Trying to open New Window takes several seconds and uses 100% of one CPU core
Not sure what exactly it's doing, the stack traces seem to be slightly different each time. Here's one:
#0 0x00007f01e5432a1a in type_node_check_conformities_UorL (node=<optimized out>, iface_node=<optimized out>, support_interfaces=<optimized out>, support_interfaces@entry=1, support_prerequisites=<optimized out>, support_prerequisites@entry=0, have_lock=have_lock@entry=0) at ../gobject/gtype.c:3546
#1 0x00007f01e543920f in type_node_conforms_to_U (support_prerequisites=0, support_interfaces=1, iface_node=<optimized out>, node=<optimized out>) at ../gobject/gtype.c:3561
#2 g_type_check_instance_cast (type_instance=type_instance@entry=0x55e3cc7aaeb0 [GtkActionMuxer], iface_type=0x55e3cac07040 [GtkActionObservable]) at ../gobject/gtype.c:4125
#3 0x00007f01e4dd0b70 in gtk_action_muxer_primary_accel_changed (muxer=0x55e3cc7aaeb0 [GtkActionMuxer], action_name=0x55e3cac4ef10 "row.remove", action_and_target=0x0) at ../gtk/gtkactionmuxer.c:601
#4 0x00007f01e4dd0b81 in gtk_action_muxer_primary_accel_changed (muxer=0x55e3cd24b980 [GtkActionMuxer], action_name=0x55e3cac4ef10 "row.remove", action_and_target=0x0) at ../gtk/gtkactionmuxer.c:601
#5 0x00007f01e4dd0b81 in gtk_action_muxer_primary_accel_changed (muxer=0x55e3cd21f040 [GtkActionMuxer], action_name=0x55e3cac4ef10 "row.remove", action_and_target=0x0) at ../gtk/gtkactionmuxer.c:601
#6 0x00007f01e4dd2ccc in notify_observers_added (parent=0x55e3cac1a180 [GtkActionMuxer], muxer=0x55e3cd287d30 [GtkActionMuxer]) at ../gtk/gtkactionmuxer.c:447
#7 gtk_action_muxer_set_parent (muxer=0x55e3cd287d30 [GtkActionMuxer], parent=<optimized out>) at ../gtk/gtkactionmuxer.c:1382
#8 0x00007f01e4db0646 in _gtk_widget_update_parent_muxer (widget=0x55e3cc7a1100 [EditorWindow]) at ../gtk/gtkwidget.c:10811
#9 0x00007f01e4dc03ee in gtk_window_set_application (window=0x55e3cc7a1100 [EditorWindow], application=<optimized out>) at ../gtk/gtkwindow.c:2826
#10 0x00007f01e541bf17 in object_set_property (object=object@entry=0x55e3cc7a1100 [EditorWindow], pspec=0x55e3cac42760 [GParamObject], value=0x7ffffd62a540, nqueue=nqueue@entry=0x55e3cd288910) at ../gobject/gobject.c:1602
#11 0x00007f01e541c348 in g_object_new_internal (class=class@entry=0x55e3cac5d160, params=params@entry=0x7ffffd62a440, n_params=n_params@entry=1) at ../gobject/gobject.c:2024
#12 0x00007f01e541dd7a in g_object_new_valist (object_type=0x55e3cab79df0 [EditorWindow/AdwApplicationWindow/GtkApplicationWindow/GtkWindow/GtkWidget/GInitiallyUnowned], first_property_name=first_property_name@entry=0x55e3c8d03e6c "application", var_args=var_args@entry=0x7ffffd62a710) at ../gobject/gobject.c:2313
#13 0x00007f01e541e31f in g_object_new (object_type=<optimized out>, first_property_name=first_property_name@entry=0x55e3c8d03e6c "application") at ../gobject/gobject.c:1813
#14 0x000055e3c8cf86e9 in _editor_window_new () at ../src/editor-window.c:702
#15 0x000055e3c8ce592d in editor_session_create_window (self=0x7f01d01132a0 [EditorSession]) at ../src/editor-session.c:663
#19 0x00007f01e5430d13 in <emit signal ??? on instance 0x55e3cabaded0 [GSimpleAction]> (instance=instance@entry=0x55e3cabaded0, signal_id=<optimized out>, detail=detail@entry=0) at ../gobject/gsignal.c:3553
#16 0x00007f01e54163e9 in g_closure_invoke (closure=0x55e3cac67860, return_value=return_value@entry=0x0, n_param_values=2, param_values=param_values@entry=0x7ffffd62a9d0, invocation_hint=invocation_hint@entry=0x7ffffd62a950) at ../gobject/gclosure.c:830
#17 0x00007f01e5429d4f in signal_emit_unlocked_R (node=node@entry=0x7f01c8008320, detail=detail@entry=0, instance=instance@entry=0x55e3cabaded0, emission_return=emission_return@entry=0x0, instance_and_params=instance_and_params@entry=0x7ffffd62a9d0) at ../gobject/gsignal.c:3742
#18 0x00007f01e5430bbf in g_signal_emit_valist (instance=<optimized out>, signal_id=<optimized out>, detail=<optimized out>, var_args=var_args@entry=0x7ffffd62ab70) at ../gobject/gsignal.c:3497
#20 0x00007f01e555c185 in g_simple_action_activate (action=0x55e3cabaded0, parameter=0x0) at ../gio/gsimpleaction.c:225
#21 0x00007f01e4e29486 in gtk_menu_tracker_item_activated (self=0x55e3cae14740 [GtkMenuTrackerItem]) at ../gtk/gtkmenutrackeritem.c:822
#22 0x00007f01e4e25178 in gtk_popover_item_activate (button=<optimized out>, user_data=0x55e3cae14740) at ../gtk/gtkmenusectionbox.c:200
#26 0x00007f01e5430d13 in <emit signal ??? on instance 0x55e3cae11570 [GtkModelButton]> (instance=<optimized out>, signal_id=<optimized out>, detail=<optimized out>) at ../gobject/gsignal.c:3553
#23 0x00007f01e54163e9 in g_closure_invoke (closure=0x55e3cae1f610, return_value=return_value@entry=0x0, n_param_values=1, param_values=param_values@entry=0x7ffffd62ae70, invocation_hint=invocation_hint@entry=0x7ffffd62adf0) at ../gobject/gclosure.c:830
#24 0x00007f01e5429d4f in signal_emit_unlocked_R (node=node@entry=0x55e3cadcf660, detail=detail@entry=0, instance=instance@entry=0x55e3cae11570, emission_return=emission_return@entry=0x0, instance_and_params=instance_and_params@entry=0x7ffffd62ae70) at ../gobject/gsignal.c:3742
#25 0x00007f01e5430bbf in g_signal_emit_valist (instance=<optimized out>, signal_id=<optimized out>, detail=<optimized out>, var_args=var_args@entry=0x7ffffd62aff0) at ../gobject/gsignal.c:3497
#27 0x00007f01e4b3f52d in _gtk_marshal_VOID__INT_DOUBLE_DOUBLEv (closure=closure@entry=0x55e3cae1d3c0, return_value=return_value@entry=0x0, instance=instance@entry=0x55e3cadf0500, args=args@entry=0x7ffffd62b2f0, marshal_data=marshal_data@entry=0x0, n_params=n_params@entry=3, param_types=0x55e3cab713e0) at gtk/gtkmarshalers.c:5445
#28 0x00007f01e5416618 in _g_closure_invoke_va (closure=closure@entry=0x55e3cae1d3c0, return_value=return_value@entry=0x0, instance=instance@entry=0x55e3cadf0500, args=args@entry=0x7ffffd62b2f0, n_params=3, param_types=0x55e3cab713e0) at ../gobject/gclosure.c:893
#29 0x00007f01e5430afb in g_signal_emit_valist (instance=0x55e3cadf0500, signal_id=<optimized out>, detail=<optimized out>, var_args=var_args@entry=0x7ffffd62b2f0) at ../gobject/gsignal.c:3406
#30 0x00007f01e5430d13 in g_signal_emit (instance=instance@entry=0x55e3cadf0500, signal_id=<optimized out>, detail=detail@entry=0) at ../gobject/gsignal.c:3553
#31 0x00007f01e4c243d3 in gtk_gesture_click_end (gesture=gesture@entry=0x55e3cadf0500 [GtkGestureClick], sequence=sequence@entry=0x0) at ../gtk/gtkgestureclick.c:276
#32 0x00007f01e54199c3 in g_cclosure_marshal_VOID__BOXEDv (closure=0x55e3caccc740, return_value=<optimized out>, instance=<optimized out>, args=<optimized out>, marshal_data=<optimized out>, n_params=<optimized out>, param_types=0x55e3cab1dab0) at ../gobject/gmarshal.c:1686
#33 0x00007f01e5416618 in _g_closure_invoke_va (closure=closure@entry=0x55e3caccc740, return_value=return_value@entry=0x0, instance=instance@entry=0x55e3cadf0500, args=args@entry=0x7ffffd62b690, n_params=1, param_types=0x55e3cab1dab0) at ../gobject/gclosure.c:893
#34 0x00007f01e5430afb in g_signal_emit_valist (instance=0x55e3cadf0500, signal_id=<optimized out>, detail=<optimized out>, var_args=var_args@entry=0x7ffffd62b690) at ../gobject/gsignal.c:3406
#35 0x00007f01e5430d13 in g_signal_emit (instance=instance@entry=0x55e3cadf0500, signal_id=<optimized out>, detail=detail@entry=0) at ../gobject/gsignal.c:3553
#36 0x00007f01e4c20aa8 in _gtk_gesture_set_recognized (sequence=0x0, recognized=0, gesture=0x55e3cadf0500 [GtkGestureClick]) at ../gtk/gtkgesture.c:339
#37 _gtk_gesture_check_recognized (gesture=gesture@entry=0x55e3cadf0500 [GtkGestureClick], sequence=sequence@entry=0x0) at ../gtk/gtkgesture.c:380
#38 0x00007f01e4c2240b in gtk_gesture_handle_event (controller=<optimized out>, event=0x55e3cd11fde0 [GdkButtonEvent], x=46.605464935302734, y=20.265626907348633) at ../gtk/gtkgesture.c:678
#39 0x00007f01e4c25a95 in gtk_gesture_single_handle_event (controller=0x55e3cadf0500 [GtkGestureClick], event=0x55e3cd11fde0 [GdkButtonEvent], x=46.605464935302734, y=20.265626907348633) at ../gtk/gtkgesturesingle.c:227
#40 0x00007f01e4bee81a in gtk_event_controller_handle_event (controller=controller@entry=0x55e3cadf0500 [GtkGestureClick], event=event@entry=0x55e3cd11fde0 [GdkButtonEvent], target=target@entry=0x55e3cae17580 [GtkLabel], x=x@entry=46.605464935302734, y=y@entry=20.265626907348633) at ../gtk/gtkeventcontroller.c:369
#41 0x00007f01e4da4f69 in gtk_widget_run_controllers (widget=widget@entry=0x55e3cae11570 [GtkModelButton], event=event@entry=0x55e3cd11fde0 [GdkButtonEvent], target=target@entry=0x55e3cae17580 [GtkLabel], x=46.605464935302734, y=20.265626907348633, phase=phase@entry=GTK_PHASE_CAPTURE) at ../gtk/gtkwidget.c:4558
#42 0x00007f01e4dad2d0 in _gtk_widget_captured_event (widget=widget@entry=0x55e3cae11570 [GtkModelButton], event=event@entry=0x55e3cd11fde0 [GdkButtonEvent], target=target@entry=0x55e3cae17580 [GtkLabel]) at ../gtk/gtkwidget.c:4721
#43 0x00007f01e4c74102 in gtk_propagate_event_internal (widget=0x55e3cae11570 [GtkModelButton], widget@entry=0x55e3cae17580 [GtkLabel], event=event@entry=0x55e3cd11fde0 [GdkButtonEvent], topmost=<optimized out>) at ../gtk/gtkmain.c:1870
#44 0x00007f01e4c74259 in gtk_propagate_event (widget=widget@entry=0x55e3cae17580 [GtkLabel], event=event@entry=0x55e3cd11fde0 [GdkButtonEvent]) at ../gtk/gtkmain.c:1952
#45 0x00007f01e4c7486b in gtk_main_do_event (event=0x55e3cd11fde0 [GdkButtonEvent]) at ../gtk/gtkmain.c:1644
#46 0x00007f01e4ca6050 in surface_event (surface=<optimized out>, event=<optimized out>, widget=<optimized out>) at ../gtk/gtkpopover.c:827
#47 0x00007f01e4eb6630 in _gdk_marshal_BOOLEAN__POINTERv (closure=closure@entry=0x55e3cd1c6120, return_value=return_value@entry=0x7ffffd62bd30, instance=instance@entry=0x55e3cc01a690, args=args@entry=0x7ffffd62be00, marshal_data=marshal_data@entry=0x0, n_params=n_params@entry=1, param_types=0x55e3cb4d98a0) at gdk/gdkmarshalers.c:302
#48 0x00007f01e4ee1f84 in gdk_surface_event_marshallerv (closure=closure@entry=0x55e3cd1c6120, return_value=return_value@entry=0x7ffffd62bd30, instance=instance@entry=0x55e3cc01a690, args=args@entry=0x7ffffd62be00, marshal_data=marshal_data@entry=0x0, n_params=n_params@entry=1, param_types=0x55e3cb4d98a0) at ../gdk/gdksurface.c:463
#49 0x00007f01e5416618 in _g_closure_invoke_va (closure=closure@entry=0x55e3cd1c6120, return_value=return_value@entry=0x7ffffd62bd30, instance=instance@entry=0x55e3cc01a690, args=args@entry=0x7ffffd62be00, n_params=1, param_types=0x55e3cb4d98a0) at ../gobject/gclosure.c:893
#50 0x00007f01e542fdec in g_signal_emit_valist (instance=0x55e3cc01a690, signal_id=<optimized out>, detail=<optimized out>, var_args=var_args@entry=0x7ffffd62be00) at ../gobject/gsignal.c:3406
#51 0x00007f01e5430d13 in g_signal_emit (instance=instance@entry=0x55e3cc01a690, signal_id=<optimized out>, detail=detail@entry=0) at ../gobject/gsignal.c:3553
#52 0x00007f01e4ee5b56 in gdk_surface_handle_event (event=event@entry=0x55e3cd11fde0 [GdkButtonEvent]) at ../gdk/gdksurface.c:2948
#53 0x00007f01e4ecc70d in _gdk_event_emit (event=event@entry=0x55e3cd11fde0 [GdkButtonEvent]) at ../gdk/gdkevents.c:490
#54 0x00007f01e4f05717 in gdk_event_source_dispatch (base=base@entry=0x55e3cab352a0, callback=<optimized out>, data=<optimized out>) at ../gdk/wayland/gdkeventsource.c:142
#55 0x00007f01e531cabb in g_main_dispatch (context=0x55e3caaf7830) at ../glib/gmain.c:3381
#56 g_main_context_dispatch (context=0x55e3caaf7830) at ../glib/gmain.c:4099
#57 0x00007f01e531cfc8 in g_main_context_iterate (context=context@entry=0x55e3caaf7830, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4175
#58 0x00007f01e531d094 in g_main_context_iteration (context=context@entry=0x55e3caaf7830, may_block=may_block@entry=1) at ../glib/gmain.c:4240
#59 0x00007f01e5552a9d in g_application_run (application=0x55e3cac1f210 [EditorApplication], argc=argc@entry=2, argv=argv@entry=0x7ffffd62c258) at ../gio/gapplication.c:2569
#60 0x000055e3c8cb6575 in main (argc=2, argv=0x7ffffd62c258) at ../src/main.c:42
Fedora 35, Wayland, Flatpak gnome-nightly.