Add a reverse list model

This is a simple wrapper list model that reverses
the order of items in the child model.

gtk/gtk.h

@@ -205,6 +205,7 @@
 #include <gtk/gtkrecentmanager.h>
 #include <gtk/gtkrender.h>
 #include <gtk/gtkrevealer.h>
+#include <gtk/gtkreverselistmodel.h>
 #include <gtk/gtkroot.h>
 #include <gtk/gtkscale.h>
 #include <gtk/gtkscalebutton.h>

gtk/gtkreverselistmodel.c

@@ -0,0 +1,290 @@
+/*
+ * Copyright © 2020 Red Hat, Inc
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Matthias Clasen
+ */
+
+#include "config.h"
+
+#include "gtkreverselistmodel.h"
+
+#include "gtkintl.h"
+#include "gtkprivate.h"
+
+/**
+ * SECTION:gtkreverselistmodel
+ * @title: GtkReverseListModel
+ * @short_description: A list model that reverses the order of a list model
+ * @see_also: #GListModel
+ *
+ * #GtkReverseListModel is a list model that takes a list model and reverses
+ * the order of that model.
+ */
+
+enum {
+  PROP_0,
+  PROP_MODEL,
+  NUM_PROPERTIES
+};
+
+struct _GtkReverseListModel
+{
+  GObject parent_instance;
+
+  GListModel *model;
+};
+
+struct _GtkReverseListModelClass
+{
+  GObjectClass parent_class;
+};
+
+static GParamSpec *properties[NUM_PROPERTIES] = { NULL, };
+
+static GType
+gtk_reverse_list_model_get_item_type (GListModel *list)
+{
+  return G_TYPE_OBJECT;
+}
+
+static guint
+gtk_reverse_list_model_get_n_items (GListModel *list)
+{
+  GtkReverseListModel *self = GTK_REVERSE_LIST_MODEL (list);
+
+  if (self->model == NULL)
+    return 0;
+
+  return g_list_model_get_n_items (self->model);
+}
+
+static gpointer
+gtk_reverse_list_model_get_item (GListModel *list,
+                                 guint       position)
+{
+  GtkReverseListModel *self = GTK_REVERSE_LIST_MODEL (list);
+  guint n_items;
+
+  if (self->model == NULL)
+    return NULL;
+
+  n_items = g_list_model_get_n_items (self->model);
+
+  if (position >= n_items)
+    return NULL;
+
+  return g_list_model_get_item (self->model, n_items - 1 - position);
+}
+
+static void
+gtk_reverse_list_model_model_init (GListModelInterface *iface)
+{
+  iface->get_item_type = gtk_reverse_list_model_get_item_type;
+  iface->get_n_items = gtk_reverse_list_model_get_n_items;
+  iface->get_item = gtk_reverse_list_model_get_item;
+}
+
+G_DEFINE_TYPE_WITH_CODE (GtkReverseListModel, gtk_reverse_list_model, G_TYPE_OBJECT,
+                         G_IMPLEMENT_INTERFACE (G_TYPE_LIST_MODEL, gtk_reverse_list_model_model_init))
+
+static void
+gtk_reverse_list_model_items_changed_cb (GListModel          *model,
+                                         guint                position,
+                                         guint                removed,
+                                         guint                added,
+                                         GtkReverseListModel *self)
+{
+  guint n_items;
+  guint position_before;
+
+  n_items = g_list_model_get_n_items (model);
+
+  position_before = (n_items - added + removed) - 1 - (position + removed - 1);
+
+  g_list_model_items_changed (G_LIST_MODEL (self), position_before, removed, added);
+}
+
+static void
+gtk_reverse_list_model_set_property (GObject      *object,
+                                     guint         prop_id,
+                                     const GValue *value,
+                                     GParamSpec   *pspec)
+{
+  GtkReverseListModel *self = GTK_REVERSE_LIST_MODEL (object);
+
+  switch (prop_id)
+    {
+    case PROP_MODEL:
+      gtk_reverse_list_model_set_model (self, g_value_get_object (value));
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+gtk_reverse_list_model_get_property (GObject     *object,
+                                     guint        prop_id,
+                                     GValue      *value,
+                                     GParamSpec  *pspec)
+{
+  GtkReverseListModel *self = GTK_REVERSE_LIST_MODEL (object);
+
+  switch (prop_id)
+    {
+    case PROP_MODEL:
+      g_value_set_object (value, self->model);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+gtk_reverse_list_model_clear_model (GtkReverseListModel *self)
+{
+  if (self->model == NULL)
+    return;
+
+  g_signal_handlers_disconnect_by_func (self->model, gtk_reverse_list_model_items_changed_cb, self);
+  g_clear_object (&self->model);
+}
+
+static void
+gtk_reverse_list_model_dispose (GObject *object)
+{
+  GtkReverseListModel *self = GTK_REVERSE_LIST_MODEL (object);
+
+  gtk_reverse_list_model_clear_model (self);
+
+  G_OBJECT_CLASS (gtk_reverse_list_model_parent_class)->dispose (object);
+};
+
+static void
+gtk_reverse_list_model_class_init (GtkReverseListModelClass *class)
+{
+  GObjectClass *gobject_class = G_OBJECT_CLASS (class);
+
+  gobject_class->set_property = gtk_reverse_list_model_set_property;
+  gobject_class->get_property = gtk_reverse_list_model_get_property;
+  gobject_class->dispose = gtk_reverse_list_model_dispose;
+
+  /**
+   * GtkReverseListModel:model:
+   *
+   * Child model to revert
+   */
+  properties[PROP_MODEL] =
+      g_param_spec_object ("model",
+                           P_("Model"),
+                           P_("Child model to revert"),
+                           G_TYPE_LIST_MODEL,
+                           GTK_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY);
+
+  g_object_class_install_properties (gobject_class, NUM_PROPERTIES, properties);
+}
+
+static void
+gtk_reverse_list_model_init (GtkReverseListModel *self)
+{
+}
+
+/**
+ * gtk_reverse_list_model_new:
+ * @model: (transfer full) (allow-none): The model to use, or %NULL
+ *
+ * Creates a new model that presents the items from @model
+ * in reverse order
+ *
+ * Returns: A new #GtkReverseListModel
+ **/
+GtkReverseListModel *
+gtk_reverse_list_model_new (GListModel *model)
+{
+  GtkReverseListModel *self;
+
+  g_return_val_if_fail (model == NULL || G_IS_LIST_MODEL (model), NULL);
+
+  self = g_object_new (GTK_TYPE_REVERSE_LIST_MODEL,
+                       "model", model,
+                       NULL);
+
+  /* consume the reference */
+  g_clear_object (&model);
+
+  return self;
+}
+
+/**
+ * gtk_reverse_list_model_set_model:
+ * @self: a #GtkReverseListModel
+ * @model: (allow-none): The model to be sliced
+ *
+ * Sets the model to revert. The model's item type must conform
+ * to @self's item type.
+ *
+ **/
+void
+gtk_reverse_list_model_set_model (GtkReverseListModel *self,
+                                  GListModel          *model)
+{
+  guint removed, added;
+
+  g_return_if_fail (GTK_IS_REVERSE_LIST_MODEL (self));
+  g_return_if_fail (model == NULL || G_IS_LIST_MODEL (model));
+
+  if (self->model == model)
+    return;
+
+  removed = g_list_model_get_n_items (G_LIST_MODEL (self));
+  gtk_reverse_list_model_clear_model (self);
+
+  if (model)
+    {
+      self->model = g_object_ref (model);
+      g_signal_connect (model, "items-changed", G_CALLBACK (gtk_reverse_list_model_items_changed_cb), self);
+      added = g_list_model_get_n_items (G_LIST_MODEL (self));
+    }
+  else
+    {
+      added = 0;
+    }
+
+  if (removed > 0 || added > 0)
+    g_list_model_items_changed (G_LIST_MODEL (self), 0, removed, added);
+
+  g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_MODEL]);
+}
+
+/**
+ * gtk_reverse_list_model_get_model:
+ * @self: a #GtkReverseListModel
+ *
+ * Gets the model that is currently being used or %NULL if none.
+ *
+ * Returns: (nullable) (transfer none): The model in use
+ **/
+GListModel *
+gtk_reverse_list_model_get_model (GtkReverseListModel *self)
+{
+  g_return_val_if_fail (GTK_IS_REVERSE_LIST_MODEL (self), NULL);
+
+  return self->model;
+}

gtk/gtkreverselistmodel.h

@@ -0,0 +1,50 @@
+/*
+ * Copyright © 2020 Red Hat, Inc
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Matthias Clasen
+ */
+
+#ifndef __GTK_REVERSE_LIST_MODEL_H__
+#define __GTK_REVERSE_LIST_MODEL_H__
+
+
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gtk/gtk.h> can be included directly."
+#endif
+
+#include <gio/gio.h>
+#include <gtk/gtkwidget.h>
+
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_REVERSE_LIST_MODEL (gtk_reverse_list_model_get_type ())
+
+GDK_AVAILABLE_IN_ALL
+G_DECLARE_FINAL_TYPE (GtkReverseListModel, gtk_reverse_list_model, GTK, REVERSE_LIST_MODEL, GObject)
+
+GDK_AVAILABLE_IN_ALL
+GtkReverseListModel *   gtk_reverse_list_model_new              (GListModel             *model);
+
+GDK_AVAILABLE_IN_ALL
+void                    gtk_reverse_list_model_set_model        (GtkReverseListModel    *self,
+                                                                 GListModel             *model);
+GDK_AVAILABLE_IN_ALL
+GListModel *            gtk_reverse_list_model_get_model        (GtkReverseListModel    *self);
+
+G_END_DECLS
+
+#endif /* __GTK_REVERSE_LIST_MODEL_H__ */

gtk/meson.build

@@ -340,6 +340,7 @@ gtk_public_sources = files([
   'gtkrendericon.c',
   'gtkrendernodepaintable.c',
   'gtkrevealer.c',
+  'gtkreverselistmodel.c',
   'gtkroot.c',
   'gtknative.c',
   'gtkroundedbox.c',