[mutter/wip/carlosg/selection-fixes: 7/8] wayland: Set dummy selection source on .set_selection(null)

[Carlos Garnacho <carlosg src gnome org>]

commit 75be765cd49ae88e6f1b665efb323320a9e567fd
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri Oct 11 18:43:00 2019 +0200

    wayland: Set dummy selection source on .set_selection(null)
    
    Requesting a selection with a NULL data source means "unset the clipboard",
    but internally we use an unset clipboard as the indication that the
    clipboard manager should take over.
    
    Moreover, this unset request may go unheard if the current owner is someone
    else than the MetaWaylandDataDevice.
    
    Instead, set a dummy data source with no mimetypes nor data, this both
    prevents the clipboard manager from taking over and ensures the selection
    is replaced with it.
    
    The MetaSelectionSourceMemory was also added some checks to allow for this
    dummy mode.
    
    Fixes: https://gitlab.gnome.org/GNOME/mutter/issues/793

 src/core/meta-selection-source-memory.c |  5 ++++-
 src/wayland/meta-wayland-data-device.c  | 25 +++++++++++++------------
 2 files changed, 17 insertions(+), 13 deletions(-)
---
diff --git a/src/core/meta-selection-source-memory.c b/src/core/meta-selection-source-memory.c
index 04b7f39a3..c8b0c83f5 100644
--- a/src/core/meta-selection-source-memory.c
+++ b/src/core/meta-selection-source-memory.c
@@ -76,6 +76,9 @@ meta_selection_source_memory_get_mimetypes (MetaSelectionSource *source)
 {
   MetaSelectionSourceMemory *source_mem = META_SELECTION_SOURCE_MEMORY (source);
 
+  if (!source_mem->mimetype)
+    return NULL;
+
   return g_list_prepend (NULL, g_strdup (source_mem->mimetype));
 }
 
@@ -84,7 +87,7 @@ meta_selection_source_memory_finalize (GObject *object)
 {
   MetaSelectionSourceMemory *source_mem = META_SELECTION_SOURCE_MEMORY (object);
 
-  g_bytes_unref (source_mem->content);
+  g_clear_pointer (&source_mem->content, g_bytes_unref);
   g_free (source_mem->mimetype);
 
   G_OBJECT_CLASS (meta_selection_source_memory_parent_class)->finalize (object);
diff --git a/src/wayland/meta-wayland-data-device.c b/src/wayland/meta-wayland-data-device.c
index 0044a80b8..f95be0bf8 100644
--- a/src/wayland/meta-wayland-data-device.c
+++ b/src/wayland/meta-wayland-data-device.c
@@ -36,6 +36,7 @@
 #include <unistd.h>
 
 #include "compositor/meta-dnd-actor-private.h"
+#include "meta/meta-selection-source-memory.h"
 #include "wayland/meta-selection-source-wayland-private.h"
 #include "wayland/meta-wayland-dnd-surface.h"
 #include "wayland/meta-wayland-pointer.h"
@@ -1627,6 +1628,7 @@ meta_wayland_data_device_set_selection (MetaWaylandDataDevice *data_device,
   MetaWaylandSeat *seat = wl_container_of (data_device, seat, data_device);
   struct wl_resource *data_device_resource;
   struct wl_client *focus_client;
+  MetaSelectionSource *selection_source;
 
   if (data_device->selection_data_source &&
       data_device->selection_serial - serial < UINT32_MAX / 2)
@@ -1646,23 +1648,22 @@ meta_wayland_data_device_set_selection (MetaWaylandDataDevice *data_device,
 
   if (source)
     {
-      MetaSelectionSource *selection_source;
-
       meta_wayland_data_source_set_seat (source, seat);
       g_object_weak_ref (G_OBJECT (source),
                          selection_data_source_destroyed,
                          data_device);
 
       selection_source = meta_selection_source_wayland_new (source);
-      set_selection_source (data_device, META_SELECTION_CLIPBOARD,
-                            selection_source);
-      g_object_unref (selection_source);
     }
   else
     {
-      unset_selection_source (data_device, META_SELECTION_CLIPBOARD);
+      selection_source = g_object_new (META_TYPE_SELECTION_SOURCE_MEMORY, NULL);
     }
 
+  set_selection_source (data_device, META_SELECTION_CLIPBOARD,
+                        selection_source);
+  g_object_unref (selection_source);
+
   focus_client = meta_wayland_keyboard_get_focus_client (seat->keyboard);
   if (focus_client)
     {
@@ -1748,6 +1749,7 @@ meta_wayland_data_device_set_primary (MetaWaylandDataDevice *data_device,
   MetaWaylandSeat *seat = wl_container_of (data_device, seat, data_device);
   struct wl_resource *data_device_resource;
   struct wl_client *focus_client;
+  MetaSelectionSource *selection_source;
 
   if (META_IS_WAYLAND_DATA_SOURCE_PRIMARY (source))
     {
@@ -1777,23 +1779,22 @@ meta_wayland_data_device_set_primary (MetaWaylandDataDevice *data_device,
 
   if (source)
     {
-      MetaSelectionSource *selection_source;
-
       meta_wayland_data_source_set_seat (source, seat);
       g_object_weak_ref (G_OBJECT (source),
                          primary_source_destroyed,
                          data_device);
 
       selection_source = meta_selection_source_wayland_new (source);
-      set_selection_source (data_device, META_SELECTION_PRIMARY,
-                            selection_source);
-      g_object_unref (selection_source);
     }
   else
     {
-      unset_selection_source (data_device, META_SELECTION_PRIMARY);
+      selection_source = g_object_new (META_TYPE_SELECTION_SOURCE_MEMORY, NULL);
     }
 
+  set_selection_source (data_device, META_SELECTION_PRIMARY,
+                        selection_source);
+  g_object_unref (selection_source);
+
   focus_client = meta_wayland_keyboard_get_focus_client (seat->keyboard);
   if (focus_client)
     {