gio/glistmodel.c

   1 /*
   2  * Copyright 2015 Lars Uebernickel
   3  * Copyright 2015 Ryan Lortie
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General
  16  * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
  17  *
  18  * Authors:
  19  *     Lars Uebernickel <lars@uebernic.de>
  20  *     Ryan Lortie <desrt@desrt.ca>
  21  */
  22
  23 #include "config.h"
  24
  25 #include "glistmodel.h"
  26 #include "glibintl.h"
  27
  28 G_DEFINE_INTERFACE (GListModel, g_list_model, G_TYPE_OBJECT);
  29
  30 /**
  31  * SECTION:glistmodel
  32  * @title: GListModel
  33  * @short_description: An interface describing a dynamic list of objects
  34  * @include: gio/gio.h
  35  * @see_also: #GListStore
  36  *
  37  * #GListModel is an interface that represents a mutable list of
  38  * #GObjects. Its main intention is as a model for various widgets in
  39  * user interfaces, such as list views, but it can also be used as a
  40  * convenient method of returning lists of data, with support for
  41  * updates.
  42  *
  43  * Each object in the list may also report changes in itself via some
  44  * mechanism (normally the #GObject::notify signal).  Taken together
  45  * with the #GListModel::items-changed signal, this provides for a list
  46  * that can change its membership, and in which the members can change
  47  * their individual properties.
  48  *
  49  * A good example would be the list of visible wireless network access
  50  * points, where each access point can report dynamic properties such as
  51  * signal strength.
  52  *
  53  * It is important to note that the #GListModel itself does not report
  54  * changes to the individual items.  It only reports changes to the list
  55  * membership.  If you want to observe changes to the objects themselves
  56  * then you need to connect signals to the objects that you are
  57  * interested in.
  58  *
  59  * All items in a #GListModel are of (or derived from) the same type.
  60  * g_list_model_get_item_type() returns that type.  The type may be an
  61  * interface, in which case all objects in the list must implement it.
  62  *
  63  * The semantics are close to that of an array:
  64  * g_list_model_get_n_items() returns the number of items in the list and
  65  * g_list_model_get_item() returns an item at a (0-based) position. In
  66  * order to allow implementations to calculate the list length lazily,
  67  * you can also iterate over items: starting from 0, repeatedly call
  68  * g_list_model_get_item() until it returns %NULL.
  69  *
  70  * An implementation may create objects lazily, but must take care to
  71  * return the same object for a given position until all references to
  72  * it are gone.
  73  *
  74  * On the other side, a consumer is expected only to hold references on
  75  * objects that are currently "user visible", in order to faciliate the
  76  * maximum level of laziness in the implementation of the list and to
  77  * reduce the required number of signal connections at a given time.
  78  *
  79  * This interface is intended only to be used from a single thread.  The
  80  * thread in which it is appropriate to use it depends on the particular
  81  * implementation, but typically it will be from the thread that owns
  82  * the [thread-default main context][g-main-context-push-thread-default]
  83  * in effect at the time that the model was created.
  84  */
  85
  86 /**
  87  * GListModelInterface:
  88  * @g_iface: parent #GTypeInterface
  89  * @get_item_type: the virtual function pointer for g_list_model_get_item_type()
  90  * @get_n_items: the virtual function pointer for g_list_model_get_n_items()
  91  * @get_item: the virtual function pointer for g_list_model_get_item()
  92  *
  93  * The virtual function table for #GListModel.
  94  *
  95  * Since: 2.44
  96  */
  97
  98 /**
  99  * GListModel:
 100  *
 101  * #GListModel is an opaque data structure and can only be accessed
 102  * using the following functions.
 103  **/
 104
 105 static guint g_list_model_changed_signal;
 106
 107 static void
 108 g_list_model_default_init (GListModelInterface *iface)
 109 {
 110   /**
 111    * GListModel::items-changed:
 112    * @list: the #GListModel that changed
 113    * @position: the position at which @list changed
 114    * @removed: the number of items removed
 115    * @added: the number of items added
 116    *
 117    * This signal is emitted whenever items were added or removed to
 118    * @list. At @position, @removed items were removed and @added items
 119    * were added in their place.
 120    *
 121    * Since: 2.44
 122    */
 123   g_list_model_changed_signal = g_signal_new (I_("items-changed"),
 124                                               G_TYPE_LIST_MODEL,
 125                                               G_SIGNAL_RUN_LAST,
 126                                               0,
 127                                               NULL, NULL,
 128                                               g_cclosure_marshal_generic,
 129                                               G_TYPE_NONE,
 130                                               3, G_TYPE_UINT, G_TYPE_UINT, G_TYPE_UINT);
 131 }
 132
 133 /**
 134  * g_list_model_get_item_type:
 135  * @list: a #GListModel
 136  *
 137  * Gets the type of the items in @list. All items returned from
 138  * g_list_model_get_type() are of that type or a subtype, or are an
 139  * implementation of that interface.
 140  *
 141  * The item type of a #GListModel can not change during the life of the
 142  * model.
 143  *
 144  * Returns: the #GType of the items contained in @list.
 145  *
 146  * Since: 2.44
 147  */
 148 GType
 149 g_list_model_get_item_type (GListModel *list)
 150 {
 151   g_return_val_if_fail (G_IS_LIST_MODEL (list), G_TYPE_NONE);
 152
 153   return G_LIST_MODEL_GET_IFACE (list)->get_item_type (list);
 154 }
 155
 156 /**
 157  * g_list_model_get_n_items:
 158  * @list: a #GListModel
 159  *
 160  * Gets the number of items in @list.
 161  *
 162  * Depending on the model implementation, calling this function may be
 163  * less efficient than iterating the list with increasing values for
 164  * @position until g_list_model_get_item() returns %NULL.
 165  *
 166  * Returns: the number of items in @list.
 167  *
 168  * Since: 2.44
 169  */
 170 guint
 171 g_list_model_get_n_items (GListModel *list)
 172 {
 173   g_return_val_if_fail (G_IS_LIST_MODEL (list), 0);
 174
 175   return G_LIST_MODEL_GET_IFACE (list)->get_n_items (list);
 176 }
 177
 178 /**
 179  * g_list_model_get_item: (skip)
 180  * @list: a #GListModel
 181  * @position: the position of the item to fetch
 182  *
 183  * Get the item at @position. If @position is greater than the number of
 184  * items in @list, %NULL is returned.
 185  *
 186  * %NULL is never returned for an index that is smaller than the length
 187  * of the list.  See g_list_model_get_n_items().
 188  *
 189  * Returns: (transfer full) (nullable) (type GObject): the item at @position.
 190  *
 191  * Since: 2.44
 192  */
 193 gpointer
 194 g_list_model_get_item (GListModel *list,
 195                        guint       position)
 196 {
 197   g_return_val_if_fail (G_IS_LIST_MODEL (list), NULL);
 198
 199   return G_LIST_MODEL_GET_IFACE (list)->get_item (list, position);
 200 }
 201
 202 /**
 203  * g_list_model_get_object: (rename-to g_list_model_get_item)
 204  * @list: a #GListModel
 205  * @position: the position of the item to fetch
 206  *
 207  * Get the item at @position. If @position is greater than the number of
 208  * items in @list, %NULL is returned.
 209  *
 210  * %NULL is never returned for an index that is smaller than the length
 211  * of the list.  See g_list_model_get_n_items().
 212  *
 213  * Returns: (transfer full) (nullable): the object at @position.
 214  *
 215  * Since: 2.44
 216  */
 217 GObject *
 218 g_list_model_get_object (GListModel *list,
 219                          guint       position)
 220 {
 221   gpointer item;
 222
 223   g_return_val_if_fail (G_IS_LIST_MODEL (list), NULL);
 224
 225   item = g_list_model_get_item (list, position);
 226
 227   return G_OBJECT (item);
 228 }
 229
 230 /**
 231  * g_list_model_items_changed:
 232  * @list: a #GListModel
 233  * @position: the position at which @list changed
 234  * @removed: the number of items removed
 235  * @added: the number of items added
 236  *
 237  * Emits the #GListModel::items-changed signal on @list.
 238  *
 239  * This function should only be called by classes implementing
 240  * #GListModel. It has to be called after the internal representation
 241  * of @list has been updated, because handlers connected to this signal
 242  * might query the new state of the list.
 243  *
 244  * Implementations must only make changes to the model (as visible to
 245  * its consumer) in places that will not cause problems for that
 246  * consumer.  For models that are driven directly by a write API (such
 247  * as #GListStore), changes can be reported in response to uses of that
 248  * API.  For models that represent remote data, changes should only be
 249  * made from a fresh mainloop dispatch.  It is particularly not
 250  * permitted to make changes in response to a call to the #GListModel
 251  * consumer API.
 252  *
 253  * Stated another way: in general, it is assumed that code making a
 254  * series of accesses to the model via the API, without returning to the
 255  * mainloop, and without calling other code, will continue to view the
 256  * same contents of the model.
 257  *
 258  * Since: 2.44
 259  */
 260 void
 261 g_list_model_items_changed (GListModel *list,
 262                             guint       position,
 263                             guint       removed,
 264                             guint       added)
 265 {
 266   g_return_if_fail (G_IS_LIST_MODEL (list));
 267
 268   g_signal_emit (list, g_list_model_changed_signal, 0, position, removed, added);
 269 }