# A sample originally provided by Richard Bell, and modified by Mark Hammond.
# This sample demonstrates how to use COM events in an aparment-threaded
# world. In this world, COM itself ensures that all calls to and events
# from an object happen on the same thread that created the object, even
# if they originated from different threads. For this cross-thread
# marshalling to work, this main thread *must* run a "message-loop" (ie,
# a loop fetching and dispatching Windows messages). Without such message
# processing, dead-locks can occur.
# See also eventsFreeThreaded.py for how to do this in a free-threaded
# world where these marshalling considerations do not exist.
# NOTE: This example uses Internet Explorer, but it should not be considerd
# a "best-practices" for writing against IE events, but for working with
# events in general. For example:
# * The first OnDocumentComplete event is not a reliable indicator that the
# URL has completed loading
# * As we are demonstrating the most efficient way of handling events, when
# running this sample you will see an IE Windows briefly appear, but
# vanish without ever being repainted.
import sys
import os
import win32com.client
import win32api
import win32event
# sys.coinit_flags not set, so pythoncom initializes apartment-threaded.
import pythoncom
import time
class ExplorerEvents:
def __init__(self):
self.event = win32event.CreateEvent(None, 0, 0, None)
def OnDocumentComplete(self,
pDisp=pythoncom.Empty,
URL=pythoncom.Empty):
thread = win32api.GetCurrentThreadId()
print "OnDocumentComplete event processed on thread %d"%thread
# Set the event our main thread is waiting on.
win32event.SetEvent(self.event)
def OnQuit(self):
thread = win32api.GetCurrentThreadId()
print "OnQuit event processed on thread %d"%thread
win32event.SetEvent(self.event)
def WaitWhileProcessingMessages(event, timeout = 2):
start = time.clock()
while True:
# Wake 4 times a second - we can't just specify the
# full timeout here, as then it would reset for every
# message we process.
rc = win32event.MsgWaitForMultipleObjects( (event,), 0,
250,
win32event.QS_ALLEVENTS)
if rc == win32event.WAIT_OBJECT_0:
# event signalled - stop now!
return True
if (time.clock() - start) > timeout:
# Timeout expired.
return False
# must be a message.
pythoncom.PumpWaitingMessages()
def TestExplorerEvents():
iexplore = win32com.client.DispatchWithEvents(
"InternetExplorer.Application", ExplorerEvents)
thread = win32api.GetCurrentThreadId()
print 'TestExplorerEvents created IE object on thread %d'%thread
iexplore.Visible = 1
try:
iexplore.Navigate(win32api.GetFullPathName('..\\readme.htm'))
except pythoncom.com_error, details:
print "Warning - could not open the test HTML file", details
# Wait for the event to be signalled while pumping messages.
if not WaitWhileProcessingMessages(iexplore.event):
print "Document load event FAILED to fire!!!"
iexplore.Quit()
#
# Give IE a chance to shutdown, else it can get upset on fast machines.
# Note, Quit generates events. Although this test does NOT catch them
# it is NECESSARY to pump messages here instead of a sleep so that the Quit
# happens properly!
if not WaitWhileProcessingMessages(iexplore.event):
print "OnQuit event FAILED to fire!!!"
iexplore = None
if __name__=='__main__':
TestExplorerEvents()
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