package lablgtk3-sourceview3

  1. Overview
  2. Docs
OCaml interface to GTK+ gtksourceview library


Dune Dependency





LablGTK3 3.1.3 : an interface to the GIMP Tool Kit


  • ocaml >= 4.05.0 (including 5.0)

  • gtk+ >= 3.18

  • dune >= 1.8

  • camlp5 (for developer build only)





LablGtk3 is still an experimental port of LablGtk2 to Gtk-3. Currently it is more or less a subset of LablGtk2.

LablGtk uses unicode (utf8) for all strings. If you use non-ascii strings, you must imperatively convert them to unicode. This can be done with the Glib.Convert.locale_to_utf8 function. If your input is already in utf8, it is still a good idea to validate it with Glib.Utf8.validate, as malformed utf8 strings may cause segmentation faults. The setlocale function is always called (except if you set GTK_SETLOCALE to 0 in the environment), but LC_NUMERIC is reverted to "C" to avoid problems with floating point conversion in OCaml.

Some widgets may be unsupported on your version of Gtk. If you use them, you will get a runtime error:

Failure "Gobject.unsafe_create : type GtkActionGroup is not yet defined"

For unsupported methods, the error message is a bit clearer:

Failure "gdk_pixbuf_get_file_info unsupported in Gtk 2.x < 2.4"

How to compile:

To compile in developer mode type:

$ dune build

this will compile all the public artifacts of all the included packages, and does require having developer tools installed [camlp5 for instance].

You must not use the developer mode to build lablgtk3 packages, for that you should use

$ dune build -p $package

where package is, as of today, one of lablgtk3, lablgtk3-gtksourceview3, lablgtk3-gtkspell3.

LablGTK uses a standard Dune build setup, see the Dune documentation for more options.


  • src/ low-level interface to the General Drawing Kit

  • src/ low-level interface to the GIMP Tool Kit

  • src/ main loop for threaded version

  • src/g[A-Z]*.ml object-oriented interface to GTK

  • src/ object-oriented interface to GDK

  • examples/*.ml various examples

  • applications/browser an ongoing port of ocamlbrowser

  • applications/camlirc an IRC client (by Nobuaki Yoshida)

How to run the examples

The examples are compiled by calling dune build @all, you can build lablgtk3 applications using a standard Dune or ocamlfind workflow.

Remember to call GMain.init () in your application, or it will fail to properly initialize.

How to use the threaded toplevel

You can start a thread session using utop:

$ dune utop src
# #thread;;
# let locale = GMain.init ();;
# let thread = GtkThread.start();;
# let w = GWindow.window ~show:true ();;
# let b = GButton.button ~packing:w#add ~label:"Hello!" ();;

You should at once see a window appear, and then a button. The GTK main loop is running in a separate thread. Any command is immediately reflected by the system. For Windows and OSX/Quartz, there are restrictions on which commands can be used in which thread. See the windows port section lower for how to use them.

When using threads in a stand-alone application, you must link with gtkThread.cmo and call GtkThread.main in place of GMain.main.

Since 2.16.0, busy waiting is no longer necessary with systems threads. (I.e., CPU usage is 0% if nothing occurs.) If you use VM threads, you have to enable busy waiting by hand, otherwise other threads won't be executed (cf. gtkThread.mli). Beware that with VM threads, you cannot switch threads within a callback. The only thread related command you may use in a callback is Thread.create. Calling blocking operations may cause deadlocks. On the other hand, all newly created threads will be run outside of the callback, so they can use all thread operations.

Structure of the (raw) Gtk* modules

These modules are composed of one submodule for each class. Signals specific to a widget are in a Signals inner module. A setter function is defined to give access to set_param functions.

Structure of the G[A-Z]* modules

These modules provide classes to wrap the raw function calls. Here are the widget classes contained in each module:

  • GPango Pango font handling

  • GDraw Gdk pixmaps, etc...

  • GObj gtkobj, widget, style

  • GData data, adjustment, tooltips

  • GContainer container, item_container

  • GWindow window, dialog, color_selection_dialog, file_selection, plug

  • GPack box, button_box, table, fixed, layout, packer, paned, notebook

  • GBin scrolled_window, event_box, handle_box, frame, aspect_frame, viewport, socket

  • GButton button, toggle_button, check_button, radio_button, toolbar

  • GMenu menu_item, tearoff_item, check_menu_item, radio_menu_item, menu_shell, menu, option_menu, menu_bar, factory

  • GMisc separator, statusbar, calendar, drawing_area, misc, arrow, image, pixmap, label, tips_query, color_selection, font_selection

  • GTree tree_item, tree, view (also tree/list_store, model)

  • GList list_item, liste, clist

  • GEdit editable, entry, spin_button, combo

  • GRange progress, progress_bar, range, scale, scrollbar

  • GText view (also buffer, iter, mark, tag, tagtable)

While subtyping follows the Gtk widget hierarchy, you cannot always use width subtyping (i.e. #super is not unifiable with all the subclasses of super). Still, it works for some classes, like #widget and #container, and allows subtyping without coercion towards these classes (cf. #container in examples/ for instance).

Practically, each widget class is composed of:

  • a coerce method, returning the object coerced to the type widget.

  • an as_widget method, returning the raw Gtk widget used for packing, etc...

  • a destroy method, sending the destroy signal to the object.

  • a get_oid method, the equivalent of for Gtk objects.

  • a connect sub-object, allowing one to widget specific signals (this is what prevents width subtyping in subclasses.)

  • a misc sub-object, giving access to miscellanous functionality of the basic gtkwidget class, and a misc#connect sub-object.

  • an event sub-object, for Xevent related functions (only if the widget has an Xwindow), and an event#connect sub-object.

  • a drag sub-object, containing drag and drop functions, and a drag#connect sub-object.

  • widget specific methods.

Here is a diagram of the structure (- for methods, + for sub-objects)

        - coerce : widget
        - as_widget : Gtk.widget obj
        - destroy : unit -> unit
        - get_oid : int
        - ...
        + connect : mywidget_signals
        |   - after
        |   - signal_name : callback:(... -> ...) ->
        + misc : misc_ops
        |   - show, hide, disconnect, ...
        |   + connect : misc_signals
        + drag : drag_ops
        |   - ...
        |   + connect : drag_signals
        + event : event_ops
        |   - add, ...
        |   + connect : event_signals

You create a widget by <Module>.<widget name> options ... (). Many optional arguments are admitted. The last two of them, packing: and show:, allow you respectively to call a function on your newly created widget, and to decide wether to show it immediately or not. By default all widgets except toplevel windows (GWindow module) are shown immediately.

Default arguments

For many constructor or method arguments, default values are provided. Generally, this default value is defined by GTK, and you must refer to GTK's documentation. For ML defined defaults, usually default values are either false, 0, None or NONE``, according to the expected type. Important exceptions are `~show`, which default to true in all widgets except those in **GWindow**, and `~fill`, which defaults to true or BOTH``.

Note about unit as method argument:

O'Caml introduces no distinction between methods having side-effects and methods simply returning a value. In practice, this is confusing, and awkward when used as callbacks. For this reason all methods having noticeable side-effects should take arguments, and unit if they have no argument.

ML-side signals

The GUtil module provides two kinds of utilities: a memo table, to be able to dynamically cast widgets to their original class, and more interesting ML-side signals. With ML-side signals, you can combine LablGTK widgets into your own components, and add signals to them. Later you can connect to these signals, just like GTK signals. This proved very efficient to develop complex applications, abstracting the plumbing between various components. Explanations are provided in GUtil.mli.

Contributed components

The GToolbox module contains contributed components to help you build your applications.

Memory management

Important efforts have been dedicated to cooperate with Gtk's reference counting mechanism. As a result you should generally be able to use Gdk/Gtk data structures without caring about memory management. They will be freed when nobody points to them any more. This also means that you do not need to pay too much attention to whether a data structure is still alive or not. If it is not, you should get an error rather than a core dump. The case of Gtk objects deserves special care. Since they are interactive, we cannot just destroy them when they are no longer referenced. They have to be explicitely destroyed. If a widget was added to a container widget, it will automatically be destroyed when its last container is destroyed. For this reason you need only destroy toplevel widgets.

Since too frequent GC can severely degrade performance, since 2.18.4 it is possible to change the contribution of custom blocks to the GC cycle, using the function GMain.Gc.set_speed. The default is 10% of what it was in 2.18.3. If you set it to 0, custom block allocation has no impact, and you should consider running the Gc by hand.

IMPORTANT: Some Gtk data structures are allocated in the Caml heap, and their use in signals (Gtk functions internally cally callbacks) relies on their address being stable during a function call. For this reason automatic compation is disabled in GtkMain. If you need it, you may use compaction through Gc.compact where it is safe (timeouts, other threads...), but do not enable automatic compaction.

Libraries support

  • GtkSourceView 3 support: This binding was contributed by Benjamin Monate, and adapted by Hugo Herbelin. It requires libgtksourceview-3.x. See examples in examples/sourceview/* The executable must be linked with lablgtksourceview3.cma.

  • GtkSpell 3 support:

Not available in Gtk3
  • LibGlade support: not available in Gtk3 (replaced by GtkBuilder)

  • GL extension: not available in Gtk3

  • SVG support: not available in Gtk3

  • GnomeCanvas support: not available in Gtk3

Running lablgtk3 in the toplevel

The X11 version of lablgt3

Windows port

If you want to use threads, you must be aware of windows specific restrictions; see for instance: I.e. all GTK related calls must occur in the same thread, the one that runs the main loop. If you want to call them from other threads you need to do some forwarding. Fortunately, with a functional language this is easy. Two functions,

val async : ('a -> unit) -> 'a -> unit
val sync : ('a -> 'b) -> 'a -> 'b

are available in the GtkThread module to help you. They will forward your call to the main thread (between handling two GUI events). This can be either asynchronous or synchronous. In the synchronous case, beware of deadlocks (the trivial case, when you are calling from the same thread, is properly avoided). Note also that since callbacks are always called from the main loop thread, you can freely use GTK in them. Also, non-graphical operations are thread-safe. Here is an example using the lablgtk toplevel with threads:

% dune utop src
# #thread;;
# GMain.init ();;
# open GtkThread;;
# let thread = start ();;
# let w = sync (GWindow.window ~show:true) ();;
# let b = sync (GButton.button ~packing:w#add ~label:"Hello!") ();;
# b#connect#clicked (fun () -> prerr_endline "Hello");;

OSX/Quartz port

Since Darwin is Unix, this port compiles as usual. Note however that Quartz imposes even stronger restrictions than Windows on threads: only the main thread of the application can do GUI work. Just apply the same techniques as described in the Windows port, being careful to ensure that your first call to GtkThread.main occurs in the main thread. This can be done by issueing the following commands

% dune utop src
# #thread;;
# GMain.init ();;
# let thread = Thread.create UTop_main.main () and () = GtkThread.main ();;
# open GtkThread;;
# let w = sync (GWindow.window ~show:true) ();;
# let b = sync (GButton.button ~packing:w#add ~label:"Hello!") ();;
# b#connect#clicked (fun () -> prerr_endline "Hello");;

This launches a toplevel thread, and runs main in the application thread. This version utop-specific; tool/ has a version for the ocaml vanilla toplevel.


For lablgtk1

Bug reports


Innovation. Community. Security.