BUG: Scrollbar Notifications Report Incorrect Position (197411)
The information in this article applies to:
This article was previously published under Q197411 SYMPTOMS
The scroll position may be reported incorrectly when SB_THUMBPOSITION and
SB_THUMBTRACK scroll notifications are received.
CAUSE
Windows CE maps the scroll position into the range 0 - (nMax - nMin) where
0 is the minimum scroll position and (nMax - nMin) is the maximum scroll
position. nMin and nMax are the minimum and maximum scroll positions set by
calling SetScrollRange or SetScrollInfo.
RESOLUTION
When handling SB_THUMBPOSITION and SB_THUMBTRACK notifications, add the
minimum scroll position to the position reported in the WM_HSCROLL or
WM_VSCROLL message (nPos) to obtain the actual position.
Sample Code
case WM_VSCROLL:
{
int nScrollCode = (int)LOWORD(wParam);
int nPos = (short int)HIWORD(wParam);
SCROLLINFO si = {sizeof(SCROLLINFO),
SIF_PAGE|SIF_POS|SIF_RANGE|SIF_TRACKPOS,
0, 0, 0, 0, 0};
GetScrollInfo (hWnd, SB_VERT, &si);
int nNewPos = si.nPos;
switch (nScrollCode)
{
[ ... ]
case SB_THUMBPOSITION:
nNewPos = nPos + si.nMin; // Adding si.nMin here
// is the workaround.
break;
}
si.fMask = SIF_POS;
si.nPos = nNewPos;
SetScrollInfo (hWnd, SB_VERT, &si, TRUE);
return TRUE;
}
STATUS
Microsoft has confirmed this to be a bug in the Microsoft products listed
at the beginning of this article.
| Modification Type: | Major | Last Reviewed: | 10/16/2002 |
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| Keywords: | kbBug kbcode kbCtrl KB197411 |
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