Moving the mouse without acceleration in C++ using mouse_event

Question

Right now when I try a loop that contains something like:

mouse_event(MOUSEEVENTF_MOVE,dx,dy,0,0);

The mouse tends to move more than (dx,dy). Researching this online, I think it's because of the acceleration applied by the operating system. How can I move the mouse an absolute amount?

MOUSEEVENTF_ABSOLUTE seems to maybe be what I'm looking for, but I can't see how to use it.

I've tried:

mouse_event(MOUSEEVENTF_ABSOLUTE || MOUSEEVENTF_MOVE,dx,dy,0,0);

but that doesn't work either. I'd prefer to use mouse_event rather than SetCursorPos or other methods, what should I do? Thanks.

Answer 1

The coordinates are not pixel coordinates and must be normalized.

#include <Windows.h>
#include <tchar.h>

int WINAPI _tWinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow ) {
  INPUT input = {0};

  int screenX = GetSystemMetrics( SM_CXVIRTUALSCREEN );
  int screenY = GetSystemMetrics( SM_CYVIRTUALSCREEN );

  for( unsigned int i = 0; i < 10; i++ ) {
    input.mi.dx = i*10 * ( 65535/screenX );
    input.mi.dy = i*10 * ( 65535/screenY );
    input.mi.dwFlags = MOUSEEVENTF_ABSOLUTE | MOUSEEVENTF_VIRTUALDESK | MOUSEEVENTF_MOVE;
    input.type = INPUT_MOUSE;

    SendInput( 1, &input, sizeof INPUT );
    Sleep( 1000 );
  }

  return ERROR_SUCCESS;
}

I have used SendInput() here instead of mouse_event() because the latter has been superseded according to the docs. If you do want to convert it back, the parameters should be much the same.

Answer 2

from winuser.h

#define MOUSEEVENTF_MOVE        0x0001
#define MOUSEEVENTF_ABSOLUTE    0x8000

MOUSEEVENTF_MOVE || MOUSEEVENTF_ABSOLUTE is the same thing as 0x0001 || 0x8001 which evaluates to true, which just happens to be 1!

Try it again with MOUSEEVENTF_ABSOLUTE | MOUSEEVENTF_MOVE and it will probably work.

Edit: after looking at the docs a bit, it appears that either you want MOUSEEVENTF_ABSOLUTE all by itself. or you need to account for the fact that the range of values it is looking for is 0-65535 scaled over the entire display.

If MOUSEEVENTF_ABSOLUTE value is specified, dx and dy contain normalized absolute coordinates between 0 and 65,535. The event procedure maps these coordinates onto the display surface. Coordinate (0,0) maps onto the upper-left corner of the display surface, (65535,65535) maps onto the lower-right corner.