# Chapter 28 The LablTk library: Tcl/Tk GUI interface

The `labltk` library provides access to the Tcl/Tk GUI from OCaml programs. This interface is generated in an automated way, and you should refer to Tcl/Tk books and man pages for detailed information on the behavior of the numerous functions. We also suggest to use `ocamlbrowser` to see the types of the various functions, that are the best documentation for the library itself.

Programs that use the `labltk` library must be linked as follows:

            ocamlc other options -I +labltk labltk.cma other files
            ocamlopt other options -I +labltk labltk.cmxa other files

> Unix: The `labltk` library is available for any system with Tcl/Tk installed, starting from Tcl 7.5/Tk 4.1 up to Tcl/Tk 8.4. Beware that some beta versions may have compatibility problems.

> If the library was not compiled correctly, try to run again the `configure` script with the option `-tkdefs` switches, where switches is a list of C-style inclusion paths leading to the right `tcl.h` and `tk.h`, for instance `"-I/usr/local/include/tcl8.4 -I/usr/local/include/tk8.4"`.

> A script is installed, to make easier the use of the `labltk` library as toplevel.

> `labltk`
>   This is a toplevel including the `labltk` library, and the path is already set as to allow the use of the various modules. It also includes code for the Unix and Str libraries. You can use it in place of `ocaml`.

> Windows: The `labltk` library has been precompiled for use with Tcl/Tk 8.4. You must first have it installed on your system. It can be downloaded from
> `http://www.activestate.com/products/ActiveTcl/`. After installing it, you must put the dynamically loaded libraries `tcl84.dll` and `tk84.dll` (from the `bin` directory of the Tcl installation) in a directory included in you path.

> No toplevel is available, but you can load the library from the standard toplevel with the following commands.

> >     # #directory "+labltk";;
> >     # #load "labltk.cma";;

> You can also load it directly from the command line.

> >     C:\ocaml\bin> ocaml -I +labltk labltk.cma

The `labltk` library is composed of a large number of modules.

>     Bell                Imagebitmap         Place
>     Button              Imagephoto          Radiobutton
>     Canvas              Label               Scale
>     Checkbutton         Listbox             Scrollbar
>     Clipboard           Menu                Selection
>     Dialog              Menubutton          Text
>     Entry               Message             Tk
>     Focus               Option              Tkwait
>     Frame               Optionmenu          Toplevel
>     Grab                Pack                Winfo
>     Grid                Palette             Wm

Giving a detailed account of each of these module would be impractical here. We will just present some of the basic functions in the module `Tk`. Note that for most other modules information can be found in the Tcl `man` page of their name.

- The `Tk` library: Basic functions and types for LablTk