Add support for calendars beside Gregorian

Add QCalendarBackend as a base class for calendar implementations and
QCalendar as a facade via which to access it.

QDate's implicit implementation of the Gregorian calendar becomes
QGregorianCalendar and QDate methods now support choice of calendar.

Convert QLocale's CLDR data for month names to a locale-data component
of each supported calendar and relevant QLocale methods now support
choice of calendar. Adapt Python scripts for locale data generation to
extract month name data from CLDR (keeping on version v35.1) into the
new calendar-locale files. The locale data for the Gregorian calendar
is held in a Roman calendar base, for sharing with other calendars.

Add tests for basic uses of the new API.

[ChangeLog][QtCore][QCalendar] Added QCalendar to support diverse
calendars, supported by implementing QCalendarBackend.

[ChangeLog][QtCore][QDate] Allow choice of calendar in various
operations, with Gregorian remaining the default.

Done-with: Lars Knoll <lars.knoll@qt.io>
Done-with: Edward Welbourne <edward.welbourne@qt.io>
Fixes: QTBUG-17110
Fixes: QTBUG-950
Change-Id: I9d6278f394269a183aee8156e990cec4d5198ab8
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 77 insertions, 0 deletions

diff --git a/src/corelib/time/qcalendarmath_p.h b/src/corelib/time/qcalendarmath_p.h
new file mode 100644
index 0000000000..61c2c5d2b5
--- /dev/null
+++ b/src/corelib/time/qcalendarmath_p.h
@@ -0,0 +1,77 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** 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 QCALENDARMATH_P_H
+#define QCALENDARMATH_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists for the convenience
+// of q*calendar.cpp.  This header file may change from version to version
+// without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtCore/private/qglobal_p.h>
+
+QT_BEGIN_NAMESPACE
+
+namespace QRoundingDown {
+/*
+  Division, rounding down (rather than towards zero).
+
+  From C++11 onwards, integer division is defined to round towards zero, so we
+  can rely on that when implementing this. This is only used with denominator b
+  > 0, so we only have to treat negative numerator, a, specially.
+*/
+
+template<typename Int> constexpr Int qDiv(Int a, unsigned b)
+{ return (a - (a < 0 ? int(b - 1) : 0)) / int(b); }
+
+template<typename Int> constexpr Int qMod(Int a, unsigned b)
+{ return a - qDiv(a, b) * b; }
+
+} // QRoundingDown
+
+QT_END_NAMESPACE
+
+#endif // QCALENDARMATH_P_H