Click here to Skip to main content
11,482,039 members (65,170 online)
Click here to Skip to main content

CDocument::DoSave revealed

, 18 Sep 2002 CPOL 138K 39
Rate this:
Please Sign up or sign in to vote.
Explains how you can suppress the File-Save-As dialog in a Doc/View app, how to save files to multiple formats, and how DoSave is implemented.

Introduction

For one of my recent projects I had a rather strange requirement. It was an image conversion program basically, and it allowed you to open bitmap files. When the user clicked on the save icon in the toolbar or if he took the save-item from the File-menu, I was to save the image in a custom format using the same name as the original bitmap, but replacing the bmp extension with a custom extension. This meant that I should suppress the File-Save-As dialog. Initially I thought I simply had to override OnSaveDocument and refrain from calling the base class, but I quickly discovered that OnSaveDocument was too late to suppress the File-Save-As dialog.

DoSave revealed

I took a look at doccore.cpp and soon figured out the order in which methods got called inside the CDocument class. Essentially when the user tries to save a file, MFC command routing routes the message to CDocument::OnFileSave or CDocument::OnFileSaveAs depending on whether you clicked on Save or on Save-As. CDocument::OnFileSave calls CDocument::DoFileSave(). CDocument::DoFileSave() checks to see if the file exists and if it does, it proceeds to call CDocument::DoSave passing the full path of the file, else it calls CDocument::DoSave passing NULL for the file path. CDocument::OnFileSaveAs simply calls CDocument::DoSave passing NULL for the file path. Thus eventually we end up in CDocument::DoSave. So I decided that this was the method to override. CDocument::DoSave is declared thus :-

BOOL CDocument::DoSave(LPCTSTR lpszPathName, BOOL bReplace);
  • lpszPathName :- This is the full path of the file to save. If this is NULL the default implementation will prompt the user for a filename and path using the File-Save-As common dialog.
  • bReplace :- If TRUE it will replace an existing file, if FALSE it won't.

In my particular case I was least bothered with the working of the DoSave method. My intention was to get rid of this method totally. So this is what I did - I overrode this member function and did not call the base class implementation.

BOOL CBmpToXyzDoc::DoSave(LPCTSTR lpszPathName, BOOL bReplace)
{   
    //SrcPath is the full path of the current file
    CString DestPath = SrcPath;

    //I replace the extension with the custom one
    DestPath.Replace("bmp","xyz");

    //Now I simply call OnSaveDocument
    OnSaveDocument(DestPath);

    //File saved successfully
    return TRUE;
}

That was just what I had wanted to accomplish. The user never gets prompted and the file is saved using the same name as the original except for the change in extension.

Other plausible applications

While I did not specifically require it for my project, I figured that DoSave can be used for some other purposes too. At least one nifty usage came to my mind. Assume that I wanted to do different things based on some flag. For example assume that I want to show a Save-As dialog with JPG filter if the current file is a GIF and might want to show a Save-As dialog with GIF filter if the current file is a JPG. If so, I could show my own CFileDialog after setting the corresponding OPENFILENAME members.

BOOL CBmpToXyzDoc::DoSave(LPCTSTR lpszPathName, BOOL bReplace)
{   
    CFileDialog fd(false);

    if(m_bgif)
    {
        fd.m_ofn.lpstrFilter="JPG Files(*.jpg)\0*.jpg\0\0";
        fd.m_ofn.lpstrDefExt="jpg";
        fd.m_ofn.lpstrTitle ="Save as JPG";
    }
    else
    {
        fd.m_ofn.lpstrFilter="GIF Files(*.gif)\0*.gif\0\0";
        fd.m_ofn.lpstrDefExt="gif";
        fd.m_ofn.lpstrTitle ="Save as GIF";
    }

    if(fd.DoModal()==IDOK)
    {
        if(m_bgif)
            OnSaveJpgDocument(fd.GetPathName());
        else
            OnSaveGifDocument(fd.GetPathName());
    }

    return TRUE;    
}

Tech notes

The CDocument::DoSave implementation is very interesting. If lpszPathName is NULL, it calls CWinApp::DoPromptFileName :-

if (!AfxGetApp()->DoPromptFileName(newName,
    bReplace ? AFX_IDS_SAVEFILE : AFX_IDS_SAVEFILECOPY,
    OFN_HIDEREADONLY | OFN_PATHMUSTEXIST, FALSE, pTemplate))
{
    return FALSE;
}

CWinApp::DoPromptFileName itself calls CDocManager::DoPromptFileName.

BOOL CWinApp::DoPromptFileName(CString& fileName, 
                               UINT nIDSTitle, 
                               DWORD lFlags,
                               BOOL bOpenFileDialog, 
                               CDocTemplate* pTemplate)
{
    ASSERT(m_pDocManager != NULL);
    return m_pDocManager->DoPromptFileName(fileName, 
        nIDSTitle, lFlags,  bOpenFileDialog, pTemplate);
}

CDocManager::DoPromptFileName simply uses CFileDialog to prompt for a filename.

BOOL CDocManager::DoPromptFileName(CString& fileName, 
                                   UINT nIDSTitle, 
                                   DWORD lFlags, 
                                   BOOL bOpenFileDialog, 
                                   CDocTemplate* pTemplate)
{
    CFileDialog dlgFile(bOpenFileDialog, NULL, NULL, 
        OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT, NULL, NULL, 0);

    CString title;
    VERIFY(title.LoadString(nIDSTitle));

    dlgFile.m_ofn.Flags |= lFlags;

    //...

    INT_PTR nResult = dlgFile.DoModal();

    //...

Of course it does a lot of stuff in addition to just showing the file dialog. For example it will append a *.* filter to your File dialogs, which is why in addition to your document filter, you'll also see a *.* filter in the file type drop-down combo-box. Knowing how the flow proceeds is handy in the sense that if you want to customize it without hooking the window, you might simply override CWinApp::DoPromptFileName and call your own CFileDialog there (remember that this will affect both Open and Save dialogs).

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Share

About the Author

Nish Nishant

United States United States
Nish Nishant is a Software Architect/Consultant based out of Columbus, Ohio. He has over 15 years of software industry experience in various roles including Lead Software Architect, Principal Software Engineer, and Product Manager. Nish is a recipient of the annual Microsoft Visual C++ MVP Award since 2002 (13 consecutive awards as of 2014).

Nish is an industry acknowledged expert in the Microsoft technology stack. He authored
C++/CLI in Action for Manning Publications in 2005, and had previously co-authored
Extending MFC Applications with the .NET Framework for Addison Wesley in 2003. In addition, he has over 140 published technology articles on CodeProject.com and another 250+ blog articles on his
WordPress blog. Nish is vastly experienced in team management, mentoring teams, and directing all stages of software development.

Contact Nish : You can reach Nish on his google email id voidnish.

Website and Blog

Comments and Discussions

 
Generalproblem in saveas Pin
partha arathy8-May-03 1:01
memberpartha arathy8-May-03 1:01 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Terms of Use | Mobile
Web01 | 2.8.150520.1 | Last Updated 19 Sep 2002
Article Copyright 2002 by Nish Nishant
Everything else Copyright © CodeProject, 1999-2015
Layout: fixed | fluid