duilib : 在对话框中增加文件拖拽功能

/// 创建能接受文件拖拽的对话框
void CMainDlg::DoTask()
{
    CAcceptFilesDlg * pDlg = NULL;

    pDlg = new CAcceptFilesDlg(XML_FILE_NAME, WND_CLASS_NAME);
    pDlg->SetOwner(this);

    /// 创建对话框时, 指定接受文件拖拽的风格
    pDlg->Create(
          this->GetHWND(), 
          WND_DISP_NAME, 
          UI_WNDSTYLE_FRAME, 
          WS_EX_WINDOWEDGE | WS_EX_ACCEPTFILES);
    
    pDlg->CenterWindow();
    HaveSubDlgOnMainDlg(TRUE);
    pDlg->ShowModal();
    HaveSubDlgOnMainDlg(FALSE);
}

/// ...
LRESULT CAcceptFilesDlg::HandleMessage(UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
    case WM_DROPFILES:
        {
            DropFileOnDlg((HDROP)wParam);
        }
        break;

        /// ...
    default:
        break;
    }
    return __super::HandleMessage(uMsg, wParam, lParam);
}

void CAcceptFilesDlg::DropFileOnDlg(HDROP hDrop)
{
    WORD                wNumFilesDropped = DragQueryFile(hDrop, -1, NULL, 0);
    WORD                wPathnameSize = 0;
    WCHAR *             pFilePathName = NULL;
    std::wstring        strFirstFile = L"";
    struct _stat64i32   info;

    // there may be many, but we'll only use the first
    if (wNumFilesDropped > 0)
    {
        wPathnameSize = DragQueryFile(hDrop, 0, NULL, 0);
        wPathnameSize++;
        pFilePathName = new WCHAR[wPathnameSize];
        if (NULL == pFilePathName)
        {
            _ASSERT(0);
            DragFinish(hDrop);
            return;
        }

        ::ZeroMemory(pFilePathName, wPathnameSize);
        DragQueryFile(hDrop, 0, pFilePathName, wPathnameSize);
        strFirstFile = pFilePathName;

        SAFE_DELETE(pFilePathName);
    }

    DragFinish(hDrop);

    if ((strFirstFile.size() > 0)
        && (0 == _wstat(strFirstFile.c_str(), &info))
        && ((info.st_mode & _S_IFREG) > 0)
        && (info.st_size > 0))
    {
        m_pLabelFilePathName->SetText(strFirstFile.c_str());
    }
}