如何在 Windows 10 (C++) 中生成全局滚动事件并禁用鼠标移动？

Question

I'm writing a program to implement chiral scrolling on a touchpad. I have the code to read the raw touchpad data, and I have a rough idea of how I want to implement the gesture. My question is how to implement the scrolling behavior. These are my requirements:

1. My program needs to be able to generate scrolling events, as if by the default touchpad gesture or the mouse scroll wheel. This should effect any program that is running, just like real mouse or touchpad scrolling. Preferably, scrolling should be smooth as well (not in large ticks).
2. While the scrolling gesture is in effect, normal mouse movement should be disabled. This is important because it will ensure that the UI element that is being scrolled will not change during scrolling.
3. Other built-in touchpad gestures should not be effected.

What are my options here?
Are there any libraries that can help?
Does this need to be implemented as some kind of driver?

I have thought of and looked into a few possible solutions, but none of them seem complete:

• There might be some sort of programmatic virtual mouse library, if so I could use this to generate scroll wheel events, but I haven't found such a library yet, and I'm not sure if it can achieve #2.
• I've read a little about Windows hooks, but it looks like that can only modify existing mouse events, which would not work here.
• I've also read a little about the SentInput function, but it also doesn't sound like it could achieve #2, and I'm not sure if it can effect all other programs.

Answer 1

I think hook and SendInput can meet your needs.

Here is a quick gif demo.

Run the code,

1. Press "L" key => install mouse hook(start)
2. Press left mouse button => Start scrolling
3. Press right mouse button => Stop scrolling
4. Press "P" key => uninstall mouse hook(end)

After the hook is installed, the mouse cannot be moved. Press the left mouse button and the mouse will scroll automatically. Press the right mouse button to stop scrolling. After pressing the P key to uninstall the hook, everything will be back to normal.

When the mouse is automatically scrolling, I can still manually scroll the mouse wheel.

Code Sample: (The code is rough, for reference only)

#include <Windows.h>
#include <iostream>
#include <thread>

using namespace std;

UINT ScrollMouse(int scroll);
void SetHook();
LRESULT __stdcall MouseHookCallback(int, WPARAM, LPARAM);

HHOOK MouseHook;
BOOL flag = 0;

void fun1()
{
    while (1)
    {
        if (GetAsyncKeyState(0x50) & 0x0001)
        {
            UnhookWindowsHookEx(MouseHook);
        }
    }
}

void fun2()
{
    while (1)
    {
        if (flag)
        {
            ScrollMouse(50);
            Sleep(100);
        }
    }
}

int fun3()
{
    while (1)
    {
        if (GetAsyncKeyState(0x4C) & 0x0001)
        {
            SetHook();
            MSG msg;

            while(GetMessage(&msg, NULL, 0, 0))
            {
                TranslateMessage(&msg);
                DispatchMessage(&msg);
            }
            return msg.wParam;
        }       
    }   
}

UINT ScrollMouse(int scroll)
{
    INPUT input;
    POINT pos;
    GetCursorPos(&pos);

    input.type = INPUT_MOUSE;
    input.mi.dwFlags = MOUSEEVENTF_WHEEL;
    input.mi.time = NULL; //Windows will do the timestamp
    input.mi.mouseData = (DWORD)scroll; //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.
    input.mi.dx = pos.x;
    input.mi.dy = pos.y;
    input.mi.dwExtraInfo = GetMessageExtraInfo();

    return SendInput(1, &input, sizeof(INPUT));
}

LRESULT __stdcall MouseHookCallback(int nCode, WPARAM wParam, LPARAM lParam)
{
    if (nCode >= 0)
    {
        switch (wParam)
        {
        case WM_MOUSEMOVE:
        {           
            return 1;         
        }
        case WM_LBUTTONDOWN:
        {
            flag = 1;            
        }
        break;
        case WM_RBUTTONDOWN:
        {
            flag = 0;
        }
        break;
        }
    }
    return CallNextHookEx(MouseHook, nCode, wParam, lParam);
}

void SetHook()
{
    if (!(MouseHook = SetWindowsHookEx(WH_MOUSE_LL, MouseHookCallback, NULL, 0)))
    {
        cout << "Failed to install MouseHook hook!" << endl;
    }
}

int main()
{
    thread t1(fun1);
    thread t2(fun2);   
    thread t3(fun3);  
    t3.join();

    return 0;
}