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GLib.md

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GLib

  • Glib is a set of libraries, GLib core, GObject and GIO.

  • GLib core provides data structure handling for C (linked lists, trees, hash tables,. . . ), portability wrappers, an event loop, threads, dynamic loading of modulesand lots of utility functions.

  • GObject – which depends on GLib core – simplifies the object-oriented pro-gramming and event-driven programming paradigms in C.

  • GIO – which depends on GLib core and GObject – provides high-level APIs forinput/output: reading a local file, a remote file, a network stream, inter-processcommunication with D-Bus, and many more.

  • GTK+ is a widget toolkit based on GLib that can be used to develop applicationswith a graphical user interface (GUI).

  • The first version of GTK+, or the GIMP Tool Kit4, was mainly written byPeter Mattis in 1996 for the GIMP (GNU Image Manipulation Program), buthas quickly become a general-purpose library.

  • GLib started as part of GTK+, but is now a standalonelibrary.

  • An important project for GLib and GTK+ is GNOME (GNU Network Object Model Environment). GNOME, which is alsopart of GNU, is a free/libre desktop environment started in 1997 by Miguel de Icazaand Federico Mena-Quintero. GNOME makes extensive use of GTK+

  • Oldversions of GNOME included an object embedding architecture called Bonobo,and GNOME 1.0 included a fast, light CORBA ORB called ORBit. Bonobo hasbeen replaced by D-Bus, an inter-process communication system.

  • Object-Oriented Design Heuristics, by Arthur Riel The Algorithm DesignManual, by Steven Skiena UNIX for the Impatient, by Paul Abrahams Pro Git, by Scott Chacon

  • Thanks to GObject Introspection, automatic bindings are available for avariety of languages for all libraries based on GObject. Official GNOME bindingsare available for the following languages: C++, JavaScript, Perl, Python andVala7. Vala is a new programming language based on GObject which integratesthe peculiarities of GObject directly in its C#-like syntax.

  • Each frontend should be a "view" and a "controller”. As a “view,” the frontendmust note any changes in the backend, and change the display accordingly. Asa “controller,” the frontend must allow the user to relay requests for change tothe backend.

  • sudo apt-get install libgtk2.0-dev

  • GLib has a few toplevel headers:

glib.h // the main header
gmodule.h // for dynamic loading of modules
glib-unix.h // for Unix-specific APIs
glib/gi18n.h and glib/gi18n-lib.h //for internationalization
glib/gprintf.h and glib/gstdio.h //to avoid pulling in all of stdio.

gint8, 
guint8,
gint16,
guint16,
gint32,
guint32,
gint64,
guint64
gboolean
gchar
gshort
glong
gint
gfloat
gdouble

  • gpointer may be more convenient to type than void*. gconstpointer gives you const void*.

  • gsize is an unsigned integer type that can hold the result of the sizeof operator.

  • CLAMP(x, low, high) means x, unless x is outside the range [low,high]; if x is below the range,low is returned; if x is above the range,high is returned.

#include<glib.h>

GINT_TO_POINTER (p);
GPOINTER_TO_INT (p);
GUINT_TO_POINTER (p);
GPOINTER_TO_UINT (p);
#include<glib.h>

g_return_if_fail (condition);
g_return_val_if_fail (condition, return_value);
gint my_int;
gpointer my_pointer;
my_int = 5;

my_pointer = GINT_TO_POINTER (my_int);
printf ("We are storing %d\n", GPOINTER_TO_INT (my_pointer));
  • GLib has a nice set of macros you can use to enforce invariants and pre-conditions in your code. They all disappear when you define G_DISABLE_CHECKS or G_DISABLE_ASSERT, so there’s no performance penalty in production code.
#include<glib.h>
g_assert (condition);
g_assert_not_reached ();

  • g_return_if_fail() prints a warning and immediately returns from the current function if condition is FALSE. g_return_val_if_fail() is similar but allows you to return some return_value.

  • All of the debugging macros print a warning using GLib’s g_log() facility, whichmeans the warning includes the name of the originating application or library,and you can optionally install a replacement warning-printing routine.

include<glib.h>
gpointer g_malloc (gsize n_bytes);
void g_free (gpointer mem);
gpointer g_realloc (gpointer mem, gsize n_bytes);
gpointer g_memdup (gconstpointer mem, guint n_bytes);
gint g_snprintf (gchar *string, gulong n, gcharconst*format, ...);
// Allocating String
#include<glib.h>
gchar * g_strdup (constgchar *str);
gchar * g_strndup (constgchar *str, gsize n);
gchar * g_strdup_printf (constgchar *format, ...);
gchar * g_strdup_vprintf (constgchar *format, va_list args);
gchar * g_strnfill (gsize length, gchar fill_char);

  • GLib implements many common data structures, like linked lists, sorted binary trees, N-ary trees, and hash tables.

  • GLib provides generic single and doubly linked lists, GSList and GList, respectively.

  • Every GTK+ widget is a subclass of the GObject base class. So knowing the basic concepts of GObject is important for using a GTK+ widget or another GObject-based utility, but also for creating your own GObject classes.

  • What GObject adds is more features such as reference counting, inheri-tance, virtual functions, interfaces, signals and more.

PyGTK

  • PyGObject is a Python module that enables developers to access GObject-based libraries such as GTK+ within Python.

  • gobject-introspection (gi)