Pls debug my scroll program

REALLY GRATEFUL if someone can help.

I've been debugging this program for very long and i still cant find the problem. If u keep scrolling the child window down, it wont end(i want it to stop scrolling at 'p'). It works fine if u keep scrolling up. In particular, you might want to check the scrolling implements which is found in scroll.cpp.

The file is zipped and attached.
Compiler:VC++ 6.0

There's some issue with oldPos. When it should be 41, its not. It's lagging by about 10 places. I'll keep debugging.

What the!! I was scrolling step by step, pausing at every call to the scroll_onVscroll() function, and the odd behavior didn't occur! Now I'm freaked out.

I'm spent. As it's not my code, I really can't figure out how each part works together as a whole. I suggest starting again. Build it slowly, compiling and checking behavior step by step.

Okay I've got it. You're letting nPos get all the way to nMax, but logically it shouldn't. Because the scroll window displays more than one entry at a time, and because nPos represents the TOP of the scrolling area, when nPos is nMax, it will be displaying an entire page past nPos. So what you need to do is stop scrolling when nPos equals nMax-nPage. I think that should fix it.

Thanks for the great help, benny!!!

If i stop scrolling when nPos reach (si.nMax-si.nPage), the scroll box never reach the bottom of the scroll bar. But i managed to solve it by using (si.nMax-si.nPage+1) instead.

Code:

---

        oldPos = si.nPos;
        newPos = si.nPos + y;
        si.nPos = max(0, min(newPos, (si.nMax-si.nPage+1)));

        if(si.nPos != oldPos)
        {

                SetScrollInfo (hwnd, SB_VERT, &si, TRUE);
                ScrollWindow(hwnd,0,cychar*(oldPos-si.nPos),NULL,NULL);
                UpdateWindow(hwnd);
        }

---

However, if i want the window to be able to scroll till only the last 'p' is on the screen. What should i do? In fact, i tried (si.nMax-si.nPage+2) for experiment and the endless scrolling problem comes again. The window kept printing '.' after the 'p'. I really dont understand where the '.' come from.

oh yeah!
I figured out the solution.
Just change the nMax during each resize:

Code:

---

        si.cbSize = sizeof(SCROLLINFO);
        si.fMask = SIF_PAGE | SIF_RANGE;
        si.nMin = 0;
        si.nPage = (height/cychar);
        si.nMax = 40 +si.nPage;
        SetScrollInfo(hwnd,SB_VERT,&si,TRUE);

---

But i wish i know where the '.' come from.

I'm glad we worked this out.

As far as I can tell, the dots shouldn't be there. The TextOut() loop only runs to si.nMax, and anyway, letter[] does not contain a dot. I believe it has something to do with the fact that you are not actively erasing the client area each time you paint. However, I am not sure. I will look into it later today.