INTRODUCTION
============
mlTk is a library for interfacing OCaml with the scripting
language Tcl/Tk (all versions since 8.0.3, but no betas).

In addition to the basic interface with Tcl/Tk, this package contains
 * the OCamlBrowser code editor / library browser written by Jacques
 Garrigue.
 * the "jpf" library, written by Jun P. Furuse; it contains a "file
 selector" and "balloon help" support
 * the "frx" library, written by Francois Rouaix
 * the "tkanim" library, which supports animated gif loading/display

mlTk = CamlTk + LablTk
======================
There existed two parallel Tcl/Tk interfaces for OCaml, CamlTk and LablTk.

CamlTk uses classical features only, therefore it is easy to understand for
the beginners of ML. It makes many conservative OCaml gurus also happy.
LablTk, on the other hand, uses rather newer features of OCaml, the labeled
optional arguments and polymorphic variants. Its syntax has much more Tcl/Tk
script flavor, but provides more powerful typing than CamlTk at the same time
(i.e. less run time type checking of widgets).
Until now, these two interfaces have been distributed and maintained
independently.

mlTk unifies these libraries into one. Since mlTk provides the both API's,
both CamlTk and LablTk users can compile their applications with mlTk,
just with little fixes.

REQUIREMENTS
============
You must have already installed
 * OCaml source, version 3.04+8 or later

 * Tcl/Tk 8.0.3 or later
    http://www.scriptics.com/ or various mirrors

PLATFORMS:
Essentially any Unix/X Window System platform. We have tested
releases on Linux (ELF x86), FreeBSD (x86), SunOS4.1.x (sparc), DEC
OSF/1 V4.0 (alpha), DGUX SVR4 (m88k) and Windows (VC++ and Cygwin).

INSTALLATION
============

0. Check-out the OCaml CVS source code tree.

1. Compile OCaml (= make world). If you want, also make opt.

2. Untar this mlTk distribution in the otherlibs directory, just like
   the labltk source tree.

3. change directory to otherlibs/mltk, and make (and make opt)

4. To install the library, make install (and make installopt)

To compile mlTk, you need the OCaml source tree, since mltk/camlbrowser
requires some modules of OCaml. If you are not interested in camlbrowser,
you can compile mlTk without the OCaml source tree, but you have to modify
support/Makefile.common.


Compile your CamlTk/LablTk applications with mlTk
=================================================

* General

The names of the additional libraries libjpf and libfrx are changed
to jpflib and frxlib respectively, to avoid the library name space confusion.

* LablTk users

Just change the occurrences of labltk in your Makefiles to mltk
(i.e. -I +labltk => -I +mltk, labltk.cma => mltk.cma, and so on)
Since the API functions are 100% compatible, you need not to change
your .ml files.

* CamlTk users

  - Makefiles : apply the same modification explained above for LablTk users.

  - open Camltk : The API modules and functions are stored in the modules
    Camltk. Therefore you need to replace the module name Tk to Camltk.
    For example, open Tk => open Camltk.

      open Camltk (* instead of open Tk *)

      let t = openTk ();;
      let b = Button.create t [];;

   - You may also need to open the Camltk module explicitly, when your
    original module source contain no open Tk phrase. Widget and the other
    Tcl/Tk related types are now under Camltk. (e.g. Widget.widget is now
    Camltk.Widget.widget) Add open Camltk at the beginning of .mli files,
    if these types are used:

      open Camltk (* added for compiling under mlTk *)

      val create_progress_bar : Widget.widget -> Widget.widget

  - Eta expansion to flush optional arguments at registering callbacks.
    Functions with the _displayof suffix are unified with their non-displayof
    versions, using optional labeled arguments. For example, Bell.ring
    had/have the following types:

        before: Bell.ring : unit -> unit
        now:    Bell.ring : ?displayof:Camltk.widget -> unit -> unit

    If you use these functions as callbacks directly like Command Bell.ring,
    you need eta-expansions to flush these new optional arguments:

        Button.create w [Command Bell.ring]

             => Button.create w [Command (fun () -> Bell.ring ())]

Use the both API's at the same time
===================================
It is possible to use the both API's in one program. If you want to use
a widget library written in the different API from you use, you need to
do it. (It will be confusing, but easier than porting the library itself
from one to the other API.)

For the users who mainly use LablTk API, CamlTk API is available
in the modules start with 'C'. For example, the source file of
the CamlTk button widget functions is CButton (and exported also as
Camltk.Button).

For the users who mainly use CamlTk API, LablTk API modules are exported
inside Labltk module. For example, LablTk's Button module can be also
accessible as Labltk.Button.

In CamlTk, we have only one widget type, [widget]. This type is equivalent
to the LablTk's type [any widget]. Therefore, if you want to apply CamlTk
functions to LablTk widget, you can use [coe] function to coerce it to
[any widget].

To do the converse, the "widget-typers" are available inside the module Labltk.
For example, to recover the type of a button widget, use Labltk.button.
These widget-typers checks the types of widgets at run-time. If the widget
type is different from the context type, a run-time exception is raised.

  open Tk (* open LablTk API *)

  let t = openTk ();; (* t is LablTk widget, toplevel widget *)
  (* CButton.create takes [any widget]; [t] must be coerced to the type. *)
  let caml_b = CButton.create (coe t) [];;
  (* caml_b is [any widget], must be explicitly typed as [button widget],
     when it is used with LablTk API functions *)
  let b = Labltk.button caml_b in (* recover the type [button widget] *)
  ...
