RGSS mouse wheel event through dll

mouse-wheel.c

// gcc -shared -Os -s -o a.dll -m32 mouse-wheel.c
#define WIN32_LEAN_AND_MEAN
#include <Windows.h>

HHOOK hook;
DWORD delta;

LRESULT CALLBACK LowLevelMouseProc(_In_ int nCode, _In_ WPARAM wParam, _In_ LPARAM lParam) {
    if (wParam == WM_MOUSEWHEEL) {
        MSLLHOOKSTRUCT *mouse = (MSLLHOOKSTRUCT *)lParam;
        delta += GET_WHEEL_DELTA_WPARAM(mouse->mouseData);
    }
    return CallNextHookEx(hook, nCode, wParam, lParam);
}

BOOL install() {
    hook = SetWindowsHookExA(WH_MOUSE_LL, LowLevelMouseProc, GetModuleHandleA(NULL), 0);
    return hook != NULL;
}

BOOL uninstall() {
    HHOOK hook_ = hook;
    hook = NULL;
    return UnhookWindowsHookEx(hook_);
}

DWORD getdelta() {
    DWORD delta_ = delta;
    delta = 0;
    return delta_;
}

mouse-wheel.rb

#encoding: utf-8
module MouseWheel
  def self.install
    if Win32API.new('a.dll', 'install', 'v', 'L').call.zero?
      puts "MouseWheel.install failed!"
    end
  end

  def self.uninstall
    Win32API.new('a.dll', 'uninstall', 'v', 'L').call
  end

  GetDelta = Win32API.new('a.dll', 'getdelta', 'v', 'i')
  def self.update
    @delta = GetDelta.call
  end

  def self.delta
    @delta
  end

  install
end

class << Input
  alias _update_mousewheel update
  def update
    _update_mousewheel
    MouseWheel.update
    unless MouseWheel.delta.zero?
      p MouseWheel.delta
    end
  end
end