Manipulating the File Open/Save Filters

This article addresses 2 issues

  • Removing *.* filter from the MFC Doc-View architecture Open/Save File dialogs
  • Displaying only selected filters in the MFC Doc-View architecture Open/Save File dialogs

The MFC Doc-View architectures “Open/Save File” functionality allows
the user to open/save file of any type using the *.* filter. Now
if you don’t want the user to do this

For example, I have created an MDI application using the AppWizard and
I have the following 2 document templates –


CDocTemplate *m_pTest1DocTemplate, m_pTest2DocTemplate

m_pTest1DocTemplate = new CMultiDocTemplate(IDR_TEST1TYPE,
RUNTIME_CLASS(CTest1Doc),
RUNTIME_CLASS(CChildFrame), // custom MDI child frame
RUNTIME_CLASS(CTest1View));

AddDocTemplate(m_pTest1DocTemplate);

m_pTest2DocTemplate = new CMultiDocTemplate(IDR_TEST2TYPE,
RUNTIME_CLASS(CTest2Doc),
RUNTIME_CLASS(CChildFrame), // custom MDI child frame
RUNTIME_CLASS(CTest2View));
AddDocTemplate(m_pTest2DocTemplate);

where…
IDR_TEST1TYPE = nTest1Test1 FilenTest1 Files(*.ts1)n.ts1nts1nTest1n
IDR_TEST2TYPE = nTest2Test2 FilenTest2 Files(*.ts2)n.ts2nts2nTest2n

You have created a new Test1 file and added data to it. Now when you
want to save the file and click on the save button. The save file
dialog comes up and you can give a name to the file and save it.
The tricky part is that this allows the file to be saved in to any
extension and WE DID NOT WANT THIS. So to remove this *.* filter
in the file types combo box I suggest the following –

Derive a class CMyDocManager from CDocManager

Provide a implentation of the virtual function DoPromptFileName which is defined in the
CDocManager base class


//Implementation of the base class virtual function
BOOL CCGPDocManager::DoPromptFileName(CString& fileName, UINT nIDSTitle, DWORD lFlags, BOOL bOpenFileDialog, CDocTemplate* pTemplate)
{
CString cstrInitialDir = “”;

//Depending on the Template you can set the Initial Folder
if(pTemplate == g_theApp.m_pTest1DocTemplate)
{
cstrInitialDir = “c:\Test\Test1Files”;
}
else if(pTemplate == g_theApp.m_pTest2DocTemplate)
{
cstrInitialDir = “c:\Test\Test2Files”;
}

return CUtility::DoPromptFileName(cstrInitialDir, fileName, nIDSTitle, lFlags, bOpenFileDialog, pTemplate);
}

In the InitApplication() function of your Application class add the following line –


//m_pDocManager is already defined in the CWinApp class
m_pDocManager = new CCGPDocManager();

Now when the user tries to save a Test1 file then the user can only save
it to a .ts1 extension

To display only selected filters in the MFC Doc-View architecture Open
File dialog

Implement the OnFileOpen function in the CMainFrame class
ON_COMMAND(ID_FILE_OPEN, OnFileOpen)


void CMainFrame::OnFileOpen()
{
CString cstrFileName;

CDocTemplate *paDocTemplate[] = {g_theApp.m_pTest1DocTemplate,
g_theApp.m_pTest2DocTemplate,
NULL};

if(!CUtility::DoPromptFileName(“”, cstrFileName, AFX_IDS_OPENFILE,
OFN_HIDEREADONLY | OFN_PATHMUSTEXIST, TRUE,
paDocTemplate))
return;

OpenDocumentFile(cstrFileName);
}

CUtility class


static BOOL DoPromptFileName(CString cstrInitialDir, CString& fileName, UINT nIDSTitle, DWORD lFlags, BOOL bOpenFileDialog, CDocTemplate **pTemplate);
static BOOL DoPromptFileName(CString cstrInitialDir, CString& fileName, UINT nIDSTitle, DWORD lFlags, BOOL bOpenFileDialog, CDocTemplate* pTemplate);
static void AppendFilterSuffix(CString& filter, OPENFILENAME& ofn, CDocTemplate* pTemplate, CString* pstrDefaultExt);

BOOL CUtility::DoPromptFileName(CString cstrInitialDir, CString& fileName,
UINT nIDSTitle, DWORD lFlags,
BOOL bOpenFileDialog,
CDocTemplate* pTemplate)
{
CFileDialog dlgFile(bOpenFileDialog);

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

dlgFile.m_ofn.Flags |= lFlags;

CString strFilter;
CString strDefault;
if(pTemplate != NULL)
{
ASSERT_VALID(pTemplate);
AppendFilterSuffix(strFilter, dlgFile.m_ofn, pTemplate, &strDefault);
}

dlgFile.m_ofn.lpstrFilter = strFilter;
#ifndef _MAC
dlgFile.m_ofn.lpstrTitle = title;
#else
dlgFile.m_ofn.lpstrPrompt = title;
#endif
dlgFile.m_ofn.lpstrFile = fileName.GetBuffer(_MAX_PATH);

dlgFile.m_ofn.lpstrInitialDir = cstrInitialDir;

BOOL bResult = dlgFile.DoModal() == IDOK ? TRUE : FALSE;
fileName.ReleaseBuffer();

CString strFilterExt;
//Get the file extension of the template
pTemplate->GetDocString(strFilterExt, CDocTemplate::filterExt);

//Get the file extension of the selected file
CString cstrSelFileExt = fileName.Right(fileName.GetLength() – fileName.ReverseFind(‘.’));

cstrSelFileExt.MakeLower();
strFilterExt.MakeLower();

//compare both if not the same extension then return false
if(strFilterExt.Find(cstrSelFileExt) == -1)
{
AfxMessageBox(“Invalid extension”, MB_OK | MB_ICONHAND);
return FALSE;
}

return bResult;
}

BOOL CUtility::DoPromptFileName(CString cstrInitialDir, CString& fileName,
UINT nIDSTitle, DWORD lFlags,
BOOL bOpenFileDialog,
CDocTemplate **pTemplate)
{
CFileDialog dlgFile(bOpenFileDialog);

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

dlgFile.m_ofn.Flags |= lFlags;

CString strFilter;
CString strDefault;

int i = 0;

while(pTemplate[i] != NULL)
{
ASSERT_VALID(pTemplate[i]);
AppendFilterSuffix(strFilter, dlgFile.m_ofn, pTemplate[i], &strDefault);
i++;
}

dlgFile.m_ofn.lpstrFilter = strFilter;
#ifndef _MAC
dlgFile.m_ofn.lpstrTitle = title;
#else
dlgFile.m_ofn.lpstrPrompt = title;
#endif
dlgFile.m_ofn.lpstrFile = fileName.GetBuffer(_MAX_PATH);

dlgFile.m_ofn.lpstrInitialDir = cstrInitialDir;

BOOL bResult = dlgFile.DoModal() == IDOK ? TRUE : FALSE;
fileName.ReleaseBuffer();

BOOL bExtMatched = FALSE;
i = 0;
while(pTemplate[i] != NULL)
{
CString strFilterExt;
//Get the file extension of the template
pTemplate[i]->GetDocString(strFilterExt, CDocTemplate::filterExt);

//Get the file extension of the selected file
CString cstrSelFileExt = fileName.Right(fileName.GetLength() – fileName.ReverseFind(‘.’));

cstrSelFileExt.MakeLower();
strFilterExt.MakeLower();

if(strFilterExt.Find(cstrSelFileExt) != -1)
{
bExtMatched = TRUE;
break;
}

i++;
}

if(!bExtMatched)
{
AfxMessageBox(“Invalid extension”, MB_OK | MB_ICONHAND);
return FALSE;
}

return bResult;
}

void CUtility::AppendFilterSuffix(CString& filter, OPENFILENAME& ofn,
CDocTemplate* pTemplate, CString* pstrDefaultExt)
{
ASSERT_VALID(pTemplate);
ASSERT_KINDOF(CDocTemplate, pTemplate);

CString strFilterExt, strFilterName;
if (pTemplate->GetDocString(strFilterExt, CDocTemplate::filterExt) &&
! strFilterExt.IsEmpty() &&
pTemplate->GetDocString(strFilterName, CDocTemplate::filterName) &&
! strFilterName.IsEmpty())
{
// a file based document template – add to filter list
#ifndef _MAC
ASSERT(strFilterExt[0] == ‘.’);
#endif
if (pstrDefaultExt != NULL)
{
// set the default extension
#ifndef _MAC
*pstrDefaultExt = ((LPCTSTR)strFilterExt) + 1; // skip the ‘.’
#else
*pstrDefaultExt = strFilterExt;
#endif
ofn.lpstrDefExt = (LPTSTR)(LPCTSTR)(*pstrDefaultExt);
ofn.nFilterIndex = ofn.nMaxCustFilter + 1; // 1 based number
}

// add to filter
filter += strFilterName;
ASSERT(!filter.IsEmpty()); // must have a file type name
filter += (TCHAR)’’; // next string please
#ifndef _MAC
filter += (TCHAR)’*’;
#endif
filter += strFilterExt;
filter += (TCHAR)’’; // next string please
ofn.nMaxCustFilter++;
}
}

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