MFC: how to differentiate "Save" vs "Save As"? - visual-studio

Question

In my previous question (MFC: how to change default file name for CFileDialog?), I overload DoSave function to supply a file name suggestion. Within this function is there way to differentiate "Save" vs "Save As"? Because I should only pop out dialog window if it is "Save As".
BOOL CMyDoc::DoSave(LPCTSTR lpszPathName, BOOL bReplace)
{
if (IsSaveAS() || m_saved_file_name.IsEmpty())
{
CString file_name = some_suggested_file_name;
CFileDialog file_dialog(false, ..., file_name, ...);
if (file_dialog.DoModal() == IDOK)
{
m_saved_file_name = file_dialog.GetPathName();
}
}
OnSaveDocument(m_saved_file_name);
return TRUE;
}

Answer 1

The dialog should be popped when lpszPathName == NULL || *lpszPathName == '\0'.
This covers the case where DoSave is called from OnFileSaveAs:
void CDocument::OnFileSaveAs()
{
if(!DoSave(NULL))
TRACE(traceAppMsg, 0, "Warning: File save-as failed.\n");
}
And also the case where the associated file is read-only and cannot be written to.
BOOL CDocument::DoFileSave()
{
DWORD dwAttrib = GetFileAttributes(m_strPathName);
if (dwAttrib & FILE_ATTRIBUTE_READONLY)
{
// we do not have read-write access or the file does not (now) exist
if (!DoSave(NULL))
{
TRACE(traceAppMsg, 0, "Warning: File save with new name failed.\n");
return FALSE;
}
}
else
{
if (!DoSave(m_strPathName))
{
TRACE(traceAppMsg, 0, "Warning: File save failed.\n");
return FALSE;
}
}
return TRUE;
}
It also matches the logic of the builtin DoSave.
BOOL CDocument::DoSave(LPCTSTR lpszPathName, BOOL bReplace)
// Save the document data to a file
// lpszPathName = path name where to save document file
// if lpszPathName is NULL then the user will be prompted (SaveAs)
// note: lpszPathName can be different than 'm_strPathName'
// if 'bReplace' is TRUE will change file name if successful (SaveAs)
// if 'bReplace' is FALSE will not change path name (SaveCopyAs)
{
CString newName = lpszPathName;
if (newName.IsEmpty())
{
// ...
if (!AfxGetApp()->DoPromptFileName(newName,
// ...