[rdnzl-devel] Generic types and default thread apartment

[Goffioul Michael]

> Hi!
> 
> On Thu, 14 Sep 2006 10:25:07 +0200, "Goffioul Michael" 
> <goffioul at imec.be> wrote:
> 
> > 1) does RDNZL support generic types? If yes, how do I 
> create such an 
> > object using RDNZL syntax?
> 
> This is something that was introduced in .NET 2.0, right?  
> No, no support yet, I haven't even thought about it.  You're 
> welcome to supply patches, I probably won't find the time to 
> look into this in the near future.

I had a look and you don't event need a patch :-) Generic objects
can be created on the fly by specifying the parameter type between
brackets, like:

(new "System.Collections.Generic.List`1[System.String]")

If you have 2 type parameters, then use "2" instead of "1" and
separate types with a comma. Of course, RDNZL could provide a wrapper
API to make the syntax simpler, but it's not mandatory.

> > 2) from a GUI perpective, it would be better to set the apartment 
> > state of the RDNZL.dll assembly to STA, otherwise various 
> components 
> > do not work properly; is there a reason to not do it?
> 
> I have to admit that I don't even know what the apartment 
> state of a DLL is.  Could you tell me what it's for and how I 
> change it?  And what doesn't work if the state is as it is now?

I'm not an expert neither, but I think this is related to Interop
and COM. In Single-Thread-Apartment (STA), all COM messages are
processed
in the same thread, while in Multi-Thread-Apartment (MTA, the default
in .NET if you don't specify anything) COM objects can be accessed by
multiple concurrent threads. In GUI, even in multithread application,
the GUI (message loop) must run in a single thread, I guess that's why
STA is preferable in Windows Forms application (In Visual Studio 2005,
when you use the wizard to start a GUI application, it set the threading
model to STA by default).

Now about the effects, I think that some .NET components are simply
based on existing COM components (which is hidden to the user). At least
I
had problems with common dialogs: the directory dialog and the file
dialog.
When using MTA, the directory selection dialog does not show the
directory
tree, and the file dialog does not list items correctly (for instance,
"My Computer" is empty, or the dialog does not update itself when you
change
the filter).

Try this (tried with .NET 2):

(rdnzl:enable-rdnzl-syntax)
(rdnzl:import-types "System.Windows.Forms" "FolderBrowserDialog")
(setq dlg (rdnzl:new "System.Windows.Forms.FolderBrowserDialog"))
[ShowDialog dlg]

This problem was the cause that made me recompile RDNZL-cpp under
VS2005.
If you look into StdAfx.cpp, you'll see how I changed the apartment
state,
but I don't know if it would work under VC.NET-2003.

Michael.