Full screen.. graphics problem

# Fullscreen++ v1.0 by Zeus81
# Description :
#   New fullscreen mode that is more smart and make a better use of the screen surface (no black frame).
#   Alt+Enter still use the old fullscreen mode, to use the new one press F5.
#   To make the game start automatically in fullscreen mode, see line 12.
# Functions :
#   Graphics.fullscreen?       : return the fullscreen state.
#   Graphics.fullscreen_mode   : go to fullscreen mode.
#   Graphics.windowed_mode     : go to windowed mode.
#   Graphics.toggle_fullscreen : toggle from one to the other.
class << Graphics
  fullscreen_start = false

  FindWindow       = Win32API.new('user32', 'FindWindow'      , 'pp'          , 'l')
  CreateWindowEx   = Win32API.new('user32', 'CreateWindowEx'  , 'lpplllllllll', 'l')
  UpdateWindow     = Win32API.new('user32', 'UpdateWindow'    , 'l'           , 'l')
  ShowWindow       = Win32API.new('user32', 'ShowWindow'      , 'll'          , 'l')
  SetWindowLong    = Win32API.new('user32', 'SetWindowLong'   , 'lll'         , 'l')
  SetWindowPos     = Win32API.new('user32', 'SetWindowPos'    , 'lllllll'     , 'l')
  GetSystemMetrics = Win32API.new('user32', 'GetSystemMetrics', 'l'           , 'l')
  GetDC            = Win32API.new('user32', 'GetDC'           , 'l'           , 'l')
  FillRect         = Win32API.new('user32', 'FillRect'        , 'lpl'         , 'l')
  CreateSolidBrush = Win32API.new('gdi32' , 'CreateSolidBrush', 'l'           , 'l')
  if first_start = !method_defined?(:zeus81_fullscreen_update)
    @@MainWindow = FindWindow.call('RGSS Player', 0)
    @@BackWindow = CreateWindowEx.call(0x08000008, 'Static', '', 0x80000000, 0, 0, 0, 0, 0, 0, 0, 0)
    @@FillRectArgs = [GetDC.call(@@BackWindow), [0,0,0xFFFF,0xFFFF].pack('L4'), CreateSolidBrush.call(0)]
    @@fullscreen = false
    alias zeus81_fullscreen_resize_screen resize_screen
    alias zeus81_fullscreen_update        update
  end
  def update
    zeus81_fullscreen_update
    toggle_fullscreen if Input.trigger?(Input::F5)
  end
  def resize_screen(width, height)
    zeus81_fullscreen_resize_screen(width, height)
    fullscreen_mode if fullscreen?
  end
  def fullscreen?() @@fullscreen end
  def toggle_fullscreen() fullscreen? ? windowed_mode : fullscreen_mode end
  def fullscreen_mode
    client_w, client_h = GetSystemMetrics.call(0), GetSystemMetrics.call(1)
    w, h = client_w, client_w * height / width
    h, w = client_h, client_h * width / height if h > client_h
    ShowWindow.call(@@BackWindow, 3)
    UpdateWindow.call(@@BackWindow)
    FillRect.call(*@@FillRectArgs)
    SetWindowPos.call(@@MainWindow, -1, (client_w-w)/2, (client_h-h)/2, w, h, 0)
    SetWindowLong.call(@@MainWindow, -16, 0x14000000)
    @@fullscreen = true
  end
  def windowed_mode
    client_w, client_h = GetSystemMetrics.call(0), GetSystemMetrics.call(1)
    w = width + GetSystemMetrics.call(5)*2 + 4
    h = height + GetSystemMetrics.call(6)*2 + 4 + GetSystemMetrics.call(4)
    ShowWindow.call(@@BackWindow, 0)
    SetWindowPos.call(@@MainWindow, -2, (client_w-w)/2, (client_h-h)/2, w, h, 0)
    SetWindowLong.call(@@MainWindow, -16, 0x14CA0000)
    @@fullscreen = false
  end
  Graphics.fullscreen_mode if first_start and fullscreen_start
end