How long will COM exist ? - COM Discussion Boards

How long will COM exist ?

24-Sep-02 2:50

That's right. I guess you know the IDirectDrawSurfaceX interface jas a method that gives you the current dc, so you can do virtually anything on the surface.
However you'll have to do this in a non visible surface, otherwise it flickers.

Nick Parker20-Sep-02 8:57

Nick Parker

20-Sep-02 8:57

I just read Mike Dunn's article on an introduction to COM last night, which was really good, however I am just wondering how long do you think COM will exist with the release of the .NET Framework this year. Will it never go away (at least due to the framework itself?). What do you think, just wondering what value it still holds as it seems to be so very powerful?

Nick Parker

So like children pointers should be left to grown ups. - Norm Alomond

Re: How long will COM exist ?

David Salter23-Sep-02 9:14

David Salter

23-Sep-02 9:14

Windows relies so heavily on COM that I don't think it will ever go away - which is just as well coz I love it Cool | :cool:

Dave

Default parameters in IDL

Jerome Conus18-Sep-02 20:21

Jerome Conus

18-Sep-02 20:21

Hello !

I would like to know if it is possible to have default parameters in a COM interface (IDL).

Anyone knows that, and how to do it ?

Thank you for your help !
Jerome

Re: Default parameters in IDL

Stephane Rodriguez.18-Sep-02 20:47

Re: Default parameters in IDL

18-Sep-02 20:47

add the [optional] attribute in front of the parameter(s).

Vi220-Sep-02 3:32

Vi2

20-Sep-02 3:32

[id(1)] HRESULT Func1([in, optional] long a);
[id(2)] HRESULT Func2([in, defaultvalue(777)] long a);
[id(3)] HRESULT Func3([in, optional] BSTR a);
[id(4)] HRESULT Func4([in, defaultvalue("xxx")] BSTR a);
And only for VARIANT
[id(5)] HRESULT Func5([in, optional] VARIANT a);

With best wishes,
Vita

OLE Object DocFiles and the Clipboard

Striker918-Sep-02 15:54

Striker9

18-Sep-02 15:54

I have a question: I have a serialized OLE Object DocFile (Excel Worksheet) that I need to copy to the clipboard and then paste into MS Word using the "PasteSpecial" method and Automation...I use StgOpenStorageEx to load the docfile and then I copy it to the clipboard using COleDataSource::CacheData and COleDataSource::SetClipboard... problem is when I try to paste special in Word, it says "Clipboard is empty or contains invalid data"...I am using the clipboard format "DataObject" when copying to the clipboard and the STGMEDIUM type is TYMED_ISTORAGE. I read that it might be that I need to use the "Embed Source" and "Object Description" clipboard formats in order to copy correctly. Is this true? How should I do this? Thanks for your help...

-Striker9

Problem registering (0x000003e6)

ssirisha18-Sep-02 2:46

18-Sep-02 2:46

I have just created an empty COM DLL with support to MFC using VC++5.0. When complied, it fails to register.

Regsvr32: LoadLibrary(".\Debug\testxyz.dll") failed.
GetLastError returns 0x000003e6.

I looked up for the error message and it is "Invalid access to memory location"

Thanks for your help in advance.

Stephane Rodriguez.18-Sep-02 3:15

18-Sep-02 3:15

Put a breakpoint in DllRegisterServer().
And if you don't export such function, well eh.. now you know! Cool | :cool:

ssirisha18-Sep-02 3:19

18-Sep-02 3:19

I tried putting a break point in DLLRegisterServer but it doesnot stop there..

Just to clarify once more this error is poping after linking while registering ActiveX Control..

Thanks

Stephane Rodriguez.18-Sep-02 3:29

18-Sep-02 3:29

The custom build-step in VC does a regsvr32 component.dll which in fact loads the component and calls DllRegisterServer() on it.

If it doesn't reach DllRegisterServer(), that's because the problem lies where the COM component itself is loaded, or during the initialisation of the global vars of your COM component.

In other words, your component links with .lib libraries. Some of these libraries export functions and thus the associated .dll file is loaded automatically by the COM component. That's where the problem is. Either you've got a missing DLL the system is trying to load (the error is sometimes weird by the way), or it loads one of the DLLs which executes wrong code in their DllMain() entry point.

What should do now is isolate the code. Use dependancy walker and list all DLLs. Then for each dlls, do a small program that loads them (::LoadLibrary() should be enough). Or if you know how to use it, use RunDll32.exe (Windows 9X) or DllHost.exe (2K/XP).

To get to know if the error is because of one of your global vars, just try loading a stripped down version of your component (all linked code removed) by doing a simple ::LoadLibrary().

Good luck!!!! Cool | :cool:

ssirisha18-Sep-02 3:37

18-Sep-02 3:37

Really appreciate you taking time and explaining. Thank you.

I have created this COM component using the wizard. After the wizard is completed I have not added any methods or any code manually to this project. I simply compiled it and that's when I get this message.

So If I understand your feedback correctly, some of the libraries that the the project has linked are missing or cannot load..
How can I investigate which Dll is having problem with ?

Thanks once again.

Stephane Rodriguez.18-Sep-02 3:55

18-Sep-02 3:55

ssirisha wrote:
I have created this COM component using the wizard.

So you probably haven't added any features from external libraries yet. Do you ?

If that's the case, then you may also get the problem if you use the wizard to create an ActiveX or ATL component, with no custom implementation inside. Tried it ?

I would suggest that if this code linking and registering is fine, that you start adding code from this point, until you reach the error. That may speed up a little bit code isolation.

Otherwise, as I said, I would load each external library separately with a ::LoadLibrary().

ssirisha18-Sep-02 4:05

18-Sep-02 4:05

No features from external libraries added.

No custom implementation added.

I soon as I finish with the wizard, I tried to compile.
Thanks.

IDispatch

Barry Lapthorn17-Sep-02 9:09

Barry Lapthorn

17-Sep-02 9:09

I have a requirement at work to produce a component that:

a. Allows the use of intellisense in VB
b. Allows the 'interface' to be updated remotely, from a server for example. Or rather the interface frequently has more methods added to it.
c. To be used in VB

Any thoughts?

My initial feeling is that only (b) is possible, and by using late binding through IDispatch. I don't think that (a) is a possibility.

Trouble is that these 'requirements' break the idea of interfaces remaining constants. The requirements come from a fairly non-techie person who claims that 'we had it in our last place'. Wink | ;)

Stephane Rodriguez.17-Sep-02 9:53

17-Sep-02 9:53

a. Yes, provided automatically by VB or other automation-language by just loading the type-library (of course all interfaces must be dispinterfaces).
b. Yes, provided by late binding (VB Automation uses late binding, which means all of your interfaces are dispinterfaces).

Barry Lapthorn17-Sep-02 11:06

Barry Lapthorn

17-Sep-02 11:06

I'm not much of a COM person, but if I do the following in VB:

dim obj as object
set obj = CreateObject("Excel.Application")

then the next line -

obj.act

doesn't bring up 'obj.activate' in intellisense, i.e. with late binding the intellisense isn't working.

If I'm dynamically loading the methods supported by my interface, then I can't use early binding, and therefore can't produce a type library. Or am I wrong?

Thanks,

B.

David Salter17-Sep-02 11:31

David Salter

17-Sep-02 11:31

If you want to use intellisense, then you need to use early binding. Using Late Binding, VB doesn't really know what it is talking to - certainly not at design time anyway.

Dave.