In MECCA 2000, the Tcl script file, /usr/bin/amgraf/tkscripts/defaults.tcl,
implements how default values for various aspects of the MECCA processing
can be set.

That file is organized into "procedures" (Tcl term "proc", subroutines):

	set_m2k_defaults
	set_gfx_defaults	;# for general graphic defaults.
	set_box_defaults	;# for things about box only.
	set_txt_defaults	;# for things about text.
	set_mictxt_defaults	;# for things about micro-text.
	set_print_defaults	;# and only for printing.

The first, set_m2k_defaults, is called on start-up, as well as each
"New Graphic" command.  It in turn calls the others, in order.  These
other procedures mainly consist of a number of Tcl "set var value"
statements, which set the "default values".

set_m2k_defaults then reads in ~/.m2k.tcl (file ".m2k.tcl" in user's
home directory) if that file exists, thereby providing a way for each
user to overwrite the defaults.

Over time, problems developed:

1. While "~/.m2k.tcl" does have its place (see /usr/mecca/misc/m2k.tcl,
   for a up-to-date view of what ~/.m2k.tcl should really contain), it was
   quickly taken to be THE file which each user can put all of the
   "set ..." statements from defaults.tcl, modify the values, and effect
   complete per-user customization.  ~/.m2.tcl was never meant to function
   that way, and when it became a file "containing all", it caused problem
   number 2:

2. set_gfx_defaults, set_box_defaults, set_txt_defaults and
   set_mictxt_defaults, is each also called directly, whenever the user
   clicks the "Reset to Start-up Defaults" button in respective
   Set-Attributes dialog.  None of these procedures reads ~/.m2k.tcl.
   And this causes some users to report: "Reset to Start-up Defaults
   does not really reset to START-UP defaults!" (whereas START-UP step
   reads ~/.m2k.tcl, reset box defaults does not).

   But ~/.m2k.tcl contains other things, so resetting box defaults,
   for instance, should not reset any other defaults; hence these
   procedures cannot read ~/.m2k.tcl.

3. It is not always desirable to let each user completely overwrite the
   values set in defaults.tcl.  Site managers should be able to edit
   defaults.tcl, and rely on it to serve as site-wide defaults, providing
   familiar, common defaults no matter who is logged in running MECCA 2000
   on which machine.


To address these problems, beginning with v3.07, the following solution
is put in place:

Each of the set_gfx_defaults, set_box_defaults, set_txt_defaults and
set_mictxt_defaults procedures now contains a statement to pull in per-
user defaults file.  Instead of the "one-and-all" ~/.m2k.tcl, it should
be split into additional files, they correspond like so:

	set_gfx_defaults     ~/.m2kgfx.tcl
	set_box_defaults     ~/.m2kbox.tcl
	set_txt_defaults     ~/.m2ktxt.tcl
	set_mictxt_defaults  ~/.m2kmictxt.tcl

while "set_m2k_defaults" still reads ~/.m2k.tcl.

Each of the per-user files should now contain only the "set ..." statements
as provided by its corresponding "set_xxx_defaults" procedure.  For example,
~/.m2kbox.tcl can contain only the "set boxData(...) ..." statements and
nothing more.

As distributed, each of these procedures, after the normal group of
"set var value" statements, contains a "#catch {source ....}" line, which
if uncommented (removing the leading # mark), will pull in the per-user
defaults file.  We distribute them in commented-out form, as we believe it
is the site manager's decision to permit per-user overwrite.

Also of note to site managers:

The "set var value" lines in each of these procedures, can be re-arranged,
and the "catch {source ...}" line placement affects what can or cannot be
overwritten by each user.  Take an example for set_box_defaults:

	#catch {source ~/.m2kbox.tcl}      ;# commented-out, no customize;
					   ;# so where this line is placed
					   ;# in the procedure is irrelevant.

	...				   ;# all of "set boxData(...)"
	set boxData(super_screen_overwrite) 0
	catch {source ~/.m2kbox.tcl}       ;# after all of "set ..." lines,
					   ;# thusly each user can overwrite
					   ;# all of box default attributes.


	...				  ;# many "set boxData(...)" lines
	set boxData(bar_units) i
	catch {source ~/.m2kbox.tcl}	  ;# everything up to bar_units can
	set boxData(panto_name) None	  ;# be overwritten by each user, but
					  ;# things from panto on, cannot.

Most of these "set_xxx_defaults" procedures, aside from having "set ..."
statements, also contain "m2k_..." statements toward the end.  It is most
important that these "m2k_..." statements be the very last things such a
set-defaults procedure does.  That is, all "set ..." and "catch {source ...}"
lines must come before any "m2k_..." statements.

Lastly, set_print_defaults currently provides no corresponding per-user
customization hook.  It didn't have this before, and as of v3.07 there
has been no requirement to provide per-user customization for it.