[gtk/wip/otte/listmodel: 128/132] gtk: Add GtkFlattenListModel

[Benjamin Otte <otte src gnome org>]

commit 5a74d3ee2a113ce858ed87db0be61822a6260ab9
Author: Benjamin Otte <otte redhat com>
Date:   Mon Sep 3 00:48:28 2018 +0200

    gtk: Add GtkFlattenListModel
    
    We can flatten lists of lists into lists now!

 docs/reference/gtk/gtk4-docs.xml     |   1 +
 docs/reference/gtk/gtk4-sections.txt |  18 ++
 gtk/gtk.h                            |   1 +
 gtk/gtkfilterlistmodel.c             |  13 +
 gtk/gtkflattenlistmodel.c            | 520 +++++++++++++++++++++++++++++++++++
 gtk/gtkflattenlistmodel.h            |  50 ++++
 gtk/meson.build                      |   2 +
 testsuite/gtk/flattenlistmodel.c     | 372 +++++++++++++++++++++++++
 testsuite/gtk/meson.build            |   1 +
 9 files changed, 978 insertions(+)
---
diff --git a/docs/reference/gtk/gtk4-docs.xml b/docs/reference/gtk/gtk4-docs.xml
index edb2529c6a..98f0c897e0 100644
--- a/docs/reference/gtk/gtk4-docs.xml
+++ b/docs/reference/gtk/gtk4-docs.xml
@@ -44,6 +44,7 @@
     <chapter id="Lists">
       <title>GListModel support</title>
       <xi:include href="xml/gtkfilterlistmodel.xml" />
+      <xi:include href="xml/gtkflattenlistmodel.xml" />
       <xi:include href="xml/gtktreelistmodel.xml" />
     </chapter>
 
diff --git a/docs/reference/gtk/gtk4-sections.txt b/docs/reference/gtk/gtk4-sections.txt
index 81f3600f94..5fa44b0201 100644
--- a/docs/reference/gtk/gtk4-sections.txt
+++ b/docs/reference/gtk/gtk4-sections.txt
@@ -1279,6 +1279,24 @@ GtkFixedChild
 gtk_fixed_get_type
 </SECTION>
 
+<SECTION>
+<FILE>gtkfattenlistmodel</FILE>
+<TITLE>GtkFattenListModel</TITLE>
+GtkFattenListModel
+gtk_fatten_list_model_new
+gtk_fatten_list_model_set_model
+gtk_fatten_list_model_get_model
+<SUBSECTION Standard>
+GTK_FLATTEN_LIST_MODEL
+GTK_IS_FLATTEN_LIST_MODEL
+GTK_TYPE_FLATTEN_LIST_MODEL
+GTK_FLATTEN_LIST_MODEL_CLASS
+GTK_IS_FLATTEN_LIST_MODEL_CLASS
+GTK_FLATTEN_LIST_MODEL_GET_CLASS
+<SUBSECTION Private>
+gtk_fatten_list_model_get_type
+</SECTION>
+
 <SECTION>
 <FILE>gtkfontbutton</FILE>
 <TITLE>GtkFontButton</TITLE>
diff --git a/gtk/gtk.h b/gtk/gtk.h
index 704f14238a..6a5f9b25dd 100644
--- a/gtk/gtk.h
+++ b/gtk/gtk.h
@@ -105,6 +105,7 @@
 #include <gtk/gtkfilechooserwidget.h>
 #include <gtk/gtkfilefilter.h>
 #include <gtk/gtkfilterlistmodel.h>
+#include <gtk/gtkflattenlistmodel.h>
 #include <gtk/gtkflowbox.h>
 #include <gtk/gtkfontbutton.h>
 #include <gtk/gtkfontchooser.h>
diff --git a/gtk/gtkfilterlistmodel.c b/gtk/gtkfilterlistmodel.c
index 4f814358e3..29ed7575a2 100644
--- a/gtk/gtkfilterlistmodel.c
+++ b/gtk/gtkfilterlistmodel.c
@@ -25,6 +25,19 @@
 #include "gtkintl.h"
 #include "gtkprivate.h"
 
+/**
+ * SECTION:gtkflattenlistmodel
+ * @title: GtkFlattenListModel
+ * @short_description: a #GListModel that flattens a goven listmodel
+ * @see_also: #GListModel
+ *
+ * #GtkFlattenModel is a list model that takes a list model containing
+ * list models and flattens it into a single model.
+ *
+ * Another term for this is concatenation: #GtkFlattenModel takes a list
+ * of lists and concatenates them into a single list.
+ */
+
 enum {
   PROP_0,
   PROP_HAS_FILTER,
diff --git a/gtk/gtkflattenlistmodel.c b/gtk/gtkflattenlistmodel.c
new file mode 100644
index 0000000000..4508221871
--- /dev/null
+++ b/gtk/gtkflattenlistmodel.c
@@ -0,0 +1,520 @@
+/*
+ * Copyright © 2018 Benjamin Otte
+ *
+ * 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: Benjamin Otte <otte gnome org>
+ */
+
+#include "config.h"
+
+#include "gtkflattenlistmodel.h"
+
+#include "gtkcssrbtreeprivate.h"
+#include "gtkintl.h"
+#include "gtkprivate.h"
+
+enum {
+  PROP_0,
+  PROP_ITEM_TYPE,
+  PROP_MODEL,
+  NUM_PROPERTIES
+};
+
+typedef struct _FlattenNode FlattenNode;
+typedef struct _FlattenAugment FlattenAugment;
+
+struct _FlattenNode
+{
+  GListModel *model;
+  GtkFlattenListModel *list;
+};
+
+struct _FlattenAugment
+{
+  guint n_items;
+  guint n_models;
+};
+
+struct _GtkFlattenListModel
+{
+  GObject parent_instance;
+
+  GType item_type;
+  GListModel *model;
+  GtkCssRbTree *items; /* NULL if model == NULL */
+};
+
+struct _GtkFlattenListModelClass
+{
+  GObjectClass parent_class;
+};
+
+static GParamSpec *properties[NUM_PROPERTIES] = { NULL, };
+
+static FlattenNode *
+gtk_flatten_list_model_get_nth (GtkCssRbTree *tree,
+                                guint         position,
+                                guint        *model_position)
+{
+  FlattenNode *node, *tmp;
+  guint model_n_items;
+
+  node = gtk_css_rb_tree_get_root (tree);
+
+  while (node)
+    {
+      tmp = gtk_css_rb_tree_get_left (tree, node);
+      if (tmp)
+        {
+          FlattenAugment *aug = gtk_css_rb_tree_get_augment (tree, tmp);
+          if (position < aug->n_items)
+            {
+              node = tmp;
+              continue;
+            }
+          position -= aug->n_items;
+        }
+
+      model_n_items = g_list_model_get_n_items (node->model);
+      if (position < model_n_items)
+        break;
+      position -= model_n_items;
+
+      node = gtk_css_rb_tree_get_right (tree, node);
+    }
+
+  if (model_position)
+    *model_position = node ? position : 0;
+
+  return node;
+}
+
+static FlattenNode *
+gtk_flatten_list_model_get_nth_model (GtkCssRbTree *tree,
+                                      guint         position,
+                                      guint        *items_before)
+{
+  FlattenNode *node, *tmp;
+  guint before;
+
+  node = gtk_css_rb_tree_get_root (tree);
+  before = 0;
+
+  while (node)
+    {
+      tmp = gtk_css_rb_tree_get_left (tree, node);
+      if (tmp)
+        {
+          FlattenAugment *aug = gtk_css_rb_tree_get_augment (tree, tmp);
+          if (position < aug->n_models)
+            {
+              node = tmp;
+              continue;
+            }
+          position -= aug->n_models;
+          before += aug->n_items;
+        }
+
+      if (position == 0)
+        break;
+      position--;
+      before += g_list_model_get_n_items (node->model);
+
+      node = gtk_css_rb_tree_get_right (tree, node);
+    }
+
+  if (items_before)
+    *items_before = before;
+
+  return node;
+}
+
+static GType
+gtk_flatten_list_model_get_item_type (GListModel *list)
+{
+  GtkFlattenListModel *self = GTK_FLATTEN_LIST_MODEL (list);
+
+  return self->item_type;
+}
+
+static guint
+gtk_flatten_list_model_get_n_items (GListModel *list)
+{
+  GtkFlattenListModel *self = GTK_FLATTEN_LIST_MODEL (list);
+  FlattenAugment *aug;
+  FlattenNode *node;
+
+  if (!self->items)
+    return 0;
+
+  node = gtk_css_rb_tree_get_root (self->items);
+  if (node == NULL)
+    return 0;
+
+  aug = gtk_css_rb_tree_get_augment (self->items, node);
+  return aug->n_items;
+}
+
+static gpointer
+gtk_flatten_list_model_get_item (GListModel *list,
+                                 guint       position)
+{
+  GtkFlattenListModel *self = GTK_FLATTEN_LIST_MODEL (list);
+  FlattenNode *node;
+  guint model_pos;
+
+  if (!self->items)
+    return NULL;
+
+  node = gtk_flatten_list_model_get_nth (self->items, position, &model_pos);
+  if (node == NULL)
+    return NULL;
+
+  return g_list_model_get_item (node->model, model_pos);
+}
+
+static void
+gtk_flatten_list_model_model_init (GListModelInterface *iface)
+{
+  iface->get_item_type = gtk_flatten_list_model_get_item_type;
+  iface->get_n_items = gtk_flatten_list_model_get_n_items;
+  iface->get_item = gtk_flatten_list_model_get_item;
+}
+
+G_DEFINE_TYPE_WITH_CODE (GtkFlattenListModel, gtk_flatten_list_model, G_TYPE_OBJECT,
+                         G_IMPLEMENT_INTERFACE (G_TYPE_LIST_MODEL, gtk_flatten_list_model_model_init))
+
+static void
+gtk_flatten_list_model_items_changed_cb (GListModel          *model,
+                                         guint                position,
+                                         guint                removed,
+                                         guint                added,
+                                         gpointer             _node)
+{
+  FlattenNode *node = _node, *parent;
+  GtkFlattenListModel *self = node->list;
+  guint real_position;
+
+  gtk_css_rb_tree_mark_dirty (self->items, node);
+
+  for (real_position = position;
+       (parent = gtk_css_rb_tree_get_parent (self->items, node)) != NULL;
+       node = parent)
+    {
+      FlattenNode *left = gtk_css_rb_tree_get_left (self->items, parent);
+      if (left != node)
+        {
+          if (left)
+            {
+              FlattenAugment *aug = gtk_css_rb_tree_get_augment (self->items, left);
+              real_position += aug->n_items;
+            }
+          real_position += g_list_model_get_n_items (parent->model);
+        }
+    }
+
+  g_list_model_items_changed (G_LIST_MODEL (self), real_position, removed, added);
+}
+
+static void
+gtk_flatten_list_model_clear_node (gpointer _node)
+{
+  FlattenNode *node= _node;
+
+  g_signal_handlers_disconnect_by_func (node->model, gtk_flatten_list_model_items_changed_cb, node);
+  g_object_unref (node->model);
+}
+
+static void
+gtk_flatten_list_model_augment (GtkCssRbTree *flatten,
+                                gpointer      _aug,
+                                gpointer      _node,
+                                gpointer      left,
+                                gpointer      right)
+{
+  FlattenNode *node= _node;
+  FlattenAugment *aug = _aug;
+
+  aug->n_items = g_list_model_get_n_items (node->model);
+  aug->n_models = 1;
+
+  if (left)
+    {
+      FlattenAugment *left_aug = gtk_css_rb_tree_get_augment (flatten, left);
+      aug->n_items += left_aug->n_items;
+      aug->n_models += left_aug->n_models;
+    }
+  if (right)
+    {
+      FlattenAugment *right_aug = gtk_css_rb_tree_get_augment (flatten, right);
+      aug->n_items += right_aug->n_items;
+      aug->n_models += right_aug->n_models;
+    }
+}
+
+static guint
+gtk_flatten_list_model_add_items (GtkFlattenListModel *self,
+                                  FlattenNode         *after,
+                                  guint                position,
+                                  guint                n)
+{
+  FlattenNode *node;
+  guint added, i;
+
+  added = 0;
+  for (i = 0; i < n; i++)
+    {
+      node = gtk_css_rb_tree_insert_before (self->items, after);
+      node->model = g_list_model_get_item (self->model, position + i);
+      g_warn_if_fail (g_type_is_a (g_list_model_get_item_type (node->model), self->item_type));
+      g_signal_connect (node->model,
+                        "items-changed",
+                        G_CALLBACK (gtk_flatten_list_model_items_changed_cb),
+                        node);
+      node->list = self;
+      added +=g_list_model_get_n_items (node->model);
+    }
+
+  return added;
+}
+
+static void
+gtk_flatten_list_model_set_property (GObject      *object,
+                                     guint         prop_id,
+                                     const GValue *value,
+                                     GParamSpec   *pspec)
+{
+  GtkFlattenListModel *self = GTK_FLATTEN_LIST_MODEL (object);
+
+  switch (prop_id)
+    {
+    case PROP_ITEM_TYPE:
+      self->item_type = g_value_get_gtype (value);
+      break;
+
+    case PROP_MODEL:
+      gtk_flatten_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_flatten_list_model_get_property (GObject     *object,
+                                     guint        prop_id,
+                                     GValue      *value,
+                                     GParamSpec  *pspec)
+{
+  GtkFlattenListModel *self = GTK_FLATTEN_LIST_MODEL (object);
+
+  switch (prop_id)
+    {
+    case PROP_ITEM_TYPE:
+      g_value_set_gtype (value, self->item_type);
+      break;
+
+    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_flatten_list_model_model_items_changed_cb (GListModel          *model,
+                                               guint                position,
+                                               guint                removed,
+                                               guint                added,
+                                               GtkFlattenListModel *self)
+{
+  FlattenNode *node;
+  guint i, real_position, real_removed, real_added;
+
+  node = gtk_flatten_list_model_get_nth_model (self->items, position, &real_position);
+
+  real_removed = 0;
+  for (i = 0; i < removed; i++)
+    {
+      FlattenNode *next = gtk_css_rb_tree_get_next (self->items, node);
+      real_removed += g_list_model_get_n_items (node->model);
+      gtk_css_rb_tree_remove (self->items, node);
+      node = next;
+    }
+
+  real_added = gtk_flatten_list_model_add_items (self, node, position, added);
+
+  if (real_removed > 0 || real_added > 0)
+    g_list_model_items_changed (G_LIST_MODEL (self), real_position, real_removed, real_added);
+}
+
+static void
+gtk_flatten_list_clear_model (GtkFlattenListModel *self)
+{
+  if (self->model)
+    {
+      g_signal_handlers_disconnect_by_func (self->model, gtk_flatten_list_model_model_items_changed_cb, 
self);
+      g_clear_object (&self->model);
+      g_clear_pointer (&self->items, gtk_css_rb_tree_unref);
+    }
+}
+
+static void
+gtk_flatten_list_model_dispose (GObject *object)
+{
+  GtkFlattenListModel *self = GTK_FLATTEN_LIST_MODEL (object);
+
+  gtk_flatten_list_clear_model (self);
+
+  G_OBJECT_CLASS (gtk_flatten_list_model_parent_class)->dispose (object);
+};
+
+static void
+gtk_flatten_list_model_class_init (GtkFlattenListModelClass *class)
+{
+  GObjectClass *gobject_class = G_OBJECT_CLASS (class);
+
+  gobject_class->set_property = gtk_flatten_list_model_set_property;
+  gobject_class->get_property = gtk_flatten_list_model_get_property;
+  gobject_class->dispose = gtk_flatten_list_model_dispose;
+
+  /**
+   * GtkFlattenListModel:item-type:
+   *
+   * The #GTpe for elements of this object
+   */
+  properties[PROP_ITEM_TYPE] =
+      g_param_spec_gtype ("item-type",
+                          P_("Item type"),
+                          P_("The type of elements of this object"),
+                          G_TYPE_OBJECT,
+                          GTK_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY | G_PARAM_EXPLICIT_NOTIFY);
+
+  /**
+   * GtkFlattenListModel:model:
+   *
+   * The model being flattened
+   */
+  properties[PROP_MODEL] =
+      g_param_spec_object ("model",
+                           P_("Model"),
+                           P_("The model being flattened"),
+                           G_TYPE_LIST_MODEL,
+                           GTK_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY);
+
+  g_object_class_install_properties (gobject_class, NUM_PROPERTIES, properties);
+}
+
+static void
+gtk_flatten_list_model_init (GtkFlattenListModel *self)
+{
+}
+
+/**
+ * gtk_flatten_list_model_new:
+ * @item_type: The type of items in the to-be-flattened models
+ * @model: (nullable) (transfer none): the item to be flattened
+ *
+ * Creates a new #GtkFlattenListModel that flattens @list. The
+ * models returned by @model must conform to the given @item_type,
+ * either by having an identical type or a subtype.
+ *
+ * Returns: a new #GtkFlattenListModel
+ **/
+GtkFlattenListModel *
+gtk_flatten_list_model_new (GType       item_type,
+                            GListModel *model)
+{
+  GtkFlattenListModel *result;
+
+  g_return_val_if_fail (g_type_is_a (item_type, G_TYPE_OBJECT), NULL);
+  g_return_val_if_fail (model == NULL || G_IS_LIST_MODEL (model), NULL);
+
+  result = g_object_new (GTK_TYPE_FLATTEN_LIST_MODEL,
+                         "item-type", item_type,
+                         "model", model,
+                         NULL);
+
+  return result;
+}
+
+/**
+ * gtk_flatten_list_model_set_model:
+ * @self: a #GtkFlattenListModel
+ * @model: (nullable) (transfer none): the new model or %NULL
+ *
+ * Sets a new model to be flattened. The model must contain items of
+ * #GtkListModel that conform to the item type of @self.
+ **/
+void
+gtk_flatten_list_model_set_model (GtkFlattenListModel *self,
+                                  GListModel          *model)
+{
+  guint removed, added;
+
+  g_return_if_fail (GTK_IS_FLATTEN_LIST_MODEL (self));
+  g_return_if_fail (model == NULL || G_IS_LIST_MODEL (model));
+  if (model)
+    {
+      g_return_if_fail (g_list_model_get_item_type (model) == G_TYPE_LIST_MODEL);
+    }
+
+  if (self->model == model)
+    return;
+
+  removed = g_list_model_get_n_items (G_LIST_MODEL (self)); 
+  gtk_flatten_list_clear_model (self);
+
+  self->model = model;
+
+  if (model)
+    {
+      g_object_ref (model);
+      g_signal_connect (model, "items-changed", G_CALLBACK (gtk_flatten_list_model_model_items_changed_cb), 
self);
+      self->items = gtk_css_rb_tree_new (FlattenNode,
+                                         FlattenAugment,
+                                         gtk_flatten_list_model_augment,
+                                         gtk_flatten_list_model_clear_node,
+                                         NULL);
+
+      added = gtk_flatten_list_model_add_items (self, NULL, 0, g_list_model_get_n_items (model));
+    }
+
+  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_flatten_list_model_get_model:
+ * @self: a #GtkFlattenListModel
+ *
+ * Gets the model set via gtk_flatten_list_model_set_model().
+ *
+ * Returns: (nullable) (transfer none): The model flattened by @self
+ **/
+GListModel *
+gtk_flatten_list_model_get_model (GtkFlattenListModel *self)
+{
+  g_return_val_if_fail (GTK_IS_FLATTEN_LIST_MODEL (self), NULL);
+
+  return self->model;
+}
diff --git a/gtk/gtkflattenlistmodel.h b/gtk/gtkflattenlistmodel.h
new file mode 100644
index 0000000000..75e39404d7
--- /dev/null
+++ b/gtk/gtkflattenlistmodel.h
@@ -0,0 +1,50 @@
+/*
+ * Copyright © 2018 Benjamin Otte
+ *
+ * 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: Benjamin Otte <otte gnome org>
+ */
+
+#ifndef __GTK_FLATTEN_LIST_MODEL_H__
+#define __GTK_FLATTEN_LIST_MODEL_H__
+
+
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gtk/gtk.h> can be included directly."
+#endif
+
+#include <gdk/gdk.h>
+
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_FLATTEN_LIST_MODEL (gtk_flatten_list_model_get_type ())
+
+GDK_AVAILABLE_IN_ALL
+G_DECLARE_FINAL_TYPE (GtkFlattenListModel, gtk_flatten_list_model, GTK, FLATTEN_LIST_MODEL, GObject)
+
+GDK_AVAILABLE_IN_ALL
+GtkFlattenListModel *    gtk_flatten_list_model_new             (GType                   item_type,
+                                                                 GListModel             *model);
+
+GDK_AVAILABLE_IN_ALL
+void                    gtk_flatten_list_model_set_model        (GtkFlattenListModel    *self,
+                                                                 GListModel             *model);
+GDK_AVAILABLE_IN_ALL
+GListModel *            gtk_flatten_list_model_get_model        (GtkFlattenListModel    *self);
+
+G_END_DECLS
+
+#endif /* __GTK_FLATTEN_LIST_MODEL_H__ */
diff --git a/gtk/meson.build b/gtk/meson.build
index cd962dc411..dbdc455467 100644
--- a/gtk/meson.build
+++ b/gtk/meson.build
@@ -231,6 +231,7 @@ gtk_public_sources = files([
   'gtkfilefilter.c',
   'gtkfilterlistmodel.c',
   'gtkfixed.c',
+  'gtkflattenlistmodel.c',
   'gtkflowbox.c',
   'gtkfontbutton.c',
   'gtkfontchooser.c',
@@ -475,6 +476,7 @@ gtk_public_headers = files([
   'gtkfilefilter.h',
   'gtkfilterlistmodel.h',
   'gtkfixed.h',
+  'gtkflattenlistmodel.h',
   'gtkflowbox.h',
   'gtkfontbutton.h',
   'gtkfontchooser.h',
diff --git a/testsuite/gtk/flattenlistmodel.c b/testsuite/gtk/flattenlistmodel.c
new file mode 100644
index 0000000000..c1ea5dfaf3
--- /dev/null
+++ b/testsuite/gtk/flattenlistmodel.c
@@ -0,0 +1,372 @@
+/* GtkRBTree tests.
+ *
+ * Copyright (C) 2011, Red Hat, Inc.
+ * Authors: Benjamin Otte <otte gnome org>
+ *
+ * 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 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/>.
+ */
+
+#include <locale.h>
+
+#include <gtk/gtk.h>
+
+static GQuark number_quark;
+static GQuark changes_quark;
+
+static guint
+get (GListModel *model,
+     guint       position)
+{
+  GObject *object = g_list_model_get_item (model, position);
+  g_assert (object != NULL);
+  return GPOINTER_TO_UINT (g_object_get_qdata (object, number_quark));
+}
+
+static char *
+model_to_string (GListModel *model)
+{
+  GString *string = g_string_new (NULL);
+  guint i;
+
+  for (i = 0; i < g_list_model_get_n_items (model); i++)
+    {
+      if (i > 0)
+        g_string_append (string, " ");
+      g_string_append_printf (string, "%u", get (model, i));
+    }
+
+  return g_string_free (string, FALSE);
+}
+
+static GListStore *
+new_store (guint start,
+           guint end,
+           guint step);
+
+static void
+splice (GListStore *store,
+        guint       pos,
+        guint       removed,
+        guint      *numbers,
+        guint       added)
+{
+  GObject *objects[added];
+  guint i;
+
+  for (i = 0; i < added; i++)
+    {
+      /* 0 cannot be differentiated from NULL, so don't use it */
+      g_assert (numbers[i] != 0);
+      objects[i] = g_object_new (G_TYPE_OBJECT, NULL);
+      g_object_set_qdata (objects[i], number_quark, GUINT_TO_POINTER (numbers[i]));
+    }
+
+  g_list_store_splice (store, pos, removed, (gpointer *) objects, added);
+
+  for (i = 0; i < added; i++)
+    g_object_unref (objects[i]);
+}
+
+static void
+insert (GListStore *store,
+        guint       pos,
+        guint       number)
+{
+  GObject *object;
+
+  /* 0 cannot be differentiated from NULL, so don't use it */
+  g_assert (number != 0);
+
+  object = g_object_new (G_TYPE_OBJECT, NULL);
+  g_object_set_qdata (object, number_quark, GUINT_TO_POINTER (number));
+  g_list_store_insert (store, pos, object);
+  g_object_unref (object);
+}
+
+static void
+add (GListStore *store,
+     guint       number)
+{
+  GObject *object;
+
+  /* 0 cannot be differentiated from NULL, so don't use it */
+  g_assert (number != 0);
+
+  object = g_object_new (G_TYPE_OBJECT, NULL);
+  g_object_set_qdata (object, number_quark, GUINT_TO_POINTER (number));
+  g_list_store_append (store, object);
+  g_object_unref (object);
+}
+
+static GListStore *
+add_store (GListStore *store,
+           guint       start,
+           guint       end,
+           guint       step)
+{
+  GListStore *child;
+
+  child = new_store (start, end, step);
+  g_list_store_append (store, child);
+  g_object_unref (child);
+
+  return child;
+}
+
+#define assert_model(model, expected) G_STMT_START{ \
+  char *s = model_to_string (G_LIST_MODEL (model)); \
+  if (!g_str_equal (s, expected)) \
+     g_assertion_message_cmpstr (G_LOG_DOMAIN, __FILE__, __LINE__, G_STRFUNC, \
+         #model " == " #expected, s, "==", expected); \
+  g_free (s); \
+}G_STMT_END
+
+#define assert_changes(model, expected) G_STMT_START{ \
+  GString *changes = g_object_get_qdata (G_OBJECT (model), changes_quark); \
+  if (!g_str_equal (changes->str, expected)) \
+     g_assertion_message_cmpstr (G_LOG_DOMAIN, __FILE__, __LINE__, G_STRFUNC, \
+         #model " == " #expected, changes->str, "==", expected); \
+  g_string_set_size (changes, 0); \
+}G_STMT_END
+
+static GListStore *
+new_empty_store (void)
+{
+  return g_list_store_new (G_TYPE_OBJECT);
+}
+
+static GListStore *
+new_store (guint start,
+           guint end,
+           guint step)
+{
+  GListStore *store = new_empty_store ();
+  guint i;
+
+  for (i = start; i <= end; i += step)
+    add (store, i);
+
+  return store;
+}
+
+static void
+items_changed (GListModel *model,
+               guint       position,
+               guint       removed,
+               guint       added,
+               GString    *changes)
+{
+  g_assert (removed != 0 || added != 0);
+
+  if (changes->len)
+    g_string_append (changes, ", ");
+
+  if (removed == 1 && added == 0)
+    {
+      g_string_append_printf (changes, "-%u", position);
+    }
+  else if (removed == 0 && added == 1)
+    {
+      g_string_append_printf (changes, "+%u", position);
+    }
+  else
+    {
+      g_string_append_printf (changes, "%u", position);
+      if (removed > 0)
+        g_string_append_printf (changes, "-%u", removed);
+      if (added > 0)
+        g_string_append_printf (changes, "+%u", added);
+    }
+}
+
+static void
+free_changes (gpointer data)
+{
+  GString *changes = data;
+
+  /* all changes must have been checked via assert_changes() before */
+  g_assert_cmpstr (changes->str, ==, "");
+
+  g_string_free (changes, TRUE);
+}
+
+static GtkFlattenListModel *
+new_model (GListStore *store)
+{
+  GtkFlattenListModel *result;
+  GString *changes;
+
+  result = gtk_flatten_list_model_new (G_TYPE_OBJECT, G_LIST_MODEL (store));
+  changes = g_string_new ("");
+  g_object_set_qdata_full (G_OBJECT(result), changes_quark, changes, free_changes);
+  g_signal_connect (result, "items-changed", G_CALLBACK (items_changed), changes);
+
+  return result;
+}
+
+static void
+test_create_empty (void)
+{
+  GtkFlattenListModel *flat;
+
+  flat = new_model (NULL);
+  assert_model (flat, "");
+  assert_changes (flat, "");
+
+  g_object_unref (flat);
+}
+
+static void
+test_create (void)
+{
+  GtkFlattenListModel *flat;
+  GListStore *model;
+  
+  model = g_list_store_new (G_TYPE_LIST_MODEL);
+  add_store (model, 1, 3, 1);
+  add_store (model, 4, 4, 1);
+  add_store (model, 5, 7, 1);
+  add_store (model, 8, 10, 1);
+  flat = new_model (model);
+  assert_model (flat, "1 2 3 4 5 6 7 8 9 10");
+  assert_changes (flat, "");
+
+  g_object_unref (model);
+  assert_model (flat, "1 2 3 4 5 6 7 8 9 10");
+  assert_changes (flat, "");
+
+  g_object_unref (flat);
+}
+
+static void
+test_model_add (void)
+{
+  GtkFlattenListModel *flat;
+  GListStore *model;
+  
+  model = g_list_store_new (G_TYPE_LIST_MODEL);
+  flat = new_model (model);
+  assert_model (flat, "");
+  assert_changes (flat, "");
+
+  add_store (model, 1, 3, 1);
+  add_store (model, 4, 4, 1);
+  add_store (model, 5, 7, 1);
+  add_store (model, 8, 10, 1);
+
+  assert_model (flat, "1 2 3 4 5 6 7 8 9 10");
+  assert_changes (flat, "0+3, +3, 4+3, 7+3");
+
+  g_object_unref (model);
+  g_object_unref (flat);
+}
+
+static void
+test_submodel_add (void)
+{
+  GtkFlattenListModel *flat;
+  GListStore *model, *store[4];
+  
+  model = g_list_store_new (G_TYPE_LIST_MODEL);
+  flat = new_model (model);
+  assert_model (flat, "");
+  assert_changes (flat, "");
+
+  store[0] = add_store (model, 2, 3, 1);
+  store[1] = add_store (model, 4, 4, 1);
+  store[2] = add_store (model, 5, 4, 1);
+  store[3] = add_store (model, 8, 8, 1);
+  assert_model (flat, "2 3 4 8");
+  assert_changes (flat, "0+2, +2, +3");
+
+  insert (store[0], 0, 1);
+  splice (store[2], 0, 0, (guint[3]) { 5, 6, 7 }, 3);
+  splice (store[3], 1, 0, (guint[2]) { 9, 10 }, 2);
+  assert_model (flat, "1 2 3 4 5 6 7 8 9 10");
+  assert_changes (flat, "+0, 4+3, 8+2");
+
+  g_object_unref (model);
+  g_object_unref (flat);
+}
+
+static void
+test_model_remove (void)
+{
+  GtkFlattenListModel *flat;
+  GListStore *model;
+  
+  model = g_list_store_new (G_TYPE_LIST_MODEL);
+  add_store (model, 1, 3, 1);
+  add_store (model, 4, 4, 1);
+  add_store (model, 5, 7, 1);
+  add_store (model, 8, 10, 1);
+  flat = new_model (model);
+  assert_model (flat, "1 2 3 4 5 6 7 8 9 10");
+  assert_changes (flat, "");
+
+  splice (model, 1, 2, NULL, 0);
+  g_list_store_remove (model, 1);
+  g_list_store_remove (model, 0);
+  g_object_unref (model);
+  assert_model (flat, "");
+  assert_changes (flat, "3-4, 3-3, 0-3");
+
+  g_object_unref (flat);
+}
+
+static void
+test_submodel_remove (void)
+{
+  GtkFlattenListModel *flat;
+  GListStore *model, *store[4];
+  
+  model = g_list_store_new (G_TYPE_LIST_MODEL);
+  store[0] = add_store (model, 1, 3, 1);
+  store[1] = add_store (model, 4, 4, 1);
+  store[2] = add_store (model, 5, 7, 1);
+  store[3] = add_store (model, 8, 10, 1);
+  flat = new_model (model);
+  assert_model (flat, "1 2 3 4 5 6 7 8 9 10");
+  assert_changes (flat, "");
+
+  g_list_store_remove (store[0], 0);
+  splice (store[2], 0, 3, NULL, 0);
+  splice (store[3], 1, 2, NULL, 0);
+  g_object_unref (model);
+
+  assert_model (flat, "2 3 4 8");
+  assert_changes (flat, "-0, 3-3, 4-2");
+
+  g_object_unref (flat);
+}
+
+int
+main (int argc, char *argv[])
+{
+  g_test_init (&argc, &argv, NULL);
+  setlocale (LC_ALL, "C");
+  g_test_bug_base ("http://bugzilla.gnome.org/show_bug.cgi?id=%s";);
+
+  number_quark = g_quark_from_static_string ("Hell and fire was spawned to be released.");
+  changes_quark = g_quark_from_static_string ("What did I see? Can I believe what I saw?");
+
+  g_test_add_func ("/flattenlistmodel/create_empty", test_create_empty);
+  g_test_add_func ("/flattenlistmodel/create", test_create);
+  g_test_add_func ("/flattenlistmodel/model/add", test_model_add);
+  g_test_add_func ("/flattenlistmodel/submodel/add", test_submodel_add);
+  g_test_add_func ("/flattenlistmodel/model/remove", test_model_remove);
+  g_test_add_func ("/flattenlistmodel/submodel/remove", test_submodel_remove);
+
+  return g_test_run ();
+}
diff --git a/testsuite/gtk/meson.build b/testsuite/gtk/meson.build
index de1bcb15a7..052de2abfa 100644
--- a/testsuite/gtk/meson.build
+++ b/testsuite/gtk/meson.build
@@ -20,6 +20,7 @@ tests = [
   ['defaultvalue'],
   ['entry'],
   ['filterlistmodel'],
+  ['flattenlistmodel'],
   ['firefox-stylecontext'],
   ['floating'],
   ['focus'],