Modularize virtual keyboard and add an extension interface

With the extension interface it is possible to add new input
method and/or languages without recompiling the Qt Virtual
Keyboard plugin itself.

The existing input methods are now isolated into plugins.
So installing a new input method is a matter of copying the
corresponding extension plugin to the plugins/virtualkeyboard
directory (and any collateral required by the extension plugin
itself).

This change also renames the HunspellInputMethod to
DefaultInputMethod. This change is necessary because some other
extension plugin may want to provide the default input method
instead.

Implementation plan
===================
[x] Create virtualkeyboard-private module
[x] Create plugin library
[x] Define interface for input method plugin
[x] Define interface for keyboard layouts
[x] Move existing input methods and layouts to plugins
    [x] HangulInputMethod
    [x] HunspellInputMethod
        [x] Maybe create a private library for sharing
            between HunspellInputMethod and LipiInputMethod
    [x] LipiInputMethod
    [x] OpenWnnInputMethod
    [x] PinyinInputMethod
    [x] T9WriteInputMethod
    [x] TCInputMethod
[o] Rename some C++ classes (too generic name?)
[x] Think again replacing the QtVirtualKeyboard namespace
[x] Update documentation
    [x] General instructions for creating a plugin
    [x] For the C++ interfaces too (previously removed)

[ChangeLog][Important Behavior Changes] Introduce an extension
interface for the virtual keyboard. All the current input methods and
some special keyboard layouts (e.g. Hunspell, OpenWnn, etc.) have been
moved to extensions. The extension interface allows third party to
create a new input method without having to modify or rebuild the
virtual keyboard. In addition, this change makes it possible to add
features and languages independently by copying the desired extension
to the system.

[ChangeLog][Important Behavior Changes] Introduce a virtualkeyboard
module, which can be linked against an extension plugin. This module
provides the C++ API necessary for creating an input method.

[ChangeLog][Important Behavior Changes] Wrap the entire virtual
keyboard API into Qt namespace (e.g. QT_BEGIN_NAMESPACE/QT_END_NAMESPACE).

Task-number: QTBUG-57602
Change-Id: I449f4429109f596a7a1df7517c81f97d4aada27c
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 66 insertions, 0 deletions

diff --git a/src/plugins/tcime/3rdparty/tcime/phrasedictionary.cpp b/src/plugins/tcime/3rdparty/tcime/phrasedictionary.cpp
new file mode 100644
index 00000000..cdeaecdd
--- /dev/null
+++ b/src/plugins/tcime/3rdparty/tcime/phrasedictionary.cpp
@@ -0,0 +1,66 @@
+/*
+ * Qt implementation of TCIME library
+ * This file is part of the Qt Virtual Keyboard module.
+ * Contact: http://www.qt.io/licensing/
+ *
+ * Copyright (C) 2015  The Qt Company
+ * Copyright 2010 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "phrasedictionary.h"
+
+using namespace tcime;
+
+PhraseDictionary::PhraseDictionary() :
+    WordDictionary()
+{
+}
+
+QStringList PhraseDictionary::getWords(const QString &input) const
+{
+    if (input.length() != 1)
+        return QStringList();
+
+    // Phrases are stored in an array consisting of three character arrays.
+    // char[0][] contains a char[] of words to look for phrases.
+    // char[2][] contains a char[] of following words for char[0][].
+    // char[1][] contains offsets of char[0][] words to map its following words.
+    // For example, there are 5 phrases: Aa, Aa', Bb, Bb', Cc.
+    // char[0][] { A, B, C }
+    // char[1][] { 0, 2, 4 }
+    // char[2][] { a, a', b, b', c}
+    const Dictionary &dict = dictionary();
+    if (dict.length() != 3)
+        return QStringList();
+
+    const DictionaryEntry &words = dict[0];
+
+    DictionaryEntry::ConstIterator word = qBinaryFind(words, input.at(0));
+    if (word == words.constEnd())
+        return QStringList();
+
+    int index = word - words.constBegin();
+    const DictionaryEntry &offsets = dict[1];
+    const DictionaryEntry &phrases = dict[2];
+    int offset = (int)offsets[index].unicode();
+    int count = (index < offsets.length() - 1) ?
+        ((int)offsets[index + 1].unicode() - offset) : (phrases.length() - offset);
+
+    QStringList result;
+    for (int i = 0; i < count; ++i)
+        result.append(phrases[offset + i]);
+
+    return result;
+}