Gtk.Template: Fix template support for GTK4

Gtk.Widget.set_connect_func() does not exist anymore and signals are
automatically connected. Instead, a GtkBuilderScope needs to be used
to create GtkBuilder's closure functions.

pygobject closure support is extended to support
functools.partial. This is used to create a GtkBuilder closure
function with an object different from the current object.

See MR https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/1204 and
https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/1230

Closes: #380

1 files changed, 41 insertions, 1 deletions

diff --git a/gi/_gtktemplate.py b/gi/_gtktemplate.py
index 4b80106c..15f6b2c5 100644
--- a/gi/_gtktemplate.py
+++ b/gi/_gtktemplate.py
@@ -17,9 +17,43 @@
 # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
 # USA
 
+from functools import partial
+
 from gi.repository import GLib, GObject, Gio
 
 
+def define_builder_scope():
+    from gi.repository import Gtk
+
+    class BuilderScope(GObject.GObject, Gtk.BuilderScope):
+
+        def __init__(self):
+            super().__init__()
+
+        def do_create_closure(self, builder, func_name, flags, obj):
+            current_object = builder.get_current_object()
+
+            if func_name not in current_object.__gtktemplate_methods__:
+                return None
+
+            current_object.__gtktemplate_handlers__.add(func_name)
+
+            swapped = int(flags & Gtk.BuilderClosureFlags.SWAPPED)
+            if swapped:
+                raise RuntimeError(
+                    "%r not supported" % GObject.ConnectFlags.SWAPPED)
+                return None
+
+            handler_name = current_object.__gtktemplate_methods__[func_name]
+            handler = getattr(current_object, handler_name)
+            if obj:
+                return partial(handler, swap_data=obj)
+
+            return handler
+
+    return BuilderScope
+
+
 def connect_func(builder, obj, signal_name, handler_name,
                  connect_object, flags, cls):
 
@@ -52,6 +86,8 @@ def connect_func(builder, obj, signal_name, handler_name,
 
 
 def register_template(cls):
+    from gi.repository import Gtk
+
     bound_methods = {}
     bound_widgets = {}
 
@@ -88,7 +124,11 @@ def register_template(cls):
     cls.__gtktemplate_methods__ = bound_methods
     cls.__gtktemplate_widgets__ = bound_widgets
 
-    cls.set_connect_func(connect_func, cls)
+    if Gtk._version == "4.0":
+        BuilderScope = define_builder_scope()
+        cls.set_template_scope(BuilderScope())
+    else:
+        cls.set_connect_func(connect_func, cls)
 
     base_init_template = cls.init_template
     cls.__dontuse_ginstance_init__ = \