search: Rework threading

Search uses GcalTimeline, an object that is meant to be single
threaded, in multple threads. That mostly worked okay because
GcalTimeline mostly relies on GcalCalendarMonitor, which is
heavily threaded. But, sometimes it failed.

Rework that to be single-threaded, and asynchronous.

Closes https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/981
Closes https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/987
Closes https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/988

src/search/gcal-search-engine.c

@@ -22,20 +22,12 @@
 
 #include "gcal-context.h"
 #include "gcal-date-time-utils.h"
+#include "gcal-debug.h"
 #include "gcal-search-engine.h"
 #include "gcal-search-model.h"
 #include "gcal-timeline.h"
 #include "gcal-timeline-subscriber.h"
 
-typedef struct
-{
-  GcalSearchEngine   *engine;
-  gchar              *query;
-  gint                max_results;
-  GDateTime          *range_start;
-  GDateTime          *range_end;
-} SearchData;
-
 struct _GcalSearchEngine
 {
   GObject             parent;
@@ -57,59 +49,10 @@ enum
 static GParamSpec *properties [N_PROPS];
 
 
-/*
- * Auxiliary methods
- */
-
-static void
-search_data_free (gpointer data)
-{
-  SearchData *search_data = data;
-
-  if (!data)
-    return;
-
-  gcal_clear_date_time (&search_data->range_start);
-  gcal_clear_date_time (&search_data->range_end);
-  g_clear_pointer (&search_data->query, g_free);
-  g_clear_object (&search_data->engine);
-  g_slice_free (SearchData, data);
-}
-
-
 /*
  * Callbacks
  */
 
-static void
-search_func (GTask        *task,
-             gpointer      source_object,
-             gpointer      task_data,
-             GCancellable *cancellable)
-{
-  g_autoptr (GcalSearchModel) model = NULL;
-  GcalSearchEngine *self;
-  SearchData *data;
-
-  self = GCAL_SEARCH_ENGINE (source_object);
-  data = (SearchData*) task_data;
-
-  model = gcal_search_model_new (cancellable,
-                                 data->max_results,
-                                 data->range_start,
-                                 data->range_end);
-
-  gcal_timeline_set_filter (self->timeline, data->query);
-  gcal_timeline_add_subscriber (self->timeline, GCAL_TIMELINE_SUBSCRIBER (model));
-
-  gcal_search_model_wait_for_hits (model, cancellable);
-
-  if (g_cancellable_is_cancelled (cancellable))
-    g_task_return_new_error (task, G_IO_ERROR, G_IO_ERROR_CANCELLED, "Cancelled");
-  else
-    g_task_return_pointer (task, g_steal_pointer (&model), g_object_unref);
-}
-
 static void
 on_manager_calendar_added_cb (GcalManager      *manager,
                               GcalCalendar     *calendar,
@@ -130,6 +73,31 @@ on_manager_calendar_removed_cb (GcalManager      *manager,
   gcal_timeline_remove_calendar (self->timeline, calendar);
 }
 
+static void
+search_model_hits_cb (GObject      *source,
+                      GAsyncResult *result,
+                      gpointer      data)
+{
+  g_autoptr (GError) error = NULL;
+  g_autoptr (GTask) task = data;
+  GcalSearchModel *search_model;
+
+  GCAL_ENTRY;
+
+  search_model = GCAL_SEARCH_MODEL (source);
+  gcal_search_model_wait_for_hits_finish (search_model, result, &error);
+
+  if (error)
+    {
+      g_task_return_error (task, g_steal_pointer (&error));
+      GCAL_RETURN ();
+    }
+
+  g_task_return_pointer (task, g_object_ref (search_model), NULL);
+
+  GCAL_EXIT;
+}
+
 
 /*
  * GObject overrides
@@ -246,9 +214,11 @@ gcal_search_engine_search (GcalSearchEngine    *self,
                            GAsyncReadyCallback  callback,
                            gpointer             user_data)
 {
+  g_autoptr (GcalSearchModel) model = NULL;
+  g_autoptr (GDateTime) range_start = NULL;
+  g_autoptr (GDateTime) range_end = NULL;
   g_autoptr (GDateTime) now = NULL;
   g_autoptr (GTask) task = NULL;
-  SearchData *data = NULL;
   GTimeZone *timezone;
 
   g_return_if_fail (GCAL_IS_SEARCH_ENGINE (self));
@@ -256,20 +226,18 @@ gcal_search_engine_search (GcalSearchEngine    *self,
 
   timezone = gcal_context_get_timezone (self->context);
   now = g_date_time_new_now (timezone);
+  range_start = g_date_time_add_weeks (now, -1);
+  range_end = g_date_time_add_weeks (now, 3);
+  model = gcal_search_model_new (cancellable, max_results, range_start, range_end);
 
-  data = g_slice_new0 (SearchData);
-  data->engine = g_object_ref (self);
-  data->query = g_strdup (search_query);
-  data->max_results = max_results;
-  data->range_start = g_date_time_add_weeks (now, -1);
-  data->range_end = g_date_time_add_weeks (now, 3);
+  gcal_timeline_set_filter (self->timeline, search_query);
+  gcal_timeline_add_subscriber (self->timeline, GCAL_TIMELINE_SUBSCRIBER (model));
 
   task = g_task_new (self, cancellable, callback, user_data);
   g_task_set_source_tag (task, gcal_search_engine_search);
   g_task_set_priority (task, G_PRIORITY_LOW);
-  g_task_set_task_data (task, data, (GDestroyNotify) search_data_free);
 
-  g_task_run_in_thread (task, search_func);
+  gcal_search_model_wait_for_hits (model, cancellable, search_model_hits_cb, g_object_ref (task));
 }
 
 GListModel*