PyQt4实现USB设备插入到弹出的检测(Windows)

直没怎么看过 QextSerialPort 中windows下枚举串口的具体实现(原因？对win32api不了解，看不懂啊_)
经过一段时间的学习，对QextSerialPort总算理清了一些，于是，就可以用python实现枚举串口了，也可以检测串口的载入与移除了。
不过呢？除了"usb转的串口"容易被移除外，想移除串口还真不太容易。所以可能没什么实际作用。于是呢？
写到最后，还是改主意了。用它来实现USB设备的插入与移除吧.
先记录一下程序编写中遇到的困难

class DEV_BROADCAST_DEVICEINTERFACE(ctypes.Structure):
_pack_ = 1
_fields_ = [("dbcc_size",  wintypes.DWORD),
("dbcc_devicetype",  wintypes.DWORD),
("dbcc_reserved",  wintypes.DWORD),
("dbcc_classguid",  GUID),
("dbcc_name",  ctypes.c_wchar*260)]

一开始就在它上面遇到了问题，因为按照win32的头文件给结构体，dbcc_name 是长度为1的数组。

我也将其定义为长度1的数组 ctypes.c_wchar*1

然后 RegisterDeviceNotification 调用不成功，通过FormatError得到“参数错误”

解决方案，添加 _pack_ = 1后错误消失

然而到最后，仅仅这样还不行，因为无法通过 dbcc_name 得到需要的字符串(因为它长度是1) 所以最终采用的方案如上

对 PyQt4 不熟，所以想当然认为其余Qt4提供的签名应该一样了：

bool QWidget::winEvent ( MSG * message, long * result )

结果运行时老是警告：参数个数不对。
原来在PyQt4里，真正的函数签名应该是：

def winEvent(self, msg):     return False,id(msg)

注：PySide 尚未提供该方法，所以本程序无法在PySide下运行：

源代码：

#!/usr/bin/env python
# -*- coding: UTF-8 -*-
'''
Copyright (C) 2010 dbzhang800
All rights reserved.
'''

import sys
import ctypes
import ctypes.wintypes as wintypes
from PyQt4.QtCore import *
from PyQt4.QtGui import *

NULL = 0
INVALID_HANDLE_VALUE = -1
DBT_DEVTYP_DEVICEINTERFACE = 5
DEVICE_NOTIFY_WINDOW_HANDLE = 0x00000000
DBT_DEVICEREMOVECOMPLETE = 0x8004
DBT_DEVICEARRIVAL = 0x8000
WM_DEVICECHANGE = 0x0219

user32 = ctypes.windll.user32
RegisterDeviceNotification = user32.RegisterDeviceNotificationW
UnregisterDeviceNotification = user32.UnregisterDeviceNotification

class GUID(ctypes.Structure):
_pack_ = 1
_fields_ = [("Data1", ctypes.c_ulong),
("Data2", ctypes.c_ushort),
("Data3", ctypes.c_ushort),
("Data4", ctypes.c_ubyte * 8)]

class DEV_BROADCAST_DEVICEINTERFACE(ctypes.Structure):
_pack_ = 1
_fields_ = [("dbcc_size",  wintypes.DWORD),
("dbcc_devicetype",  wintypes.DWORD),
("dbcc_reserved",  wintypes.DWORD),
("dbcc_classguid",  GUID),
("dbcc_name",  ctypes.c_wchar*260)]

class DEV_BROADCAST_HDR(ctypes.Structure):
_fields_ = [("dbch_size", wintypes.DWORD),
("dbch_devicetype", wintypes.DWORD),
("dbch_reserved", wintypes.DWORD)]

GUID_DEVCLASS_PORTS = GUID(0x4D36E978, 0xE325, 0x11CE,
(ctypes.c_ubyte*8)(0xBF, 0xC1, 0x08, 0x00, 0x2B, 0xE1, 0x03, 0x18))
GUID_DEVINTERFACE_USB_DEVICE = GUID(0xA5DCBF10L, 0x6530,0x11D2,
(ctypes.c_ubyte*8)(0x90, 0x1F, 0x00,0xC0, 0x4F, 0xB9, 0x51, 0xED))

class Window(QWidget):
def __init__(self,  parent=None):
super(Window,  self).__init__(parent)
self.resize(QSize(600,  320))
self.setWindowTitle("Device Notify")
self.setupNotification()
vbox = QVBoxLayout(self)
vbox.addWidget(QLabel("Log window:",  self))
self.logEdit = QPlainTextEdit(self)
vbox.addWidget(self.logEdit)
self.setLayout(vbox)

def setupNotification(self):
dbh = DEV_BROADCAST_DEVICEINTERFACE()
dbh.dbcc_size = ctypes.sizeof(DEV_BROADCAST_DEVICEINTERFACE)
dbh.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE
dbh.dbcc_classguid = GUID_DEVINTERFACE_USB_DEVICE #GUID_DEVCLASS_PORTS
self.hNofity = RegisterDeviceNotification(int(self.winId()),
ctypes.byref(dbh),
DEVICE_NOTIFY_WINDOW_HANDLE)
if self.hNofity == NULL:
print ctypes.FormatError(), int(self.winId())
print "RegisterDeviceNotification failed"

def closeEvent(self,  evt):
if self.hNofity:
UnregisterDeviceNotification(self.hNofity)
super(Window,  self).closeEvent(evt)

def winEvent(self, message):
if message.message == WM_DEVICECHANGE:
self.onDeviceChanged(message.wParam, message.lParam)
return True, id(message)
return False, id(message)

def onDeviceChanged(self, wParam, lParam):
if DBT_DEVICEARRIVAL == wParam:
self.logEdit.appendHtml("<font color=blue>Device Arrival:</font>")
elif DBT_DEVICEREMOVECOMPLETE == wParam:
self.logEdit.appendHtml("<font color=red>Device Removed:</font>")

if (DBT_DEVICEARRIVAL == wParam or DBT_DEVICEREMOVECOMPLETE == wParam):
dbh = DEV_BROADCAST_HDR.from_address(lParam)
if dbh.dbch_devicetype == DBT_DEVTYP_DEVICEINTERFACE:
dbd = DEV_BROADCAST_DEVICEINTERFACE.from_address(lParam)
self.logEdit.appendPlainText(dbd.dbcc_name)

if __name__ == '__main__':
app = QApplication(sys.argv)
w = Window()
w.show()
sys.exit(app.exec_())