portal: Rework cancellation, reworking error reporting and adding X fallback

With this gnome-screencast will fall back to trying to use a simple
ximagesrc rather than the portal if the portal API is missing.

meson.build

@@ -5,13 +5,10 @@ project('gnome-screencast', 'c',        version: '0.1.0',
 gnome = import('gnome')
 i18n = import('i18n')
 
-have_screencast_portal = get_option('screencast_portal')
-
 config_h = configuration_data()
 config_h.set_quoted('PACKAGE_VERSION', meson.project_version())
 config_h.set_quoted('GETTEXT_PACKAGE', 'gnome-screencast')
 config_h.set_quoted('LOCALEDIR', join_paths(get_option('prefix'), get_option('localedir')))
-config_h.set10('HAVE_SCREENCAST_PORTAL', have_screencast_portal)
 configure_file(
   output: 'gnome-screencast-config.h',
   configuration: config_h,

meson_options.txt

-option('screencast_portal',
-  type: 'boolean',
-  value: true,
-  description: 'Use the screencast portal, if unset uses X11 image source'
-)

src/gnome-screencast-window.c

@@ -27,9 +27,7 @@
 
 #include <gst/gst.h>
 
-#if HAVE_SCREENCAST_PORTAL
 #include "screencast-portal.h"
-#endif
 
 struct _GnomeScreencastWindow
 {
@@ -38,9 +36,8 @@ struct _GnomeScreencastWindow
   ScreencastMetaProvider   *meta_provider;
   ScreencastWFDP2PRegistry *wfd_p2p_registry;
 
-#if HAVE_SCREENCAST_PORTAL
   ScreencastPortal *portal;
-#endif
+  gboolean          use_x11;
 
   GCancellable   *cancellable;
 
@@ -71,11 +68,11 @@ sink_create_source_cb (GnomeScreencastWindow * self, ScreencastSink * sink)
   GstElement *src, *dst, *res;
 
   bin = GST_BIN (gst_bin_new ("screencast source bin"));
-#if HAVE_SCREENCAST_PORTAL
-  src = screencast_portal_get_source (self->portal);
-#else
-  src = gst_element_factory_make ("ximagesrc", "X11 screencast source");
-#endif
+  g_debug ("use x11: %d", self->use_x11);
+  if (self->use_x11)
+    src = gst_element_factory_make ("ximagesrc", "X11 screencast source");
+  else
+    src = screencast_portal_get_source (self->portal);
   gst_bin_add (bin, src);
 
   dst = gst_element_factory_make ("intervideosink", "inter video sink");
@@ -176,13 +173,11 @@ find_sink_list_row_activated_cb (GnomeScreencastWindow *self, ScreencastSinkRow
 {
   ScreencastSink *sink;
 
-#if HAVE_SCREENCAST_PORTAL
-  if (!self->portal)
+  if (!self->portal && ! self->use_x11)
     {
       g_warning ("Cannot start streaming right now as we don't have a portal!");
       return;
     }
-#endif
 
   g_assert (SCREENCAST_IS_SINK_ROW (row));
 
@@ -244,7 +239,6 @@ gnome_screencast_window_class_init (GnomeScreencastWindowClass *klass)
   gtk_widget_class_bind_template_child (widget_class, GnomeScreencastWindow, error_return);
 }
 
-#if HAVE_SCREENCAST_PORTAL
 static void
 screencast_portal_init_async_cb (GObject      *source_object,
                                  GAsyncResult *res,
@@ -260,9 +254,17 @@ screencast_portal_init_async_cb (GObject      *source_object,
         {
           g_warning ("Error initing screencast portal: %s", error->message);
 
-          /* XXX: This is fatal! */
           window = GNOME_SCREENCAST_WINDOW (user_data);
-          gtk_widget_destroy (GTK_WIDGET (window));
+
+          /* If this the error was for an unknown method, then we likely
+           * don't have a gnome-shell or it does not support the screen casting
+           * portal.
+           * In this case we assume that an xvimagesrc is usable, in all other
+           * cases it is a fatal error. */
+          if (!g_error_matches (error, G_DBUS_ERROR, G_DBUS_ERROR_UNKNOWN_METHOD))
+            gtk_widget_destroy (GTK_WIDGET (window));
+          else
+            window->use_x11 = TRUE;
         }
 
       g_object_unref (source_object);
@@ -272,7 +274,6 @@ screencast_portal_init_async_cb (GObject      *source_object,
   window = GNOME_SCREENCAST_WINDOW (user_data);
   window->portal = SCREENCAST_PORTAL (source_object);
 }
-#endif
 
 static void
 stream_stop_clicked_cb (GnomeScreencastWindow *self)
@@ -286,9 +287,7 @@ stream_stop_clicked_cb (GnomeScreencastWindow *self)
 static void
 gnome_screencast_window_init (GnomeScreencastWindow *self)
 {
-#if HAVE_SCREENCAST_PORTAL
   ScreencastPortal *portal;
-#endif
   gtk_widget_init_template (GTK_WIDGET (self));
 
   self->meta_provider = screencast_meta_provider_new ();
@@ -332,12 +331,10 @@ gnome_screencast_window_init (GnomeScreencastWindow *self)
                            self,
                            G_CONNECT_SWAPPED);
 
-#if HAVE_SCREENCAST_PORTAL
   portal = screencast_portal_new ();
   g_async_initable_init_async (G_ASYNC_INITABLE (portal),
                                G_PRIORITY_LOW,
                                self->cancellable,
                                screencast_portal_init_async_cb,
                                self);
-#endif
 }

src/meson.build

@@ -15,12 +15,9 @@ gnome_screencast_sources = [
   'screencast-wfd-p2p-registry.c',
   'screencast-dummy-provider.c',
   'screencast-dummy-wfd-sink.c',
+  'screencast-portal.c',
 ]
 
-if have_screencast_portal
-  gnome_screencast_sources += [ 'screencast-portal.c' ]
-endif
-
 enum_headers = files('screencast-sink.h')
 
 gnome_screencast_sources += gnome.mkenums_simple(

src/screencast-portal.c

@@ -13,6 +13,8 @@ struct _ScreencastPortal
   gint        portal_signal_id;
   GDBusProxy *screencast;
   guint32     stream_node_id;
+
+  GCancellable *cancellable;
 };
 
 static void      screencast_portal_async_initable_iface_init (GAsyncInitableIface *iface);
@@ -90,15 +92,20 @@ init_check_dbus_error (GObject      *source_object,
                                      &error);
   if (result == NULL)
     {
-      GCancellable *cancellable;
-      g_warning ("Error calling DBus method during Screencast portal initialization: %s",
-                 error->message);
+      /* Do nothing if the operation was cancelled, the task was likely
+       * already returned from elsewhere. */
+      if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
+        {
+          ScreencastPortal *self = SCREENCAST_PORTAL (g_task_get_source_object (task));
 
-      cancellable = g_task_get_cancellable (task);
-      g_cancellable_cancel (cancellable);
+          g_warning ("Error calling DBus method during Screencast portal initialization: %s",
+                     error->message);
 
-      g_task_return_error (task, g_steal_pointer (&error));
-      g_object_unref (task);
+          g_cancellable_cancel (self->cancellable);
+
+          g_task_return_error (task, g_steal_pointer (&error));
+          g_object_unref (task);
+        }
     }
 }
 
@@ -132,7 +139,7 @@ portal_start_response_received (GDBusConnection *connection,
       g_task_return_new_error (task,
                                G_IO_ERROR,
                                G_IO_ERROR_FAILED,
-                               "Failed to create portal sesssion");
+                               "Failed to create portal session");
       g_object_unref (task);
       return;
     }
@@ -220,7 +227,7 @@ portal_select_source_response_received (GDBusConnection *connection,
                      g_variant_builder_end (&builder),
                      G_DBUS_CALL_FLAGS_NONE,
                      1000,
-                     g_task_get_cancellable (task),
+                     self->cancellable,
                      init_check_dbus_error,
                      task);
 }
@@ -287,7 +294,7 @@ portal_create_session_response_received (GDBusConnection *connection,
                      g_variant_builder_end (&builder),
                      G_DBUS_CALL_FLAGS_NONE,
                      1000,
-                     g_task_get_cancellable (task),
+                     self->cancellable,
                      init_check_dbus_error,
                      task);
 }
@@ -314,7 +321,7 @@ on_portal_screencast_proxy_acquired (GObject      *source_object,
   if (screencast == NULL)
     {
       if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
-        g_warning ("Could not get session bus: %s", error->message);
+        g_warning ("Could not create screencast portal proxy: %s", error->message);
 
       g_task_return_error (task, g_steal_pointer (&error));
       return;
@@ -339,7 +346,7 @@ on_portal_screencast_proxy_acquired (GObject      *source_object,
                                                                NULL);
 
 
-  g_variant_builder_open (&builder, "a{sv}");
+  g_variant_builder_open (&builder, G_VARIANT_TYPE ("a{sv}"));
   g_variant_builder_add (&builder, "{sv}", "session_handle_token", g_variant_new_string (session_token));
   g_variant_builder_add (&builder, "{sv}", "handle_token", g_variant_new_string (token));
   g_variant_builder_close (&builder);
@@ -349,7 +356,7 @@ on_portal_screencast_proxy_acquired (GObject      *source_object,
                      g_variant_builder_end (&builder),
                      G_DBUS_CALL_FLAGS_NONE,
                      1000,
-                     g_task_get_cancellable (task),
+                     self->cancellable,
                      init_check_dbus_error,
                      task);
 }
@@ -361,6 +368,25 @@ screencast_portal_async_initable_iface_init (GAsyncInitableIface *iface)
   iface->init_finish = screencast_portal_async_initable_init_finish;
 }
 
+static void
+init_cancelable_cancelled_cb (GTask *task, GCancellable *external)
+{
+  ScreencastPortal *self = SCREENCAST_PORTAL (g_task_get_source_object (task));
+
+  /* Ensure no further callbacks are called. */
+  if (self->portal_signal_id)
+    {
+      g_dbus_connection_signal_unsubscribe (g_dbus_proxy_get_connection (self->screencast),
+                                            self->portal_signal_id);
+      self->portal_signal_id = 0;
+    }
+
+  /* Cancel the task and return it immediately. */
+  g_cancellable_cancel (self->cancellable);
+  g_task_return_error_if_cancelled (task);
+  g_object_unref (task);
+}
+
 static void
 screencast_portal_async_initable_init_async (GAsyncInitable     *initable,
                                              int                 io_priority,
@@ -369,19 +395,20 @@ screencast_portal_async_initable_init_async (GAsyncInitable     *initable,
                                              gpointer            user_data)
 {
   ScreencastPortal *self = SCREENCAST_PORTAL (initable);
-
-  g_autoptr(GCancellable) internal_cancellable = NULL;
-  //g_autoptr(GTask) task = NULL;
   GTask *task = NULL;
 
-  task = g_task_new (initable, cancellable, callback, user_data);
+  self->cancellable = g_cancellable_new ();
+  if (cancellable)
+    g_signal_connect_object (cancellable,
+                             "cancelled",
+                             (GCallback) init_cancelable_cancelled_cb,
+                             self->cancellable,
+                             G_CONNECT_SWAPPED);
 
-  /* Use an internal cancellable if we did not get one. */
-  if (!cancellable)
-    {
-      internal_cancellable = g_cancellable_new ();
-      cancellable = internal_cancellable;
-    }
+  if (g_cancellable_is_cancelled (cancellable))
+    g_cancellable_cancel (self->cancellable);
+
+  task = g_task_new (initable, cancellable, callback, user_data);
 
   g_dbus_proxy_new_for_bus (G_BUS_TYPE_SESSION,
                             G_DBUS_PROXY_FLAGS_DO_NOT_LOAD_PROPERTIES,
@@ -389,7 +416,7 @@ screencast_portal_async_initable_init_async (GAsyncInitable     *initable,
                             "org.freedesktop.portal.Desktop",
                             "/org/freedesktop/portal/desktop",
                             SCREEN_CAST_IFACE,
-                            cancellable,
+                            self->cancellable,
                             on_portal_screencast_proxy_acquired,
                             task);
 }
@@ -415,6 +442,9 @@ screencast_portal_finalize (GObject *object)
 
   G_OBJECT_CLASS (screencast_portal_parent_class)->finalize (object);
 
+  g_cancellable_cancel (self->cancellable);
+  g_clear_object (&self->cancellable);
+
   g_clear_pointer (&self->session_handle, g_free);
   if (self->portal_signal_id)
     {

src/wfd/wfd-video-codec.c

@@ -297,7 +297,7 @@ wfd_video_codec_new_from_desc (gint native, const gchar *descr)
 
   native_res = resolution_table_lookup (native & 0x7, native >> 3);
   if (native_res)
-    res->native = wfd_resolution_copy (native_res);
+    res->native = wfd_resolution_copy ((WfdResolution*) native_res);
 
   return g_steal_pointer (&res);
 }