Re: UIThreads, dialogs & messaging problem

From:

David Wilkinson <no-reply@effisols.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Thu, 04 May 2006 07:51:00 -0400

Message-ID:

<OyGU8D3bGHA.2068@TK2MSFTNGP02.phx.gbl>

Simon L wrote:

In eVC4 .... I've built a CWinthread derived class to display a logon
dialog non-modally and it communicates with the main app thread via
messaging. So every 30 seconds or so, if the user hasn't been doing
anything, a dialog pops up on top of everything else requiring a logon.

(Comments on the validity of this mechanism welcome).

Calls to show the dialog are made in the Main app as
pThread->PostThreadMessage( WM_SHOWME .... )
and handled in the thread
ON_MESSAGE( WM_SHOWME , OnShow ) [changed from ON_THREAD_MESSAGE
after googling this group about a problem that was fixed in VC7 - not
sure how this applies to eVC]
afx_msg LRESULT MyThread::OnShow (WPARAM, LPARAM)
{
Create if necessary, and show a dialog
}

When the logon dialog closes (hides), it posts a message to the main
app (via AfxGetApp()->m_pMainWnd->PostMessage(WM_CREW ) , 45 , 18 )
and handled in a CView derived class as
ON_MESSAGE( WM_CREW , OnLogon )
afx_msg LRESULT MyView::OnLogon(WPARAM wParam , LPARAM lParam)

Problem:
If I make this call in the dialog's OnOK event, the message takes over
a second to get to the message handler & the parameters are wrong ( 0).

Simon:

1. 30 seconds seems a very short time. Won't this be mega-annoying for
the user? Try putting your screen saver on a 30-second fuse.

2. It seems that you have the logon dialog itself in a separate thread.
It is almost always a mistake not to have all the GUI in the main thread.

3. I'm not even sure why you need a thread here, or why the dialog is
non-modal. Why not just use a timer and a modal dialog, if the user is
not allowed to do anything until he/she logs back on.

David Wilkinson