[TCLCORE] trace command patch

[Eric M. <er...@aj...>]

Vince Darley submitted a patch for 8.4 to provide [trace command]
capabilities.  Before I go ahead and merge it, I wanted to get one last
review of the API by everybody here.  I've CC'd Vince so he stays in the
loop on this, and can maybe answer some questions if we have any.

The specific problem we wanted to solve was this:  when creating
megawidgets, it's common practice to do the following:

frame .f
rename .f .f:real
interp alias {} .f {} MegawidgetProc .f

But now, if the user does:

rename .f {}

to delete the megawidget, it will destroy the command, but not actually
clean up the megawidget, as it would if it were a "real" widget.  So we
wanted to be able to trace command deletion.  While we were at it, we
figured, let's trace command renaming, and command execution too, what the
heck, right?

Vince put together a nice patch to do just this, and to clean up the
[trace] syntax as well.  It updates trace with the following syntax:

trace {add|remove|list} {variable|command|execution} ops ...

while retaining [trace variable], etc, for backwards compatibility.  

Variable traces support read, write, and unset operations; command traces
support rename and delete operations; execution traces are used to trace
command execution, and have several additional options:

trace add execution name ops ?-minlevel m -maxlevel n -truncate t -depth d?

The full patch is at

ftp://ftp.ucsd.edu/pub/alpha/tcl/tracecommand.patch.gz

If you are so inclined, please take a look at it and give us some
comments.  I think the patch looks very good; I've tested it out and it
works as advertised, has tests, and doc's.  My only concern is with the
syntax of the execution traces.  I think that "execution" should just be
another operation for command traces, rather than an entirely separate set
of traces.  My guess is that Vince split it out because of the need for
the extra options.  But I don't feel strongly that it should be changed.
Does anybody else have any comments on this, or on any other parts of the
patch?

   Eric Melski                            The Other Tcl Guy
   ericm at ajubasolutions.com            Ajuba Solutions

--
The TclCore mailing list is sponsored by Ajuba Solutions
To unsubscribe:  email tcl...@aj... with the 
                 word UNSUBSCRIBE as the subject.