From e1c4e5588061610b5016766253fa2930e0054826 Mon Sep 17 00:00:00 2001
From: Sebastian Keller <skeller@gnome.org>
Date: Tue, 14 Jul 2020 19:02:06 +0200
Subject: [PATCH] x11: Handle selection windows being destroyed before new
 selection

Wine destroys its old selection window immediately before creating a new
selection. This would trigger restoring the clipboard, which would
overwrite the new selection with the old one. The selection window
however can also be destroyed as part of the shutdown process of
applications, such as Chromium for example. In those cases we want the
clipboard to be restored after the selection window has been destroyed.

Solve this by not immediately restoring the clipboard but instead using
a timeout which can be canceled by any new selection owner, such as in
the Wine case.

Fixes https://gitlab.gnome.org/GNOME/mutter/-/issues/1338
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1369
---
 src/x11/meta-x11-display-private.h |  1 +
 src/x11/meta-x11-selection.c       | 35 ++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/src/x11/meta-x11-display-private.h b/src/x11/meta-x11-display-private.h
index 36d4bad38..d53073e11 100644
--- a/src/x11/meta-x11-display-private.h
+++ b/src/x11/meta-x11-display-private.h
@@ -127,6 +127,7 @@ struct _MetaX11Display
 
   struct {
     Window xwindow;
+    guint timeout_id;
     MetaSelectionSource *owners[META_N_SELECTION_TYPES];
     GCancellable *cancellables[META_N_SELECTION_TYPES];
 
diff --git a/src/x11/meta-x11-selection.c b/src/x11/meta-x11-selection.c
index 8f068dedc..77659fcfa 100644
--- a/src/x11/meta-x11-selection.c
+++ b/src/x11/meta-x11-selection.c
@@ -311,6 +311,22 @@ source_new_cb (GObject      *object,
   g_free (data);
 }
 
+static gboolean
+unset_clipboard_owner (gpointer data)
+{
+  MetaDisplay *display = meta_get_display ();
+  MetaSelection *selection = meta_display_get_selection (display);
+  MetaX11Display *x11_display = meta_display_get_x11_display (display);
+
+  meta_selection_unset_owner (selection, META_SELECTION_CLIPBOARD,
+                              x11_display->selection.owners[META_SELECTION_CLIPBOARD]);
+  g_clear_object (&x11_display->selection.owners[META_SELECTION_CLIPBOARD]);
+
+  x11_display->selection.timeout_id = 0;
+
+  return G_SOURCE_REMOVE;
+}
+
 static gboolean
 meta_x11_selection_handle_xfixes_selection_notify (MetaX11Display *x11_display,
                                                    XEvent         *xevent)
@@ -325,6 +341,9 @@ meta_x11_selection_handle_xfixes_selection_notify (MetaX11Display *x11_display,
 
   selection = meta_display_get_selection (meta_get_display ());
 
+  if (selection_type == META_SELECTION_CLIPBOARD)
+    g_clear_handle_id (&x11_display->selection.timeout_id, g_source_remove);
+
   if (x11_display->selection.cancellables[selection_type])
     {
       g_cancellable_cancel (x11_display->selection.cancellables[selection_type]);
@@ -345,6 +364,19 @@ meta_x11_selection_handle_xfixes_selection_notify (MetaX11Display *x11_display,
           meta_selection_set_owner (selection, selection_type, source);
           g_object_unref (source);
         }
+      else if (event->subtype == XFixesSelectionWindowDestroyNotify &&
+               selection_type == META_SELECTION_CLIPBOARD)
+        {
+          /* Selection window might have gotten destroyed as part of application
+           * shutdown. Trigger restoring clipboard, but wait a bit, because some
+           * clients, like wine, destroy the old window immediately before a new
+           * selection. Restoring the clipboard in this case would overwrite the
+           * new selection, so this will be cancelled when a new selection
+           * arrives. */
+          x11_display->selection.timeout_id = g_timeout_add (10,
+                                                             unset_clipboard_owner,
+                                                             NULL);
+        }
       else
         {
           /* An X client went away, clear the selection */
@@ -422,6 +454,7 @@ meta_x11_selection_init (MetaX11Display *x11_display)
   attributes.event_mask = PropertyChangeMask | SubstructureNotifyMask;
   attributes.override_redirect = True;
 
+  x11_display->selection.timeout_id = 0;
   x11_display->selection.xwindow =
     XCreateWindow (x11_display->xdisplay,
                    x11_display->xroot,
@@ -482,4 +515,6 @@ meta_x11_selection_shutdown (MetaX11Display *x11_display)
       XDestroyWindow (x11_display->xdisplay, x11_display->selection.xwindow);
       x11_display->selection.xwindow = None;
     }
+
+  g_clear_handle_id (&x11_display->selection.timeout_id, g_source_remove);
 }