dcsimg

Make Modal Dialogs Behave Like Modeless Dialogs

WEBINAR:
On-Demand

Desktop-as-a-Service Designed for Any Cloud ? Nutanix Frame


Environment: Visual C++ 4.0 (and above)

Description

This template class simulates the behaviour of a modeless dialog while allowing some of the programmatic control of a modal dialog. When modal dialog are closed control is immediately returned to the caller of the DoModal member function:
CMyDialog dlg;

if( dlg.DoModal() ) { ... }

However, the same can not be said of modal dialogs where the Create/ShowWindow member function pair need to be used in order to display the dialog.

CMyDialog dlg;
dlg.Create( IDD_MY_DIALOG );
dlg.ShowWindow();

...

if( you receive some message that the non-modal has closed ) 
{
...
}

The above code segment creates and activates a non-modal dialog. How and when you get control back generally involves some rather tricky programming - in other words, it's not nearly as straight-forward as using a modal dialog.

Usage

NonModalDialog<MyDlg>myDlg( AfxGetMainWnd() );
myDlg.DoModal();

...

class CWnd;

template <class ModalDialog>class NonModalDialog 
: public ModalDialog
{
public :
 NonModalDialog( CWnd *pParent ) 
 : ModalDialog( pParent ) { }

 virtual int DoModal();
 virtual void EndModalLoop( int );
protected:
 int m_nStillActive;
};

template <class ModalDialog>
inline int NonModalDialog<ModalDialog>::DoModal()
{
 MSG			l_objMessage;
 CWinThread*	l_pThread = AfxGetThread();

 ASSERT_VALID( l_pThread );

 Create( ModalDialog::IDD );	
 ShowWindow( SW_SHOW );
 m_nStillActive = 1;

 //--------- Thanks to Microsoft. This block 
 //--------- is from CWinThread::Run
 // from Thrdcore.cpp, with appropriate changes.
 ASSERT_VALID(this);
 // for tracking the idle time state
 BOOL l_nIdle = TRUE;
 LONG l_nIdleCount = 0;

 // acquire and dispatch messages until 
 // a WM_QUIT message is received,
 // or the dialog box is closed.
 for (;;) 
 {
  // phase1: check to see if we can do idle work
  while( l_nIdle && !::PeekMessage( &l_objMessage, 
                                    NULL, 
                                    NULL, 
                                    NULL, 
                                    PM_NOREMOVE ) ) 
  {
   // call OnIdle while in bIdle state
   if( !l_pThread->OnIdle( l_nIdleCount++ ) )
    l_nIdle = FALSE; // assume "no idle" state
  }
  
  // phase2: pump messages while available
  do 
  {
   // Relent control back to Windows if the dialog 
   // box has closed.
   if( !m_nStillActive )
    return m_nModalResult;

   if( l_objMessage.message == WM_SYSCOMMAND 
   && l_objMessage.wParam == SC_CLOSE )
    OnCancel();	// Close the dialog box first.

   // pump message, but quit on WM_QUIT
   if( !l_pThread->PumpMessage() )
    return l_pThread->ExitInstance();

   // reset "no idle" state after pumping 
   // "normal" message
   if( l_pThread->IsIdleMessage( &l_objMessage ) )
    l_nIdle = TRUE, l_nIdleCount = 0;
  } while( ::PeekMessage( &l_objMessage, 
                          NULL, 
                          NULL, 
                          NULL, 
                          PM_NOREMOVE ) );
 }
 ASSERT(FALSE);  // not reachable
 //---------------------
}

template <class ModalDialog>inline void 
NonModalDialog<ModalDialog>::EndModalLoop(int p_nResult)
{
 m_nStillActive = 0;
 ModalDialog::EndModalLoop( p_nResult );
}

Limitations

  1. Applies only to MFC versions that properly support OCX containment. ( v4.0 and later )
  2. From inside the dialog, you close it using EndDialog( ... ) only.
  3. You MUST take only two parameters, one is the IDD of your dialog, and the next is CWnd*, in your dialog's constructor.


This article was originally published on January 29th, 2001

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date