Trackbar Notifications

Question

I am trying to get some notification messages when a trackbar slider is moved and when the slider is released by releasing a mouse press.

I am already getting the NM_RELEASEDCAPTURE notification when the mouse button is released. I cannot figure out what notification is sent when the trackbar thumb is moved.

Thanks in advance.

Answer 1

When the slider is moved with a mouse drag it sends WM_HSCROLL (or WM_VSCROLL) with nSBCode == TB_THUMBTRACK.

When the user releases the slider it sends the same scroll message with nSBCode == TB_THUMBPOSITION.

Answer 2

I'm not sure why but I can never see those notifications occurring. I can see notifications such as NM_RELEASEDCAPTURE. Maybe I'm checking notifications on the wrong CWnd?

In case it is important, This slider is part of a dialog window which is a child window of a save dialog.

Answer 3

You are seeing WM_NOTIFY messages, but the control also sends WM_HSCROLL (or WM_VSCROLL) messages.  Does your message handling intercept those messages?

Answer 4

I have an OnNotify method that seems to intercept all of the WM_NOTIFY messages. I tried using an OnHScroll method but I still cannot get a TB_THUMBTRACK or TB_THUMBPOSITION message.

Answer 5

Show your code for OnHScroll.  Is it called?

 

Answer 6

Nothing is inside my OnHScroll function yet. I just have a variable assignment so that I can set a breakpoint to check if the function is called. It has not been called in my program but the OnNotify function continues to be called.

void CAlphaImgFileSave::OnHScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)
{
   int i = 0;
}

Answer 7

I think I just figured out my problem. It was a very small and stupid mistake on my part. I forgot to add:

BEGIN_MESSAGE_MAP(CAlphaImgFileSave, CFileDialog)
   ON_WM_HSCROLL()
END_MESSAGE_MAP()

Answer 8

The OnHScroll must be in the control's parent window.  Is your OnHScroll in the same class that receives the OnNotify?  Does that class have ON_WM_HSCROLL() in its message map?

Answer 9

Yes, it is in the same class as OnNotify. At first, it was not in the message map. I noticed that mistake and pointed it out above. It was a dumb mistake on my part but I think my problem is solved now.

Thanks!