_PARENTRELATIVEFORADDRESSBAR) << TEXT(", ")
                            << GetShellItemDisplayName(pShellItem, SIGDN::SIGDN_PARENTRELATIVE) << TEXT(", ")
                            << GetShellItemDisplayName(pShellItem, SIGDN::SIGDN_PARENTRELATIVEFORUI) << TEXT(", ")
                            << TEXT("\r\n");
                    }
                    pShellItem->Release();
                }
                SetWindowText(m_hwndEdit, ss.str().c_str());
            }
            pShellItems->Release();
        }

        *pdwEffect = DROPEFFECT_LINK;
        return S_OK;
    }

    HWND GetEditWindowHandle() const
    {
        return m_hwndEdit;
    }
};

CMyDropTarget *pDropTarget = nullptr;

LRESULT CALLBACK MyWndProc(HWND hWnd, UINT uiMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uiMsg)
    {
    case WM_CREATE:
    {
        // データ表示用のテキストボックス作成
        auto hwndEdit1 = CreateWindowEx(
            WS_EX_CLIENTEDGE,
            TEXT("edit"),
            TEXT("ファイルやURLをドロップしてください。"),
            WS_CHILD | WS_VISIBLE | WS_HSCROLL | WS_VSCROLL | ES_MULTILINE,
            0, 0, 0, 0,
            hWnd,
            nullptr,
            nullptr,
            nullptr);
        SendMessage(hwndEdit1, WM_SETFONT,
            (WPARAM)GetStockObject(DEFAULT_GUI_FONT),
            MAKELPARAM(FALSE, 0));
        // ドロップ対象として登録
        pDropTarget = new CMyDropTarget(hwndEdit1);
        RegisterDragDrop(hWnd, pDropTarget);
        pDropTarget->Release();
        return 0;
    }
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    case WM_QUIT:
        RevokeDragDrop(hWnd);
        return 0;
    case WM_SIZE:
        MoveWindow(
            pDropTarget->GetEditWindowHandle(),
            0, 0,
            LOWORD(lParam), HIWORD(lParam),
            TRUE);
        return 0;
    }

    return DefWindowProc(hWnd, uiMsg, wParam, lParam);
}

出力例

デスクトップのPCをドロップした場合

SIGDN_NORMALDISPLAY, SIGDN_PARENTRELATIVEPARSING, SIGDN_DESKTOPABSOLUTEPARSING, SIGDN_PARENTRELATIVEEDITING, SIGDN_DESKTOPABSOLUTEEDITING, SIGDN_FILESYSPATH, SIGDN_URL, SIGDN_PARENTRELATIVEFORADDRESSBAR, SIGDN_PARENTRELATIVE, SIGDN_PARENTRELATIVEFORUI
コントロール パネル, ::{5399E694-6CE5-4D6C-8FCE-1D8870FDCBA0}, ::{5399E694-6CE5-4D6C-8FCE-1D8870FDCBA0}, コントロール パネル, コントロール パネル, , , コントロール パネル, コントロール パネル, コントロール パネル, 
PC, ::{20D04FE0-3AEA-1069-A2D8-08002B30309D}, ::{20D04FE0-3AEA-1069-A2D8-08002B30309D}, PC, PC, , , PC, PC, PC,