kms/result-listener: Allow setting a custom main context

While the default when passing NULL will be the main context of the main
thread, make it possible to specify another main context, so that
result handlers can be invoked on the right thread.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>

src/backends/native/meta-cursor-renderer-native.c

@@ -361,6 +361,7 @@ assign_cursor_plane (MetaCursorRendererNative *native,
                                                 cursor_hotspot_y);
 
   meta_kms_update_add_result_listener (kms_update,
+                                       NULL,
                                        on_kms_update_result,
                                        native);
 

src/backends/native/meta-kms-update-private.h

@@ -128,6 +128,7 @@ typedef struct _MetaKmsPageFlipListener
 
 struct _MetaKmsResultListener
 {
+  GMainContext *main_context;
   MetaKmsResultListenerFunc func;
   gpointer user_data;
 
@@ -191,8 +192,11 @@ MetaKmsCustomPageFlip * meta_kms_update_take_custom_page_flip_func (MetaKmsUpdat
 void meta_kms_update_drop_plane_assignment (MetaKmsUpdate *update,
                                             MetaKmsPlane  *plane);
 
+META_EXPORT_TEST
 GList * meta_kms_update_take_result_listeners (MetaKmsUpdate *update);
 
+GMainContext * meta_kms_result_listener_get_main_context (MetaKmsResultListener *listener);
+
 void meta_kms_result_listener_set_feedback (MetaKmsResultListener *listener,
                                             MetaKmsFeedback       *feedback);
 

src/backends/native/meta-kms-update.c

@@ -607,6 +607,7 @@ meta_kms_plane_assignment_set_cursor_hotspot (MetaKmsPlaneAssignment *plane_assi
 
 void
 meta_kms_update_add_result_listener (MetaKmsUpdate             *update,
+                                     GMainContext              *main_context,
                                      MetaKmsResultListenerFunc  func,
                                      gpointer                   user_data)
 {
@@ -614,6 +615,7 @@ meta_kms_update_add_result_listener (MetaKmsUpdate             *update,
 
   listener = g_new0 (MetaKmsResultListener, 1);
   *listener = (MetaKmsResultListener) {
+    .main_context = main_context,
     .func = func,
     .user_data = user_data,
   };
@@ -628,6 +630,12 @@ meta_kms_update_take_result_listeners (MetaKmsUpdate *update)
   return g_steal_pointer (&update->result_listeners);
 }
 
+GMainContext *
+meta_kms_result_listener_get_main_context (MetaKmsResultListener *listener)
+{
+  return listener->main_context;
+}
+
 void
 meta_kms_result_listener_set_feedback (MetaKmsResultListener *listener,
                                        MetaKmsFeedback       *feedback)

src/backends/native/meta-kms-update.h

@@ -92,6 +92,7 @@ GList * meta_kms_feedback_get_failed_planes (const MetaKmsFeedback *feedback);
 
 const GError * meta_kms_feedback_get_error (const MetaKmsFeedback *feedback);
 
+META_EXPORT_TEST
 void meta_kms_feedback_dispatch_result (MetaKmsFeedback *feedback,
                                         MetaKms         *kms,
                                         GList           *result_listeners);
@@ -183,6 +184,7 @@ void meta_kms_plane_assignment_set_cursor_hotspot (MetaKmsPlaneAssignment *plane
 
 META_EXPORT_TEST
 void meta_kms_update_add_result_listener (MetaKmsUpdate             *update,
+                                          GMainContext              *main_context,
                                           MetaKmsResultListenerFunc  func,
                                           gpointer                   user_data);
 

src/backends/native/meta-kms.c

@@ -169,8 +169,11 @@ void
 meta_kms_queue_result_callback (MetaKms               *kms,
                                 MetaKmsResultListener *listener)
 {
+  GMainContext *main_context =
+    meta_kms_result_listener_get_main_context (listener);
+
   meta_kms_queue_callback  (kms,
-                            NULL,
+                            main_context,
                             invoke_result_listener,
                             listener,
                             (GDestroyNotify) meta_kms_result_listener_free);

src/backends/native/meta-onscreen-native.c

@@ -1171,6 +1171,7 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
       kms_update = meta_frame_native_ensure_kms_update (frame_native,
                                                         kms_device);
       meta_kms_update_add_result_listener (kms_update,
+                                           NULL,
                                            on_swap_buffer_update_result,
                                            onscreen_native);
 
@@ -1389,6 +1390,7 @@ meta_onscreen_native_direct_scanout (CoglOnscreen   *onscreen,
   kms_update = meta_frame_native_ensure_kms_update (frame_native, kms_device);
 
   meta_kms_update_add_result_listener (kms_update,
+                                       NULL,
                                        on_scanout_update_result,
                                        onscreen_native);
 
@@ -1542,6 +1544,7 @@ meta_onscreen_native_finish_frame (CoglOnscreen *onscreen,
     }
 
   meta_kms_update_add_result_listener (kms_update,
+                                       NULL,
                                        on_finish_frame_update_result,
                                        onscreen_native);
 

src/backends/native/meta-renderer-native.c

@@ -865,6 +865,7 @@ post_mode_set_updates (MetaRendererNative *renderer_native)
       g_hash_table_iter_steal (&iter);
 
       meta_kms_update_add_result_listener (kms_update,
+                                           NULL,
                                            on_mode_sets_update_result,
                                            NULL);
 

src/tests/native-kms-render.c

@@ -376,6 +376,7 @@ on_scanout_fallback_before_paint (ClutterStage     *stage,
 
   kms_update = meta_frame_native_ensure_kms_update (frame_native, kms_device);
   meta_kms_update_add_result_listener (kms_update,
+                                       NULL,
                                        on_scanout_fallback_result, test);
 
   test->scanout_fallback.scanout_failed_view = stage_view;

src/tests/native-kms-updates.c

@@ -22,6 +22,7 @@
 
 #include <dlfcn.h>
 
+#include "backends/native/meta-backend-native.h"
 #include "backends/native/meta-kms-connector.h"
 #include "backends/native/meta-kms-crtc.h"
 #include "backends/native/meta-kms-device.h"
@@ -744,6 +745,110 @@ meta_test_kms_update_off_thread_page_flip (void)
   g_mutex_clear (&data.init_mutex);
 }
 
+typedef struct
+{
+  GMutex init_mutex;
+  GCond init_cond;
+  gboolean initialized;
+
+  GMainContext *thread_main_context;
+  GMainLoop *thread_loop;
+  GThread *thread;
+
+  GMainLoop *main_thread_loop;
+} CallbackData;
+
+static gpointer
+off_thread_callback_thread_func (gpointer user_data)
+{
+  CallbackData *data = user_data;
+  MetaBackend *backend = meta_context_get_backend (test_context);
+  MetaBackendNative *backend_native = META_BACKEND_NATIVE (backend);
+  MetaKms *kms = meta_backend_native_get_kms (backend_native);
+
+  meta_thread_register_callback_context (META_THREAD (kms),
+                                         data->thread_main_context);
+
+  data->thread_loop = g_main_loop_new (data->thread_main_context, FALSE);
+
+  g_mutex_lock (&data->init_mutex);
+  data->initialized = TRUE;
+  g_cond_signal (&data->init_cond);
+  g_mutex_unlock (&data->init_mutex);
+
+  g_assert (data->thread == g_thread_self ());
+
+  g_main_loop_run (data->thread_loop);
+  g_main_loop_unref (data->thread_loop);
+
+  meta_thread_unregister_callback_context (META_THREAD (kms),
+                                           data->thread_main_context);
+
+  return GINT_TO_POINTER (TRUE);
+}
+
+static void
+on_main_thread_result (const MetaKmsFeedback *feedback,
+                       gpointer               user_data)
+{
+  CallbackData *data = user_data;
+
+  g_main_loop_quit (data->main_thread_loop);
+}
+
+static void
+on_callback_thread_result (const MetaKmsFeedback *feedback,
+                           gpointer               user_data)
+{
+  CallbackData *data = user_data;
+
+  g_main_loop_quit (data->thread_loop);
+}
+
+static void
+meta_test_kms_update_feedback (void)
+{
+  CallbackData data = {};
+  MetaKmsDevice *device;
+  MetaKmsUpdate *update;
+  g_autoptr (MetaDrmBuffer) buffer = NULL;
+  g_autoptr (MetaKmsFeedback) kms_feedback = NULL;
+
+  data.main_thread_loop = g_main_loop_new (NULL, FALSE);
+
+  g_mutex_init (&data.init_mutex);
+  g_cond_init (&data.init_cond);
+  g_mutex_lock (&data.init_mutex);
+  data.thread_main_context = g_main_context_new ();
+  data.thread = g_thread_new ("Callback test thread",
+                              off_thread_callback_thread_func,
+                              &data);
+  while (!data.initialized)
+    g_cond_wait (&data.init_cond, &data.init_mutex);
+  g_mutex_unlock (&data.init_mutex);
+
+  device = meta_get_test_kms_device (test_context);
+  update = meta_kms_update_new (device);
+  populate_update (update, &buffer, POPULATE_UPDATE_FLAG_MODE);
+
+  meta_kms_update_add_result_listener (update, NULL,
+                                       on_main_thread_result,
+                                       &data);
+  meta_kms_update_add_result_listener (update, data.thread_main_context,
+                                       on_callback_thread_result,
+                                       &data);
+
+  kms_feedback = meta_kms_device_process_update_sync (device, update,
+                                                      META_KMS_UPDATE_FLAG_NONE);
+
+  g_main_loop_run (data.main_thread_loop);
+
+  g_assert_cmpint (GPOINTER_TO_INT (g_thread_join (data.thread)), ==, TRUE);
+  g_main_context_unref (data.thread_main_context);
+  g_mutex_clear (&data.init_mutex);
+  g_cond_clear (&data.init_cond);
+}
+
 static void
 init_tests (void)
 {
@@ -761,6 +866,8 @@ init_tests (void)
                    meta_test_kms_update_merge);
   g_test_add_func ("/backends/native/kms/update/off-thread-page-flip",
                    meta_test_kms_update_off_thread_page_flip);
+  g_test_add_func ("/backends/native/kms/update/feedback",
+                   meta_test_kms_update_feedback);
 }
 
 int