[Dev-C++] Control Bar problems in Win32

[Richard P. E. <ev...@ma...>]

I am studying from a book titled "Windows 98 Programming from the Ground 
Up" by Herbert Schildt and seem to be running into an unusual problem. I 
have entered the source code for the scroll bar examples and they work when 
compiled but not totally. When I grab the slider in the horizontal scroll 
bar it will move to where I want it and my position readout registered the 
movement but when I release the mouse button it snaps back to the zero 
position. Also, when I do a control scroll bar, in this case a vertical 
one, I can not drag the slider with the mouse. If I click on the down 
arrowed button the position readout registers movement but the slider just 
sits there and "blinks". I can't find any mistakes in my code as I typed it 
but maybe some one else has experienced similar problems and can tell me 
what they found to solve these problems.  I have included the portions of 
the resource file and source code where these are entered.
Can some one help?  Thanks.

Richard P. Evans

from the resource file:

MyDB DIALOG 18, 18, 142, 92
CAPTION "Adding a Control Scroll Bar"
STYLE DS_MODALFRAME | WS_POPUP | WS_CAPTION | WS_SYSMENU
       | WS_VSCROLL | WS_HSCROLL
{
  GROUPBOX "Slider Positions", ID_GB1, 2, 2, 100, 60
  SCROLLBAR ID_SB1, 110, 10, 10, 70, SBS_VERT | WS_TABSTOP
}

from my source code:

/* Dialog Function */
BOOL CALLBACK DialogFunc(HWND hdwnd, UINT message,
                          WPARAM wParam, LPARAM lParam)
{
  char str[255];
  static int vpos = 0;  /* vertical slider box position */
  static int hpos = 0;  /* horizontasl slider box position */
  static int cntlpos = 0;  /* control slider box position */
  static SCROLLINFO si;  /* scroll bar info structure */

  HDC hdc;
  PAINTSTRUCT paintstruct;

  switch(message)
     {
      case WM_COMMAND:
           switch(LOWORD(wParam))
              {
               case IDCANCEL:
                    EndDialog(hdwnd, 0);
                    return 1;
               }
               break;
      case WM_INITDIALOG:
           si.cbSize = sizeof(SCROLLINFO);
           si.fMask = SIF_RANGE;
           si.nMin = 0; si.nMax = VERTRANGEMAX;

           /* set range of standard vertical scroll bar */
           SetScrollInfo(hdwnd, SB_VERT, &si, 1);

           /* set range of scroll bar control */
           SetScrollInfo(GetDlgItem(hdwnd, ID_SB1), SB_CTL, &si, 1);

           si.nMax = HORZRANGEMAX;
           /* set range of standard horizontal scroll bar */
           SetScrollInfo(hdwnd, SB_HORZ, &si, 1);

           vpos = hpos = 0;
           return 1;
      case WM_PAINT:
           hdc = BeginPaint(hdwnd, &paintstruct);
           sprintf(str, "Vertical: %d", vpos);
           TextOut(hdc, 20, 30, str, strlen(str));
           sprintf(str, "Horizontal: %d", hpos);
           TextOut(hdc, 20, 60, str, strlen(str));
           sprintf(str, "Scroll Bar Control: %d   ", cntlpos);
           TextOut(hdc, 20, 90, str, strlen(str));
           EndPaint(hdwnd, &paintstruct);
           return 1;
      case WM_VSCROLL:
           /* Now we must determine whether the control
              scroll bar or the standard scroll bar generated
              the message. */
           switch(LOWORD(wParam))
              {
               case SB_LINEDOWN:
                    if ((HWND)lParam == GetDlgItem(hdwnd, ID_SB1))
                       {
                       /* is control scroll bar */
                       cntlpos++;
                       if(cntlpos>VERTRANGEMAX) cntlpos = VERTRANGEMAX;
                       }
                    else /* is window scroll bar */
                       {
                       vpos++;
                       if(vpos>VERTRANGEMAX) vpos = VERTRANGEMAX;
                       }
                       break;
               case SB_LINEUP:
                    if((HWND)lParam == GetDlgItem(hdwnd, ID_SB1))
                       {
                       /* is control bar scroll */
                       cntlpos--;
                       if(cntlpos<0) cntlpos = 0;
                       }
                    else
                       {
                       /* is window scroll bar */
                       vpos--;
                       if(vpos<0) vpos = 0;
                       }
                       break;
               case SB_THUMBPOSITION:
                    if((HWND)lParam == GetDlgItem(hdwnd, ID_SB1))
                      {
                      /* is control scroll bar */
                      cntlpos = HIWORD(wParam);  /* get current position */
                      }
                    else
                      {
                      /* is window scroll bar */
                      vpos = HIWORD(wParam);  /* get current position */
                      }
                    break;
               case SB_THUMBTRACK:
                     if((HWND)lParam == GetDlgItem(hdwnd, ID_SB1))
                      {
                      /* is control scroll bar */
                      cntlpos = HIWORD(wParam);  /* get current position */
                      }
                    else
                      {
                      /* is window scroll bar */
                      vpos = HIWORD(wParam);  /* get current position */
                      }
                    break;
               case SB_PAGEDOWN:
                    if((HWND)lParam == GetDlgItem(hdwnd, ID_SB1))
                      {
                      /* is control scroll bar */
                      cntlpos += 5;
                      if(cntlpos>VERTRANGEMAX) cntlpos = VERTRANGEMAX;
                      }
                    else
                      {
                      /* is window scroll bar */
                      vpos += 5;
                      if(vpos>VERTRANGEMAX) vpos = VERTRANGEMAX;
                      }
                    break;
               case SB_PAGEUP:
                    if((HWND)lParam == GetDlgItem(hdwnd, ID_SB1))
                      {
                      /* is control scroll bar */
                      cntlpos -= 5;
                      if(cntlpos<0) cntlpos = 0;
                      }
                    else
                      {
                      /* is window scroll bar */
                      vpos -= 5;
                      if(vpos<0) vpos = 0;
                      }
                    break;
              }

              if((HWND)lParam == GetDlgItem(hdwnd, ID_SB1))
                {
                /* update standard scroll bar position */
                si.fMask = SIF_POS;
                si.nPos = vpos;
                SetScrollInfo(hdwnd, SB_VERT, &si, 1);
                hdc = GetDC(hdwnd);
                sprintf(str, "Scroll Bar Control: %d  ", cntlpos);
                TextOut(hdc, 20, 90, str, strlen(str));
                ReleaseDC(hdwnd, hdc);
                }
              else
                {
                /* update standard scroll bar position */
                si.fMask = SIF_POS;
                si.nPos = vpos;
                SetScrollInfo(hdwnd, SB_VERT, &si, 1);
                hdc = GetDC(hdwnd);
                sprintf(str, "Vertical: %d    ", vpos);
                TextOut(hdc, 20, 30, str, strlen(str));
                ReleaseDC(hdwnd, hdc);
                }
              return 1;
      case WM_HSCROLL:
           switch(LOWORD(wParam))
              {
              /* Try adding the other event handling code
                 for the horizontal scroll bar here. */
              case SB_LINERIGHT:
                   hpos++;
                   if(hpos>HORZRANGEMAX) hpos = HORZRANGEMAX;
                   break;
              case SB_LINELEFT:
                   hpos--;
                   if(hpos<0) hpos = 0;
              }
              /* update horizontal bar position */
              si.fMask = SIF_POS;
              si.nPos = hpos;
              SetScrollInfo(hdwnd, SB_HORZ, &si, 1);
              hdc = GetDC(hdwnd);
              sprintf(str, "Horizontal: %d   ", hpos);
              TextOut(hdc, 20, 60, str, strlen(str));
              ReleaseDC(hdwnd, hdc);
              return 1;
      }
      return 0;
}