Modal vs Modeless Dialogs

Posted on 2001-06-27
Last Modified: 2013-11-20
Dear Experts,

I am using VC++6/MFC Win 98.

I would like to know if it is possible to make a Dialog Object which can act both modally & modelessly.

i.e Display the Object using both the following methods:

1. MyDialog.DoModal().
2. MyDialog = new CMyDialog(this,...)

If so, how do I detect which it is in the Dialog Constructor?

For modeless dialogs, I normally use the follwing code to create & show the dialog object:

CMyDialog(CWnd* pParent,...)

Obviously, I don't need to execute the Create & ShowWindow commands if the dialog is Modal.
So, I need some way of detecting if Dialog is Modal or not.

I look forward to you answers.

Question by:beanjasper
  • 3
  • 3
LVL 49

Expert Comment

ID: 6230330
There may be a simple build-in command, but the easiset would be to simply add a variable, m_fIsModal to the derived class.  Then...

  m_dlg= new CMyDlg(...)
  m_dlg.m_fIsModal= TRUE;
  m_dlg= new CMyDlg(...)
  m_dlg.m_fIsModal= FALSE;

-- Dan

Author Comment

ID: 6230653
Hi Dan,

Thats so simple I'm embarassed!

If you don't mind, I'll leave this question open for a couple of days to see if anyone knows of a 'Built In' function.

If not, the points are yours.


LVL 32

Expert Comment

ID: 6231205
Perhaps there is a flag buried in the data returned by GetWindowLongPtr() that specifies modal vs. non-modal.  

Obviously Windows knows which it is and the information is almost certainly kept in the window itself...

Just a thought.
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LVL 49

Expert Comment

ID: 6232533
Actually Windows probably doesn't know -- It just sends messages.  MFC uses a technique in which all dialog boxes are actually modeless -- MFC does *not* call the DialoxBox API (which implements an interal message pump).  MFC wants more control so it implements its own message pump to simulate "Modal Dialog" type action.

You could take a look at the m_nFlags member.  I think that if...
   (m_nFlags & WF_CONTINUEMODAL) != 0
then it is a modal dialog.

-- Dan


Author Comment

ID: 6234346

m_nFlags - Is this a member of CDialog or is it inherited from CWnd?

I can't find mention of it in the CDialog or CWnd documentation.

Also, where is the list of WF_.. flags such as the one you mentioned above?

I have bumped the points to 75 to recompense you for the extra time required to answer these.


LVL 49

Accepted Solution

DanRollins earned 75 total points
ID: 6237042
It appears that these flags are not officially documented.  However m_nFlags is a public data member of CWnd.  You can find the flag value constants in the file AFXWIN.H, in the  ... \MFC\Include directory.

You can also glean a little more info by searching MDSN for m_fFlags

-- Dan

Author Comment

ID: 6237103
Yup, 10/10!

Heres an A for your troubles.



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