Manually changing the mouse sensitivity with windows hooks

William Hemsworth 1 3K Views

Heres a code that allows you to manually change the sensitivity of the mouse by using windows hooks.

/*
 *  Make sure project type is windows application
 */

#define _WIN32_WINNT 0x0500
#include<windows.h>
#include<cmath>

float sensitivity = 0.1f;


LRESULT CALLBACK mouseHookProc(int nCode, WPARAM wParam, LPARAM lParam) {

   // Let windows handle mouse clicks
   if (wParam != WM_MOUSEMOVE) {
      return CallNextHookEx(NULL, nCode, wParam, lParam);
   }

   // Get event information
   PMSLLHOOKSTRUCT p = reinterpret_cast<PMSLLHOOKSTRUCT>( lParam );

   // Old mouse location
   static float ox = static_cast<float>( p->pt.x );
   static float oy = static_cast<float>( p->pt.y );

   // Mouse location without sensitivity changed
   float x = static_cast<float>( p->pt.x );
   float y = static_cast<float>( p->pt.y );
   
   // New mouse location
   float nx = ox + (x - ox) * sensitivity;
   float ny = oy + (y - oy) * sensitivity;

   // Set cursor position
   SetCursorPos(
      static_cast<int>( nx ),
      static_cast<int>( ny )
   );

   // Set old location ready for next time
   ox = nx;
   oy = ny;

   return 1;
}

int WINAPI WinMain(HINSTANCE hInstance,
                   HINSTANCE hPrevInstance,
                   LPSTR lpCmdLine,
                   int nShowCmd) {

   // Set mouse hook
   HHOOK mouseHook = SetWindowsHookEx(
                  WH_MOUSE_LL,      /* Type of hook */
                  mouseHookProc,    /* Hook process */
                  hInstance,        /* Instance */
                  NULL);

   // Wait for user to exit
   MessageBox(NULL, "Press OK to close.", "", MB_OK);
   return 0;
}

Dani AI

Generated

Nice snippet, @William Hemsworth. Two quick hardening tips for anyone tweaking sensitivity via WH_MOUSE_LL:

  • Ignore your own injected moves to prevent feedback loops, and keep the hook fast. A minimal pattern is below. It scales the delta, posts a synthetic move, swallows the original, and skips any injected events to avoid jitter.
LRESULT CALLBACK mouseHookProc(int code, WPARAM wp, LPARAM lp) {
    if (code != HC_ACTION) return CallNextHookEx(NULL, code, wp, lp);
    const MSLLHOOKSTRUCT* m = reinterpret_cast<const MSLLHOOKSTRUCT*>(lp);
    if (m->flags & LLMHF_INJECTED) return CallNextHookEx(NULL, code, wp, lp);

    static POINT last = m->pt;
    if (wp == WM_MOUSEMOVE) {
        const double scale = 1.5;              // your sensitivity
        double dx = (m->pt.x - last.x) * (scale - 1.0);
        double dy = (m->pt.y - last.y) * (scale - 1.0);
        if (dx || dy) {
            INPUT in{}; in.type = INPUT_MOUSE;
            in.mi.dx = (LONG)lround(dx); in.mi.dy = (LONG)lround(dy);
            in.mi.dwFlags = MOUSEEVENTF_MOVE;
            SendInput(1, &in, sizeof(in));
            last = m->pt;
            return 1; // consume original
        }
        last = m->pt;
    }
    return CallNextHookEx(NULL, code, wp, lp);
}

The hook runs on the thread that installed it, so you need a message loop and you should return quickly or Windows may remove the hook (LowLevelHooksTimeout). Low-level hooks are global and can be called alongside 32-bit/64-bit hooks in the chain. (learn.microsoft.com)

Build notes:

  • , your C2664 is Unicode vs ANSI. Either call MessageBoxW with wide literals (L"...") or wrap strings in TEXT() instead of disabling Unicode. The API aliases map MessageBox to A/W based on UNICODE, which is why the mismatch occurs. (learn.microsoft.com)
  • , rather than casting to HOOKPROC, ensure the exact signature: LRESULT CALLBACK mouseHookProc(int, WPARAM, LPARAM); This matches HOOKPROC across compilers. Also remember WH_MOUSE_LL callbacks are not injected into target processes. (learn.microsoft.com)

If you just want system-wide pointer speed, prefer SystemParametersInfo(SPI_SETMOUSESPEED) instead of a hook; and when synthesizing movement, use SendInput (supersedes mouse_event). (learn.microsoft.com)

Member Avatar for William Hemsworth
William Hemsworth 1,339 Posting Virtuoso

Small bug when using a higher sensitivity, to fix it, add this function at the beginning. (line 10)

int round(float a) {
   return int(a + 0.5f);
}

and on line 36 & 37, change them to this.

round( nx ),
round( ny )

Now the mouse doesn't jump about unexpectedly.

Member Avatar for mksafi
mksafi 0 Newbie Poster

This doesn't even compile in Visual C++ Express.

1>c:\path\visual studio 2008\projects\two\two\two.cpp(63) : error C2664: 'MessageBoxW' : cannot convert parameter 2 from 'const char [19]' to 'LPCWSTR'

Member Avatar for William Hemsworth
William Hemsworth 1,339 Posting Virtuoso

That's because you've not set up your compiler properly, don't blame the code. Turn off UNICODE then try compiling again.

Member Avatar for CppBuilder2006
CppBuilder2006 -5 Junior Poster

Thanks. I needed such a program!
but it has an error in my Borland compiler. to fix the error instead of:

HHOOK mouseHook = SetWindowsHookEx(
                  WH_MOUSE_LL,      /* Type of hook */
                 mouseHookProc,    /* Hook process */
                  hInstance,        /* Instance */
				  NULL);

write:

HHOOK mouseHook = SetWindowsHookEx(
                  WH_MOUSE_LL,      /* Type of hook */
                  (HOOKPROC)mouseHookProc,    /* Hook process */
                  hInstance,        /* Instance */
				  NULL);

And do you have a program for hooking keyboard? or the shell?

Member Avatar for Freaky_Chris
Freaky_Chris 299 Master Poster

@CppBuilder

I'd recommend getting an upto date compiler. You might find that they work properly then ;)

Member Avatar for CppBuilder2006
CppBuilder2006 -5 Junior Poster

I'd recommend getting an upto date compiler

I have a 2006 version! ;)

Member Avatar for William Hemsworth
William Hemsworth 1,339 Posting Virtuoso

And do you have a program for hooking keyboard? or the shell?

Look at my other snippets, indeed I do ;]

I dont mind any changes people make to the code if it makes it compatiable with a wider range of compilers.

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