history-box: Switch to GtkSliceListModel

Having more than ~200 widgets in a GtkListBox comes with a very
performance impact. This is especially noticable during while the main
window is being realized (even if Calls already runs in daemon mode).

We can limit the amount of widgets by using a slice list model.

Fixes: #374

src/calls-history-box.c

@@ -25,6 +25,7 @@
 #include "calls-history-box.h"
 #include "calls-call-record.h"
 #include "calls-call-record-row.h"
+#include "gtklistmodels/gtkmodels.h"
 #include "util.h"
 
 #include <glib/gi18n.h>
@@ -37,6 +38,8 @@ struct _CallsHistoryBox {
   GtkListBox *history;
 
   GListModel *model;
+  GtkSliceListModel *slice_model;
+
   gulong      model_changed_handler_id;
 
 };
@@ -149,13 +152,15 @@ constructed (GObject *object)
 
   G_OBJECT_CLASS (calls_history_box_parent_class)->constructed (object);
 
+  self->slice_model = gtk_slice_list_model_new (self->model, 0, 75);
+
   self->model_changed_handler_id =
     g_signal_connect_swapped
       (self->model, "items-changed", G_CALLBACK (update), self);
   g_assert (self->model_changed_handler_id != 0);
 
   gtk_list_box_bind_model (self->history,
-                           self->model,
+                           G_LIST_MODEL (self->slice_model),
                            (GtkListBoxCreateWidgetFunc) create_row_cb,
                            self,
                            NULL);
@@ -169,6 +174,7 @@ dispose (GObject *object)
 {
   CallsHistoryBox *self = CALLS_HISTORY_BOX (object);
 
+  g_clear_object (&self->slice_model);
   g_clear_object (&self->model);
 
   G_OBJECT_CLASS (calls_history_box_parent_class)->dispose (object);