[pywin32-bugs] [ pywin32-Bugs-797078 ] WithEvents interferes with IE "frames" attribute

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Bugs item #797078, was opened at 2003-08-28 22:42
Message generated for change (Settings changed) made by gcash
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Category: com
Group: None
>Status: Closed
Resolution: None
Priority: 5
Submitted By: Gene Cash (gcash)
Assigned to: Nobody/Anonymous (nobody)
Summary: WithEvents interferes with IE "frames" attribute

Initial Comment:
It seems that if you use WithEvents, that the IE

Document object

"frames" attribute has problems. The "frames" attribute

is the

collection of the "documents" objects for each of the

subframes.



Example 1 - "correct" behaviour w/o events



>>> import win32com.client as wc

>>> ie=wc.Dispatch('InternetExplorer.Application.1')

>>> ie.Visible=1

>>>

ie.Navigate('http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&threadm=37835B30.BFCC4A05%40phoenix-edv.netzservice.de&rnum=5&prev=/groups%3Fas_q%3Dwin32%26safe%3Dimages%26ie%3DUTF-8%26oe%3DUTF-8%26as_ugroup%3Dcomp.lang.python%26lr%3D%26hl%3Den')

>>> ie

<COMObject InternetExplorer.Application.1>

>>> ie.Document.links

<COMObject <unknown>>

>>> ie.Document.links.length

0

>>> ie.Document.frames

 <COMObject <unknown>>

>>> ie.Document.frames.length

1

>>> ie.Document.frames[0].name

u'left'

>>> ie.Document.frames[1].name

u'right'



Example 2 - 'No such interface supported' crash using

events



>>> import win32com.client as wc

>>>

ie_class=wc.gencache.EnsureModule('{EAB22AC0-30C1-11CF-A7EB-0000C05BAE0B}',

0, 1, 1)

>>> class IE_Events(ie_class.DWebBrowserEvents2):

>>>    pass



>>>

ie=wc.DispatchWithEvents('InternetExplorer.Application.1',

IE_Events)

>>> ie.Visible=1

>>>

ie.Navigate('http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&threadm=37835B30.BFCC4A05%40phoenix-edv.netzservice.de&rnum=5&prev=/groups%3Fas_q%3Dwin32%26safe%3Dimages%26ie%3DUTF-8%26oe%3DUTF-8%26as_ugroup%3Dcomp.lang.python%26lr%3D%26hl%3Den')

>>> ie

<win32com.gen_py.Microsoft Internet

Controls.IWebBrowser2 instance at 0x8296408>

>>> ie.Document.links

<COMObject <unknown>>

>>> ie.Document.links.length

0

>>> ie.Document.frames

Traceback (most recent call last):

  File "<stdin>", line 1, in ?

  File

"C:\Python\lib\site-packages\win32com\client\dynamic.py",

line 454, in __

getattr__

    raise pythoncom.com_error, details

pywintypes.com_error: (-2147467262, 'No such interface

supported', None, None)

>>>



What's strange is the "forms" & "links" attributes

still work, even

though they're object collections as well. I saw in

Google that

"vtable" support is iffy... how do you tell if

something is a "vtable"

interface?



Now even if I change to attaching an event class by:

>>> ie=wc.Dispatch('InternetExplorer.Application.1')

>>> IE_Events(ie)



It crashes the same way.



Or if I change the event class to:

>>> class

IE_Events(wc.getevents('InternetExplorer.Application.1')):

>>>   pass



it also crashes the same way.



The first example has no problem with makepy support

being present.



Any ideas? This is on a fresh Win2k Pro box with SP4

and all the

critical patches applied via Windows Update.



I can reproduce this in builds 154, 155, 156, and 157

(with the

appropriate version of Python) The above line number is

build 157, I

think.



I've looked at the code for getevents(), Dispatch(), and

DispatchWithEvents() and I'm not a good enough Windows

hacker to see a

problem.



- Gene Cash gc...@cf... / gen...@or...



----------------------------------------------------------------------

Comment By: Gene Cash (gcash)
Date: 2003-08-29 14:07

Message:
Logged In: YES 
user_id=141974

OK, it appears I just needed to read Appendix D of The Book,

where it discusses threading, especially "What are the

apartment rules". On the other hand, I now actually

understand it, where before it was gibberish.



I have learned to read the Dark Runes. Does this mean I no

longer have a soul?



WithEvents() starts another thread, so parentWindow & Frames

- which are COM pointers - can't be passed between the threads.



I'll close this one.

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