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HDN_BEGINTRACK notification code

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Notifies a header control's parent window that the user has begun dragging a divider in the control (that is, the user has pressed the left mouse button while the mouse cursor is on a divider in the header control). This notification code is sent in the form of a WM_NOTIFY message.

HDN_BEGINTRACK

    pNMHeader = (LPNMHEADER) lParam;

Parameters

lParam

A pointer to an NMHEADER structure that contains information about the header control and the item whose divider is to be dragged.

Return value

Returns FALSE to allow tracking of the divider, or TRUE to prevent tracking.

Requirements

Requirement Value
Minimum supported client
 Windows Vista [desktop apps only]
Minimum supported server
 Windows Server 2003 [desktop apps only]
Header
Commctrl.h
Unicode and ANSI names
 HDN_BEGINTRACKW (Unicode) and HDN_BEGINTRACKA (ANSI)