README file for TDebug, an alternative tcl/tk-debugger.

$Id: README,v 4.1 1994/01/30 20:56:01 schmid Exp schmid $

This file documents TDebug Version 0.3.
It was written with emacs using Jamie Lokier's folding mode
That's what the funny {{{ marks are there for.

Please send comments, suggestions, bug-reports etc to
	schmid@fb3-s7.math.tu-berlin.de
Any feedback is welcome!

{{{ Disclaimer

This code is still under development. Among other things this means
that:

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

}}}
{{{ Files

README		this file
TdChoose.tcl	the TDebug front end
TdDebug.tcl	the debugger
ChangeLog	development history

}}}
{{{ General

TDebug uses a different approach than any other debugger I've seen for
tcl/tk.  If you know the emacs-lisp debugger `edebug' the following
may seem familiar. 

TDebug is totally based on tcl/tk, there is no C-code (yet), which
makes it very easy to install. It works by parsing and redefining
tcl/tk-procs, inserting calls to `td_eval' at certain points, which
takes care of the display, stepping, breakpoints, variables etc.

The advantages are, that TDebug knows which statement in what proc is
currently being executed and can give visual feedback by highlighting
it. All currently accessible variables and their values are displayed
as well. Code can be evaluated in the context of the current proc.
Breakpoints can be set and deleted with the mouse.

On the other hand there is a heavy penalty on speed and flexibility.
This has been alleviated somewhat with the introduction of partial
preparation of procs. There is still no possibility to get at code
running in global context, but I'm not sure if that would be useful
anyway.

I have also tried Don Libes' debugger provided with expect (and
standalone) and Karl Lehenbauer's experimental debugger that comes
with extended tcl (tclX). Both of them are more powerful than TDebug
though Karl's is far from using its full potential. On the other hand,
neither is as easy to install as TDebug, and neither comes with a
graphical interface. I'm working on an extension to Don's debugger
though.  Drop me a line if you want some alpha test version.

If you have to debug large applications or huge procs or need to have
control over code not inside of a proc, you are probably best off
using Don's debugger (which is the one I use to debug TDebug :-), but
for a quick look inside a proc, TDebug may become your debugger of
choice.

}}}
{{{ News

New since version 0.3

* display any proc without preparing it first

* partial preparing and restoring

* detach from applications on exit

* faster parsing (thanks to Alessandro Rubini)

* parsing bugs fixed, should now parse any proc

* cline extensions included for `Eval:' line

* can eval at global level

* optionally hide global variables and arrays

* optionally hide tk_* procs and others

* chooser now recognizes if procs are redefined

* a LOT more configuration options:

	* Geometry for all toplevels

	* Style of tags in listing


}}}
{{{ Installation

Please keep TdChoose.tcl and TdDebug.tcl in the same directory.

There are really two versions of TDebug, but contained in one source.

Under normal circumstances, TdChoose.tcl, the TDebug frontend,
provides a standalone application that talks to other tcl/tk-based
applications via send.  To debug a running application, TDebug sends a
`source TdDebug.tcl' to it, making the debugger available. You can
then choose procs to prepare for debugging.

There are however lots of people for whom send doesn't work. In this
case you have to source TdChoose.tcl inside the application you want
to debug,

	BUT DOING   `set td_priv(send) 0'   FIRST!

You can put this into a file called .tdebugrc in your home directory
(see Configuration section of README).

}}}
{{{ Usage

The Chooser:
 
Running TdChoose.tcl will bring up a toplevel window that let's you
select the application you wish to debug, if it is already running.
If you cannot use send and have installed TdChoose.tcl correctly, the
current application will be used instead.

The listbox displays all procs available for preparing or restoring
from the selected interpreter. 

You can control whether TDebug specific procs and Tk specific procs
are displayed as well. See Configuration section.

Press <Button-3> on a proc to get its body displayed in the main
debugger window.

To prepare a proc for debugging, click <Button-1> once on it while the
`Prepare' radiobutton is active, to restore it to it's original form,
do the same with the `Restore' button active.

You can force a rescan of the available procs by pressing the
`Prepare' or `Restore' button accordingly.

The Debugger:
 
The debugger window is divided into the main region with the name of
the current proc, a listing in which the expression just executed is
highlighted, the result of this execution and the currently
available variables and their values, an entry to eval expressions
in the context of the current proc and some controls for the state
of the debugger.

A proc listing displayed in the main region will have a darker
background on all lines that have been prepared. You can prepare or
restore additional lines by selecting a region (<Button-1>, standard
selection) and choosing `Prepare' or `Restore' from the Selection menu
(or by pressing ^P or ^R). 

`Prepare' and `Restore' try to be smart about what you intend to
do. If you select just a single word (plus some optional whitespace)
it will be interpreted as the name of a proc to prepare or
restore. Otherwise, if the selection is owned by the listing, the
corresponding lines will be used.

Be careful with partial prepare or restore! If you prepare random
lines inside a `switch' or `bind' expression, you may get surprising
results on execution, because the parser doesn't know about the
surrounding expression and can't try to prevent problems.


There are seven possible debugger states, one for each button and an
`idle' or `waiting' state when no button is active. The others are:

Stop - Stop after next expression, used to get out of 
	 slow/fast/nonstop mode.

Next - Execute one expression, then revert to idle.

Slow - Execute until end of proc, stopping at breakpoints or when the
	 state changes to stop. After each execution, stop for `delay'
 	 milliseconds. The delay can be changed with the `+' and `-'
	 buttons.

Fast - Execute until end of proc, stopping at breakpoints.

Nonstop - Execute until end of proc without stopping at breakpoints or
	    updating the display.

Break - Terminate execution of current proc.

The menus should be obvious (Sorry better docs MAY be available some
day:-).

Closing the debugger doesn't quit it, it only does `wm withdraw'.  The
debugger window will pop up the next time a prepared proc is called.

Breakpoints:
To set/unset a breakpoint, double-click inside the listing. The
breakpoint will be set at the innermost available expression that
contains the position of the click.
There's no support for conditional or counted breakpoints yet.

The `Eval: ' entry supports a simple history mechanism available via
the <Up> and <Down> keys. If you evaluate a command while stepping
through a proc, the command will be evaluated in the context of the
proc, otherwise at global level. The result will be displayed in the
result field. 

This entry is useful for a lot of things, but especially to get access
to variables outside the current scope. Try entering the line
`global td_priv' and watch the `Variables' box (with global and array
variables enabled of course).

}}}
{{{ Configuration

You can customize TDebug by setting up a file named .tdebugrc in your
home directory.

The following variables have special effects:

Relevant for the Debugger window:


Variable		Value	Effect
-----------------------------------------------------------------------

td_priv(wrap)		none	Don't wrap listing of current proc
			word    Word-wrap listing
td_priv(wrapback)	none	Don't wrap backtrace
			word	Word-wrap backtrace
td_priv(fullnames)	1	Display full widget names
			0 	Display the last part only
td_priv(update)		slow	Always update variables
			fast	Update variables in idle state only
td_priv(detail)		low	Don't check for subexpressions when 
				preparing procs
			high	Do check for subexpressions

td_priv(delay)			Delay in milliseconds used with slow 
				stepping (100-1500)

td_priv(globalvars)	1	Display global variables accessible from 
				current proc
			0	Don't display global variables
td_priv(arrayvars)	1	Display array variables similar to parray
			0	Don't display arrays (they take too much space)

td_priv(scrollbarside)	left	Place all scrollbars at the left side
			right	Place all scrollbars at the right side

td_priv(constrainscroll) 1	Don't scroll after last line in listing
			 0      Normal scrolling

td_priv(height)			Height of proc listing
td_priv(listwidth)		Width of proc listing
td_priv(varwidth)		Width of variable display
td_priv(geometry)		Geometry of Debugger window. Use for position only!

td_priv(preparedtag)		tag style for prepared lines
td_priv(activetag)		tag style for currently active expression
td_priv(breaktag)		tag style for breakpoints
				Tag styles are used for .widget tag configure ...
				For example "-background red -foreground blue" etc.

td_priv(tagpriority)		priority of tags, lowest priority first.
				Legal tag values are (default priority):
					prepared sel active break
td_priv(useblt)		0	Don't use BLT, even if available
				If unset, use BLT if it is available



Relevant for the Chooser window:

Variable		Value	Effect
-----------------------------------------------------------------------

td_priv(send)		0	Can't use send
			1	Can use it

td_priv(scrollbarside)	left	Place all scrollbars at the left side
			right	Place all scrollbars at the right side

td_priv(constrainscroll) 1	Don't scroll after last line in listing
			 0      Normal scrolling

td_priv(chooseheight)		Height of chooser box
td_priv(choosewidth)		Width of chooser box
td_priv(choosegeometry)		Geometry of Choose window. Use for position only!

td_priv(hideownprocs)	1	Don't display procs belonging to TDebug
			0	Display those procs (be careful!)
td_priv(hidetkprocs)	1	Don't display procs belonging to Tk, i.e.
				tk_*, auto_* and unknown.
			0	Display those procs
td_priv(debugdir)		Set to the directory containing TdDebug.tcl.
				Not necessary if it is the same as TdChoose.tcl.



Relevant for the Backtrace window:

Variable		Value	Effect
-----------------------------------------------------------------------

td_priv(backtraceheight)		Height of backtrace
td_priv(backtracewidth)			Width of backtrace
td_priv(backtracegeometry)		Geometry of Backtrace window.
					Use for position only!

Relevant for the ErrorTrace window:

Variable		Value	Effect
-----------------------------------------------------------------------

td_priv(errorheight)		Height of error trace
td_priv(errorwidth)		Width of error trace
td_priv(errorgeometry)		Geometry of ErrorTrace window.
				Use for position only!

Relevant for the WidgetHierarchy window:

Variable		Value	Effect
-----------------------------------------------------------------------

td_priv(widgetsheight)		Height of hierarchy
td_priv(widgetswidth)		Width of hierarchy
td_priv(widgetsgeometry)	Geometry of WidgetHierarchy window.
				Use for position only!


}}}
{{{ Todo

TDebug is nearing version 1.0. Nevertheless there are quite a few
things left to do, including Bug/Feature-fixes as well as
documentation and real development:

* Better parsing. Switch statements don't work well yet.

* Conditional breakpoints, watchpoints.

* Better documentation !!!!

* A real Help button, not just a dummy.

* Make a dialog to display widget information - selectable from hierarchy
  Maybe like TkInspekt ?

* Support for [incr tcl]
  How about a class browser ?

}}}
{{{ Credits

Thanks to:
	John Ousterhout	<ouster@sprite.berkeley.edu> for tcl/tk
	Alessandro Rubini <rubini@ipvvis.unipv.it> for numerous good ideas
		and speedups for parsing

}}}

{{{ Emacs local variables


Local variables:
mode: text
folded-file: t
End:

}}}
