WM_VSCROLL message
Applies to: desktop apps only
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.
WM_VSCROLL
WPARAM wParam
LPARAM lParam;
Parameters
- wParam
-
The HIWORD specifies the current position of the scroll box if the LOWORD is SB_THUMBPOSITION or SB_THUMBTRACK; otherwise, this word is not used.
The LOWORD specifies a scroll bar value that indicates the user's scrolling request. This parameter can be one of the following values.
Value Meaning - 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 HIWORD 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 HIWORD 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.
Remarks
The SB_THUMBTRACK request code is typically used by applications that provide feedback as the user drags the scroll box.
If an application scrolls the content of the window, it must also reset the position of the scroll box by using the SetScrollPos function.
Note that the WM_VSCROLL message carries only 16 bits of scroll box position data. Thus, applications that rely solely on WM_VSCROLL (and WM_HSCROLL) for scroll position data have a practical maximum position value of 65,535.
However, because the SetScrollInfo, SetScrollPos, SetScrollRange, GetScrollInfo, GetScrollPos, and GetScrollRange functions support 32-bit scroll bar position data, there is a way to circumvent the 16-bit barrier of the WM_HSCROLL and WM_VSCROLL messages. See GetScrollInfo for a description of the technique.
Requirements
|
Minimum supported client | Windows 2000 Professional |
|---|---|
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Minimum supported server | Windows 2000 Server |
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Header |
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See also
- Reference
- GetScrollInfo
- GetScrollPos
- GetScrollRange
- SetScrollInfo
- SetScrollPos
- SetScrollRange
- WM_HSCROLL
- WM_VSCROLL (Trackbar)
Send comments about this topic to Microsoft
Build date: 3/6/2012
- lParam
-
If the message is sent by a scroll bar, then this parameter is the handle to the scroll bar control. If the message is not sent by a scroll bar, this parameter is NULL.
WRONG, in case of a scroll event sent by a trackbar control, lParam holds the handle of that control.
Example :
if((HWND)lParam == GetDlgItem(hWnd, ID_TRACKBAR)){
// your code here
}
This works!
- 9/2/2011
- MikeBen86
Use LVM_SCROLL intstead !
- 9/1/2011
- ElmueSoft
http://msdn.microsoft.com/en-us/library/bb760149%28v=VS.85%29.aspx#tkb_notifications
(Thankfully they're different in name only; the numerical values are the same.)
- 1/14/2011
- stickboy
WM_VSCROLL = &H115
Public Enum WM_HSCROLL_low As Short
SB_ENDSCROLL = 8
SB_LEFT = 6
SB_RIGHT = 7
SB_LINELEFT = 0
SB_LINERIGHT = 1
SB_PAGELEFT = 2
SB_PAGERIGHT = 3
SB_THUMBPOSITION = 4
SB_THUMBTRACK = 5
End Enum
Public Enum WM_VSCROLL_low As Short
SB_BOTTOM = 7
SB_ENDSCROLL = WM_HSCROLL_low.SB_ENDSCROLL
SB_LINEDOWN = 1
SB_LINEUP = 0
SB_PAGEDOWN = 3
SB_PAGEUP = 2
SB_THUMBPOSITION = WM_HSCROLL_low.SB_THUMBPOSITION
SB_THUMBTRACK = WM_HSCROLL_low.SB_THUMBTRACK
SB_TOP = 6
End Enum
