module Mouse
  
  Point = Struct.new(:x, :y) if !const_defined?(:Point)
  
  Message = Struct.new(:message, :wparam, :lparam, :pt) if !const_defined?(:Message)
  
  Param = Struct.new(:x, :y, :scroll) if !const_defined?(:Param)
  
  Scroll = 0x0000020A if !const_defined?(:Scroll)
  
  Get_Message = Win32API.new('user32', 'GetMessage', 'plll', 'l') if !const_defined?(:Get_Message)
  
  module_function
  
  def hiword(dword)
    return((dword & 0xffff0000) >> 16) & 0x0000ffff
  end
  
  def loword(dword)
    return dword & 0x0000ffff
  end
    
  def word2signed_short(value)
    return value if (value & 0x8000) == 0
    return -1 *((~value & 0x7fff) + 1)
  end
  
  def unpack_dword(buffer, offset = 0)
    bitso = buffer.bytes.to_a
    ret = bitso[offset + 0] & 0x000000ff
    ret |=(bitso[offset + 1] << (8 * 1)) & 0x0000ff00
    ret |=(bitso[offset + 2] << (8 * 2)) & 0x00ff0000
    ret |=(bitso[offset + 3] << (8 * 3)) & 0xff000000
    return ret
  end
  
  def unpack_msg(buffer)
    msg = Message.new
    msg.pt = Point.new
    msg.message = unpack_dword(buffer,4 * 1)
    msg.wparam = unpack_dword(buffer, 4 * 2)
    msg.lparam = unpack_dword(buffer,4 * 3)
    msg.pt.x = unpack_dword(buffer, 4 * 5)
    msg.pt.y = unpack_dword(buffer, 4 * 6)
    return msg
  end
  
  def wmcallback(msg)
    return unless msg.message == Scroll
    param = Param.new
    param.x = word2signed_short(loword(msg.lparam))
    param.y = word2signed_short(hiword(msg.lparam))
    param.scroll = word2signed_short(hiword(msg.wparam))
    return [param.x, param.y, param.scroll]
  end
  
  def scroll
    msg = "\0" * 32
    Get_Message.call(msg, @handle || @hwnd || 0, 0, 0)
    r = wmcallback(unpack_msg(msg))
    return r if !r.nil?
  end
end

class Window_Selectable
  
  alias jet1085_update update
  def update(*args, &block)
    update_scroll if self.active && self.visible
    jet1085_update(*args, &block)
  end
  
  def update_scroll
    if true#Jet::MouseSystem::USE_WHEEL_DETECTION
      f = Mouse.scroll
      if !f.nil?
        if f[2] < 0
          if contents.height > self.height && self.oy - contents.height < -self.height + 32
            self.top_row = self.top_row + 1
          end
        else
          self.top_row = self.top_row - 1 if contents.height > self.height
        end
      end
    end
  end
end