Plugins: store the metadata in CBOR instead of binary JSON

In preparation for Qt 6 deprecating the binary JSON format. Also reduces
the size of the metadata a little: for the xcb platform plugin, it went
down from 264 bytes to 138; for the jpeg image plugin, it went from 320
to 135.

I've had to change the signature so older versions of Qt won't try to
parse the CBOR data as Binary JSON. Unfortunately, before QJsonDocument
could get a chance to reject it, qJsonFromRawLibraryMetaData() needed to
allocate memory and that causes crashes with Qt < 5.11.2.

Change-Id: Ieb48f7c0dd0e4e0fb35efffd153bee34e16ce347
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 77 insertions, 0 deletions

diff --git a/src/corelib/plugin/qplugin_p.h b/src/corelib/plugin/qplugin_p.h
new file mode 100644
index 0000000000..99ee16a3e8
--- /dev/null
+++ b/src/corelib/plugin/qplugin_p.h
@@ -0,0 +1,77 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 Intel Corporation.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtCore 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 The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/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 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QPLUGIN_P_H
+#define QPLUGIN_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists for the convenience
+// of the QLibrary class.  This header file may change from
+// version to version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <private/qglobal_p.h>
+
+QT_BEGIN_NAMESPACE
+
+enum class QtPluginMetaDataKeys {
+    QtVersion,
+    Debug,
+    IID,
+    ClassName,
+    MetaData
+};
+
+// F(IntKey, StringKey, Description)
+// Keep this list sorted in the order moc should output.
+#define QT_PLUGIN_FOREACH_METADATA(F) \
+    F(QtPluginMetaDataKeys::QtVersion, "version", "Qt version built against")   \
+    F(QtPluginMetaDataKeys::Debug, "debug", "Whether it is a debug build")      \
+    F(QtPluginMetaDataKeys::IID, "IID", "Plugin's Interface ID")                \
+    F(QtPluginMetaDataKeys::ClassName, "className", "Plugin class name")        \
+    F(QtPluginMetaDataKeys::MetaData, "MetaData", "Other meta data")
+
+QT_END_NAMESPACE
+
+#endif // QPLUGIN_P_H