c++ - 在鼠标 Hook 中，滚轮增量始终为 0

Question

#include <iostream>
#include <windows.h>

LRESULT CALLBACK mouseProc(int nCode, WPARAM wParam, LPARAM lParam){
  if(wParam == WM_MOUSEWHEEL){
    std::cout << "wheel: " << GET_WHEEL_DELTA_WPARAM(wParam) << std::endl;
  }else{
    MOUSEHOOKSTRUCT* mouselparam = (MOUSEHOOKSTRUCT*)lParam;
    std::cout << "etc: " << wParam << " - " << mouselparam->pt.x << "x" << mouselparam->pt.y << std::endl;
  }
  return CallNextHookEx(NULL, nCode, wParam, lParam);
}

int main(int argc, char *argv[]) {

    HHOOK hhkLowLevelMouse = SetWindowsHookEx(WH_MOUSE_LL, mouseProc, 0, 0);

    MSG msg;
    while (!GetMessage(&msg, NULL, NULL, NULL)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    UnhookWindowsHookEx(hhkLowLevelMouse);

    return 0;
}

这是完整的代码。

“etc:”完全按照我的预期工作。

“wheel:”始终输出 0。

我错过了什么吗？

使用 HIWORD 而不是 GET_WHEEL_DELTA_WPARAM 会得到相同的结果。

Answer 1

GET_WHEEL_DELTA_WPARAM() 仅适用于真实 WM_MOUSEWHEEL 窗口消息的 wParam，而不是一个 WH_MOUSE_LL 钩子(Hook)。

在钩子(Hook)中，wParam本身只是消息标识符，仅此而已。所有鼠标详细信息都存储在 lParam 指向的 MSLLHOOKSTRUCT 结构中。您试图查看除 WM_MOUSEWHEEL 之外的所有鼠标消息，但您查看的是错误的结构(MOUSEHOOKSTRUCT 由 使用>WH_MOUSE，而不是WH_MOUSE_LL)。

根据 LowLevelMouseProc callback function文档:

• wParam [in]
  Type: WPARAM

  The identifier of the mouse message. This parameter can be one of the following messages: WM_LBUTTONDOWN, WM_LBUTTONUP, WM_MOUSEMOVE, WM_MOUSEWHEEL, WM_MOUSEHWHEEL, WM_RBUTTONDOWN, or WM_RBUTTONUP.

• lParam [in]
  Type: LPARAM

  A pointer to an MSLLHOOKSTRUCT structure.

还有MSLLHOOKSTRUCT structure文档:

mouseData
Type: DWORD

If the message is WM_MOUSEWHEEL, the high-order word of this member is the wheel delta. The low-order word is reserved. 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. One wheel click is defined as WHEEL_DELTA, which is 120.

试试这个:

LRESULT CALLBACK mouseProc(int nCode, WPARAM wParam, LPARAM lParam){
    if (nCode == HC_ACTION) {
        MSLLHOOKSTRUCT* mouselparam = (MSLLHOOKSTRUCT*)lParam;
        if (wParam == WM_MOUSEWHEEL) {
            short delta = HIWORD(mouselparam->mouseData); 
            // alternatively, GET_WHEEL_DELTA_WPARAM() would also work here:
            // short delta = GET_WHEEL_DELTA_WPARAM(mouselparam->mouseData);
            std::cout << "wheel: " << delta << std::endl;
        }else{
            std::cout << "etc: " << wParam << " - " << mouselparam->pt.x << "x" << mouselparam->pt.y << std::endl;
        }
    }
    return CallNextHookEx(NULL, nCode, wParam, lParam);
}