Plug GtkATContext into GtkAccessible

An Accessible implementation must create an ATContext object. UI
elements are supposed to interact with the GtkAccessible API, but we
expose GtkATContext to allow patterns like delegation.

gtk/gtkaccessible.c

@@ -18,9 +18,36 @@
  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  */
 
+/**
+ * SECTION:gtkaccessible
+ * @Title: GtkAccessible
+ * @Short_description: Accessible interface
+ *
+ * GtkAccessible provides an interface for describing a UI element, like a
+ * #GtkWidget, in a way that can be consumed by Assistive Technologies, or
+ * “AT”. Every accessible implementation has:
+ *
+ *  - a “role”, represented by a value of the #GtkAccessibleRole enumeration
+ *  - a “state”, represented by a set of #GtkAccessibleState and
+ *    #GtkAccessibleProperty values
+ *
+ * The role cannot be changed after instantiating a #GtkAccessible
+ * implementation.
+ *
+ * The state is updated every time a UI element's state changes in a way that
+ * should be reflected by assistive technologies. For instance, if a #GtkWidget
+ * visibility changes, the %GTK_ACCESSIBLE_STATE_HIDDEN state will also change
+ * to reflect the #GtkWidget:visible property.
+ */
+
 #include "config.h"
 
-#include "gtkaccessible.h"
+#include "gtkaccessibleprivate.h"
+
+#include "gtkatcontextprivate.h"
+#include "gtkenums.h"
+
+#include <stdarg.h>
 
 G_DEFINE_INTERFACE (GtkAccessible, gtk_accessible, G_TYPE_OBJECT)
 
@@ -28,3 +55,97 @@ static void
 gtk_accessible_default_init (GtkAccessibleInterface *iface)
 {
 }
+
+GtkATContext *
+gtk_accessible_get_at_context (GtkAccessible *self)
+{
+  g_return_val_if_fail (GTK_IS_ACCESSIBLE (self), NULL);
+
+  return GTK_ACCESSIBLE_GET_IFACE (self)->get_at_context (self);
+}
+
+/**
+ * gtk_accessible_update_state:
+ * @self: a #GtkAccessible
+ * @first_state: the first #GtkAccessibleState
+ * @...: a list of state and value pairs, terminated by %GTK_ACCESSIBLE_STATE_NONE
+ *
+ * Updates a list of accessible states.
+ *
+ * This function should be called by #GtkWidget types whenever an accessible
+ * state change must be communicated to assistive technologies.
+ */
+void
+gtk_accessible_update_state (GtkAccessible *self,
+                             GtkAccessibleState  first_state,
+                             ...)
+{
+  GtkAccessibleState state;
+  GtkATContext *context;
+  va_list args;
+
+  g_return_if_fail (GTK_IS_ACCESSIBLE (self));
+
+  context = gtk_accessible_get_at_context (self);
+  if (context == NULL)
+    return;
+
+  va_start (args, first_state);
+
+  state = first_state;
+
+  while (state != GTK_ACCESSIBLE_STATE_NONE)
+    {
+      GtkAccessibleValue *value = gtk_accessible_value_collect_for_state (state, &args);
+
+      if (value == NULL)
+        goto out;
+
+      gtk_at_context_set_state (context, state, value);
+      gtk_accessible_value_unref (value);
+
+      state = va_arg (args, int);
+    }
+
+  gtk_at_context_update_state (context);
+
+out:
+  va_end (args);
+}
+
+/**
+ * gtk_accessible_update_state_value:
+ * @self: a #GtkAccessible
+ * @state: a #GtkAccessibleState
+ * @value: a #GValue with the value for @state
+ *
+ * Updates an accessible state.
+ *
+ * This function should be called by #GtkWidget types whenever an accessible
+ * state change must be communicated to assistive technologies.
+ *
+ * This function is meant to be used by language bindings.
+ */
+void
+gtk_accessible_update_state_value (GtkAccessible      *self,
+                                   GtkAccessibleState  state,
+                                   const GValue       *value)
+{
+  GtkATContext *context;
+
+  g_return_if_fail (GTK_IS_ACCESSIBLE (self));
+
+  context = gtk_accessible_get_at_context (self);
+  if (context == NULL)
+    return;
+
+  GtkAccessibleValue *real_value =
+    gtk_accessible_value_collect_for_state_value (state, value);
+
+  if (real_value == NULL)
+    return;
+
+  gtk_at_context_set_state (context, state, real_value);
+  gtk_accessible_value_unref (real_value);
+  gtk_at_context_update_state (context);
+}

gtk/gtkaccessible.h

@@ -31,9 +31,13 @@ G_BEGIN_DECLS
 GDK_AVAILABLE_IN_ALL
 G_DECLARE_INTERFACE (GtkAccessible, gtk_accessible, GTK, ACCESSIBLE, GObject)
 
-struct _GtkAccessibleInterface
-{
-  GTypeInterface g_iface;
-};
+GDK_AVAILABLE_IN_ALL
+void    gtk_accessible_update_state             (GtkAccessible      *self,
+                                                 GtkAccessibleState  first_state,
+                                                 ...);
+GDK_AVAILABLE_IN_ALL
+void    gtk_accessible_update_state_value       (GtkAccessible      *self,
+                                                 GtkAccessibleState  state,
+                                                 const GValue       *value);
 
 G_END_DECLS

gtk/gtkaccessibleprivate.h

@@ -0,0 +1,37 @@
+/* gtkaccessibleprivate.h: Accessible interface
+ *
+ * Copyright 2020  GNOME Foundation
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * 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/>.
+ */
+
+#pragma once
+
+#include "gtkaccessible.h"
+#include "gtkatcontext.h"
+
+G_BEGIN_DECLS
+
+struct _GtkAccessibleInterface
+{
+  GTypeInterface g_iface;
+
+  GtkATContext *        (* get_at_context)      (GtkAccessible *self);
+};
+
+GtkATContext *  gtk_accessible_get_at_context   (GtkAccessible *self);
+
+G_END_DECLS