TCL_OBJECT by Stephan Herrmann (stephan@cs.tu-berlin.de)

CONCEPTS:

This is another approach on combining C++ and tcl:
The idea was to write the whole funcionality of an application in C++,
then decide which objects need to be represented by screen objects,
add a tcl interface to these objects and write the whole user interface
in tcl. This proceeding should enable the writing of maintainable (because
of C++ (ok, I'd prefer EIFFEL; Eiffel encapsulation exists as well))
and adaptable (because of tcl) software.

Furthermore I definitly wanted to use xf to build my screen objects! :-)

(ok. I know read about "objectify" by Wayne Christopher, but his approach
differs from mine in that he gives full control to tcl whereas I prefer
to leave the control (including creating and destructing objects) on the
C++ side. Additionally I will automatically have modular tcl-code as
you will just see).

I'm  introducing the notion of "Tcl_Object" described by a base class
for all (complex) objects that shall be represented on the screen.
Each Tcl_Object will have its own interpreter that executes a given
tcl script. There will normaly be one script per class that is derived
from Tcl_Object. The filename for this script is given by a virtual function
to be defined in every derived class. (In my case these files are generated
by xf, so in fact I hardly write any tcl code myself).

The interface is now given by 
  - installing C++ member functions into tcl and
  - exchanging data via tcl variables 
      (I do this explicitly, which seems to be the safest way).
both activitys are (slightly) supported by Tcl_Object. The only little Hack 
is the embedding of C++ member functions into plain-C before exporting them
to tcl. 

FILES:

  - The files Tcl_Object.[hC] realise this baseclass. 
  - tcltest.C is a simply application of this principle.
  - tcltest.tcl is a xf-output file.
I don't have to tell you, how little time it took to create tcltest.tcl
by the means of xf.

I hope you enjoy this light weigth solution

STATUS:

  13.Jan.1993	: placed on ftp.
		  compiles with tcl7.3 - tk3.6