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Overview |
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Group |
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Quick Info
Windows NT
| Yes
| Win95
| Yes
| Win32s
| Yes
| Import Library
| -
| Header File
| winuser.h
| Unicode
| No
| Platform Notes
| None
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WM_HSCROLL
The WM_HSCROLL message is sent to a window when a scroll event occurs in the
window's standard horizontal scroll bar. This message is also sent to the owner
of a horizontal scroll bar control when a scroll event occurs in the control.
WM_HSCROLL
nScrollCode = (int) LOWORD(wParam); // scroll bar value
nPos = (short int) HIWORD(wParam); // scroll box position
hwndScrollBar = (HWND) lParam; // handle of scroll bar
Parameters
nScrollCode
Value of the low-order word of wParam. 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_LINELEFT
| Scrolls left by one unit.
| SB_LINERIGHT
| Scrolls right by one unit.
| SB_PAGELEFT
| Scrolls left by the width of the window.
| SB_PAGERIGHT
| Scrolls right by the width of the window.
| SB_THUMBPOSITION
| Scrolls to the absolute position. The current position is specified by the nPos parameter.
| SB_THUMBTRACK
| Drags scroll box to the specified position. The current position is specified
by the nPos parameter.
| SB_TOP
| Scrolls to the upper left.
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nPos
Value of the high-order word of wParam. Specifies the current position of the scroll box if the nScrollCode parameter is SB_THUMBPOSITION or SB_THUMBTRACK; otherwise, nPos is not used.
hwndScrollBar
Value of lParam. Identifies the control if WM_HSCROLL is sent by a scroll bar control. If
WM_HSCROLL is sent by a window's standard scroll bar, hwndScrollBar is not used.
Return Values
If an application processes this message, it should return zero.
Remarks
The SB_THUMBTRACK notification message 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_HSCROLL message carries only 16 bits of scroll box position
data. Thus, applications that rely solely on WM_HSCROLL (and WM_VSCROLL) for
scroll position data have a practical maximum position value of 65,535.
However, because the SetScrollPos, SetScrollRange, 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 GetScrollPos for a description of the technique and its limits.
See Also
GetScrollPos, GetScrollRange, SetScrollPos, SetScrollRange, WM_VSCROLL
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