[Oorexx-bugs] [ oorexx-Bugs-1068288 ] OLEObject-event not invoked!

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Bugs item #1068288, was opened at 2004-11-17 16:42
Message generated for change (Comment added) made by bigrixx
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Category: Classes
Group: None
>Status: Pending
>Resolution: Fixed
Priority: 5
Submitted By: Rony G. Flatscher (orexx)
Assigned to: Nobody/Anonymous (nobody)
Summary: OLEObject-event not invoked!

Initial Comment:
Working with an ActiveX control to drive the TWAIN
interface (cameras, scanners, etc.) using a great
product (test-version available) from Vintasoft corp.
<http://www.vintasoft.com> reveals the phenomenon that
the event "PostEvent" (indicating scanning/acquiring is
over and result fully available) is not invoked by
Object Rexx.

It works with all other products (MS Office) and
languages (VB, C, C++, ...).

Accompanying file contains the (very short) Rexx
program ("simpleWithEvent.rex") with a subclass of
OLEObject possessing the event-handling method. If you
download the demo-package from
<http://www.vintasoft.com> and install it, you can test
for yourself.

[There is a version of the Rexx program ("simple.rex")
in the package, demonstrating how one could acquire via
the Twain interface without an event callback.]



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>Comment By: Rick McGuire (bigrixx)
Date: 2006-09-27 05:47

Message:
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Thanks again to Mark Miesfeld. 

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Comment By: Mark Miesfeld (miesfeld)
Date: 2006-09-25 20:32

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I have submitted patch # 1565431 that fixes this bug.

A few words about the bug.  For one thing, the bug 
affected not just the Vintasoft ActiveX control but also a 
number of other OLE / COM objects, most notably Microsoft 
Word.

It is interesting to note this:  apparently several years 
ago Lee Pendin opened up a bug with IBM for events not 
being supported with the Micosoft ControlAgent.  IBM fixed 
the bug by special casing the ControlAgent.  From the code:

  else if (IsEqualIID(riid, DIID__AgentEvents))
    /* special handling for Microsoft ControlAgent */
    /* The agent do not ask for the dynamic IDispatch 
interface, but for it's own special one   */
    /* which is in reality a IDispatch interface. Thats 
the reason why here is checked for the  */
    /* control agenst query and the Interface is 
returned                                       */

Well, obviously ooRexx can not special case an object 
every time a new one is discovered.

The fix is to reply in a generic way to the query 
interface from connectable objects.  ooRexx already, in 
the OLEObject code, goes to some length to determine 
exactly which interface is the outgoing event interface 
for the OLE / COM object being proxied.

Unfortunately, once the proper IID was determined, it was 
discarded.  This fix passes the IID on to the 
OLEObjectEvent object.  The event object instance saves 
the IID and then returns true if queried about supporting 
that interface.  This is the correct behavior, because the 
event list for this OLEObjectEvent instance has been 
dervied from exactly that interface. 

With the fix, the special case for the Microsoft 
ControlAgent is removed.

Rony and I have been testing this for several weeks.  All 
the COM objects where events used to work, (IE, Excel, and 
Outlook) still work.  And, in addition, the Vintsoft, 
Word, and ControlAgent also work.

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