Clang: Restrict warning options edit to single line

...to avoid confusion.

Use a customized QPlainTextEdit instead of a QLineEdit because the
latter does not allow wrapping of long lines. Horizontal scrolling in a
QLineEdit for long/many options is inconvenient.

Change-Id: I15b5f034e04920d0ca955c4f822d882b05e9c235
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/cpptools/wrappablelineedit.cpp

@@ -0,0 +1,59 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** 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 General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** 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-3.0.html.
+**
+****************************************************************************/
+
+#include "wrappablelineedit.h"
+
+#include <QMimeData>
+
+namespace CppTools {
+
+WrappableLineEdit::WrappableLineEdit(QWidget *parent)
+    : QPlainTextEdit(parent)
+{
+    setMaximumBlockCount(1); // Restrict to a single line.
+}
+
+void WrappableLineEdit::keyPressEvent(QKeyEvent *event)
+{
+    switch (event->key()) {
+    case Qt::Key_Enter:
+    case Qt::Key_Return:
+        return; // Eat these to avoid new lines.
+    case Qt::Key_Backtab:
+    case Qt::Key_Tab:
+        // Let the parent handle these because they might be used for navigation purposes.
+        event->ignore();
+        return;
+    default:
+        return QPlainTextEdit::keyPressEvent(event);
+    }
+}
+
+void WrappableLineEdit::insertFromMimeData(const QMimeData *source)
+{
+    insertPlainText(source->text().simplified()); // Filter out new lines.
+}
+
+} // namespace CppTools