Cache QAccessibleInterfaces.

Since there already is a one-to-one relationship
between QObject and QAccessibleInterface it makes
little sense to create and destroy the interfaces
on each call to queryAccessibleInterface.

Add a cache and keep created interfaces around for
the lifetime of the corresponding QObject.

This changes the memory management rules: accessible
interfaces must no longer be deleted. If you get an
QAccessibleIntrface pointer that pointer will stay
valid as long as the corresponding QObject is not
deleted.

This also re-enables accessibility for Mac.

We limit the range of the IDs so that they are
useable for Windows directly.
That means we can get rid of the event cache there.

This is based on: Iebf2f374916fc70a9dd29e95f45a6444b85f6cee

Change-Id: I9fe6531812c0dbc5b41101ac05830a6dd75e13a3
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>

1 files changed, 116 insertions, 0 deletions

diff --git a/src/gui/accessible/qaccessiblecache.cpp b/src/gui/accessible/qaccessiblecache.cpp
new file mode 100644
index 0000000000..1b79c30b6c
--- /dev/null
+++ b/src/gui/accessible/qaccessiblecache.cpp
@@ -0,0 +1,116 @@
+/****************************************************************************
+**
+** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qaccessiblecache_p.h"
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class QAccessibleCache
+    \internal
+    \brief Maintains a cache of accessible interfaces.
+*/
+
+/*
+  The ID is always in the range [INT_MAX+1, UINT_MAX].
+  This makes it easy on windows to reserve the positive integer range
+  for the index of a child and not clash with the unique ids.
+*/
+QAccessible::Id QAccessibleCache::acquireId() const
+{
+    static const QAccessible::Id FirstId = QAccessible::Id(INT_MAX) + 1;
+    static QAccessible::Id lastUsedId = FirstId;
+
+    while (idToInterface.contains(lastUsedId)) {
+        if (lastUsedId == UINT_MAX) // (wrap back when when we reach UINT_MAX)
+            lastUsedId = FirstId;
+        else
+            ++lastUsedId;
+    }
+
+    return lastUsedId;
+}
+
+QAccessibleInterface *QAccessibleCache::interfaceForId(QAccessible::Id id) const
+{
+    return idToInterface.value(id);
+}
+
+QAccessible::Id QAccessibleCache::insert(QObject *object, QAccessibleInterface *iface) const
+{
+    Q_ASSERT(iface);
+    Q_UNUSED(object)
+
+    // object might be 0
+    Q_ASSERT(!objectToId.contains(object));
+    Q_ASSERT_X(!idToInterface.values().contains(iface), "", "Accessible interface inserted into cache twice!");
+
+    QAccessible::Id id = acquireId();
+    QObject *obj = iface->object();
+    Q_ASSERT(object == obj);
+    if (obj) {
+        objectToId.insert(obj, id);
+        connect(obj, SIGNAL(destroyed(QObject *)), this, SLOT(objectDestroyed(QObject *)));
+    }
+    idToInterface.insert(id, iface);
+    return id;
+}
+
+void QAccessibleCache::objectDestroyed(QObject* obj)
+{
+    QAccessible::Id id = objectToId.value(obj);
+    if (id) {
+        Q_ASSERT_X(idToInterface.contains(id), "", "QObject with accessible interface deleted, where interface not in cache!");
+        deleteInterface(id, obj);
+    }
+}
+
+void QAccessibleCache::deleteInterface(QAccessible::Id id, QObject *obj)
+{
+    QAccessibleInterface *iface = idToInterface.take(id);
+    if (!obj)
+        obj = iface->object();
+    if (obj)
+        objectToId.remove(obj);
+    delete iface;
+}
+
+QT_END_NAMESPACE