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a11y: Rework accessible name/description computation
The ARIA spec determines the name and description of accessible elements in a more complex way that simply mapping to a single property; instead, it will chain up multiple definitions (if it finds them). For instance, let's assume we have a button that saves a file selected from a file selection widget; the widgets have the following attributes: - the file selection widget has a "label" attribute set to the selected file, e.g. "Final paper.pdf" - the "download" button has a "label" attribute set to the "Download" string - the "download" button has a "labelled-by" attribute set to reference the file selection widget The ARIA spec says that the accessible name of the "Download" button should be computed as "Download Final paper.pdf". The algorithm defined in section 4.3 of the WAI-ARIA specification applies to both accessible names (using the "label" and "labelled-by" attributes), and to accessible descriptions (using the "description" and "described-by" attributes).
This commit is contained in:
Emmanuele Bassi
parent
94729b4880
commit
7c7dabae8c
@ -606,7 +606,14 @@ handle_accessible_get_property (GDBusConnection *connection,
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}
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else if (g_strcmp0 (property_name, "Description") == 0)
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{
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char *label = gtk_at_context_get_label (GTK_AT_CONTEXT (self));
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char *label = gtk_at_context_get_description (GTK_AT_CONTEXT (self));
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if (label == NULL || *label == '\0')
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{
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g_free (label);
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label = gtk_at_context_get_name (GTK_AT_CONTEXT (self));
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}
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res = g_variant_new_string (label);
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g_free (label);
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}
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@ -932,7 +939,14 @@ gtk_at_spi_context_state_change (GtkATContext *ctx,
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if (changed_properties & GTK_ACCESSIBLE_PROPERTY_CHANGE_LABEL)
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{
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char *label = gtk_at_context_get_label (GTK_AT_CONTEXT (self));
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char *label = gtk_at_context_get_name (GTK_AT_CONTEXT (self));
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GVariant *v = g_variant_new_take_string (label);
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emit_property_changed (self, "accessible-name", v);
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}
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if (changed_properties & GTK_ACCESSIBLE_PROPERTY_CHANGE_DESCRIPTION)
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{
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char *label = gtk_at_context_get_description (GTK_AT_CONTEXT (self));
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GVariant *v = g_variant_new_take_string (label);
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emit_property_changed (self, "accessible-description", v);
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}
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@ -730,47 +730,34 @@ gtk_at_context_get_accessible_relation (GtkATContext *self,
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return gtk_accessible_attribute_set_get_value (self->relations, relation);
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}
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/*< private >
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* gtk_at_context_get_label:
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* @self: a #GtkATContext
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*
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* Retrieves the accessible label of the #GtkATContext.
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*
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* This is a convenience function meant to be used by #GtkATContext implementations.
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*
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* Returns: (transfer full): the label of the #GtkATContext
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*/
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char *
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gtk_at_context_get_label (GtkATContext *self)
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/* See the WAI-ARIA § 4.3, "Accessible Name and Description Computation" */
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static void
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gtk_at_context_get_name_accumulate (GtkATContext *self,
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GPtrArray *names,
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gboolean recurse)
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{
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g_return_val_if_fail (GTK_IS_AT_CONTEXT (self), NULL);
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GtkAccessibleValue *value = NULL;
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if (gtk_accessible_attribute_set_contains (self->states, GTK_ACCESSIBLE_STATE_HIDDEN))
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{
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value = gtk_accessible_attribute_set_get_value (self->states, GTK_ACCESSIBLE_STATE_HIDDEN);
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if (gtk_boolean_accessible_value_get (value))
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return g_strdup ("");
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}
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if (gtk_accessible_attribute_set_contains (self->properties, GTK_ACCESSIBLE_PROPERTY_LABEL))
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{
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value = gtk_accessible_attribute_set_get_value (self->properties, GTK_ACCESSIBLE_PROPERTY_LABEL);
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return g_strdup (gtk_string_accessible_value_get (value));
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g_ptr_array_add (names, (char *) gtk_string_accessible_value_get (value));
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}
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if (gtk_accessible_attribute_set_contains (self->relations, GTK_ACCESSIBLE_RELATION_LABELLED_BY))
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if (recurse && gtk_accessible_attribute_set_contains (self->relations, GTK_ACCESSIBLE_RELATION_LABELLED_BY))
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{
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value = gtk_accessible_attribute_set_get_value (self->relations, GTK_ACCESSIBLE_RELATION_LABELLED_BY);
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GList *list = gtk_reference_list_accessible_value_get (value);
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GtkAccessible *rel = GTK_ACCESSIBLE (list->data);
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GtkATContext *rel_context = gtk_accessible_get_at_context (rel);
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return gtk_at_context_get_label (rel_context);
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for (GList *l = list; l != NULL; l = l->data)
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{
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GtkAccessible *rel = GTK_ACCESSIBLE (l->data);
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GtkATContext *rel_context = gtk_accessible_get_at_context (rel);
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gtk_at_context_get_name_accumulate (rel_context, names, FALSE);
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}
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}
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GtkAccessibleRole role = gtk_at_context_get_accessible_role (self);
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@ -784,6 +771,7 @@ gtk_at_context_get_label (GtkATContext *self)
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GTK_ACCESSIBLE_PROPERTY_VALUE_NOW,
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};
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value = NULL;
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for (int i = 0; i < G_N_ELEMENTS (range_attrs); i++)
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{
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if (gtk_accessible_attribute_set_contains (self->properties, range_attrs[i]))
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@ -794,7 +782,7 @@ gtk_at_context_get_label (GtkATContext *self)
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}
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if (value != NULL)
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return g_strdup (gtk_string_accessible_value_get (value));
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g_ptr_array_add (names, (char *) gtk_string_accessible_value_get (value));
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}
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break;
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@ -802,13 +790,185 @@ gtk_at_context_get_label (GtkATContext *self)
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break;
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}
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/* If there is no label or labelled-by attribute, hidden elements
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* have no name
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*/
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if (gtk_accessible_attribute_set_contains (self->states, GTK_ACCESSIBLE_STATE_HIDDEN))
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{
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value = gtk_accessible_attribute_set_get_value (self->states, GTK_ACCESSIBLE_STATE_HIDDEN);
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if (gtk_boolean_accessible_value_get (value))
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return;
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}
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/* This fallback is in place only for unlabelled elements */
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if (names->len != 0)
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return;
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GEnumClass *enum_class = g_type_class_peek (GTK_TYPE_ACCESSIBLE_ROLE);
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GEnumValue *enum_value = g_enum_get_value (enum_class, role);
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if (enum_value != NULL)
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return g_strdup (enum_value->value_nick);
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g_ptr_array_add (names, (char *) enum_value->value_nick);
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}
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return g_strdup ("widget");
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static void
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gtk_at_context_get_description_accumulate (GtkATContext *self,
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GPtrArray *labels,
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gboolean recurse)
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{
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GtkAccessibleValue *value = NULL;
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if (gtk_accessible_attribute_set_contains (self->properties, GTK_ACCESSIBLE_PROPERTY_DESCRIPTION))
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{
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value = gtk_accessible_attribute_set_get_value (self->properties, GTK_ACCESSIBLE_PROPERTY_DESCRIPTION);
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g_ptr_array_add (labels, (char *) gtk_string_accessible_value_get (value));
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}
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if (recurse && gtk_accessible_attribute_set_contains (self->relations, GTK_ACCESSIBLE_RELATION_DESCRIBED_BY))
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{
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value = gtk_accessible_attribute_set_get_value (self->relations, GTK_ACCESSIBLE_RELATION_DESCRIBED_BY);
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GList *list = gtk_reference_list_accessible_value_get (value);
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for (GList *l = list; l != NULL; l = l->data)
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{
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GtkAccessible *rel = GTK_ACCESSIBLE (l->data);
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GtkATContext *rel_context = gtk_accessible_get_at_context (rel);
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gtk_at_context_get_description_accumulate (rel_context, labels, FALSE);
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}
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}
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GtkAccessibleRole role = gtk_at_context_get_accessible_role (self);
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switch ((int) role)
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{
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case GTK_ACCESSIBLE_ROLE_RANGE:
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{
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int range_attrs[] = {
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GTK_ACCESSIBLE_PROPERTY_VALUE_TEXT,
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GTK_ACCESSIBLE_PROPERTY_VALUE_NOW,
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};
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value = NULL;
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for (int i = 0; i < G_N_ELEMENTS (range_attrs); i++)
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{
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if (gtk_accessible_attribute_set_contains (self->properties, range_attrs[i]))
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{
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value = gtk_accessible_attribute_set_get_value (self->properties, range_attrs[i]);
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break;
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}
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}
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if (value != NULL)
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g_ptr_array_add (labels, (char *) gtk_string_accessible_value_get (value));
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}
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break;
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default:
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break;
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}
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/* If there is no label or labelled-by attribute, hidden elements
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* have no name
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*/
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if (gtk_accessible_attribute_set_contains (self->states, GTK_ACCESSIBLE_STATE_HIDDEN))
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{
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value = gtk_accessible_attribute_set_get_value (self->states, GTK_ACCESSIBLE_STATE_HIDDEN);
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if (gtk_boolean_accessible_value_get (value))
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return;
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}
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/* This fallback is in place only for unlabelled elements */
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if (labels->len != 0)
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return;
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GEnumClass *enum_class = g_type_class_peek (GTK_TYPE_ACCESSIBLE_ROLE);
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GEnumValue *enum_value = g_enum_get_value (enum_class, role);
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if (enum_value != NULL)
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g_ptr_array_add (labels, (char *) enum_value->value_nick);
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}
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/*< private >
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* gtk_at_context_get_name:
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* @self: a #GtkATContext
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*
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* Retrieves the accessible name of the #GtkATContext.
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*
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* This is a convenience function meant to be used by #GtkATContext implementations.
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*
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* Returns: (transfer full): the label of the #GtkATContext
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*/
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char *
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gtk_at_context_get_name (GtkATContext *self)
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{
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g_return_val_if_fail (GTK_IS_AT_CONTEXT (self), NULL);
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GPtrArray *names = g_ptr_array_new ();
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gtk_at_context_get_name_accumulate (self, names, TRUE);
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if (names->len == 0)
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{
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g_ptr_array_unref (names);
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return g_strdup ("");
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}
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GString *res = g_string_new ("");
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g_string_append (res, g_ptr_array_index (names, 0));
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for (guint i = 1; i < names->len; i++)
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{
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g_string_append (res, " ");
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g_string_append (res, g_ptr_array_index (names, i));
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}
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g_ptr_array_unref (names);
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return g_string_free (res, FALSE);
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}
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/*< private >
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* gtk_at_context_get_description:
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* @self: a #GtkATContext
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*
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* Retrieves the accessible description of the #GtkATContext.
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*
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* This is a convenience function meant to be used by #GtkATContext implementations.
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*
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* Returns: (transfer full): the label of the #GtkATContext
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*/
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char *
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gtk_at_context_get_description (GtkATContext *self)
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{
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g_return_val_if_fail (GTK_IS_AT_CONTEXT (self), NULL);
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GPtrArray *names = g_ptr_array_new ();
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gtk_at_context_get_description_accumulate (self, names, TRUE);
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if (names->len == 0)
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{
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g_ptr_array_unref (names);
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return g_strdup ("");
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}
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GString *res = g_string_new ("");
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g_string_append (res, g_ptr_array_index (names, 0));
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for (guint i = 1; i < names->len; i++)
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{
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g_string_append (res, " ");
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g_string_append (res, g_ptr_array_index (names, i));
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}
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g_ptr_array_unref (names);
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return g_string_free (res, FALSE);
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}
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void
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@ -148,7 +148,8 @@ gboolean gtk_at_context_has_accessible_relation (GtkATContext
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GtkAccessibleValue * gtk_at_context_get_accessible_relation (GtkATContext *self,
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GtkAccessibleRelation relation);
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char * gtk_at_context_get_label (GtkATContext *self);
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char * gtk_at_context_get_name (GtkATContext *self);
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char * gtk_at_context_get_description (GtkATContext *self);
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void gtk_at_context_platform_changed (GtkATContext *self,
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GtkAccessiblePlatformChange change);
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