This is version 1.0 of the "extension" command.  It creates a 
vanilla version of "wish" with one added command to load shared
libraries as extensions.  This command reflects the proposal
made last year for an extension loader.  It is not the last word
on extension loading.  I any welcome comments or suggestions to
improve this or any other loader.

The command requires no patching of the Tcl or Tk libraries.
It works with the following releases of Tcl.

	Tcl 7.3
	Tcl 7.2
	Tcl 7.1
	Tcl 7.0

The "extension" command has been tested on HP-UX, SunOS 4.x, and
SunOS 5.x.  It should work also on ISIX 5.x, OSF1.

---------

How to build and test:

0. Run ./configure

   Run the auto-configuration script "./configure"

	./configure 

   * If you want to use gcc, it's "./configure -with-gcc"

	./configure -with-gcc

   * By default, the "wish" program and manual pages will be installed 
     in "/usr/local/blt".  You can change this by giving the -prefix 
     option to ./configure.

	./configure -prefix=/depot/stuff/blt
    
  You may be queried for the location of the Tcl and Tk libraries, if
  "configure" can't find them in the standard locations.

  The configure script creates an include file "./extConfig.h".
  It will also generate a new Makefile from its template (Makefile.in).
  If "configure" can't find something (e.g. it can't find the X libraries),
  edit the file "config.status" and run it.

	./config.status

  Otherwise, you'll have to edit the Makefiles files by hand.


1. Compile 

	make 

2. Edit the "extensions.tcl" file.

   The first time the "extension" command is used it tries to source 
   the file "[tcl library]/extensions.tcl".  This file can be used to 
   specify the extensions available and their respective libraries.
   You can always use the low-level commands to load a library too.

   This file sets two global variables which the "extension" command 
   uses to find shared libraries.

   The first is an associative array "tcl_extensions".  This array
   maps an extension name (such as "blt") with the proper initialization
   routine and shared libraries.

           set tcl_extensions(blt) { Blt_Init libBLT.so.1.7 }

   The second variable is "tcl_extloadpath".  This variable is a list
   of directories to search for the library.  

	   set tcl_extloadpath { 
	        /usr/local/tcl/extensions/lib 
		/usr/local/lib 
           }

   Edit the file "./extensions.tcl" to reflect where things are on
   your system and install it in the Tcl library directory.

   By default, the "extension" command looks for the file 
   "[tcl library]/extensions.tcl".  But you can override this by 
   setting the environment variable TCL_EXTMAP.  

	   set env(TCL_EXTMAP) /u/mydir/my_extensions.tcl


3. Test by running the demos. 

   
   Go into the demos/blt directory
    
	cd demos/blt

   and run the test scripts.
	
	./graph

   If your system doesn't support "#!" in shell scripts, then it's

	../../wish -f ./graph

   * These demos assume you have previously built a BLT as shared 
     library and that it still resides in the directory 
     ../../src/shared.
   
4. Install the new "wish" binary and "extensions.tcl" file.

   By default, the "wish" is installed in /usr/local/blt/bin and
   the manual page for the extension command is installed in
   /usr/local/blt/man
   
   You can change the top directory by supplying the -prefix option to
   ./configure.


5. Send bugs reports, correspondence, etc. to

   	george.howlett@att.com