Make the widgets work in KDE Wayland session

This has two parts:

1. Set GDK_BACKEND=x11, so that GDK3 chooses to use X11 as its backend.
   This must be done while only one thread is running, as otherwise
   undefined behavior results.  It also must be done before
   gi.overrides.Gdk is imported, as otherwise it will be too late to set
   the GDK backend.  Therefore, this code is run very early, and
   RuntimeError is raised if the preconditions are violated.

2. Create a fullscreen invisible window for mouse input.  This works
   around Xwayland not passing all pointer input to X11.  The menu is
   dismissed if the user clicks on the fullscreen window.  This hack
   is only used if WAYLAND_DISPLAY is set.

qui/clipboard.py

@@ -26,6 +26,10 @@
 via Qubes RPC """
 # pylint: disable=invalid-name,wrong-import-position
 
+# Must be imported before creating threads
+from .tray.gross_gtk3_bug_workaround \
+    import DisgustingX11FullscreenWindowHack # isort:skip
+
 import asyncio
 import contextlib
 import json
@@ -285,6 +289,7 @@ def __init__(self, wm, qapp, dispatcher, **properties):
         self.set_application_id("org.qubes.qui.clipboard")
         self.register()  # register Gtk Application
 
+        self.disgusting_hack = DisgustingX11FullscreenWindowHack.get()
         self.qapp = qapp
         self.vm = self.qapp.domains[self.qapp.local_name]
         self.dispatcher = dispatcher
@@ -373,6 +378,7 @@ def setup_ui(self, *_args, **_kwargs):
         )
 
         self.menu = Gtk.Menu()
+        self.disgusting_hack.show_for_widget(self.menu)
 
         title_label = Gtk.Label(xalign=0)
         title_label.set_markup(_("<b>Current clipboard</b>"))

qui/devices/device_widget.py

@@ -17,6 +17,11 @@
 #
 # You should have received a copy of the GNU Lesser General Public License along
 # with this program; if not, see <http://www.gnu.org/licenses/>.
+
+# Must be imported before creating threads
+from ..tray.gross_gtk3_bug_workaround \
+    import DisgustingX11FullscreenWindowHack # isort:skip
+
 from typing import Set, List, Dict
 import asyncio
 import sys
@@ -73,6 +78,7 @@ class DevicesTray(Gtk.Application):
     """Tray application for handling devices."""
     def __init__(self, app_name, qapp, dispatcher):
         super().__init__()
+        self.disgusting_hack = DisgustingX11FullscreenWindowHack.get()
         self.name: str = app_name
 
         # maps: port to connected device (e.g., sys-usb:sda -> block device)
@@ -300,6 +306,7 @@ def load_css(widget) -> str:
     def show_menu(self, _unused, _event):
         """Show menu at mouse pointer."""
         tray_menu = Gtk.Menu()
+        self.disgusting_hack.show_for_widget(tray_menu)
         theme = self.load_css(tray_menu)
         tray_menu.set_reserve_toggle_size(False)
 

qui/tray/disk_space.py

@@ -1,4 +1,9 @@
 # pylint: disable=wrong-import-position,import-error
+
+# Must be imported before creating threads
+from .gross_gtk3_bug_workaround \
+    import DisgustingX11FullscreenWindowHack # isort:skip
+
 import sys
 import subprocess
 from typing import List
@@ -19,7 +24,6 @@
 WARN_LEVEL = 0.9
 URGENT_WARN_LEVEL = 0.95
 
-
 class VMUsage:
     def __init__(self, vm):
         self.vm = vm
@@ -338,6 +342,7 @@ class DiskSpace(Gtk.Application):
     def __init__(self, **properties):
         super().__init__(**properties)
 
+        self.disgusting_hack = DisgustingX11FullscreenWindowHack.get()
         self.pool_warned = False
         self.vms_warned = set()
 
@@ -423,6 +428,7 @@ def make_menu(self, _unused, _event):
         vm_data = VMUsageData(self.qubes_app)
 
         menu = Gtk.Menu()
+        self.disgusting_hack.show_for_widget(menu)
 
         menu.append(self.make_top_box(pool_data))
 

qui/tray/domains.py

@@ -2,6 +2,11 @@
 # -*- coding: utf-8 -*-
 # pylint: disable=wrong-import-position,import-error,superfluous-parens
 ''' A menu listing domains '''
+
+# Must be imported before creating threads
+from .gross_gtk3_bug_workaround \
+    import DisgustingX11FullscreenWindowHack # isort:skip
+
 import abc
 import asyncio
 import subprocess
@@ -537,6 +542,8 @@ def __init__(self, app_name, qapp, dispatcher, stats_dispatcher):
             _('<b>Qubes Domains</b>\nView and manage running domains.'))
 
         self.tray_menu = Gtk.Menu()
+        self.disgusting_hack = DisgustingX11FullscreenWindowHack.get()
+        self.disgusting_hack.show_for_widget(self.tray_menu)
 
         self.icon_cache = IconCache()
 

qui/tray/gross_gtk3_bug_workaround.py

@@ -0,0 +1,148 @@
+#!/usr/bin/python3 --
+import os
+import sys
+from typing import Optional
+
+# Modifying the environment while multiple threads
+# are running leads to use-after-free in glibc, so
+# ensure that only one thread is running.
+if len(os.listdir("/proc/self/task")) != 1:
+    raise RuntimeError("threads already running")
+# If gi.override.Gdk has been imported, the GDK
+# backend has already been set and it is too late
+# to override it.
+if "gi.override.Gdk" in sys.modules:
+    raise RuntimeError("must import this module before loading GDK")
+# Only the X11 backend is supported
+os.environ["GDK_BACKEND"] = "x11"
+
+import gi
+
+gi.require_version("Gdk", "3.0")
+gi.require_version("Gtk", "3.0")
+from gi.repository import Gtk, Gdk
+
+
+is_xwayland = "WAYLAND_DISPLAY" in os.environ
+
+
+class DisgustingX11FullscreenWindowHack:
+    """
+    No-op implementation of the hack, for use on stock X11.
+    """
+
+    __slots__ = ()
+
+    @classmethod
+    def get(cls, /) -> "DisgustingX11FullscreenWindowHack":
+        if is_xwayland:
+            return DisgustingX11FullscreenWindowHackXWayland()
+        return cls()
+
+    def clear_widget(self, /) -> None:
+        pass
+
+    def show_for_widget(self, _widget: Gtk.Widget, /) -> None:
+        pass
+
+
+class DisgustingX11FullscreenWindowHackXWayland(
+    DisgustingX11FullscreenWindowHack
+):
+    """
+    GTK3 menus have a horrible bug under Xwayland: if the user clicks on a
+    native Wayland surface, the menu is not dismissed.  This class works around
+    the problem by using evil X11 hacks, such as a fullscreen override-redirect
+    window that is made transparent.
+    """
+
+    _window: Gtk.Window
+    _widget: Optional[Gtk.Widget]
+    _unmap_signal_id: int
+    _map_signal_id: int
+    __slots__ = ("_window", "_widget", "_unmap_signal_id", "_map_signal_id")
+
+    def __init__(self) -> None:
+        self._widget = None
+        # Get the default GDK screen.
+        screen = Gdk.Screen.get_default()
+        # This is deprecated, but it gets the total width and height
+        # of all screens, which is what we want.  It will go away in
+        # GTK4, but this code will never be ported to GTK4.
+        width = screen.get_width()
+        height = screen.get_height()
+        # Create a window that will fill the screen.
+        window = self._window = Gtk.Window()
+        # Move that window to the top left.
+        # pylint: disable=no-member
+        window.move(0, 0)
+        # Make the window fill the whole screen.
+        # pylint: disable=no-member
+        window.resize(width, height)
+        # Request that the window not be decorated by the window manager.
+        window.set_decorated(False)
+        # Connect a signal so that the window and menu can be
+        # unmapped (no longer shown on screen) once clicked.
+        window.connect("button-press-event", self.on_button_press)
+        # When the window is created, mark it as override-redirect
+        # (invisible to the window manager) and transparent.
+        window.connect("realize", self._on_realize)
+        self._unmap_signal_id = self._map_signal_id = 0
+
+    def clear_widget(self, /) -> None:
+        """
+        Clears the connected widget.  Automatically called by
+        show_for_widget().
+        """
+        widget = self._widget
+        map_signal_id = self._map_signal_id
+        unmap_signal_id = self._unmap_signal_id
+
+        # Double-disconnect is C-level undefined behavior, so ensure
+        # it cannot happen.  It is better to leak memory if an exception
+        # is thrown here.  GObject.disconnect_by_func() is buggy
+        # (https://gitlab.gnome.org/GNOME/pygobject/-/issues/106),
+        # so avoid it.
+        if widget is not None:
+            if map_signal_id != 0:
+                # Clear the signal ID to avoid double-disconnect
+                # if this method is interrupted and then called again.
+                self._map_signal_id = 0
+                widget.disconnect(map_signal_id)
+            if unmap_signal_id != 0:
+                # Clear the signal ID to avoid double-disconnect
+                # if this method is interrupted and then called again.
+                self._unmap_signal_id = 0
+                widget.disconnect(unmap_signal_id)
+        self._widget = None
+
+    def show_for_widget(self, widget: Gtk.Widget, /) -> None:
+        # Clear any existing connections.
+        self.clear_widget()
+        # Store the new widget.
+        self._widget = widget
+        # Connect map and unmap signals.
+        self._unmap_signal_id = widget.connect("unmap", self._hide)
+        self._map_signal_id = widget.connect("map", self._show)
+
+    @staticmethod
+    def _on_realize(window: Gtk.Window, /) -> None:
+        window.set_opacity(0)
+        window.get_window().set_override_redirect(True)
+
+    def _show(self, widget: Gtk.Widget, /) -> None:
+        assert widget is self._widget, "signal not properly disconnected"
+        # pylint: disable=no-member
+        self._window.show_all()
+
+    def _hide(self, widget: Gtk.Widget, /) -> None:
+        assert widget is self._widget, "signal not properly disconnected"
+        self._window.hide()
+
+    # pylint: disable=line-too-long
+    def on_button_press(
+        self, window: Gtk.Window, _event: Gdk.EventButton, /
+    ) -> None:
+        # Hide the window and the widget.
+        window.hide()
+        self._widget.hide()

qui/tray/updates.py

@@ -3,6 +3,11 @@
 # pylint: disable=wrong-import-position,import-error
 ''' A widget that monitors update availability and notifies the user
  about new updates to templates and standalone VMs'''
+
+# Must be imported before creating threads
+from .gross_gtk3_bug_workaround \
+    import DisgustingX11FullscreenWindowHack # isort:skip
+
 import asyncio
 import sys
 import subprocess
@@ -23,7 +28,6 @@
 t = gettext.translation("desktop-linux-manager", fallback=True)
 _ = t.gettext
 
-
 class TextItem(Gtk.MenuItem):
     def __init__(self, text):
         super().__init__()
@@ -59,6 +63,7 @@ def __init__(self, app_name, qapp, dispatcher):
         super().__init__()
         self.name = app_name
 
+        self.disgusting_hack = DisgustingX11FullscreenWindowHack.get()
         self.dispatcher = dispatcher
         self.qapp = qapp
 
@@ -76,6 +81,7 @@ def __init__(self, app_name, qapp, dispatcher):
         self.obsolete_vms = set()
 
         self.tray_menu = Gtk.Menu()
+        self.disgusting_hack.show_for_widget(self.tray_menu)
 
     def run(self):  # pylint: disable=arguments-differ
         self.check_vms_needing_update()
@@ -107,6 +113,8 @@ def setup_menu(self):
 
     def show_menu(self, _unused, _event):
         self.tray_menu = Gtk.Menu()
+        # TODO: disconnect
+        self.disgusting_hack.show_for_widget(self.tray_menu)
 
         self.setup_menu()
 

rpm_spec/qubes-desktop-linux-manager.spec.in

@@ -137,7 +137,6 @@ gtk-update-icon-cache %{_datadir}/icons/Adwaita &>/dev/null || :
 %{python3_sitelib}/qui/devices/actionable_widgets.py
 %{python3_sitelib}/qui/devices/backend.py
 %{python3_sitelib}/qui/devices/device_widget.py
-%{python3_sitelib}/qui/devices/device_widget.py
 %{python3_sitelib}/qui/qubes-devices-dark.css
 %{python3_sitelib}/qui/qubes-devices-light.css
 %{python3_sitelib}/qui/devices/AttachConfirmationWindow.glade
@@ -155,6 +154,7 @@ gtk-update-icon-cache %{_datadir}/icons/Adwaita &>/dev/null || :
 %{python3_sitelib}/qui/tray/domains.py
 %{python3_sitelib}/qui/tray/disk_space.py
 %{python3_sitelib}/qui/tray/updates.py
+%{python3_sitelib}/qui/tray/gross_gtk3_bug_workaround.py
 
 %dir %{python3_sitelib}/qubes_config
 %dir %{python3_sitelib}/qubes_config/__pycache__