用什么方法可以判断鼠标滚轮的滚动方向？

[tangible7788]

用什么方法可以判断鼠标滚轮的滚动方向？
比如某个API

[topwork]

重载窗口的OnMouseWheel事件，中间那个参数zDelta是正的就是向前滚，是负的说明向后滚，一般来说是120和-120

[dzqsuper]

zDelta

Indicates distance rotated. The zDelta value is expressed in multiples or divisions of WHEEL_DELTA, which is 120. A value less than zero indicates rotating back (toward the user) while a value greater than zero indicates rotating forward (away from the user). The user can reverse this response by changing the Wheel setting in the mouse software. See the Remarks for more information about this parameter.

[tangible7788]

我想在底层获得滚轮滚动的方向，不晓得改如何做？

[chocobo]

DirectInput 中 DirectMouse 可以拿到，不过要求自己在屏幕上画出鼠标。

[COOL099]

WM_MOUSEWHEEL
The WM_MOUSEWHEEL message is sent to the focus window when the mouse wheel is rotated. The DefWindowProc function propagates the message to the window's parent. There should be no internal forwarding of the message, since DefWindowProc propagates it up the parent chain until it finds a window that processes it.

WM_MOUSEWHEEL
fwKeys = LOWORD(wParam); // key flags
zDelta = (short) HIWORD(wParam); // wheel rotation
xPos = (short) LOWORD(lParam); // horizontal position of pointer
yPos = (short) HIWORD(lParam); // vertical position of pointer

zDelta
The value of the high-order word of wParam. Indicates the distance that the wheel is rotated, expressed in multiples or divisions of WHEEL_DELTA, which is 120. A positive value indicates that the wheel was rotated forward, away from the user; a negative value indicates that the wheel was rotated backward, toward the user.

[kingofvc]

LPARAM old;
OnRegisteredMouseWheel( WPARAM wParam, LPARAM lParam );
if (old<lParam) 向下
if (old>lParam) 向上
old=lParam;