gappinfo: Add launch-started signal

Emit this when we're about to spawn or DBus activate a GAppInfo.  This
allows lauchers to keep the appinfo associated with a startup id.

We use a GVariant to allow for future exansion of the supplied data.

gio/gappinfo.c

@@ -1103,6 +1103,7 @@ g_app_info_delete (GAppInfo *appinfo)
 
 enum {
   LAUNCH_FAILED,
+  LAUNCH_STARTED,
   LAUNCHED,
   LAST_SIGNAL
 };
@@ -1160,6 +1161,41 @@ g_app_launch_context_class_init (GAppLaunchContextClass *klass)
                                          NULL, NULL, NULL,
                                          G_TYPE_NONE, 1, G_TYPE_STRING);
 
+  /**
+   * GAppLaunchContext::launch-started:
+   * @context: the object emitting the signal
+   * @info: the #GAppInfo that is about to be launched
+   * @platform_data: (nullable): additional platform-specific data for this launch
+   *
+   * The #GAppLaunchContext::launch-started signal is emitted when a #GAppInfo is
+   * about to be launched. If non-null the @platform_data is an
+   * GVariant dictionary mapping strings to variants (ie `a{sv}`), which
+   * contains additional, platform-specific data about this launch. On
+   * UNIX, at least the `startup-notification-id` keys will be
+   * present.
+   *
+   * The value of the `startup-notification-id` key (type `s`) is a startup
+   * notification ID corresponding to the format from the [startup-notification
+   * specification](https://specifications.freedesktop.org/startup-notification-spec/startup-notification-0.1.txt).
+   * It allows tracking the progress of the launchee through startup.
+   *
+   * It is guaranteed that this signal is followed by either a #GAppLaunchContext::launched or
+   * #GAppLaunchContext::launch-failed signal.
+   *
+   * Since: 2.72
+   */
+  signals[LAUNCH_STARTED] = g_signal_new (I_("launch-started"),
+                                          G_OBJECT_CLASS_TYPE (object_class),
+                                          G_SIGNAL_RUN_LAST,
+                                          G_STRUCT_OFFSET (GAppLaunchContextClass, launch_started),
+                                          NULL, NULL,
+                                          _g_cclosure_marshal_VOID__OBJECT_VARIANT,
+                                          G_TYPE_NONE, 2,
+                                          G_TYPE_APP_INFO, G_TYPE_VARIANT);
+  g_signal_set_va_marshaller (signals[LAUNCH_STARTED],
+                              G_TYPE_FROM_CLASS (klass),
+                              _g_cclosure_marshal_VOID__OBJECT_VARIANTv);
+
   /**
    * GAppLaunchContext::launched:
    * @context: the object emitting the signal

gio/gappinfo.h

@@ -293,12 +293,14 @@ struct _GAppLaunchContextClass
   void   (* launched)              (GAppLaunchContext *context,
                                     GAppInfo          *info,
                                     GVariant          *platform_data);
+  void   (* launch_started)        (GAppLaunchContext *context,
+                                    GAppInfo          *info,
+                                    GVariant          *platform_data);
 
   /* Padding for future expansion */
   void (*_g_reserved1) (void);
   void (*_g_reserved2) (void);
   void (*_g_reserved3) (void);
-  void (*_g_reserved4) (void);
 };
 
 GLIB_AVAILABLE_IN_ALL

gio/gdesktopappinfo.c

@@ -2731,6 +2731,26 @@ notify_desktop_launch (GDBusConnection  *session_bus,
   g_object_unref (msg);
 }
 
+static void
+emit_launch_started (GAppLaunchContext *context,
+                     GDesktopAppInfo   *info,
+                     const gchar       *startup_id)
+{
+  GVariantBuilder builder;
+  GVariant *platform_data = NULL;
+
+  if (startup_id)
+    {
+      g_variant_builder_init (&builder, G_VARIANT_TYPE_ARRAY);
+      g_variant_builder_add (&builder, "{sv}",
+                             "startup-notification-id",
+                             g_variant_new_string (startup_id));
+      platform_data = g_variant_ref_sink (g_variant_builder_end (&builder));
+    }
+  g_signal_emit_by_name (context, "launch-started", info, platform_data);
+  g_clear_pointer (&platform_data, g_variant_unref);
+}
+
 #define _SPAWN_FLAGS_DEFAULT (G_SPAWN_SEARCH_PATH)
 
 static gboolean
@@ -2826,6 +2846,8 @@ g_desktop_app_info_launch_uris_with_spawn (GDesktopAppInfo            *info,
             }
 
           g_list_free_full (launched_files, g_object_unref);
+
+          emit_launch_started (launch_context, info, sn_id);
         }
 
       /* Wrap the @argv in a command which will set the
@@ -3057,6 +3079,9 @@ launch_uris_with_dbus (GDesktopAppInfo    *info,
   g_variant_dict_init (&dict, platform_data);
   g_variant_dict_lookup (&dict, "desktop-startup-id", "s", &data->startup_id);
 
+  if (launch_context)
+    emit_launch_started (launch_context, info, data->startup_id);
+
   g_dbus_connection_call (session_bus, info->app_id, object_path, "org.freedesktop.Application",
                           uris ? "Open" : "Activate", g_variant_builder_end (&builder),
                           NULL, G_DBUS_CALL_FLAGS_NONE, -1,

gio/tests/desktop-app-info.c

@@ -728,6 +728,20 @@ test_show_in (void)
   assert_shown ("invalid-desktop.desktop", FALSE, "../invalid/desktop:../invalid/desktop");
 }
 
+static void
+on_launch_started (GAppLaunchContext *context, GAppInfo *info, GVariant *platform_data, gpointer data)
+{
+  gboolean *invoked = data;
+
+  g_assert_true (G_IS_APP_LAUNCH_CONTEXT (context));
+  g_assert_true (G_IS_APP_INFO (info));
+  /* Our default context doesn't fill in any platform data */
+  g_assert_null (platform_data);
+
+  g_assert_false (*invoked);
+  *invoked = TRUE;
+}
+
 /* Test g_desktop_app_info_launch_uris_as_manager() and
  * g_desktop_app_info_launch_uris_as_manager_with_fds()
  */
@@ -738,6 +752,8 @@ test_launch_as_manager (void)
   GError *error = NULL;
   gboolean retval;
   const gchar *path;
+  gboolean invoked = FALSE;
+  GAppLaunchContext *context;
 
   if (g_getenv ("DISPLAY") == NULL || g_getenv ("DISPLAY")[0] == '\0')
     {
@@ -754,23 +770,31 @@ test_launch_as_manager (void)
       return;
     }
 
-  retval = g_desktop_app_info_launch_uris_as_manager (appinfo, NULL, NULL, 0,
+  context = g_app_launch_context_new ();
+  g_signal_connect (context, "launch-started",
+                    G_CALLBACK (on_launch_started),
+                    &invoked);
+  retval = g_desktop_app_info_launch_uris_as_manager (appinfo, NULL, context, 0,
                                                       NULL, NULL,
                                                       NULL, NULL,
                                                       &error);
   g_assert_no_error (error);
   g_assert_true (retval);
+  g_assert_true (invoked);
 
+  invoked = FALSE;
   retval = g_desktop_app_info_launch_uris_as_manager_with_fds (appinfo,
-                                                               NULL, NULL, 0,
+                                                               NULL, context, 0,
                                                                NULL, NULL,
                                                                NULL, NULL,
                                                                -1, -1, -1,
                                                                &error);
   g_assert_no_error (error);
   g_assert_true (retval);
+  g_assert_true (invoked);
 
   g_object_unref (appinfo);
+  g_assert_finalize_object (context);
 }
 
 int