쉬운 것은 올바르다

case WM_MOUSEWHEEL:

POINT window_position_in_screen = {};

ClientToScreen(window_handle, &window_position_in_screen);

UINT wheel_scroll_line;

SystemParametersInfo(SPI_GETWHEELSCROLLLINES, 0, &wheel_scroll_line, 0);

POINT cursor_position_in_client =

{

GET_X_LPARAM(l_parameter) - window_position_in_screen.x,

GET_Y_LPARAM(l_parameter) - window_position_in_screen.y

};

int wheel_delta = GET_WHEEL_DELTA_WPARAM(w_parameter) / WHEEL_DELTA * wheel_scroll_line;

...

break;