[gtk/ebassi/a11y/accessible-range: 1/14] Introduce GtkAccessibleRange

[Emmanuele Bassi <ebassi src gnome org>]

commit a7814a0963daca3383d38e48c1fb5cbdb09830dc
Author: Lukáš Tyrychtr <lukastyrychtr gmail com>
Date:   Wed Sep 14 14:40:54 2022 +0200

    Introduce GtkAccessibleRange
    
    This introduces GtkAccessibleRange, an interface which allows the accessibility backend to work with a 
control which can adjust a value.

 gtk/gtk.h                  |  1 +
 gtk/gtkaccessible.c        | 27 ++++++++++++++++
 gtk/gtkaccessibleprivate.h |  2 ++
 gtk/gtkaccessiblerange.c   | 76 ++++++++++++++++++++++++++++++++++++++++++++++
 gtk/gtkaccessiblerange.h   | 50 ++++++++++++++++++++++++++++++
 gtk/meson.build            |  2 ++
 6 files changed, 158 insertions(+)
---
diff --git a/gtk/gtk.h b/gtk/gtk.h
index f995ba4689..e889c68677 100644
--- a/gtk/gtk.h
+++ b/gtk/gtk.h
@@ -34,6 +34,7 @@
 #include <gtk/gtkaboutdialog.h>
 #include <gtk/gtkaccelgroup.h>
 #include <gtk/gtkaccessible.h>
+#include <gtk/gtkaccessiblerange.h>
 #include <gtk/gtkactionable.h>
 #include <gtk/gtkactionbar.h>
 #include <gtk/gtkadjustment.h>
diff --git a/gtk/gtkaccessible.c b/gtk/gtkaccessible.c
index 1daab9b0c3..ce79f750b4 100644
--- a/gtk/gtkaccessible.c
+++ b/gtk/gtkaccessible.c
@@ -656,6 +656,33 @@ gtk_accessible_role_to_name (GtkAccessibleRole  role,
   return role_names[role];
 }
 
+/*< private >
+ * gtk_accessible_role_is_range_subclass:
+ * @role: a `GtkAccessibleRole`
+ * 
+ * Checks if @role is considered to be a subclass of %GTK_ACCESSIBLE_ROLE_RANGE
+ * according to the WAI-ARIA specification.
+ * 
+ * Returns: whether the @role is range-like
+ */
+gboolean
+gtk_accessible_role_is_range_subclass (GtkAccessibleRole role)
+{
+  /* Same trick as in gtkatcontext.c */
+  switch ((int) role)
+    {
+    case GTK_ACCESSIBLE_ROLE_METER:
+    case GTK_ACCESSIBLE_ROLE_PROGRESS_BAR:
+    case GTK_ACCESSIBLE_ROLE_SCROLLBAR:
+    case GTK_ACCESSIBLE_ROLE_SLIDER:
+    case GTK_ACCESSIBLE_ROLE_SPIN_BUTTON:
+      return true;
+    default:
+      break;
+    }
+  return false;
+}
+
 /*<private>
  * gtk_accessible_platform_changed:
  * @self: a `GtkAccessible`
diff --git a/gtk/gtkaccessibleprivate.h b/gtk/gtkaccessibleprivate.h
index 873af7009a..eefd30a38b 100644
--- a/gtk/gtkaccessibleprivate.h
+++ b/gtk/gtkaccessibleprivate.h
@@ -40,6 +40,8 @@ GtkATContext *  gtk_accessible_get_at_context   (GtkAccessible *self);
 const char *    gtk_accessible_role_to_name     (GtkAccessibleRole  role,
                                                  const char        *domain);
 
+gboolean gtk_accessible_role_is_range_subclass (GtkAccessibleRole role);
+
 gboolean        gtk_accessible_should_present   (GtkAccessible     *self);
 
 void            gtk_accessible_platform_changed (GtkAccessible                *self,
diff --git a/gtk/gtkaccessiblerange.c b/gtk/gtkaccessiblerange.c
new file mode 100644
index 0000000000..555e1eb921
--- /dev/null
+++ b/gtk/gtkaccessiblerange.c
@@ -0,0 +1,76 @@
+/* gtkaccessiblerange.c: Accessible range interface
+ *
+ * Copyright © 2022 Red Hat Inc.
+ * 
+ * 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/>.
+ */
+
+/**
+ * GtkAccessibleRange:
+ * 
+ * This interface describes range controls, e. g. controls which have a single
+ * value which can optionally be changed by the user.
+ * 
+ * This interface is expected to be implemented by controls of the
+ * %GTK_ACCESSIBLE_ROLE_METER, %GTK_ACCESSIBLE_ROLE_PROGRESS_BAR,
+ * %GTK_ACCESSIBLE_ROLE_SCROLLBAR, %GTK_ACCESSIBLE_ROLE_SLIDER and %GTK_ACCESSIBLE_ROLE_SPIN_BUTTON
+ * role. If that is not the case, a warning will be issued at runtime.
+ * 
+ * In addition to this interface, its implementors are expected to provide the
+ * correct values for the following properties: %GTK_ACCESSIBLE_PROPERTY_VALUE_MAX,
+ * %GTK_ACCESSIBLE_PROPERTY_VALUE_MIN and %GTK_ACCESSIBLE_PROPERTY_VALUE_NOW.
+ */
+
+#include "config.h"
+
+#include "gtkaccessiblerange.h"
+
+G_DEFINE_INTERFACE (GtkAccessibleRange, gtk_accessible_range, GTK_TYPE_ACCESSIBLE)
+
+static void
+gtk_accessible_range_default_init (GtkAccessibleRangeInterface *iface)
+{
+}
+
+ /*
+ * gtk_accessible_range_get_minimum_increment:
+ * @self: a `GtkAccessibleRange`
+ *
+ * Returns the minimum increment which this `GtkAccessibleRange` supports.
+ *
+ * Returns: the minimum increment
+ */
+double
+gtk_accessible_range_get_minimum_increment (GtkAccessibleRange *self)
+{
+  g_return_val_if_fail (GTK_IS_ACCESSIBLE_RANGE (self), .0);
+
+  return GTK_ACCESSIBLE_RANGE_GET_IFACE (self)->get_minimum_increment (self);
+}
+
+ /*
+ * gtk_accessible_range_set_current_value:
+ * @self: a `GtkAccessibleRange`
+ *
+ * Sets the current value of this `GtkAccessibleRange`.
+ */
+void
+gtk_accessible_range_set_current_value (GtkAccessibleRange *self, double value)
+{
+  g_return_if_fail (GTK_IS_ACCESSIBLE_RANGE (self));
+
+  return GTK_ACCESSIBLE_RANGE_GET_IFACE (self)->set_current_value (self, value);
+}
\ No newline at end of file
diff --git a/gtk/gtkaccessiblerange.h b/gtk/gtkaccessiblerange.h
new file mode 100644
index 0000000000..45ffefc257
--- /dev/null
+++ b/gtk/gtkaccessiblerange.h
@@ -0,0 +1,50 @@
+/* gtkaccessiblerange.h: Accessible range interface
+ *
+ * Copyright © 2022 Red Hat Inc.
+ * 
+ * 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
+
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gtk/gtk.h> can be included directly."
+#endif
+
+#include <glib-object.h>
+#include <gtk/gtkaccessible.h>
+
+G_BEGIN_DECLS
+#define GTK_TYPE_ACCESSIBLE_RANGE (gtk_accessible_range_get_type())
+
+GDK_AVAILABLE_IN_ALL
+G_DECLARE_INTERFACE (GtkAccessibleRange, gtk_accessible_range, GTK, ACCESSIBLE_RANGE, GtkAccessible)
+
+struct _GtkAccessibleRangeInterface
+{
+  GTypeInterface g_iface;
+
+  double (* get_minimum_increment) (GtkAccessibleRange *self);
+  void (* set_current_value) (GtkAccessibleRange *self, double value);
+};
+
+GDK_AVAILABLE_IN_ALL
+double gtk_accessible_range_get_minimum_increment (GtkAccessibleRange *self);
+
+GDK_AVAILABLE_IN_ALL
+void gtk_accessible_range_set_current_value (GtkAccessibleRange *self, double value);
+
+G_END_DECLS
\ No newline at end of file
diff --git a/gtk/meson.build b/gtk/meson.build
index bfb03d7575..1aab513f36 100644
--- a/gtk/meson.build
+++ b/gtk/meson.build
@@ -156,6 +156,7 @@ gtk_public_sources = files([
   'gtkaboutdialog.c',
   'gtkaccelgroup.c',
   'gtkaccessible.c',
+  'gtkaccessiblerange.c',
   'gtkactionable.c',
   'gtkactionbar.c',
   'gtkadjustment.c',
@@ -448,6 +449,7 @@ gtk_public_headers = files([
   'gtkaboutdialog.h',
   'gtkaccelgroup.h',
   'gtkaccessible.h',
+  'gtkaccessiblerange.h',
   'gtkactionable.h',
   'gtkactionbar.h',
   'gtkadjustment.h',