CODEWITHSUNDEEP
c++multithreadingvisual-c++mfc
Kumar
Kumar

Reputation: 636

how to access mfc controls using messages?

I would like to access drag slider control of my dialog box from worker thread. I read many warnings regarding accessing main window controls from worker thread. Since they have a high chances of resulting in a dead lock. In this case, how to access the control using messages? I know how to create user defined messages (WM_USER) and write our own handlers. What it would like to know is that is there any system defined message for each controls and if it is there, how to post those messages to access the control?

Upvotes: 0

Views: 295

Answers (1)

snowdude
snowdude

Reputation: 3874

You can use PostMessage to send a message to the control and the main UI thread will actually dispatch the message to the control, ie the work will happen on the UI thread (assuming the UI thread is pumping messages). Looking at afxcmn.inl you can see what SetPos is doing:

_AFXCMN_INLINE void CSliderCtrl::SetPos(_In_ int nPos)
{ ASSERT(::IsWindow(m_hWnd)); ::SendMessage(m_hWnd, TBM_SETPOS, TRUE, nPos); }

Changing that for PostMessage:

::PostMessage(hSlider, TBM_SETPOS, TRUE, nPos);

If you want something more complicated post a WM_USER message to a the parent window and handle your control managing functionality there because, again, the WM_USER message will be dispatched by the UI thread so you can work with your control safely.

Upvotes: 1

Related Questions