Utils: Introduce CompletingLineEdit

* Works around QTCREATORBUG-9453
* Triggers completion on Key_Down with empty prefix
* Replace current filters in HistoryCompleter and FancyLineEdit

Change-Id: I56bfd4e0ee969c5ae674de2f2de1081fcf6dc176
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/libs/utils/completinglineedit.cpp

@@ -0,0 +1,74 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Orgad Shaneh <orgads@gmail.com>.
+** Contact: http://www.qt-project.org/legal
+**
+** 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 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.
+**
+****************************************************************************/
+
+#include "completinglineedit.h"
+
+#include <QAbstractItemView>
+#include <QCompleter>
+#include <QEvent>
+#include <QKeyEvent>
+
+namespace Utils {
+
+CompletingLineEdit::CompletingLineEdit(QWidget *parent) :
+    QLineEdit(parent)
+{
+}
+
+bool CompletingLineEdit::event(QEvent *e)
+{
+    // workaround for QTCREATORBUG-9453
+    if (e->type() == QEvent::ShortcutOverride) {
+        if (QCompleter *comp = completer()) {
+            if (comp->popup() && comp->popup()->isVisible()) {
+                QKeyEvent *ke = static_cast<QKeyEvent *>(e);
+                if (ke->key() == Qt::Key_Escape && !ke->modifiers()) {
+                    ke->accept();
+                    return true;
+                }
+            }
+        }
+    }
+    return QLineEdit::event(e);
+}
+
+void CompletingLineEdit::keyPressEvent(QKeyEvent *e)
+{
+    if (e->key() == Qt::Key_Down && !e->modifiers()) {
+        if (QCompleter *comp = completer()) {
+            if (text().isEmpty() && !comp->popup()->isVisible()) {
+                comp->setCompletionPrefix(QString());
+                comp->complete();
+            }
+        }
+    }
+    return QLineEdit::keyPressEvent(e);
+}
+
+} // namespace Utils