[gnome-todo] Introduce GtdTaskListViewModel

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 2a8d048935ff2a205307a2c4c8b4a55621b3c1f8
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Sat May 8 21:35:36 2021 -0300

    Introduce GtdTaskListViewModel
    
    It's a tiny wrapper around GListModel that exposes the model's model,
    and a sentinel item. This sentinel item will represent the new task
    row.

 src/gui/gtd-task-list-view-model.c | 216 +++++++++++++++++++++++++++++++++++++
 src/gui/gtd-task-list-view-model.h |  43 ++++++++
 src/meson.build                    |   1 +
 3 files changed, 260 insertions(+)
---
diff --git a/src/gui/gtd-task-list-view-model.c b/src/gui/gtd-task-list-view-model.c
new file mode 100644
index 00000000..d569d29b
--- /dev/null
+++ b/src/gui/gtd-task-list-view-model.c
@@ -0,0 +1,216 @@
+/* gtd-task-list-view-model.c
+ *
+ * Copyright 2020 Georges Basile Stavracas Neto <georges stavracas gmail com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#include "gtd-task-list.h"
+#include "gtd-task-list-view-model.h"
+
+
+/*
+ * Sentinel
+ */
+
+struct _GtdSentinel
+{
+  GObject parent_instance;
+};
+
+G_DEFINE_TYPE (GtdSentinel, gtd_sentinel, G_TYPE_OBJECT);
+
+static void
+gtd_sentinel_init (GtdSentinel *self)
+{
+}
+
+static void
+gtd_sentinel_class_init (GtdSentinelClass *klass)
+{
+}
+
+
+
+struct _GtdTaskListViewModel
+{
+  GObject             parent_instance;
+
+  GtdSentinel        *sentinel;
+
+  GListModel         *model;
+  guint               n_items;
+};
+
+static void g_list_model_iface_init (GListModelInterface *iface);
+
+G_DEFINE_TYPE_WITH_CODE (GtdTaskListViewModel, gtd_task_list_view_model, G_TYPE_OBJECT,
+                         G_IMPLEMENT_INTERFACE (G_TYPE_LIST_MODEL, g_list_model_iface_init))
+
+
+/*
+ * Auxiliary methods
+ */
+
+static void
+update_n_items (GtdTaskListViewModel *self,
+                guint                 position,
+                guint                 removed,
+                guint                 added)
+{
+  self->n_items = self->n_items - removed + added;
+  g_list_model_items_changed (G_LIST_MODEL (self), position, removed, added);
+}
+
+
+/*
+ * Callbacks
+ */
+
+static void
+on_model_items_changed_cb (GListModel           *model,
+                           guint                 position,
+                           guint                 removed,
+                           guint                 added,
+                           GtdTaskListViewModel *self)
+{
+  update_n_items (self, position, removed, added);
+}
+
+
+/*
+ * GListModel interface
+ */
+
+static guint
+gtd_task_list_view_model_get_n_items (GListModel *model)
+{
+  GtdTaskListViewModel *self = (GtdTaskListViewModel *)model;
+
+  return self->n_items + 1;
+}
+
+static GType
+gtd_task_list_view_model_get_item_type (GListModel *model)
+{
+  return G_TYPE_OBJECT;
+}
+
+static gpointer
+gtd_task_list_view_model_get_item (GListModel *model,
+                                   guint       position)
+{
+  GtdTaskListViewModel *self = (GtdTaskListViewModel *)model;
+
+  if (gtd_task_list_view_model_is_sentinel (self, position))
+    return g_object_ref (self->sentinel);
+
+  return g_list_model_get_item (self->model, position);
+}
+
+static void
+g_list_model_iface_init (GListModelInterface *iface)
+{
+  iface->get_n_items = gtd_task_list_view_model_get_n_items;
+  iface->get_item_type = gtd_task_list_view_model_get_item_type;
+  iface->get_item = gtd_task_list_view_model_get_item;
+}
+
+
+/*
+ * GObject overrides
+ */
+
+static void
+gtd_task_list_view_model_finalize (GObject *object)
+{
+  GtdTaskListViewModel *self = (GtdTaskListViewModel *)object;
+
+  g_clear_object (&self->model);
+  g_clear_object (&self->sentinel);
+
+  G_OBJECT_CLASS (gtd_task_list_view_model_parent_class)->finalize (object);
+}
+
+static void
+gtd_task_list_view_model_class_init (GtdTaskListViewModelClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->finalize = gtd_task_list_view_model_finalize;
+}
+
+static void
+gtd_task_list_view_model_init (GtdTaskListViewModel *self)
+{
+  self->sentinel = g_object_new (GTD_TYPE_SENTINEL, NULL);
+}
+
+GtdTaskListViewModel *
+gtd_task_list_view_model_new (void)
+{
+  return g_object_new (GTD_TYPE_TASK_LIST_VIEW_MODEL, NULL);
+}
+
+GListModel *
+gtd_task_list_view_model_get_model (GtdTaskListViewModel *self)
+{
+  return self->model;
+}
+
+void
+gtd_task_list_view_model_set_model (GtdTaskListViewModel *self,
+                                    GListModel           *model)
+{
+  guint old_n_items = 0;
+  guint new_n_items = 0;
+
+  if (G_UNLIKELY (self->model == model))
+    return;
+
+  old_n_items = self->n_items;
+
+  if (self->model)
+    {
+      g_signal_handlers_disconnect_by_func (self->model,
+                                            on_model_items_changed_cb,
+                                            self);
+    }
+
+  g_clear_object (&self->model);
+
+  if (model)
+    {
+      self->model = g_object_ref (model);
+
+      g_signal_connect_object (model,
+                               "items-changed",
+                               G_CALLBACK (on_model_items_changed_cb),
+                               self,
+                               0);
+
+      new_n_items = g_list_model_get_n_items (model);
+    }
+
+  update_n_items (self, 0, old_n_items, new_n_items);
+}
+
+gboolean
+gtd_task_list_view_model_is_sentinel (GtdTaskListViewModel *self,
+                                      guint                 position)
+{
+  return position == self->n_items;
+}
diff --git a/src/gui/gtd-task-list-view-model.h b/src/gui/gtd-task-list-view-model.h
new file mode 100644
index 00000000..7323f3ac
--- /dev/null
+++ b/src/gui/gtd-task-list-view-model.h
@@ -0,0 +1,43 @@
+/* gtd-task-list-view-model.h
+ *
+ * Copyright 2020 Georges Basile Stavracas Neto <georges stavracas gmail com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include <gio/gio.h>
+
+G_BEGIN_DECLS
+
+#define GTD_TYPE_SENTINEL (gtd_sentinel_get_type ())
+G_DECLARE_FINAL_TYPE (GtdSentinel, gtd_sentinel, GTD, SENTINEL, GObject)
+
+#define GTD_TYPE_TASK_LIST_VIEW_MODEL (gtd_task_list_view_model_get_type())
+G_DECLARE_FINAL_TYPE (GtdTaskListViewModel, gtd_task_list_view_model, GTD, TASK_LIST_VIEW_MODEL, GObject)
+
+GtdTaskListViewModel* gtd_task_list_view_model_new (void);
+
+GListModel* gtd_task_list_view_model_get_model (GtdTaskListViewModel *self);
+
+void gtd_task_list_view_model_set_model (GtdTaskListViewModel *self,
+                                         GListModel           *model);
+
+gboolean gtd_task_list_view_model_is_sentinel (GtdTaskListViewModel *self,
+                                               guint                 position);
+
+G_END_DECLS
diff --git a/src/meson.build b/src/meson.build
index c6601281..88654299 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -140,6 +140,7 @@ sources += files(
   'gui/gtd-new-task-row.c',
   'gui/gtd-task-list-popover.c',
   'gui/gtd-task-list-view.c',
+  'gui/gtd-task-list-view-model.c',
   'gui/gtd-task-row.c',
   'gui/gtd-color-button.c',
   'gui/gtd-empty-list-widget.c',