demo: Use a FixedItemSeletion instead of a NoSelection

Simple demo of how to use FixedItemSelection.

demos/gtk-demo/listview_words.c

@@ -177,6 +177,15 @@ file_open_cb (GtkWidget     *button,
   gtk_native_dialog_show (GTK_NATIVE_DIALOG (dialog));
 }
 
+static void
+listview_activate_cb (GtkListView *listview,
+                      guint        pos,
+                      gpointer     unused)
+{
+  gtk_fixed_item_selection_set_selected_position (GTK_FIXED_ITEM_SELECTION (gtk_list_view_get_model (listview)),
+                                                  pos);
+}
+
 GtkWidget *
 do_listview_words (GtkWidget *do_widget)
 {
@@ -185,6 +194,7 @@ do_listview_words (GtkWidget *do_widget)
       GtkWidget *header, *listview, *sw, *vbox, *search_entry, *open_button, *overlay;
       GtkFilterListModel *filter_model;
       GtkStringList *stringlist;
+      GtkFixedItemSelection *selection;
       GtkFilter *filter;
       GFile *file;
 
@@ -241,11 +251,15 @@ do_listview_words (GtkWidget *do_widget)
       gtk_widget_set_vexpand (sw, TRUE);
       gtk_overlay_set_child (GTK_OVERLAY (overlay), sw);
 
+      selection = gtk_fixed_item_selection_new (G_LIST_MODEL (filter_model));
+
       listview = gtk_list_view_new (
-          GTK_SELECTION_MODEL (gtk_no_selection_new (G_LIST_MODEL (filter_model))),
+          GTK_SELECTION_MODEL (selection),
           gtk_builder_list_item_factory_new_from_bytes (NULL,
               g_bytes_new_static (factory_text, strlen (factory_text))));
       gtk_scrolled_window_set_child (GTK_SCROLLED_WINDOW (sw), listview);
+      gtk_list_view_set_single_click_activate (GTK_LIST_VIEW (listview), TRUE);
+      g_signal_connect (listview, "activate", G_CALLBACK (listview_activate_cb), NULL);
 
       g_signal_connect (filter_model, "items-changed", G_CALLBACK (update_title_cb), progress);
       g_signal_connect (filter_model, "notify::pending", G_CALLBACK (update_title_cb), progress);

gtk/gtk.h

@@ -117,6 +117,7 @@
 #include <gtk/gtkexpander.h>
 #include <gtk/gtkexpression.h>
 #include <gtk/gtkfixed.h>
+#include <gtk/gtkfixeditemselection.h>
 #include <gtk/gtkfixedlayout.h>
 #include <gtk/gtkfilechooser.h>
 #include <gtk/gtkfilechooserdialog.h>

gtk/gtkfixeditemselection.c

@@ -0,0 +1,510 @@
+/*
+ * Copyright © 2019 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 "gtkfixeditemselection.h"
+
+#include "gtkbitset.h"
+#include "gtkintl.h"
+#include "gtkselectionmodel.h"
+
+/**
+ * GtkFixedItemSelection:
+ *
+ * `GtkFixedItemSelection` is a `GtkSelectionModel` that displays a single
+ * fixed item as selected. The fixed item can be any item or `%NULL` and does
+ * not need to be part of the list. In that case, no item will be displayed
+ * as selected.
+ *
+ * The item can only be cahnged via application code, for example with
+ * `gtk_fixed_item_selection_set_selected_item()`. It can not be changed via the
+ * `GtkSelectionModel` APIs.
+ *
+ * This model was primarily designed for use in sidebars that allow selecting
+ * a single item for display in the main view, but can be modified by filtering
+ * the displayed list or expanding/collapsing certain parts without changing the
+ * main view.
+ *
+ * Since: 4.6
+ */
+struct _GtkFixedItemSelection
+{
+  GObject parent_instance;
+
+  GListModel *model;
+  GObject *item;
+  guint item_position;
+};
+
+struct _GtkFixedItemSelectionClass
+{
+  GObjectClass parent_class;
+};
+
+enum {
+  PROP_0,
+  PROP_MODEL,
+  PROP_SELECTED_ITEM,
+  N_PROPS
+};
+
+static GParamSpec *properties[N_PROPS] = { NULL, };
+
+static GType
+gtk_fixed_item_selection_get_item_type (GListModel *list)
+{
+  return G_TYPE_OBJECT;
+}
+
+static guint
+gtk_fixed_item_selection_get_n_items (GListModel *list)
+{
+  GtkFixedItemSelection *self = GTK_FIXED_ITEM_SELECTION (list);
+
+  if (self->model == NULL)
+    return 0;
+
+  return g_list_model_get_n_items (self->model);
+}
+
+static gpointer
+gtk_fixed_item_selection_get_item (GListModel *list,
+                                   guint       position)
+{
+  GtkFixedItemSelection *self = GTK_FIXED_ITEM_SELECTION (list);
+
+  if (self->model == NULL)
+    return NULL;
+
+  return g_list_model_get_item (self->model, position);
+}
+
+static void
+gtk_fixed_item_selection_list_model_init (GListModelInterface *iface)
+{
+  iface->get_item_type = gtk_fixed_item_selection_get_item_type;
+  iface->get_n_items = gtk_fixed_item_selection_get_n_items;
+  iface->get_item = gtk_fixed_item_selection_get_item;
+}
+
+static gboolean
+gtk_fixed_item_selection_is_selected (GtkSelectionModel *model,
+                                      guint              position)
+{
+  GtkFixedItemSelection *self = GTK_FIXED_ITEM_SELECTION (model);
+  
+  if (self->item_position == GTK_INVALID_LIST_POSITION)
+    return FALSE;
+
+  return position == self->item_position;
+}
+
+static GtkBitset *
+gtk_fixed_item_selection_get_selection_in_range (GtkSelectionModel *model,
+                                                 guint              pos,
+                                                 guint              n_items)
+{
+  GtkFixedItemSelection *self = GTK_FIXED_ITEM_SELECTION (model);
+  GtkBitset *result;
+
+  result = gtk_bitset_new_empty ();
+  if (self->item_position != GTK_INVALID_LIST_POSITION)
+    gtk_bitset_add (result, self->item_position);
+
+  return result;
+}
+
+static void
+gtk_fixed_item_selection_selection_model_init (GtkSelectionModelInterface *iface)
+{
+  iface->is_selected = gtk_fixed_item_selection_is_selected;
+  iface->get_selection_in_range = gtk_fixed_item_selection_get_selection_in_range;
+}
+
+G_DEFINE_TYPE_EXTENDED (GtkFixedItemSelection, gtk_fixed_item_selection, G_TYPE_OBJECT, 0,
+                        G_IMPLEMENT_INTERFACE (G_TYPE_LIST_MODEL,
+                                               gtk_fixed_item_selection_list_model_init)
+                        G_IMPLEMENT_INTERFACE (GTK_TYPE_SELECTION_MODEL,
+                                               gtk_fixed_item_selection_selection_model_init))
+
+static guint
+gtk_fixed_item_selection_find_item_position (GtkFixedItemSelection *self,
+                                             GObject *              item,
+                                             guint                  start_pos,
+                                             guint                  end_pos)
+{
+  guint pos;
+
+  if (self->model == NULL)
+    return GTK_INVALID_LIST_POSITION;
+
+  for (pos = start_pos; pos < end_pos; pos++)
+    {
+      GObject *check = g_list_model_get_item (self->model, pos);
+
+      g_object_unref (check);
+
+      if (check == item)
+        return pos;
+    }
+
+  return GTK_INVALID_LIST_POSITION;
+}
+
+static void
+gtk_fixed_item_selection_items_changed_cb (GListModel            *model,
+                                           guint                  position,
+                                           guint                  removed,
+                                           guint                  added,
+                                           GtkFixedItemSelection *self)
+{
+  if (self->item == NULL)
+    {
+      /* no item to update */
+    }
+  else if (self->item_position == GTK_INVALID_LIST_POSITION)
+    {
+      /* maybe the item got newly added */
+      self->item_position = gtk_fixed_item_selection_find_item_position (self, self->item, position, position + added);
+    }
+  else if (self->item_position < position)
+    {
+      /* nothing to do, position stays the same */
+    }
+  else if (self->item_position < position + removed)
+    {
+      self->item_position = gtk_fixed_item_selection_find_item_position (self, self->item, position, position + added);
+    }
+  else
+    {
+      self->item_position += added - removed;
+    }
+
+  g_list_model_items_changed (G_LIST_MODEL (self), position, removed, added);
+}
+
+static void
+gtk_fixed_item_selection_clear_model (GtkFixedItemSelection *self)
+{
+  if (self->model == NULL)
+    return;
+
+  g_signal_handlers_disconnect_by_func (self->model, 
+                                        gtk_fixed_item_selection_items_changed_cb,
+                                        self);
+  g_clear_object (&self->model);
+}
+
+static void
+gtk_fixed_item_selection_set_property (GObject      *object,
+                                       guint         prop_id,
+                                       const GValue *value,
+                                       GParamSpec   *pspec)
+
+{
+  GtkFixedItemSelection *self = GTK_FIXED_ITEM_SELECTION (object);
+
+  switch (prop_id)
+    {
+    case PROP_MODEL:
+      gtk_fixed_item_selection_set_model (self, g_value_get_object (value));
+      break;
+
+    case PROP_SELECTED_ITEM:
+      gtk_fixed_item_selection_set_selected_item (self, g_value_get_object (value));
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+gtk_fixed_item_selection_get_property (GObject    *object,
+                                       guint       prop_id,
+                                       GValue     *value,
+                                       GParamSpec *pspec)
+{
+  GtkFixedItemSelection *self = GTK_FIXED_ITEM_SELECTION (object);
+
+  switch (prop_id)
+    {
+    case PROP_MODEL:
+      g_value_set_object (value, self->model);
+      break;
+
+    case PROP_SELECTED_ITEM:
+      g_value_set_object (value, self->item);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+gtk_fixed_item_selection_dispose (GObject *object)
+{
+  GtkFixedItemSelection *self = GTK_FIXED_ITEM_SELECTION (object);
+
+  gtk_fixed_item_selection_clear_model (self);
+
+  g_clear_object (&self->item);
+
+  G_OBJECT_CLASS (gtk_fixed_item_selection_parent_class)->dispose (object);
+}
+
+static void
+gtk_fixed_item_selection_class_init (GtkFixedItemSelectionClass *klass)
+{
+  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
+
+  gobject_class->get_property = gtk_fixed_item_selection_get_property;
+  gobject_class->set_property = gtk_fixed_item_selection_set_property;
+  gobject_class->dispose = gtk_fixed_item_selection_dispose;
+
+  /**
+   * GtkFixedItemSelection:selected-item: (attributes org.gtk.property.get=gtk_fixed_item_selection_get_selected_item org.gtk.Property.set=gtk_fixed_item_selection_set_selected_item)
+   *
+   * The selected item.
+   *
+   * Since: 4.6
+   */
+  properties[PROP_SELECTED_ITEM] =
+    g_param_spec_object ("selected-item",
+                       P_("The selected item"),
+                       P_("The selected item"),
+                       G_TYPE_OBJECT,
+                       G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS);
+
+  /**
+   * GtkFixedItemSelection:model: (attributes org.gtk.property.get=gtk_fixed_item_selection_get_model org.gtk.Property.set=gtk_fixed_item_selection_set_model)
+   *
+   * The model being managed.
+   *
+   * Since: 4.6
+   */
+  properties[PROP_MODEL] =
+    g_param_spec_object ("model",
+                       P_("The model"),
+                       P_("The model being managed"),
+                       G_TYPE_LIST_MODEL,
+                       G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS);
+
+  g_object_class_install_properties (gobject_class, N_PROPS, properties);
+}
+
+static void
+gtk_fixed_item_selection_init (GtkFixedItemSelection *self)
+{
+  self->item_position = GTK_INVALID_LIST_POSITION;
+}
+
+/**
+ * gtk_fixed_item_selection_new:
+ * @model: (nullable) (transfer full): the `GListModel` to manage
+ *
+ * Creates a new selection to handle @model.
+ *
+ * Returns: (transfer full) (type GtkFixedItemSelection): a new `GtkFixedItemSelection`
+ *
+ * Since: 4.6
+ */
+GtkFixedItemSelection *
+gtk_fixed_item_selection_new (GListModel *model)
+{
+  GtkFixedItemSelection *self;
+
+  g_return_val_if_fail (model == NULL || G_IS_LIST_MODEL (model), NULL);
+
+  self = g_object_new (GTK_TYPE_FIXED_ITEM_SELECTION,
+                       "model", model,
+                       NULL);
+
+  /* consume the reference */
+  g_clear_object (&model);
+
+  return self;
+}
+
+/**
+ * gtk_fixed_item_selection_get_model: (attributes org.gtk.Method.get_property=model)
+ * @self: a `GtkFixedItemSelection`
+ *
+ * Gets the model that @self is wrapping.
+ *
+ * Returns: (transfer none): The model being wrapped
+ *
+ * Since: 4.6
+ */
+GListModel *
+gtk_fixed_item_selection_get_model (GtkFixedItemSelection *self)
+{
+  g_return_val_if_fail (GTK_IS_FIXED_ITEM_SELECTION (self), NULL);
+
+  return self->model;
+}
+
+/**
+ * gtk_fixed_item_selection_set_model: (attributes org.gtk.Method.set_property=model)
+ * @self: a `GtkFixedItemSelection`
+ * @model: (nullable): A `GListModel` to wrap
+ *
+ * Sets the model that @self should wrap.
+ *
+ * If @model is %NULL, this model will be empty.
+ *
+ * Since: 4.6
+ */
+void
+gtk_fixed_item_selection_set_model (GtkFixedItemSelection *self,
+                                    GListModel            *model)
+{
+  guint n_items_before;
+
+  g_return_if_fail (GTK_IS_FIXED_ITEM_SELECTION (self));
+  g_return_if_fail (model == NULL || G_IS_LIST_MODEL (model));
+
+  if (self->model == model)
+    return;
+
+  n_items_before = self->model ? g_list_model_get_n_items (self->model) : 0;
+  gtk_fixed_item_selection_clear_model (self);
+
+  if (model)
+    {
+      self->model = g_object_ref (model);
+      g_signal_connect (self->model, "items-changed",
+                        G_CALLBACK (gtk_fixed_item_selection_items_changed_cb),
+                        self);
+    }
+
+  g_list_model_items_changed (G_LIST_MODEL (self),
+                              0,
+                              n_items_before,
+                              model ? g_list_model_get_n_items (self->model) : 0);
+
+  g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_MODEL]);
+}
+
+/**
+ * gtk_fixed_item_selection_get_selected_item: (attributes org.gtk.Method.get_property=selected-item)
+ * @self: a `GtkFixedItemSelection`
+ *
+ * Gets the item that is selected
+ *
+ * Returns: (transfer none) (type GObject) (nullable): The selected item
+ *
+ * Since: 4.6
+ */
+gpointer
+gtk_fixed_item_selection_get_selected_item (GtkFixedItemSelection *self)
+{
+  g_return_val_if_fail (GTK_IS_FIXED_ITEM_SELECTION (self), NULL);
+
+  return self->item;
+}
+
+static void
+gtk_fixed_item_selection_set_selected_item_internal (GtkFixedItemSelection *self,
+                                                     GObject               *item,
+                                                     guint                  position)
+{
+  guint old_position;
+
+  if (!g_set_object (&self->item, item))
+    return;
+
+  old_position = self->item_position;
+  self->item_position = position;
+
+  if (old_position == GTK_INVALID_LIST_POSITION)
+    gtk_selection_model_selection_changed (GTK_SELECTION_MODEL (self), position, 1);
+  else if (position == GTK_INVALID_LIST_POSITION)
+    gtk_selection_model_selection_changed (GTK_SELECTION_MODEL (self), old_position, 1);
+  else if (position < old_position)
+    gtk_selection_model_selection_changed (GTK_SELECTION_MODEL (self), position, old_position - position + 1);
+  else
+    gtk_selection_model_selection_changed (GTK_SELECTION_MODEL (self), old_position, position - old_position + 1);
+
+  g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_SELECTED_ITEM]);
+}
+
+/**
+ * gtk_fixed_item_selection_set_selected_item: (attributes org.gtk.Method.set_property=selected-item)
+ * @self: a `GtkFixedItemSelection`
+ * @item: (type GObject) (nullable): The item to display as selected
+ *
+ * Sets the item that @self should display as selected.
+ *
+ * Consider using gtk_fixed_item_selection_set_selected_position() instead, so that
+ * the item's position is known in advance.
+ *
+ * If @item is %NULL, no item will be selected.
+ *
+ * Since: 4.6
+ */
+void
+gtk_fixed_item_selection_set_selected_item (GtkFixedItemSelection *self,
+                                            gpointer               item)
+{
+  guint position;
+
+  g_return_if_fail (GTK_IS_FIXED_ITEM_SELECTION (self));
+  g_return_if_fail (item == NULL || G_IS_OBJECT (item));
+
+  if (self->item == item)
+    return;
+
+  if (item)
+    position = gtk_fixed_item_selection_find_item_position (self, item, 0, g_list_model_get_n_items (G_LIST_MODEL (self)));
+  else
+    position = GTK_INVALID_LIST_POSITION;
+
+  gtk_fixed_item_selection_set_selected_item_internal (self, item, position);
+}
+
+/**
+ * gtk_fixed_item_selection_set_selected_position:
+ * @self: a `GtkFixedItemSelection`
+ * @position: the current position of the item to select
+ *
+ * Selects the item at the given position. When the list gets modified, the
+ * position of the item might change.
+ *
+ * If the positon is larger than the number of items in the list, this function
+ * selects no item.
+ *
+ * Since: 4.6
+ **/
+void
+gtk_fixed_item_selection_set_selected_position (GtkFixedItemSelection  *self,
+                                                guint                   position)
+{
+  GObject *item;
+
+  g_return_if_fail (GTK_IS_FIXED_ITEM_SELECTION (self));
+
+  item = g_list_model_get_item (G_LIST_MODEL (self), position);
+  gtk_fixed_item_selection_set_selected_item_internal (self, item, position);
+  g_clear_object (&item);
+}

gtk/gtkfixeditemselection.h

@@ -0,0 +1,52 @@
+/*
+ * Copyright © 2021 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_FIXED_ITEM_SELECTION_H__
+#define __GTK_FIXED_ITEM_SELECTION_H__
+
+#include <gtk/gtktypes.h>
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_FIXED_ITEM_SELECTION (gtk_fixed_item_selection_get_type ())
+
+GDK_AVAILABLE_IN_4_6
+G_DECLARE_FINAL_TYPE (GtkFixedItemSelection, gtk_fixed_item_selection, GTK, FIXED_ITEM_SELECTION, GObject)
+
+GDK_AVAILABLE_IN_4_6
+GtkFixedItemSelection * gtk_fixed_item_selection_new                    (GListModel             *model);
+
+GDK_AVAILABLE_IN_4_6
+GListModel *            gtk_fixed_item_selection_get_model              (GtkFixedItemSelection  *self);
+GDK_AVAILABLE_IN_4_6
+void                    gtk_fixed_item_selection_set_model              (GtkFixedItemSelection  *self,
+                                                                         GListModel             *model);
+GDK_AVAILABLE_IN_4_6
+gpointer                gtk_fixed_item_selection_get_selected_item      (GtkFixedItemSelection  *self);
+GDK_AVAILABLE_IN_4_6
+void                    gtk_fixed_item_selection_set_selected_item      (GtkFixedItemSelection  *self,
+                                                                         gpointer                item);
+GDK_AVAILABLE_IN_4_6
+void                    gtk_fixed_item_selection_set_selected_position  (GtkFixedItemSelection  *self,
+                                                                         guint                   position);
+
+
+G_END_DECLS
+
+#endif /* __GTK_FIXED_ITEM_SELECTION_H__ */

gtk/meson.build

@@ -250,6 +250,7 @@ gtk_public_sources = files([
   'gtkfilter.c',
   'gtkfilterlistmodel.c',
   'gtkfixed.c',
+  'gtkfixeditemselection.c',
   'gtkfixedlayout.c',
   'gtkflattenlistmodel.c',
   'gtkflowbox.c',
@@ -539,6 +540,7 @@ gtk_public_headers = files([
   'gtkfilter.h',
   'gtkfilterlistmodel.h',
   'gtkfixed.h',
+  'gtkfixeditemselection.h',
   'gtkfixedlayout.h',
   'gtkflattenlistmodel.h',
   'gtkflowbox.h',