Accept ZWNJ, ZWJ and PUA characters in input widgets

Private Use Area characters are quite valid input characters when used
in combination with a custom font. Joiners also serve an important language
purpose in semitic writing systems.

Note that there is a hack where we disregard any character produced
using CTRL or CTRL+SHIFT specifically because of German keyboards. I have chosen to
keep the hack in this patch to limit the change (though I have made an exception
for ZWJ and ZWNJ since both are produced using Ctrl+Shift on Windows), but it
will probably have to be reverted.

[ChangeLog][QtWidgets][Input] Accept characters in Private Use Area, as well as
zero-width joiners and zero-width non-joiners in input in QLineEdit and QTextEdit.

Task-number: QTBUG-42074
Task-number: QTBUG-57003
Change-Id: I73f3b7d587a8670de24e902dc52a51f7721dba5a
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 82 insertions, 0 deletions

diff --git a/src/gui/text/qinputcontrol.cpp b/src/gui/text/qinputcontrol.cpp
new file mode 100644
index 0000000000..c2c198866a
--- /dev/null
+++ b/src/gui/text/qinputcontrol.cpp
@@ -0,0 +1,82 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** 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 http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://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 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** As a special exception, The Qt Company gives you certain additional
+** rights. These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qinputcontrol_p.h"
+#include <QtGui/qevent.h>
+
+QT_BEGIN_NAMESPACE
+
+QInputControl::QInputControl(Type type, QObject *parent)
+    : QObject(parent)
+    , m_type(type)
+{
+}
+
+QInputControl::QInputControl(Type type, QObjectPrivate &dd, QObject *parent)
+    : QObject(dd, parent)
+    , m_type(type)
+{
+}
+
+bool QInputControl::isAcceptableInput(const QKeyEvent *event) const
+{
+    const QString text = event->text();
+    if (text.isEmpty())
+        return false;
+
+    const QChar c = text.at(0);
+
+    // ZWNJ and ZWJ. This needs to go before the next test, since CTRL+SHIFT is
+    // used to input it on Windows.
+    if (c == QChar(0x200C) || c == QChar(0x200D))
+        return true;
+
+    // QTBUG-35734: ignore Ctrl/Ctrl+Shift; accept only AltGr (Alt+Ctrl) on German keyboards
+    if (event->modifiers() == Qt::ControlModifier
+            || event->modifiers() == (Qt::ShiftModifier | Qt::ControlModifier)) {
+        return false;
+    }
+
+    if (c.isPrint())
+        return true;
+
+    if (c.category() == QChar::Other_PrivateUse)
+        return true;
+
+    if (m_type == TextEdit && c == QLatin1Char('\t'))
+        return true;
+
+    return false;
+}
+
+QT_END_NAMESPACE