Analysis of Classes without Constructors (bug 675581)

There are a number of classes in the GNOME APIs that are not intended for direct creation. The issue is there is not an accurate way to generically determine this. GI bindings are general and expose everything they can, this makes a number of classes available which crash when an attempt is made to instantiate them. However, we can look at classes which do not explicitly implement constructors as a hint. The following script and table attempts some analysis as to what classes do not have constructors and why.

Script Used to Generate Initial Table

This script iterates a number of Python GI imported namespaces and looks for GObject.Object based classes which do not provide a public constructor.

   1 import inspect
   2 import gi
   3 from gi.repository import GObject, Gtk, Gdk, GdkPixbuf, Gio
   4 
   5 repo = gi.gi.Repository.get_default()
   6 modules = dict(GObject=GObject,
   7                Gtk=Gtk, Gdk=Gdk,
   8                GdkPixbuf=GdkPixbuf,
   9                Gio=Gio)
  10 
  11 print("||'''Name'''||'''Bug'''||'''Alternative'''||'''Reason'''||")
  12 for modname, mod in sorted(modules.items()):
  13     for name in dir(mod):
  14         obj = getattr(mod, name)
  15         if not inspect.isclass(obj) or not issubclass(obj, GObject.Object):
  16             continue
  17         info = repo.find_by_name(modname, name)
  18         if isinstance(info, (gi.types.ObjectInfo, )) and not info.get_abstract():
  19             if not any(meth.is_constructor() for meth in info.get_methods()):
  20                 print('||`%s.%s` ||  ||  ||  ||' % (modname, name))

Classes without Constructors

Name	Bug	Alternative	Reason
`GObject.Binding`	675581	GObject.Object.bind_property(...)	Non-generic semantics, requires construct only arguments.
`GObject.InitiallyUnowned`			[1]
`Gdk.Display`		Gdk.Display.get_default()	Singleton
`Gdk.DisplayManager`		Gdk.Display.get_default() or Gdk.Display.get()	Singleton
`Gdk.DragContext`		Gdk.drag_begin()	[1]
`Gdk.Keymap`		Gdk.Keymap.get_default()	Singleton
`Gdk.Screen`	687792	Screen.get_default()	Singleton
`Gdk.Visual`			[1]
`GdkPixbuf.PixbufAnimationIter`			[1]
`GdkPixbuf.PixbufSimpleAnimIter`			[1]
`Gio.ApplicationCommandLine`			[1] (Usually created by GApplication)
`Gio.DBusActionGroup`		Gio.DBusActionGroup.get()	[1]
`Gio.DBusMenuModel`		Gio.DBusMenuModel.get()	[1]
`Gio.DBusMethodInvocation`			[1] Received as argument to the handle_method_call() function
`Gio.FileEnumerator`		Gio.File.enumerate_children()	[1]
`Gio.FileIOStream`			unknown
`Gio.FileInputStream`			unknown
`Gio.FileOutputStream`			unknown
`Gio.MemoryOutputStream`			unknown
`Gio.ProxyAddressEnumerator`		Gio.SocketConnectable.enumerate()	[1]
`Gio.Resolver`		Gio.Resolver	[1]
`Gio.SocketConnection`			unknown
`Gio.TcpConnection`			unknown
`Gio.TlsInteraction`			unknown
`Gio.UnixConnection`			unknown
`Gio.Vfs`		Gio.Vfs.get_default() or Gio.Vfs.get_local()	Singleton
`Gio.VolumeMonitor`	647731	Gio.VolumeMonitor.get()	Singleton
`Gtk.AccelMap`		Gtk.AccelMap.get()	[1]
`Gtk.Accessible`			unknown
`Gtk.CellAreaContext`		Gtk.CellAreaClass.create_context()	[1]
`Gtk.Clipboard`		Gtk.Clipboard.get()	[1]
`Gtk.FileChooserDialog`			Generic creation works and is necessary. Constructor skipped do to variadic arguments.
`Gtk.MessageDialog`			Generic creation works and is necessary. Constructor skipped do to variadic arguments.
`Gtk.NumerableIcon`			Works. gtk_numerable_icon_new marked as function not constructor do to annotation problem?
`Gtk.PrintContext`			[1] Gtk.PrintContext objects gets passed to the ::begin-print, ::end-print, ::request-page-setup and ::draw-page signals on the Gtk.PrintOperation.
`Gtk.RecentChooserDialog`			Generic creation works and is necessary. Constructor skipped do to variadic arguments.
`Gtk.Settings`		Gtk.Settings.get_default()	[1]
`Gtk.ThemingEngine`			[1]
`Gtk.Tooltip`			[1] Instance passed to "query-tooltip" signal handler
`Gtk.TreeModelFilter`		Gtk.TreeModel.filter_new()	[1]
`Xkl.Engine`	680202	Xkl.Engine.get_instance(display)

[1] - Generic creation works but the class might not be necessary in Python.