从调用弹出对话框到用户可见对话框，如何显示等待光标？

Question

所以，我想向用户显示CDialog：

void CMeetingScheduleAssistantDlg::OnOptionsOutlookCalendarOptions()
{
    COutlookCalendarSettingsDlg dlgSettings(this);

    dlgSettings.DoModal();
}

现在，弹出对话框（OnInitDialog）在后台运行一个控制台应用程序。此控制台应用程序正在与 Microsoft Graph 进行通信。

因此，显示对话框可能需要几秒钟。

我用这个方法执行控制台应用程序：

bool CMeetingScheduleAssistantApp::ExecuteProgram(CString strCommand, DWORD& rExitCode)
{
    PROCESS_INFORMATION processInformation = { nullptr };
    STARTUPINFO         startupInfo = { 0 };
    int                 nStrBuffer;
    BOOL                bProcessResult, bExitCodeProcess;
    bool                bOK = false;
    CWaitCursor         wait;

    SetProgramExecuting(true);

    rExitCode = -1;

    startupInfo.cb = sizeof(startupInfo);
    nStrBuffer = strCommand.GetLength() + 50;

    bProcessResult = CreateProcess(nullptr, strCommand.GetBuffer(nStrBuffer),
        nullptr, nullptr, FALSE,
        NORMAL_PRIORITY_CLASS | CREATE_NO_WINDOW,
        nullptr, nullptr, &startupInfo, &processInformation);
    strCommand.ReleaseBuffer();

    if (!bProcessResult)
    {
        // CreateProcess() failed
        // Get the error from the system
        LPVOID lpMsgBuf;
        DWORD dw = GetLastError();
        FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
            nullptr, dw, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPTSTR)&lpMsgBuf, 0, nullptr);

        // Display the error
        CString strError = (LPTSTR)lpMsgBuf;
        TRACE(_T("Authenticate failed at CreateProcess()\nCommand=%s\nMessage=%s\n\n"), strCommand, strError);

        // Free resources created by the system
        LocalFree(lpMsgBuf);

        SetProgramExecuting(false);

        // We failed.
        return false;
    }
    else
    {
        // Successfully created the process.  Wait for it to finish.
        DWORD WaitResult;
        do
        {
            WaitResult = MsgWaitForMultipleObjects(1,
                // only 1 wait object
                &processInformation.hProcess, // worker thread
                FALSE,   // stop if any
                INFINITE,  // no timeout
                QS_ALLINPUT);
            if (WaitResult == WAIT_OBJECT_0 + 1)
            {
                // Handle windows message
                MSG Msg;
                while (PeekMessage(&Msg, nullptr, 0, (UINT)-1, PM_REMOVE))
                {
                    TRACE3("%d %d %d\n", Msg.message, Msg.wParam, Msg.lParam);
                    TranslateMessage(&Msg);
                    DispatchMessage(&Msg);
                }
            }
        } while (WaitResult != WAIT_OBJECT_0);
        ASSERT(WaitResult == WAIT_OBJECT_0);

        // Get the exit code.
        bExitCodeProcess = GetExitCodeProcess(processInformation.hProcess, &rExitCode);

        // Close the handles.
        CloseHandle(processInformation.hProcess);
        CloseHandle(processInformation.hThread);

        if (!bExitCodeProcess)
        {
            // Could not get exit code.
            TRACE(_T("Executed command but couldn't get exit code.\nCommand=%s\n"), strCommand);
            SetProgramExecuting(false);
            return false;
        }

        SetProgramExecuting(false);
        return true;
    }
}

在OnInitDialog 内部，就在调用ExecuteProgram 之前，我尝试使用：

CWaitCursor wait;

但这并没有什么区别。那么如何从调用弹出对话框的那一刻起直到对话框对用户可见为止显示等待光标？

Answer 1

一种解决方案是使用Modeless Dialog。您可以创建一个类似于wait cursor 对话框的对话框。

您在代码中的 dlgSettings.DoModal(); 语句之前显示了 Modeless Dialog。请在显示Modeless Dialog 时使用TOP_MOST。

最后，一旦处理结束，从OnInitDialog() 隐藏/关闭Modeless Dialog。

另一种方法可能是：

在COutlookCalendarSettingsDlg 类中添加public 的CWaitCursor* m_pWaitCursor 成员。现在修改代码为

void CMeetingScheduleAssistantDlg::OnOptionsOutlookCalendarOptions()
{
    COutlookCalendarSettingsDlg dlgSettings(this);
    dlgSettings->m_pWaitCursor = new CWaitCursor();
    dlgSettings.DoModal();
}

然后在返回之前将COutlookCalendarSettingsDlg 的OnInitDialog 修改为delete 的CWaitCursor 实例。

delete m_pWaitCursor;

更新

我想我会在此答案中添加适用于其他情况的更新。您所做的是改用CPersistantWaitCursor。文章提供了一个小例子：

#include "PersistentWaitCursor.h"

void CMyWnd::DoSomeLengthyOperation()
{
    // Create and show the wait cursor
    CPersistentWaitCursor waitCursor;

    // Do some lengthy operation
    ...

    // waitCursor goes out of scope and cursor is restored
}

BOOL CMyWnd::OnSetCursor(CWnd* pWnd, UINT nHitTest, UINT message)
{
    if (CPersistentWaitCursor::WaitCursorShown())
    {
        // We are showing the wait cursor
        RestoreWaitCursor();
        return TRUE;
    }

    // Let the base class deal with this one
    return CWnd::OnSetCursor(pWnd, nHitTest, message);
}

查看文章以获取有关其工作原理的完整详细信息。但我可以确认，对于我其他一些冗长的操作，这个增强的CPersistantWaitCursor 起到了作用。