Utilize timer to update MFC Document/View application

0
votes

I'm experimenting with a basic (template) MFC application, and I am looking to update the CDocument (representing the model) instance according to a timer event, for example, move a circle from one point in the client area to another point, according to elapsed time and velocity of the circle.

I've added the code to start the timer in the application class:

m_timer = m_pMainWnd->SetTimer( 16, 1000, NULL);

Which should send a timer message 60 times per second. However, I'm encountering several issues:

Adding a ON_WM_TIMER() entry to the message map for the derived CDocument .cpp file does not work, citing a c2446 error (casting a member function pointer to void pointer).

Trying the same with the concrete CView class does not cause an error, but the OnTimer function is never invoked.

The only place where OnTimer is ever invoked is in the derived CFrameWndEx class, using the following signature:

afx_msg void OnTimer( UINT_PTR nIDEvent );

As far as I can tell, there is no way for the CFrameWndEx to invoke changes in either the CView or CDocument derived classes.

I'm pretty sure this is simply down to my seriously lacking knowledge of MFC architecture, so I would appreciate some pointers.

2
c++timermfc
You can pass your own callback to CWnd::SetTimer if you don't want the window class to handle timer messages. - IInspectable
@IInspectable Yes I'm aware of that, but it doesn't address the core issue, which is that I don't know how to use that to update the document/view based on the timer message. As far as I can tell, the CFrameWndEx object has no knowledge of either. - Ian Young
Can you post the signature of your CMyDocument::OnTimer() function? - sergiol
People seeing your question are not getting the full picture. You need to say where you are putting the ON_WM_TIMER(), and the OnTimer() function. ON_WM_TIMER() on a CDocument will never be handled, because it is defined to be treated by OnTimer, which is in CWnd. In the message loop there is some point on a CWnd that is calling OnTimer, a fact not happening on CDocument derived classes. I suggest you to use Spy++ (Spy++ 64 on 64 bits build) to see the message workflow running. - sergiol
There is no MVC on MFC. What you have is Document/View Architecture: msdn.microsoft.com/en-us/library/4x1xy43a.aspx - sergiol

2 Answers

3
votes

Add an OnTimer function and and ON_WM_TIMER message macro to your CView derived class. From the CView, you can call GetDocument(). That's the easiest way. Documents are not windows so they cannot handle window messages. The only thing they can handle is WM_COMMAND messages because of the way MFC gives the document a chance to respond to those messages via its command message routing.

Another way is to create a TIMERPROC function.

I recommend the first way.

1
votes

Like Joe Willcoxson suggested, simply put the OnTimer method within your concrete CView. However you then can't use the SetTimer method like you posted:

m_timer = m_pMainWnd->SetTimer( 16, 1000, NULL);

You have to call it somehere in your CView class, without m_pMainWnd, e.g. like:

CMyView::OnInitialUpdate()
{
    m_timer = SetTimer( 16, 1000, NULL); // also nullptr instead of NULL would be nice
}

Otherwise the main window will always be the CWnd that handles the message.