WM_VSCROLL Notification

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The WM_VSCROLL message is sent to a window when a scroll event occurs in the window's standard vertical scroll bar. This message is also sent to the owner of a vertical scroll bar control when a scroll event occurs in the control.

A window receives this message through its WindowProc function.

 

Syntax

WM_VSCROLL
WPARAM wParam
LPARAM lParam;

Parameters

wParam

The high-order word specifies the current position of the scroll box if the low-order word is SB_THUMBPOSITION or SB_THUMBTRACK; otherwise, this word is not used.

The low-order word specifies a scroll bar value that indicates the user's scrolling request. This parameter can be one of the following values.

SB_BOTTOM

Scrolls to the lower right.

SB_ENDSCROLL

Ends scroll.

SB_LINEDOWN

Scrolls one line down.

SB_LINEUP

Scrolls one line up.

SB_PAGEDOWN

Scrolls one page down.

SB_PAGEUP

Scrolls one page up.

SB_THUMBPOSITION

The user has dragged the scroll box (thumb) and released the mouse button. The high-order word indicates the position of the scroll box at the end of the drag operation.

SB_THUMBTRACK

The user is dragging the scroll box. This message is sent repeatedly until the user releases the mouse button. The high-order word indicates the position that the scroll box has been dragged to.

SB_TOP

Scrolls to the upper left.

lParam

If the message is sent by a scroll bar, this parameter is the handle to the scroll bar control. If the message is not sent by a scroll bar, this parameter is NULL.

Return Value

If an application processes this message, it should return zero.

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    本文转自 OldHawk  博客园博客，原文链接：

http://www.cnblogs.com/taobataoma/archive/2007/05/25/759715.html

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