python wia and RegisterEvent

[gelonida]

Hi,

I'd like to register an event in order to be informed, whenever a
Windows WIA device is connected or disconnected.

In python I can use WIA devices, but I don't know how to register
events

I have existing C# code, which works and looks like.

class MgrHandlerClass
{
public void devManager_OnEvent(string eventID, string
deviceID, string itemID)
{ } // her emy handler code

public void addhandler(DeviceManager manager)
{
Console.WriteLine("adding handler!");
manager.OnEvent += new
WIA._IDeviceManagerEvents_OnEventEventHandler(
devManager_OnEvent);
}

static void Main(string[] args)
{

MgrHandlerClass mgrhndlr;
mgrhndlr = new MgrClass();
DeviceManager manager;

manager = new DeviceManagerClass();

manager.RegisterEvent(WIA.EventID.wiaEventDeviceConnected, "*");

manager.RegisterEvent(WIA.EventID.wiaEventDeviceDisconnected, "*");
mgrhndlr.addhandler(manager);
// wait for callbacks or do other stuff
}


Now in python I'm stuck

import win32com.client
import wia_defs # created with makepy.py
manager = win32com.client.Dispatch("WIA.DeviceManager")
mgrhndlr = MgrClass()
manager.RegisterEvent(EventID=constants.wiaEventDeviceConnected,DeviceID=u'*')
manager.RegisterEvent(EventID=constants.wiaEventDeviceDisconnected,DeviceID=u'*')
mgrhndlr.addhandler(manager)


class MgrHandlerClass:
def OnEvent(self, EventID=defaultNamedNotOptArg,
DeviceID=defaultNamedNotOptArg, ItemID=defaultNamedNotOptArg):
print "Called back with (%s) (%s) (%s)" %
(EventID,DeviceID,ItemID)

def addhandler(self,manager):
# here I'm stuck :-(
# the following line doesn't work as it seems, that manager
does not have attr
# onevent

manager.OnEvent.append( WIA._IDeviceManagerEvents_OnEventEventHandler(self.OnEvent) )



The autogenerated file contains:
class IDeviceManager(DispatchBaseClass):
CLSID = IID('{73856D9A-2720-487A-A584-21D5774E9D0F}')
coclass_clsid = IID('{E1C5D730-7E97-4D8A-9E42-BBAE87C2059F}')

def RegisterEvent(self, EventID=defaultNamedNotOptArg,
DeviceID=u'*'):
"""Registers the specified EventID for the specified DeviceID. If
DeviceID is "*" then OnEvent will be called whenever the event
specified occurs for any device. Otherwise, OnEvent will only be
called if the event specified occurs on the device specified."""
return self._ApplyTypes_(2, 1, (24, 32), ((8, 1), (8, 49)),
u'RegisterEvent', None,EventID
, DeviceID)



but I do not know where to place (how to create the function)
OnEvent()


Any help would be appreciated.

 

[Mark Hammond]

Hi,

I'd like to register an event in order to be informed, whenever a
Windows WIA device is connected or disconnected.

In python I can use WIA devices, but I don't know how to register
events

I have existing C# code, which works and looks like.

class MgrHandlerClass
{
public void devManager_OnEvent(string eventID, string
deviceID, string itemID)
{ } // her emy handler code

public void addhandler(DeviceManager manager)
{
Console.WriteLine("adding handler!");
manager.OnEvent += new
WIA._IDeviceManagerEvents_OnEventEventHandler(
devManager_OnEvent);
}

static void Main(string[] args)
{

MgrHandlerClass mgrhndlr;
mgrhndlr = new MgrClass();
DeviceManager manager;

manager = new DeviceManagerClass();

manager.RegisterEvent(WIA.EventID.wiaEventDeviceConnected, "*");

manager.RegisterEvent(WIA.EventID.wiaEventDeviceDisconnected, "*");
mgrhndlr.addhandler(manager);
// wait for callbacks or do other stuff
}


Now in python I'm stuck

import win32com.client
import wia_defs # created with makepy.py
manager = win32com.client.Dispatch("WIA.DeviceManager")
mgrhndlr = MgrClass()
manager.RegisterEvent(EventID=constants.wiaEventDeviceConnected,DeviceID=u'*')
manager.RegisterEvent(EventID=constants.wiaEventDeviceDisconnected,DeviceID=u'*')
mgrhndlr.addhandler(manager)


class MgrHandlerClass:
def OnEvent(self, EventID=defaultNamedNotOptArg,
DeviceID=defaultNamedNotOptArg, ItemID=defaultNamedNotOptArg):
print "Called back with (%s) (%s) (%s)" %
(EventID,DeviceID,ItemID)

def addhandler(self,manager):
# here I'm stuck :-(
# the following line doesn't work as it seems, that manager
does not have attr
# onevent

manager.OnEvent.append( WIA._IDeviceManagerEvents_OnEventEventHandler(self.OnEvent) )

The model used by pywin32 is more "low level" than that exposed by some
of the MS languages. You probably need something closer to:


class MgrHandlerClass:
def OnEvent(self, EventID=defaultNamedNotOptArg, ...):
print "Called back with ..."


manager = win32com.client.DispatchWithEvents("WIA.DeviceManager",
MgrHandlerClass)
manager.RegisterEvent(EventID=constants.wiaEventDeviceConnected,DeviceID=u'*')
manager.RegisterEvent(EventID=constants.wiaEventDeviceDisconnected,DeviceID=u'*')

And magically your OnEvent should be called when the event happens.
Googling for 'DispatchWithEvents' might find some good hits for more
information.

HTH,

Mark

 

[gelonida]

Hi Mark,

On 16/04/2010 7:15 AM,gelonidawrote:

The model used by pywin32 is more "low level" than that exposed by some
of the MS languages.  You probably need something closer to:

  class MgrHandlerClass:
       def OnEvent(self, EventID=defaultNamedNotOptArg, ...):
           print "Called back with ..."

manager = win32com.client.DispatchWithEvents("WIA.DeviceManager",
MgrHandlerClass)
manager.RegisterEvent(EventID=constants.wiaEventDeviceConnected,DeviceID=u'*')
manager.RegisterEvent(EventID=constants.wiaEventDeviceDisconnected,DeviceID=u'*')

And magically your OnEvent should be called when the event happens.
Googling for 'DispatchWithEvents' might find some good hits for more
information.

I'm still stuck. Please look at following code snippet.
I tried to reduce it to the absolute minimum.
running under WinXP and python 2.6.4


import win32com.client,pythoncom,time

defaultNamedNotOptArg=pythoncom.Empty
wiaEventDeviceConnected =u'{A28BBADE-64B6-11D2-
A231-00C04FA31809}' # from enum EventID

class MgrHandlerClass: # doesn't work either
def OnEvent(self, EventID=defaultNamedNotOptArg,
DeviceID=defaultNamedNotOptArg, ItemID=defaultNamedNotOptArg):
print "Called back with ..."

manager = win32com.client.DispatchWithEvents("WIA.DeviceManager",
MgrHandlerClass)
manager.RegisterEvent(EventID=wiaEventDeviceConnected,DeviceID=u'*')

while True:
print "sleep"
time.sleep(10)

When I plug / unplug a USB WIA device nothing shows up.
My C# implementation prints messages on wiaEventDeviceConnected /
wiaEventDeviceDisconnected events if I register them.

What am I missing?

Should MgrHandlerClass inherit from some kind of default class?

 

[Roger Upole]

gelonida wrote:
....

while True:
print "sleep"
time.sleep(10)

When I plug / unplug a USB WIA device nothing shows up.
My C# implementation prints messages on wiaEventDeviceConnected /
wiaEventDeviceDisconnected events if I register them.

What am I missing?

You need to be processing messages to receive COM events.
Try replacing your sleep loop with pythoncom.PumpMessages().

Roger

 

[News123]

Hi Roger,

gelonida wrote:
...

You need to be processing messages to receive COM events.
Try replacing your sleep loop with pythoncom.PumpMessages().

Thanks a lot

Indeed the only thing missing was a call to pythoncom.PumpMessages()

I fell over another tiny detail though, as I wanted to keep my main
application running ( the place holder was my sleep loop)

Tt seems, that PumpMessages() cannot be in another thread.


So I ended up with:

import win32com.client,pythoncom,time,threading

defaultNamedNotOptArg=pythoncom.Empty
wiaEventDeviceConnected =u'{A28BBADE-64B6-11D2-A231-00C04FA31809}'

class MgrHandlerClass:
def OnEvent(self, EventID=defaultNamedNotOptArg,
DeviceID=defaultNamedNotOptArg,
ItemID=defaultNamedNotOptArg):
print "Called back with ..."


mgrhndlr = MgrHandlerClass()
manager = win32com.client.DispatchWithEvents("WIA.DeviceManager",
MgrHandlerClass)
manager.RegisterEvent(EventID=wiaEventDeviceConnected,DeviceID=u'*')

def sleeploop():
while True:
print "sleep"
time.sleep(10)

thrd = threading.Thread(target=sleeploop)
thrd.start()
# doesn't work if pump is in another thread
pythoncom.PumpMessages()


bye



N