[gtk/ebassi/issue-4883] Keep FileChooserNative alive while a portal is running

[Emmanuele Bassi <ebassi src gnome org>]

commit 196ec107d1756aa3ef18bdb7b4d384402f5bd1a2
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Fri Apr 29 15:18:02 2022 +0100

    Keep FileChooserNative alive while a portal is running
    
    Even if the FileChooserNative instance drops out on us while we're still
    waiting for the portal to answer, we should keep the data and pointers
    alive until the sequence of asynchronous operations is running. The code
    already tries to do that, by acquiring a strong reference to the
    GtkFileChooserNative instance, but it's also freeing data as soon as the
    dialog is hidden, while asynchronous callbacks that will look at the
    fields on that data are still in flight.
    
    To avoid that, we defer freeing the data until the asynchronous
    callbacks are invoked, and we keep a reference on the dialog while we're
    emitting signals on it.
    
    Fixes: #4883

 gtk/gtkfilechoosernativeportal.c | 65 ++++++++++++++++++++++++++--------------
 1 file changed, 43 insertions(+), 22 deletions(-)
---
diff --git a/gtk/gtkfilechoosernativeportal.c b/gtk/gtkfilechoosernativeportal.c
index d31337931e..00b28e5597 100644
--- a/gtk/gtkfilechoosernativeportal.c
+++ b/gtk/gtkfilechoosernativeportal.c
@@ -60,30 +60,42 @@ typedef struct {
 
 
 static void
-filechooser_portal_data_free (FilechooserPortalData *data)
+filechooser_portal_data_clear (FilechooserPortalData *data)
 {
   if (data->portal_response_signal_id != 0)
-    g_dbus_connection_signal_unsubscribe (data->connection,
-                                          data->portal_response_signal_id);
+    {
+      g_dbus_connection_signal_unsubscribe (data->connection,
+                                            data->portal_response_signal_id);
+      data->portal_response_signal_id = 0;
+    }
 
-  g_object_unref (data->connection);
+  g_clear_object (&data->connection);
 
   if (data->grab_widget)
     {
       gtk_grab_remove (data->grab_widget);
-      g_object_unref (data->grab_widget);
+      g_clear_object (&data->grab_widget);
     }
 
   g_clear_object (&data->self);
 
   if (data->exported_window)
-    gtk_window_unexport_handle (data->exported_window);
-
-  g_clear_object (&data->exported_window);
+    {
+      gtk_window_unexport_handle (data->exported_window);
+      g_clear_object (&data->exported_window);
+    }
 
-  g_free (data->portal_handle);
+  g_clear_pointer (&data->portal_handle, g_free);
+}
 
-  g_free (data);
+static void
+filechooser_portal_data_free (FilechooserPortalData *data)
+{
+  if (data != NULL)
+    {
+      filechooser_portal_data_clear (data);
+      g_free (data);
+    }
 }
 
 static void
@@ -175,10 +187,18 @@ response_cb (GDBusConnection  *connection,
       break;
     }
 
+  /* Keep a reference on the native dialog until we can emit the response
+   * signal; filechooser_portal_data_free() will drop a reference on the
+   * dialog as well
+   */
+  g_object_ref (self);
+
   filechooser_portal_data_free (data);
   self->mode_data = NULL;
 
   _gtk_native_dialog_emit_response (GTK_NATIVE_DIALOG (self), gtk_response);
+
+  g_object_unref (self);
 }
 
 static void
@@ -239,7 +259,6 @@ open_file_msg_cb (GObject *source_object,
   if (data->hidden)
     {
       /* The dialog was hidden before we got the handle, close it now */
-      send_close (data);
       filechooser_portal_data_free (data);
       self->mode_data = NULL;
     }
@@ -344,15 +363,15 @@ show_portal_file_chooser (GtkFileChooserNative *self,
 
   data->portal_handle = gtk_get_portal_request_path (data->connection, &token);
   data->portal_response_signal_id =
-        g_dbus_connection_signal_subscribe (data->connection,
-                                            PORTAL_BUS_NAME,
-                                            PORTAL_REQUEST_INTERFACE,
-                                            "Response",
-                                            data->portal_handle,
-                                            NULL,
-                                            G_DBUS_SIGNAL_FLAGS_NO_MATCH_RULE,
-                                            response_cb,
-                                            self, NULL);
+    g_dbus_connection_signal_subscribe (data->connection,
+                                        PORTAL_BUS_NAME,
+                                        PORTAL_REQUEST_INTERFACE,
+                                        "Response",
+                                        data->portal_handle,
+                                        NULL,
+                                        G_DBUS_SIGNAL_FLAGS_NO_MATCH_RULE,
+                                        response_cb,
+                                        self, NULL);
 
   multiple = gtk_file_chooser_get_select_multiple (GTK_FILE_CHOOSER (self));
   directory = gtk_file_chooser_get_action (GTK_FILE_CHOOSER (self)) == GTK_FILE_CHOOSER_ACTION_SELECT_FOLDER;
@@ -527,7 +546,9 @@ gtk_file_chooser_native_portal_hide (GtkFileChooserNative *self)
   if (data->portal_handle)
     send_close (data);
 
-  filechooser_portal_data_free (data);
-
+  /* We clear the data because we might have in-flight async
+   * operations that can still access it
+   */
+  filechooser_portal_data_clear (data);
   self->mode_data = NULL;
 }