platforminputcontexts: use libxkbcommon compose key API

Our implementation of compose table parser was added on Mar, 2013.
libxkbcommon added APIs for the same thing in Oct, 2014 (ver: 0.5.0).
After removing RHEL 6.6 from the list of supported platforms we were
able to move the minimal required libxkbcommon version to 0.5.0. Now
we can use the xkbcommon-compose APIs on all supported platforms.

With this patch we can drop nearly 1000 lines of maintenance burden.
This patch fixes user reported issues with our implementation.

Known issues:

- Testing revealed that xkbcommon-compose does not support non-utf8 locales,
and that is by design - https://github.com/xkbcommon/libxkbcommon/issues/76
Our implementation did work for those locales too, but it is unclear
if anyone actually uses non-utf8 locales. It is a corner case (work-arounds
existing) and likely a configuration error on the users' system.

- Looking at the release notes for versions above 0.6.1, only one issue
that stands out. Compose input does not work on system with tr_TR.UTF-8
locale, fixed in 0.7.1. Compose input works fine when using e.g. en_US.UTF-8
locale with Turkish keyboard layout.

Note:

With Qt 5.13 we have removed Ubuntu 16.04 and openSUSE 42.3 from CI:

Ubuntu 16.04  - 0.5.0
openSUSE 42.3 - 0.6.1

CI for Qt 5.13 has:

Ubuntu 18.04  - 0.8.0
RHEL-7.4      - 0.7.1
openSUSE 15.0 - 0.8.1

Currently the minimal required libxkbcommon version in src/gui/configure.json
is set to 0.5.0, but we could bump it to 0.7.1 to avoid known issues from above,
but that is a decision for a separate patch.

[ChangeLog][plugins][platforminputcontexts] Now using libxkbcommon-compose
APIs for compose key input, instead of Qt's own implementation.

Fixes: QTBUG-42181
Fixes: QTBUG-53663
Fixes: QTBUG-48657
Change-Id: I79aafe2bc601293844066e7e5f5eddd3719c6bba
Reviewed-by: Giulio Camuffo <giulio.camuffo@kdab.com>
Reviewed-by: Johan Helsing <johan.helsing@qt.io>

1 files changed, 17 insertions, 16 deletions

diff --git a/src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontext.h b/src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontext.h
index 4830959665..b1de1b1094 100644
--- a/src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontext.h
+++ b/src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontext.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the plugins of the Qt Toolkit.
@@ -36,24 +36,24 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-
 #ifndef QCOMPOSEPLATFORMINPUTCONTEXT_H
 #define QCOMPOSEPLATFORMINPUTCONTEXT_H
 
-#include <qpa/qplatforminputcontext.h>
+#include <QtCore/QLoggingCategory>
 
-#include <QtCore/QList>
+#include <qpa/qplatforminputcontext.h>
 
-#include "generator/qtablegenerator.h"
+#include <xkbcommon/xkbcommon-compose.h>
 
 QT_BEGIN_NAMESPACE
 
+Q_DECLARE_LOGGING_CATEGORY(lcXkbCompose)
+
 class QEvent;
 
 class QComposeInputContext : public QPlatformInputContext
 {
     Q_OBJECT
-
 public:
     QComposeInputContext();
     ~QComposeInputContext();
@@ -62,21 +62,22 @@ public:
     void setFocusObject(QObject *object) override;
     void reset() override;
     void update(Qt::InputMethodQueries) override;
+
     bool filterEvent(const QEvent *event) override;
 
+    // This invokable is called from QXkbCommon::setXkbContext().
+    Q_INVOKABLE void setXkbContext(struct xkb_context *context) { m_XkbContext = context; }
+
 protected:
-    void clearComposeBuffer();
-    bool ignoreKey(int keyval) const;
-    bool composeKey(int keyval) const;
-    bool checkComposeTable();
-    void commitText(uint character) const;
+    void ensureInitialized();
 
 private:
-    QObject *m_focusObject;
-    QVector<QComposeTableElement> m_composeTable;
-    uint m_composeBuffer[QT_KEYSEQUENCE_MAX_LEN];
-    TableGenerator::TableState m_tableState;
-    bool m_compositionTableInitialized;
+    bool m_initialized = false;
+    xkb_context *m_context = nullptr;
+    xkb_compose_table *m_composeTable = nullptr;
+    xkb_compose_state *m_composeState = nullptr;
+    QObject *m_focusObject = nullptr;
+    struct xkb_context *m_XkbContext = nullptr;
 };
 
 QT_END_NAMESPACE