PRB: Drag List Box Does Not Send DL_DRAGGING Notification (183115)
The information in this article applies to:
- Microsoft Platform Software Development Kit (SDK) 1.0
This article was previously published under Q183115 SYMPTOMS
A drag list box in an improperly coded dialog box sends DL_BEGINDRAG and
DL_DROPPED notifications, but no DL_DRAGGING notifications.
CAUSE
The DragList control relies on the value that is returned in response to
its DL_BEGINDRAG notification in order to acknowledge the start of the
drag. If this value is not returned properly, the further drag messages
will not be sent.
RESOLUTION
In a Dialog Box, the value returned from the dialog box procedure is a BOOL
that tells DefDlgProc whether or not the message has been handled. The
returned value is not the value that is returned as the result of a sent
message. To properly return a value from a dialog box procedure, the return
value needs to be placed in the DWL_MSGRESULT window long position, and
then TRUE must be returned from the dialog box procedure:
case DL_BEGINDRAG:
// Keep track of the item number that is being dragged.
// In this case, store the number in the dialog box's
// DWL_USER position.
SetWindowLong(hwnd,DWL_USER,
LBItemFromPt(dli->hWnd,dli->ptCursor,FALSE));
// Store the return value in DWL_MSGRESULT.
SetWindowLong(hwnd,DWL_MSGRESULT,TRUE);
return TRUE;
STATUS
This behavior is by design.
| Modification Type: | Minor | Last Reviewed: | 7/11/2005 |
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| Keywords: | kbCtrl kbprb KB183115 |
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