TextEditor: add document content completer

Add completion based on words of the document. This provides basic
assistance for programming languages without a code model.

Task-number: QTCREATORBUG-13869
Change-Id: I3a9c59c741dfd6895442fc0524cfd1bd3b2b0111
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/texteditor/codeassist/documentcontentcompletion.h

@@ -0,0 +1,49 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 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.
+**
+****************************************************************************/
+
+#pragma once
+
+#include "completionassistprovider.h"
+
+#include "texteditor/texteditorconstants.h"
+
+namespace TextEditor {
+
+class AssistInterface;
+
+class TEXTEDITOR_EXPORT DocumentContentCompletionProvider : public CompletionAssistProvider
+{
+public:
+    DocumentContentCompletionProvider(
+            const QString &snippetGroup = QString(Constants::TEXT_SNIPPET_GROUP_ID));
+
+    RunType runType() const override;
+    IAssistProcessor *createProcessor() const override;
+
+private:
+    QString m_snippetGroup;
+};
+
+} // TextEditor