diff -r 000000000000 -r 6474c204b198 accessible/src/atk/nsMaiInterfaceValue.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/accessible/src/atk/nsMaiInterfaceValue.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,108 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "InterfaceInitFuncs.h"
+
+#include "AccessibleWrap.h"
+#include "nsMai.h"
+
+#include "mozilla/FloatingPoint.h"
+#include "mozilla/Likely.h"
+
+using namespace mozilla;
+using namespace mozilla::a11y;
+
+extern "C" {
+
+static void
+getCurrentValueCB(AtkValue *obj, GValue *value)
+{
+  AccessibleWrap* accWrap = GetAccessibleWrap(ATK_OBJECT(obj));
+  if (!accWrap)
+    return;
+
+  memset (value,  0, sizeof (GValue));
+  double accValue = accWrap->CurValue();
+  if (IsNaN(accValue))
+    return;
+
+  g_value_init (value, G_TYPE_DOUBLE);
+  g_value_set_double (value, accValue);
+}
+
+static void
+getMaximumValueCB(AtkValue *obj, GValue *value)
+{
+  AccessibleWrap* accWrap = GetAccessibleWrap(ATK_OBJECT(obj));
+  if (!accWrap)
+    return;
+
+  memset(value,  0, sizeof (GValue));
+  double accValue = accWrap->MaxValue();
+  if (IsNaN(accValue))
+    return;
+
+  g_value_init(value, G_TYPE_DOUBLE);
+  g_value_set_double(value, accValue);
+}
+
+static void
+getMinimumValueCB(AtkValue *obj, GValue *value)
+{
+  AccessibleWrap* accWrap = GetAccessibleWrap(ATK_OBJECT(obj));
+  if (!accWrap)
+    return;
+
+  memset(value,  0, sizeof (GValue));
+  double accValue = accWrap->MinValue();
+  if (IsNaN(accValue))
+    return;
+
+  g_value_init(value, G_TYPE_DOUBLE);
+  g_value_set_double(value, accValue);
+}
+
+static void
+getMinimumIncrementCB(AtkValue *obj, GValue *minimumIncrement)
+{
+  AccessibleWrap* accWrap = GetAccessibleWrap(ATK_OBJECT(obj));
+  if (!accWrap)
+    return;
+
+  memset(minimumIncrement,  0, sizeof (GValue));
+  double accValue = accWrap->Step();
+  if (IsNaN(accValue))
+    accValue = 0; // zero if the minimum increment is undefined
+
+  g_value_init(minimumIncrement, G_TYPE_DOUBLE);
+  g_value_set_double(minimumIncrement, accValue);
+}
+
+static gboolean
+setCurrentValueCB(AtkValue *obj, const GValue *value)
+{
+  AccessibleWrap* accWrap = GetAccessibleWrap(ATK_OBJECT(obj));
+  if (!accWrap)
+    return FALSE;
+
+  double accValue =g_value_get_double(value);
+  return accWrap->SetCurValue(accValue);
+}
+}
+
+void
+valueInterfaceInitCB(AtkValueIface* aIface)
+{
+  NS_ASSERTION(aIface, "Invalid aIface");
+  if (MOZ_UNLIKELY(!aIface))
+    return;
+
+  aIface->get_current_value = getCurrentValueCB;
+  aIface->get_maximum_value = getMaximumValueCB;
+  aIface->get_minimum_value = getMinimumValueCB;
+  aIface->get_minimum_increment = getMinimumIncrementCB;
+  aIface->set_current_value = setCurrentValueCB;
+}