				    README
			   Written by Stu Grossman
	      Updated 9/26/95 by Fred Fish for gdb 4.15 release
              Updated 4/18/97 by Martin Hunt
	      Updated 7/6/09 by Keith Seitz

This file describes how to build, install, use and hack on Insight (formerly
GDBtk), a TK-based GUI for GDB, the GNU debugger.

Introduction
============

Insight is a version of GDB that uses Tcl/Tk to implement a graphical
user interface.  It is a fully integrated GUI, not a separate
front-end program.  The interface consists of several separate
windows, which use standard elements like buttons, scrollbars, entry
boxes and such to create a fairly easy to use interface.  Each window
has a distinct content and purpose, and can be enabled or disabled
individually.  The windows contain things like the current source
file, a disassembly of the current function, text commands (for things
that aren't accessible via a button), and so forth.

Building and Installing
=======================

Building Insight is very straightforward.  It is configured/built by
default when you checkout or download Insight. Insight may be built
with the supplied Tcl, Tk, and Itcl or with your system's or vendor's
supplied versions (minimum requirement Tcl/Tk 8.4). When you checkout
Insight from the repository, you will automatically checkout tcl, tk,
and itcl.  If you wish to use your system's installed versions, simply 
erase the checked out versions:

$ rm -rf src/tcl src/tk src/itcl

If you downloaded a snapshot, you may optionally download these versions
of tcl, tk, and itcl. To use them (and not your system's installed
versions), simply unpack the tcltk tarball (the leading "src/" prefix
has been left intact).

On Unix machines, you will also need to have X11 (R4/R5/R6) installed 
(this is a prerequisite to installing Tk).  

Insight inherits much of GDB's configuration options (like where it is
to be installed).  See the GDB README file for more details on configure
options and such for GDB.

It is recommended that Insight, like GDB, be built outside of the source
directory in order to preserve the integrity of the source directory.  This
is very useful, for example, when building GDB/Insight for multiple hosts
or targets.

For example:

	host> ls
	src/
	host> mkdir insight; cd insight
	host> ../src/configure
	host> make
	host> make install

Environment Variables
=====================

Insight and all of its support infrastructure read various environment variables
for optional startup information. All of these environment variables are
optional: Insight and its packages know how to find their files in both the
install and the source trees.

	Name			Description
	----			-----------
	TCL_LIBRARY		The location of the Tcl library files
	TK_LIBRARY		The location of the Tk library files
	REDHAT_GUI_LIBRARY	The location of the libgui library files
	GDBTK_LIBRARY		The location of the Insight library files
	INSIGHT_PLUGINS		A colon-separated list of directories
				to search for plugins (see gdb/gdbtk/plugins/HOW-TO)
	GDBTK_DEBUG		Controls runtime loading of the Debug Window.
				(This is the most useful debug option.)
	GDBTK_TRACE		Controls runtime tracing of the tcl code
	GDBTK_DEBUGFILE		Filename to send debug output
	GDBTK_TEST_RUNNING	Testsuite variable. See gdb/testsuite/gdb.gdbtk/README
				for more information.
	INSIGHT_FORCE_READ_PREFERENCES
				If set, read .gdbtkinit (or gdb.ini on windows)
				even when -nx is passed to GDB.
	DISPLAY			The display to use on unix/X platforms.
				Not used on Windows platforms.

All of the environment variables for controlling Insight are well documented
in gdb/gdbtk/library/main.tcl. Search for "env" to find them all.

Using Insight
=============

You can start Insight by running the `insight' executable (for cross-platform
targets, include the build triple, i.e., `powerpc-elf-insight'). Alternatively start
Insight by telling GDB to start it with `gdb -w' or `gdb -i=insight'. If
everything goes well, you should have several windows pop up.  To get going,
hit the Run button, and go exploring.

If you want to use GDB in command line mode, just use the -nw option or the
console interpreter (`insight -i=console').

Insight comes with all your standard debugger windows, including:

	o Console Window
	o Source Window
	o Register Window
	o Memory Window
	o Locals Window
	o Watch Window
	o Stack Window
	o Thread/Process Window
	o Function Browser Window
	o Debug Window (for developers)

Insight also has an extensive (if outdated) online help system which describes
all the windows and explains how to use them.  Users are urged to browse this
help system for information on using Insight.

Hacking Insight
===============

The GUI is primarily implemented by Tcl/Tk code which lives in gdb/gdbtk/library
 and bunch of C files in gdb/gdbtk/generic.  The Tcl/Tk code determines the look
and feel, the layout, and the functions associated with all of the interface
elements.  The C code is mostly just glue between GDB internals and Tcl-land.
In essence, all of the policy is implemented in Tcl/Tk, and is easily changed
without recompiling.

To make more serious changes to the interface, such as adding a new window or
changing the framework, you will have to hack the tcl code (and probably the C
code as well).  The tcl library install directory is $(libdir) (probably
/usr/local/lib/insight1.0).  But, you will probably want to hack on your own
private copy before putting it up for the rest of the users.  To find the GDB tcl
code, GDB first checks for the environment variable GDBTK_LIBRARY.  GDB will check
this directory for the file "main.tcl".  If GDBTK_LIBRARY is not set, GDB will
look for main.tcl in the install directory, and finally it will try to find 
the tcl directory in the sources.

A word about the different files in Insight is in order.  Insight is a hybrid of
C code and "Tcl" code (actually Incr Tcl code).  We use the following conventions
for naming our tcl files (most of the time!).  Any file with a ".tcl" extension
is simply vanilla tcl code.  Any file ending with ".itcl" is an Itcl file,
class definition and implementation all in one.  So far so good.  Now comes the
toughy: Files ending in ".ith" are Itcl class definition files, and they all
must have a corresponding implementation file, ending in ".itb".  Why do we do
this? Simple.  With Itcl, one can reread class implementations at runtime, but
one cannot change the class definition.  So all those ".itcl" files can only
be reread be restarting Insight.  The same is not true, though, of the ".itb"
files.  Those files can be changed and immediately reread and used in Insight
without having to restart (as long as the class definition doesn't change).  This
is a nifty Itcl feature which is fully exploited by the Debug Window, which
has a "ReSource" menu on it to reread the Tcl files.  (To get to the Debug Window,
hit Ctrl-Alt-F11 in the Source Window or type "tk ManagedWin::open DebugWin" in
the Console Window.)

Internally, Insight is basically GDB, linked with Tcl/Tk, some Tcl/Tk extensions,
and some glue code that interfaces GDB internals to Tcl-land.  This means that
Insight operates as a single program, not a front-end to GDB.  All GDB commands,
and a great deal of the target program state are accessible to the Tcl programmer.
In addition, there are many callbacks from GDB to notify Tcl-land of important
events.  Many of these are accomplished via "hooks" in GDB, and others are
accomplished using event notifications.  GDB is slowly deprecating the use of
"hooks" in favor of its new event mechanism.

All of the below commands have lots of nice comments before them explaining what
they all do, how they are to be used, etc.  The source code is the definitive
authority (other than a maintainer) for the definition/usage of a command in
Insight.  Hackers are urged to read through the source code for any commands
which may need explaining.

New Tcl Commands:

Here is a brief, if incomplete, summary of the Tcl commands that are created
by Insight.  These are installed into the Tcl interpreter in the C files.

	Name			Description
	----			-----------
	gdb_cmd			Sends a text command to gdb.  Returns the result.
				DEPRECATED: Do not use any more.
	gdb_loc			Returns a list of useful tidbits about the specified
				GDB linespec
	gdb_sourcelines		Returns a list of executable lines for a source file
	gdb_listfiles		Returns a list of all of the source files
	gdb_stop		Stops the target process (or at least tries to)
	gdb_reginfo		Returns information about registers (names, numbers,
	              		values, size, etc.)
	gdb_disassemble		Returns the text of a disassembly of the entire
				function.  No longer used.
	gdb_load_disassembly	Loads the disassembly of a location into a
				source window's textbox
	gdb_eval		Returns the value of a given expression
	gdb_get_breakpoint_list	Returns a list of all breakpoints
	gdb_get_breakpoint_info Returns a list of info about a breakpoint

Tcl procedures that are hooked into GDB:

This is a list, albeit incomplete, of the "hook" functions that are installed
into GDB.  The actual "hooks" are installed/initialized in
gdb/gdbtk/generic/gdbtk-hooks.c (and maybe one or two in gdbtk.c).  The list
below is the Tcl side of the hook.

	Name			Description
	----			-----------
	gdb_tcl_fputs		Sends output into Tcl for the command window
	gdb_tcl_query		Pops up a query window
	gdbtk_tcl_breakpoint	Notifies Tcl of changes to a breakpoint
	gdbtk_tcl_idle		Notifies Tcl that debugged process is now idle
	gdbtk_tcl_busy		Notifies Tcl that debugged process is now running

Events:

Starting with GDB 5.0, GDB has had an event loop.  Although largely unused right
now, with it came some useful "baggage", especially event notifications, even
though they, too, were largely incomplete.  The list of events continues to grow,
and Insight and GDB often "share" overlapping events, but the list below is
complete (since there are only a few defined events).  The source for these
events can be found in gdb/gdbtk/library/gdbevents.it[hb].

	Name			Description
	----			-----------
	BreakpointEvent		A breakpoint has been created/modified/deleted
	TracepointEvent		A tracepoint has been created/modified/deleted
	SetVariableEvent	User has issued a "set" command in Console
	BusyEvent		The debugger is "busy"
	IdleEvent		The debugger is "idle"
	UpdateEvent		The state of the target has changed (or the
				GDB's view of the target has changed)
	ArchChangedEvent	The architecture of the system has changed
				(this can happen when GDB defaults to using
				some basic CPU and detects that a more elaborate
				CPU is actually being used, e.g., SH5)

GDB Commands:

Insight installs a few GDB commands, which are available with the Console Window.

	Name			Description
	----			-----------
	tk			Executes the arguments in the Insight Tcl
				interpreter
	view			Displays the given linespec in the Source Window

Problems
========

During building, you may run into problems with finding Tcl, Tk or X11.  Look
in gdb/Makefile, and fix TCL_CFLAGS, TCL, TK_CFLAGS, TK, and ENABLE_CLIBS as
appropriate.

If you one of the following messages when you run gdb:

	Tcl_Init failed: can't find init.tcl; perhaps you need to
	install Tcl or set your TCL_LIBRARY environment variable?
or
	Tk_Init failed: can't find tk.tcl; perhaps you need to
	install Tk or set your TK_LIBRARY environment variable?

then you haven't installed Tcl or TK properly.  Fix the appropriate environment
variable to point at the {tcl tk}/library directory, and restart gdb.

Known Bugs
==========

generic problems

    o	Using the GDB commands "up"/"down"/"frame" in Console Window
	can cause GDB and Insight to get out of sync.  If this happens,
	simply use the Stack Window or the frame navigation buttons on
	the Source Window's toolbar to resync the two.

    o	Not really a problem, but it might be nice to have a frame/stack
	window that displays the last N words on the stack, along with
	indications about which function owns a particular frame, how the
	frame pointers are chained, and possibly the names of variables
	alongside their frame slots.

host- or target-specific problems

    o	Windows is hosed. Tk8.3 in sources.redhat.com is not stable
	on windows. Wanna help?

Where to find help
==================

The first place to turn for help is the online help system.  It may be old, but
it is still largely correct: it explains what everything does.  If that fails,
search the mailing list archives for other users who may have had similar problems
or questions.  The archives are online at

http://sources.redhat.com/insight/mailinglist.htm .

If all else fails, send a note to the mailing list, insight@sources.redhat.com,
where users and maintainers lurk.  This is a very low traffic list, so don't
be afraid to join the list.  Instructions for joining are on our homepage,
http://sources.redhat.com/insight .
