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I have an active control which is published. Now I want to add two new methods to this control to provide new functionality. Just like COM is the activex immutable ? If yes, how do I achieve it. I mean we declare new interfaces in COM when providing new functionality and QueryInterface determines whether the new functionality exists or not. How can I achieve this in activex control.
"C makes it easy to shoot yourself in the foot. C++ makes it
harder, but when you do, it blows away your whole leg."
- Bjarne Stroustrup
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Well, an ActiveX control IS a COM component that exposes one or more interfaces inherited from IDispatch, AKA an Automation interface.
The IDispatch interface is built on providing an index for the method or property that is used from the client side and the virtual table only contains the IDispatch methods, in short terms. There's more to it but that's irrelevant at this moment.
When creating an ActiveX you the possibility to declare the Automation interface as dual. This means that the interface has a virtual table which contains the methods that are specific to the interface derived from IDispatch and hence is immutable. Clients can use both v-table calls and the index style as desired. V-table calls are usually preferred when using C++.
Now to your question whether you can declare new methods in an existing Automation interface or not.
As you might have guessed you cannot modify an Automation interface that is a dual interface since it uses v-table calls, exactly like ordinary COM interfaces.
If, and only if, the interface is not a dual interface it is possible to add methods and properties to an existing Automation interface, given that the already existing properties and methods are unchanged and always keep their original index. Otherwise existing clients will fail to work properly.
However, even though this is technically possible, I wouldn't encourage anyone to do this.
I've seen this done at a customer of mine with all the good intentions, but later they found it difficult to tell whether the client or the server actually supported the extended interface or not.
In other words: they found themselves in similar dilemma as if they would have changed an ordinary COM interface.
If this situation is acceptable for you, or anyone that is suppose to use you ActiveX control is for you to decide. Personally I would go nuts if I was to create clients to this server. 
Hope this helps
--
Roger
It's supposed to be hard, otherwise anybody could do it!
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Thanks for the detailed reply. I was wondering if instead of making changes to the original interface, is it possible to define and use a new interface. So the new clients can use the new interface while the old ones continue to use the old interface ? Thanks again.
"C makes it easy to shoot yourself in the foot. C++ makes it
harder, but when you do, it blows away your whole leg."
- Bjarne Stroustrup
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Identity Undisclosed wrote: I was wondering if instead of making changes to the original interface, is it possible to define and use a new interface. So the new clients can use the new interface while the old ones continue to use the old interface
This would be the correct (distributable, controlled) way of doing it.
Clients that want to use the new functionality should ask for the new interface with QueryInterface().
--
Roger
It's suppose to be hard, otherwise anybody could do it!
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Hi all,
I have to create a custom control to show html files. I need to process the link click inside that also.
Is CHtmlView is suitable for this purpose? Or is there any other useful class to do so?
Thank you.
- NS -
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Thank you. 
Let me try...
- NS -
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I have a dialog with 2 radio buttons (beside many others).
Both buttons appear OK in the .h, .rc and .clw files, but the class wizard shows only one (even after deleting the .clw file and rebuilding).
MFC.
thanks
alex
'Architecture is music frozen in space.'
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Class wizard shows radio buttons with group property set. If you want these radio to be a group, you have to set the group property only for the first ctrl. If you set it for both, class wizard will show both the ctrls, but you will lose the auto selection switching property.
- NS -
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Thank You.
Does that mean that if i .SetCheck() for one of them, the other is automatically unchecked?
alex
'Architecture is music frozen in space.'
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I meant that if the user clicks one of the radio then the other will not be automatically unchecked.
- NS -
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damn, how did you understand his question ?!
lol, well done anyway... 
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Thank you. Actually I went in your same way for a while...
- NS -
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Sorry about the 'understandability'.
Maybe it's my English.
alex
'Architecture is music frozen in space.'
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I have a dialog with 2 radio buttons (beside many others).
Both buttons appear OK in the .h, .rc and .clw files, but the class wizard shows only one (even after deleting the .clw file and rebuilding).
MFC.
???
thanks
alex
'Architecture is music frozen in space.'
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1. aren't they overlapping ?
2. isn't there one which is set to hidden ?
3. do you create them ?
please give more infos, especially about the code...
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1. NO
2. NO
3. What do you mean 'create'?
4. There is no code; that is the problem: without the class wizard showing the control, i can't attach a handler to it.
alex
'Architecture is music frozen in space.'
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man,
you have to know that Class wizard is only a tool that fasts what you can do by hand...
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i know. it's just i would like to keep them synchronized - it's handyer.
any idea how to fix it?
alex
'Architecture is music frozen in space.'
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I hope it's on topic because I want to be compiling and using this in VC6+ on a Windows platform. I just wondered if anyone had any experience with this or could help or advise in any way. I just want to get a running app going that uses the RPC library so that i can open and manipulate some files that contain the XDR file format. No point in reinventing the wheel if it's been done already
Would be very grateful if anyone had anything to offer
regards,
Lee Harris
-- modified at 6:28 Thursday 13th April, 2006
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you could try http://netbula.com/oncrpc/[^] (I havnt used this one...) the one I have used is by a gentleman called Martin Gergleit (sp may be wrong or its Gergeleit) but I cant find a link for that anymore (my work has a commercial license so I cant give you a copy)
there were a couple of other companies offering commercial onc rpc for windows, I cant seem to recall them
(FYI : I was issuing RPC calls from Solaris to a Windows Service quite happily)
try searching for :-
win32 onc rpc
hope this helps, 'G'
-- modified at 8:14 Thursday 13th April, 2006
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PS
Is this the same XDR as the image format? Hope I am not getting two different things confused!
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well, XDR is an acronym for eXternal Data Representation - so I see no reason why it cant be both data being transmitted across the wire, or a way of describing an image - a quick google search would suggest either
except in this case I suspect you're correct, XDR as an image format may not quite be what Ive shown...
I wonder if GNU has an XDR library ....
ok, the only two things I can find are :-
http://members.tripod.com/martin_leese/Personal/ipox.html[^]
and of course, an RFC
http://www.faqs.org/rfcs/rfc1014.html[^]
as I said (somewhere), I know there was a set of XDR articles on CUJ a long while back, they may be the best if you find no other starting point ... you also said ".SCAN files from a Synergy kilovoltage imaging unit " can Synergy not tell you what 'tags' they have used in the XDR files ?
sorry, may not have been much help
'g'
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sorry to bombard you - found something useful - I remembered that Martin/His work sprang from RWTH Aachen (University/Tech institute in Germany ?) and just trolled their archives .... here's a link that may give you what you want (ok, its mostely in German, but its a start)
http://www.plt.rwth-aachen.de/index.php?id=258&L=1[^]
CUJ also ran a series of (B)leeding Edge Articles a long while back, on XDR for serialisation (didnt include network stuff as far as I remember) - you may be able to troll their archives ... if you want to go this route let me know and I'll try and search my CDROM of their index
'g'
-- modified at 8:29 Thursday 13th April, 2006
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Many thanks
basically I have some .SCAN files from a Synergy kilovoltage imaging unit on a medical linear accelerator and want to manipulate the raw image data (3d image cube) which I'm told is an XDR format. I'm going to be changing the pixel values, then reimporting the files and testing image registration performance
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