Thanks to Lars Wirzenius for the
original version
of this tutorial written for PyGtk. Changes to the document were only to
reflect the current state of the Gtk+ codebase and to be applicable to PHP-Gtk2.
Version 2.0 of Gtk+ introduces its third generation of tree
and list widgets. Version 1.0 had GtkList and GtkTree, version 1.2
had GtkCList and GtkCTree,
and now version 2.0 has GtkTreeView,
which servers both as a list and a tree. With each version, the
power and usefulness of the widgets have increased.
GtkTreeView uses a Model/View/Controller approach.
This means that the code is divided into a data structure representing
user's data ("the model"), the widgets that display the data and
interact with the user ("the view"), and some logic to tie things
nicely together ("the controller"). The model is implemented by
GtkTreeModel (actually, classes implementing that interface), the
view by GtkTreeView with some helpers, and the controller by the
user code.
This sounds unnecessarily complicated, but the complexity
is local, and this aproach actually simplifies overall program
structure. For example, it is often necessary to view the same data
(i.e., model) in different ways, or in different windows. Think,
for example, of a programmer's editor: the same source code may
be viewed in several windows at the same time, and changes in one
window should be shown in all the others, as well. Thus, it makes
sense to separate the storage of the text from its display, rather
than storing the text in each window widget.
The example application in this article lets the user manage
a folder tree. The folders are virtual, not real directories in
the filesystem, to keep the code simpler. The example is actually
derived from Lodju, in which the folders have nothing to do with
the filesystem.
The official Gtk+ 2.0
API reference documentation for GtkTreeView
should be read together with this tutorial, even if it is a bit sparse in
some details.
I thank the people on the
Gtk+ developer IRC channel for
encouragement and feedback.
