9d51a8f53a
This is the excellent explanation from Emmanuele at
https://gitlab.gnome.org/GNOME/gtk/merge_requests/402#note_361210:
"
Every time you instantiate a type, the instance_init() function is called for each
parent type T_p of your type T; to preserve invariants, the class pointer inside
the instance data is set to the parent type before each invocation, until you hit
your type T. This means that calling GET_CLASS() inside an instance_init() function
will give you a pointer to the class vtable for the parent type T_p while you're
iterating over parent types. What if you want to access the actual class vtable of
the type T, though? Well, you can because the actual signature of instance_init() is:
void (* GInstanceInitFunc) (GTypeInstance *instance, gpointer g_class);
i.e. all instance_init() functions get passed the instance they are initialising
and the class vtable of the real type you're instantiating.
This is how GtkToolButton works: it "peeks ahead" at instance initialisation time,
to use the button_type class field of the actual type you're instantiating,
and calls g_object_new() with it to store the resulting object in its own private
data structure.
This whole contrived mechanism is needed to allow out-of-tree tool buttons to just
set the button type on their class init, and have their parent class create the
button they want, instead of asking all tool buttons to do this themselves and have
a virtual function called get_button() for GtkToolButton to call whenever it needs
to operate on the button instance.
Now we're coming to a close: we cannot use the G_DEFINE_TYPE macro because the
instance_init() function it creates internally will not pass the class pointer
to your custom instance_init(). Since we cannot use G_DEFINE_TYPE, we also cannot use
G_ADD_PRIVATE either.
This is the reason why, when I ported GTK 3 to the new private instance data structure
macros, I left GtkToolButton alone. I should have left a comment there, because @matthiasc
tried doing that as well, and then had to revert it in commit 1c4a7bd5. So: my bad,
sorry about that.
If we want to drop the G_TYPE_INSTANCE_GET_PRIVATE and the g_type_class_add_private() calls,
we cannot use G_DEFINE_TYPE, but what we can do is unrolling what the macros do themselves:
- add a global GtkToolButton_private_offset variable
- add a static inline gtk_tool_button_get_instance_private() that does return
(G_STRUCT_MEMBER_P (self, GtkToolButton_private_offset));
- call g_type_add_instance_private (g_define_type_id, sizeof (GtkToolButtonPrivate)) inside
gtk_tool_button_get_type() and store the result in GtkToolButton_private_offset
- replace g_type_class_add_private() inside gtk_tool_button_class_init() with
g_type_class_adjust_private_offset (klass, &GtkToolButton_private_offset)
"
GTK+ — The GTK toolkit
General information
GTK+ is a multi-platform toolkit for creating graphical user interfaces. Offering a complete set of widgets, GTK+ is suitable for projects ranging from small one-off projects to complete application suites.
GTK+ is free software and part of the GNU Project. However, the licensing terms for GTK+, the GNU LGPL, allow it to be used by all developers, including those developing proprietary software, without any license fees or royalties.
The official download location
The official web site
The official developers blog
Information about mailing lists can be found at
Nightly documentation can be found at
- Gtk: https://gnome.pages.gitlab.gnome.org/gtk/gtk/
- Gdk: https://gnome.pages.gitlab.gnome.org/gtk/gdk/
- Gsk: https://gnome.pages.gitlab.gnome.org/gtk/gsk/
Building and installing
In order to build GTK+ you will need:
You will also need various dependencies, based on the platform you are building for:
If you are building the X11 backend, you will also need:
- Xlib, and the following X extensions:
- xrandr
- xrender
- xi
- xext
- xfixes
- xcursor
- xdamage
- xcomposite
- atk-bridge-2.0
If you are building the Wayland backend, you will also need:
- Wayland-client
- Wayland-protocols
- Wayland-cursor
- Wayland-EGL
Once you have all the necessary dependencies, you can build GTK+ by using Meson:
$ meson _build .
$ cd _build
$ ninja
You can run the test suite using:
$ meson test
And, finally, you can install GTK+ using:
$ sudo ninja install
Complete information about installing GTK+ and related libraries can be found in the file:
docs/reference/gtk/html/gtk-building.html
Or online
How to report bugs
Bugs should be reported on the issues page.
In the bug report please include:
-
Information about your system. For instance:
- which version of GTK+ you are using
- what operating system and version
- for Linux, which distribution
- if you built GTK+, the list of options used to configure the build
And anything else you think is relevant.
-
How to reproduce the bug.
If you can reproduce it with one of the demo applications that are built in the demos/ subdirectory, on one of the test programs that are built in the tests/ subdirectory, that will be most convenient. Otherwise, please include a short test program that exhibits the behavior. As a last resort, you can also provide a pointer to a larger piece of software that can be downloaded.
-
If the bug was a crash, the exact text that was printed out when the crash occurred.
-
Further information such as stack traces may be useful, but is not necessary.
Release notes
The release notes for GTK+ are part of the migration guide in the API reference. See:
Licensing terms
GTK+ is released under the terms of the GNU Lesser General Public License, version 2.1 or, at your option, any later version, as published by the Free Software Foundation.
Please, see the COPYING file for further information.