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>

14 files changed, 206 insertions, 1047 deletions

diff --git a/src/platformsupport/input/xkbcommon/qxkbcommon.cpp b/src/platformsupport/input/xkbcommon/qxkbcommon.cpp
index 4bee868fa9..877c5d848f 100644
--- a/src/platformsupport/input/xkbcommon/qxkbcommon.cpp
+++ b/src/platformsupport/input/xkbcommon/qxkbcommon.cpp
@@ -41,7 +41,12 @@
 
 #include <private/qmakearray_p.h>
 
+#include <QtCore/QMetaMethod>
 #include <QtGui/QKeyEvent>
+#include <QtGui/private/qguiapplication_p.h>
+
+#include <qpa/qplatforminputcontext.h>
+#include <qpa/qplatformintegration.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -794,4 +799,30 @@ xkb_keysym_t QXkbCommon::lookupLatinKeysym(xkb_state *state, xkb_keycode_t keyco
     return sym;
 }
 
+void QXkbCommon::setXkbContext(QPlatformInputContext *inputContext, struct xkb_context *context)
+{
+    if (!inputContext || !context)
+        return;
+
+    const char *const inputContextClassName = "QComposeInputContext";
+    const char *const normalizedSignature = "setXkbContext(xkb_context*)";
+
+    if (inputContext->objectName() != QLatin1String(inputContextClassName))
+        return;
+
+    static const QMetaMethod setXkbContext = [&]() {
+        int methodIndex = inputContext->metaObject()->indexOfMethod(normalizedSignature);
+        QMetaMethod method = inputContext->metaObject()->method(methodIndex);
+        Q_ASSERT(method.isValid());
+        if (!method.isValid())
+            qCWarning(lcXkbcommon) << normalizedSignature << "not found on" << inputContextClassName;
+        return method;
+    }();
+
+    if (!setXkbContext.isValid())
+        return;
+
+    setXkbContext.invoke(inputContext, Qt::DirectConnection, Q_ARG(struct xkb_context*, context));
+}
+
 QT_END_NAMESPACE
diff --git a/src/platformsupport/input/xkbcommon/qxkbcommon_p.h b/src/platformsupport/input/xkbcommon/qxkbcommon_p.h
index 475c51ad91..561eae03db 100644
--- a/src/platformsupport/input/xkbcommon/qxkbcommon_p.h
+++ b/src/platformsupport/input/xkbcommon/qxkbcommon_p.h
@@ -64,7 +64,9 @@ QT_BEGIN_NAMESPACE
 
 Q_DECLARE_LOGGING_CATEGORY(lcXkbcommon)
 
+class QEvent;
 class QKeyEvent;
+class QPlatformInputContext;
 
 class QXkbCommon
 {
@@ -99,6 +101,8 @@ public:
         return sym >= XKB_KEY_KP_Space && sym <= XKB_KEY_KP_9;
     }
 
+    static void setXkbContext(QPlatformInputContext *inputContext, struct xkb_context *context);
+
     struct XKBStateDeleter {
         void operator()(struct xkb_state *state) const { return xkb_state_unref(state); }
     };
diff --git a/src/plugins/platforminputcontexts/compose/compose.pro b/src/plugins/platforminputcontexts/compose/compose.pro
index 68bc2c3466..2e2f8600c3 100644
--- a/src/plugins/platforminputcontexts/compose/compose.pro
+++ b/src/plugins/platforminputcontexts/compose/compose.pro
@@ -3,18 +3,14 @@ TARGET = composeplatforminputcontextplugin
 QT += core-private gui-private
 
 SOURCES += $$PWD/qcomposeplatforminputcontextmain.cpp \
-           $$PWD/qcomposeplatforminputcontext.cpp \
-           $$PWD/generator/qtablegenerator.cpp \
+           $$PWD/qcomposeplatforminputcontext.cpp
 
-HEADERS += $$PWD/qcomposeplatforminputcontext.h \
-           $$PWD/generator/qtablegenerator.h \
+HEADERS += $$PWD/qcomposeplatforminputcontext.h
 
 QMAKE_USE_PRIVATE += xkbcommon
 
 include($$OUT_PWD/../../../gui/qtgui-config.pri)
 
-DEFINES += X11_PREFIX='\\"$$QMAKE_X11_PREFIX\\"'
-
 OTHER_FILES += $$PWD/compose.json
 
 PLUGIN_TYPE = platforminputcontexts
diff --git a/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.cpp b/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.cpp
deleted file mode 100644
index b5a0a5bbeb..0000000000
--- a/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.cpp
+++ /dev/null
@@ -1,658 +0,0 @@
-/****************************************************************************
-**
-** Copyright (C) 2016 The Qt Company Ltd.
-** Contact: https://www.qt.io/licensing/
-**
-** This file is part of the plugins of the Qt Toolkit.
-**
-** $QT_BEGIN_LICENSE:LGPL$
-** 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 Lesser General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU Lesser
-** General Public License version 3 as published by the Free Software
-** Foundation and appearing in the file LICENSE.LGPL3 included in the
-** packaging of this file. Please review the following information to
-** ensure the GNU Lesser General Public License version 3 requirements
-** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
-**
-** GNU General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU
-** General Public License version 2.0 or (at your option) the GNU General
-** Public license version 3 or any later version approved by the KDE Free
-** Qt Foundation. The licenses are as published by the Free Software
-** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
-** 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-2.0.html and
-** https://www.gnu.org/licenses/gpl-3.0.html.
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-#include "qtablegenerator.h"
-
-#include <QtCore/QByteArray>
-#include <QtCore/QTextCodec>
-#include <QtCore/QDebug>
-#include <QtCore/QDir>
-#include <QtCore/QStringList>
-#include <QtCore/QString>
-#include <QtCore/QSaveFile>
-#include <QtCore/QStandardPaths>
-#include <private/qcore_unix_p.h>
-
-#include <algorithm>
-
-#include <xkbcommon/xkbcommon.h>
-
-#include <locale.h> // LC_CTYPE
-#include <string.h> // strchr, strncmp, etc.
-#include <strings.h> // strncasecmp
-#include <clocale> // LC_CTYPE
-
-static const quint32 SupportedCacheVersion = 1;
-
-/*
-    In short on how and why the "Compose" file is cached:
-
-    The "Compose" file is large, for en_US it's likely located at:
-    /usr/share/X11/locale/en_US.UTF-8/Compose
-    and it has about 6000 string lines.
-    Q(Gui)Applications parse this file each time they're created. On modern CPUs
-    it incurs a 4-10 ms startup penalty of each Qt gui app, on older CPUs -
-    tens of ms or more.
-    Since the "Compose" file (almost) never changes using a pre-parsed
-    cache file instead of the "Compose" file is a good idea to improve Qt5
-    application startup time by about 5+ ms (or tens of ms on older CPUs).
-
-    The cache file contains the contents of the QComposeCacheFileHeader struct at the
-    beginning followed by the pre-parsed contents of the "Compose" file.
-
-    struct QComposeCacheFileHeader stores
-    (a) The cache version - in the unlikely event that some day one might need
-    to break compatibility.
-    (b) The (cache) file size.
-    (c) The lastModified field tracks if anything changed since the last time
-    the cache file was saved.
-    If anything did change then we read the compose file and save (cache) it
-    in binary/pre-parsed format, which should happen extremely rarely if at all.
-*/
-
-struct QComposeCacheFileHeader
-{
-    quint32 cacheVersion;
-    // The compiler will add 4 padding bytes anyway.
-    // Reserve them explicitly to possibly use in the future.
-    quint32 reserved;
-    quint64 fileSize;
-    qint64 lastModified;
-};
-
-// localHostName() copied from qtbase/src/corelib/io/qlockfile_unix.cpp
-static QByteArray localHostName()
-{
-    QByteArray hostName(512, Qt::Uninitialized);
-    if (gethostname(hostName.data(), hostName.size()) == -1)
-        return QByteArray();
-    hostName.truncate(strlen(hostName.data()));
-    return hostName;
-}
-
-/*
-    Reads metadata about the Compose file. Later used to determine if the
-    compose cache should be updated. The fileSize field will be zero on failure.
-*/
-static QComposeCacheFileHeader readFileMetadata(const QString &path)
-{
-    quint64 fileSize = 0;
-    qint64 lastModified = 0;
-    const QByteArray pathBytes = QFile::encodeName(path);
-    QT_STATBUF st;
-    if (QT_STAT(pathBytes.data(), &st) == 0) {
-        lastModified = st.st_mtime;
-        fileSize = st.st_size;
-    }
-    QComposeCacheFileHeader info = { 0, 0, fileSize, lastModified };
-    return info;
-}
-
-static const QString getCacheFilePath()
-{
-    QFile machineIdFile("/var/lib/dbus/machine-id");
-    QString machineId;
-    if (machineIdFile.exists()) {
-        if (machineIdFile.open(QIODevice::ReadOnly))
-            machineId = QString::fromLatin1(machineIdFile.readAll().trimmed());
-    }
-    if (machineId.isEmpty())
-        machineId = localHostName();
-    const QString dirPath = QStandardPaths::writableLocation(QStandardPaths::GenericCacheLocation);
-
-    if (QSysInfo::ByteOrder == QSysInfo::BigEndian)
-        return dirPath + QLatin1String("/qt_compose_cache_big_endian_") + machineId;
-    return dirPath + QLatin1String("/qt_compose_cache_little_endian_") + machineId;
-}
-
-// Returns empty vector on failure
-static QVector<QComposeTableElement> loadCache(const QComposeCacheFileHeader &composeInfo)
-{
-    QVector<QComposeTableElement> vec;
-    const QString cacheFilePath = getCacheFilePath();
-    QFile inputFile(cacheFilePath);
-
-    if (!inputFile.open(QIODevice::ReadOnly))
-        return vec;
-    QComposeCacheFileHeader cacheInfo;
-    // use a "buffer" variable to make the line after this one more readable.
-    char *buffer = reinterpret_cast<char*>(&cacheInfo);
-
-    if (inputFile.read(buffer, sizeof cacheInfo) != sizeof cacheInfo)
-        return vec;
-    if (cacheInfo.fileSize == 0)
-        return vec;
-    // using "!=" just in case someone replaced with a backup that existed before
-    if (cacheInfo.lastModified != composeInfo.lastModified)
-        return vec;
-    if (cacheInfo.cacheVersion != SupportedCacheVersion)
-        return vec;
-    const QByteArray pathBytes = QFile::encodeName(cacheFilePath);
-    QT_STATBUF st;
-    if (QT_STAT(pathBytes.data(), &st) != 0)
-        return vec;
-    const off_t fileSize = st.st_size;
-    if (fileSize > 1024 * 1024 * 5) {
-        // The cache file size is usually about 150KB, so if its size is over
-        // say 5MB then somebody inflated the file, abort.
-        return vec;
-    }
-    const off_t bufferSize = fileSize - (sizeof cacheInfo);
-    const size_t elemSize = sizeof (struct QComposeTableElement);
-    const int elemCount = bufferSize / elemSize;
-    const QByteArray ba = inputFile.read(bufferSize);
-    const char *data = ba.data();
-    // Since we know the number of the (many) elements and their size in
-    // advance calling vector.reserve(..) seems reasonable.
-    vec.reserve(elemCount);
-
-    for (int i = 0; i < elemCount; i++) {
-        const QComposeTableElement *elem =
-            reinterpret_cast<const QComposeTableElement*>(data + (i * elemSize));
-        vec.push_back(*elem);
-    }
-    return vec;
-}
-
-// Returns true on success, false otherwise.
-static bool saveCache(const QComposeCacheFileHeader &info, const QVector<QComposeTableElement> &vec)
-{
-    const QString filePath = getCacheFilePath();
-#if QT_CONFIG(temporaryfile)
-    QSaveFile outputFile(filePath);
-#else
-    QFile outputFile(filePath);
-#endif
-    if (!outputFile.open(QIODevice::WriteOnly))
-        return false;
-    const char *data = reinterpret_cast<const char*>(&info);
-
-    if (outputFile.write(data, sizeof info) != sizeof info)
-        return false;
-    data = reinterpret_cast<const char*>(vec.constData());
-    const qint64 size = vec.size() * (sizeof (struct QComposeTableElement));
-
-    if (outputFile.write(data, size) != size)
-        return false;
-#if QT_CONFIG(temporaryfile)
-    return outputFile.commit();
-#else
-    return true;
-#endif
-}
-
-TableGenerator::TableGenerator() : m_state(NoErrors),
-    m_systemComposeDir(QString())
-{
-    initPossibleLocations();
-    QString composeFilePath = findComposeFile();
-#ifdef DEBUG_GENERATOR
-// don't use cache when in debug mode.
-    if (!composeFilePath.isEmpty())
-        qDebug() << "Using Compose file from: " << composeFilePath;
-#else
-    QComposeCacheFileHeader fileInfo = readFileMetadata(composeFilePath);
-    if (fileInfo.fileSize != 0)
-        m_composeTable = loadCache(fileInfo);
-#endif
-    if (m_composeTable.isEmpty() && cleanState()) {
-        if (composeFilePath.isEmpty()) {
-            m_state = MissingComposeFile;
-        } else {
-            QFile composeFile(composeFilePath);
-            composeFile.open(QIODevice::ReadOnly);
-            parseComposeFile(&composeFile);
-            orderComposeTable();
-            if (m_composeTable.isEmpty()) {
-                m_state = EmptyTable;
-#ifndef DEBUG_GENERATOR
-// don't save cache when in debug mode
-            } else {
-                fileInfo.cacheVersion = SupportedCacheVersion;
-                saveCache(fileInfo, m_composeTable);
-#endif
-            }
-        }
-    }
-#ifdef DEBUG_GENERATOR
-    printComposeTable();
-#endif
-}
-
-void TableGenerator::initPossibleLocations()
-{
-    // Compose files come as a part of Xlib library. Xlib doesn't provide
-    // a mechanism how to retrieve the location of these files reliably, since it was
-    // never meant for external software to parse compose tables directly. Best we
-    // can do is to hardcode search paths. To add an extra system path use
-    // the QTCOMPOSE environment variable
-    m_possibleLocations.reserve(7);
-    if (qEnvironmentVariableIsSet("QTCOMPOSE"))
-        m_possibleLocations.append(QString::fromLocal8Bit(qgetenv("QTCOMPOSE")));
-    m_possibleLocations.append(QStringLiteral("/usr/share/X11/locale"));
-    m_possibleLocations.append(QStringLiteral("/usr/local/share/X11/locale"));
-    m_possibleLocations.append(QStringLiteral("/usr/lib/X11/locale"));
-    m_possibleLocations.append(QStringLiteral("/usr/local/lib/X11/locale"));
-    m_possibleLocations.append(QStringLiteral(X11_PREFIX "/share/X11/locale"));
-    m_possibleLocations.append(QStringLiteral(X11_PREFIX "/lib/X11/locale"));
-}
-
-QString TableGenerator::findComposeFile()
-{
-    // check if XCOMPOSEFILE points to a Compose file
-    if (qEnvironmentVariableIsSet("XCOMPOSEFILE")) {
-        const QString path = QFile::decodeName(qgetenv("XCOMPOSEFILE"));
-        if (QFile::exists(path))
-            return path;
-        else
-            qWarning("$XCOMPOSEFILE doesn't point to an existing file");
-    }
-
-    // check if user’s home directory has a file named .XCompose
-    if (cleanState()) {
-        QString path = qgetenv("HOME") + QLatin1String("/.XCompose");
-        if (QFile::exists(path))
-            return path;
-    }
-
-    // check for the system provided compose files
-    if (cleanState()) {
-        QString table = composeTableForLocale();
-        if (cleanState()) {
-            if (table.isEmpty())
-                // no table mappings for the system's locale in the compose.dir
-                m_state = UnsupportedLocale;
-            else {
-                QString path = QDir(systemComposeDir()).filePath(table);
-                if (QFile::exists(path))
-                    return path;
-            }
-        }
-    }
-    return QString();
-}
-
-QString TableGenerator::composeTableForLocale()
-{
-    QByteArray loc = locale().toUpper().toUtf8();
-    QString table = readLocaleMappings(loc);
-    if (table.isEmpty())
-        table = readLocaleMappings(readLocaleAliases(loc));
-    return table;
-}
-
-bool TableGenerator::findSystemComposeDir()
-{
-    bool found = false;
-    for (int i = 0; i < m_possibleLocations.size(); ++i) {
-        QString path = m_possibleLocations.at(i);
-        if (QFile::exists(path + QLatin1String("/compose.dir"))) {
-            m_systemComposeDir = path;
-            found = true;
-            break;
-        }
-    }
-
-    if (!found) {
-        // should we ask to report this in the qt bug tracker?
-        m_state = UnknownSystemComposeDir;
-        qWarning("Qt Warning: Could not find a location of the system's Compose files. "
-             "Consider setting the QTCOMPOSE environment variable.");
-    }
-
-    return found;
-}
-
-QString TableGenerator::systemComposeDir()
-{
-    if (m_systemComposeDir.isNull()
-            && !findSystemComposeDir()) {
-        return QLatin1String("$QTCOMPOSE");
-    }
-
-    return m_systemComposeDir;
-}
-
-QString TableGenerator::locale() const
-{
-    char *name = setlocale(LC_CTYPE, (char *)0);
-    return QLatin1String(name);
-}
-
-QString TableGenerator::readLocaleMappings(const QByteArray &locale)
-{
-    QString file;
-    if (locale.isEmpty())
-        return file;
-
-    QFile mappings(systemComposeDir() + QLatin1String("/compose.dir"));
-    if (mappings.open(QIODevice::ReadOnly)) {
-        const int localeNameLength = locale.size();
-        const char * const localeData = locale.constData();
-
-        char l[1024];
-        // formating of compose.dir has some inconsistencies
-        while (!mappings.atEnd()) {
-            int read = mappings.readLine(l, sizeof(l));
-            if (read <= 0)
-                break;
-
-            char *line = l;
-            if (*line >= 'a' && *line <= 'z') {
-                // file name
-                while (*line && *line != ':' && *line != ' ' && *line != '\t')
-                    ++line;
-                if (!*line)
-                    continue;
-                const char * const composeFileNameEnd = line;
-                *line = '\0';
-                ++line;
-
-                // locale name
-                while (*line && (*line == ' ' || *line == '\t'))
-                    ++line;
-                const char * const lc = line;
-                while (*line && *line != ' ' && *line != '\t' && *line != '\n')
-                    ++line;
-                *line = '\0';
-                if (localeNameLength == (line - lc) && !strncasecmp(lc, localeData, line - lc)) {
-                    file = QString::fromLocal8Bit(l, composeFileNameEnd - l);
-                    break;
-                }
-            }
-        }
-        mappings.close();
-    }
-    return file;
-}
-
-QByteArray TableGenerator::readLocaleAliases(const QByteArray &locale)
-{
-    QFile aliases(systemComposeDir() + QLatin1String("/locale.alias"));
-    QByteArray fullLocaleName;
-    if (aliases.open(QIODevice::ReadOnly)) {
-        while (!aliases.atEnd()) {
-            char l[1024];
-            int read = aliases.readLine(l, sizeof(l));
-            char *line = l;
-            if (read && ((*line >= 'a' && *line <= 'z') ||
-                         (*line >= 'A' && *line <= 'Z'))) {
-                const char *alias = line;
-                while (*line && *line != ':' && *line != ' ' && *line != '\t')
-                    ++line;
-                if (!*line)
-                    continue;
-                *line = 0;
-                if (locale.size() == (line - alias)
-                        && !strncasecmp(alias, locale.constData(), line - alias)) {
-                    // found a match for alias, read the real locale name
-                    ++line;
-                    while (*line && (*line == ' ' || *line == '\t'))
-                        ++line;
-                    const char *fullName = line;
-                    while (*line && *line != ' ' && *line != '\t' && *line != '\n')
-                        ++line;
-                    *line = 0;
-                    fullLocaleName = fullName;
-#ifdef DEBUG_GENERATOR
-                    qDebug() << "Alias for: " << alias << "is: " << fullLocaleName;
-                    break;
-#endif
-                }
-            }
-        }
-        aliases.close();
-    }
-    return fullLocaleName;
-}
-
-bool TableGenerator::processFile(const QString &composeFileName)
-{
-    QFile composeFile(composeFileName);
-    if (composeFile.open(QIODevice::ReadOnly)) {
-        parseComposeFile(&composeFile);
-        return true;
-    }
-    qWarning() << QString(QLatin1String("Qt Warning: Compose file: \"%1\" can't be found"))
-                  .arg(composeFile.fileName());
-    return false;
-}
-
-TableGenerator::~TableGenerator()
-{
-}
-
-QVector<QComposeTableElement> TableGenerator::composeTable() const
-{
-    return m_composeTable;
-}
-
-void TableGenerator::parseComposeFile(QFile *composeFile)
-{
-#ifdef DEBUG_GENERATOR
-    qDebug() << "TableGenerator::parseComposeFile: " << composeFile->fileName();
-#endif
-
-    char line[1024];
-    while (!composeFile->atEnd()) {
-        composeFile->readLine(line, sizeof(line));
-        if (*line == '<')
-            parseKeySequence(line);
-        else if (!strncmp(line, "include", 7))
-            parseIncludeInstruction(QString::fromLocal8Bit(line));
-    }
-
-    composeFile->close();
-}
-
-void TableGenerator::parseIncludeInstruction(QString line)
-{
-    // Parse something that looks like:
-    // include "/usr/share/X11/locale/en_US.UTF-8/Compose"
-    QString quote = QStringLiteral("\"");
-    line.remove(0, line.indexOf(quote) + 1);
-    line.chop(line.length() - line.indexOf(quote));
-
-    // expand substitutions if present
-    line.replace(QLatin1String("%H"), QString(qgetenv("HOME")));
-    line.replace(QLatin1String("%L"), systemComposeDir() +  QLatin1Char('/')  + composeTableForLocale());
-    line.replace(QLatin1String("%S"), systemComposeDir());
-
-    processFile(line);
-}
-
-ushort TableGenerator::keysymToUtf8(quint32 sym)
-{
-    QByteArray chars;
-    int bytes;
-    chars.resize(8);
-    bytes = xkb_keysym_to_utf8(sym, chars.data(), chars.size());
-    if (bytes == -1)
-        qWarning("TableGenerator::keysymToUtf8 - buffer too small");
-
-    chars.resize(bytes-1);
-
-#ifdef DEBUG_GENERATOR
-    QTextCodec *codec = QTextCodec::codecForLocale();
-    qDebug() << QString("keysym - 0x%1 : utf8 - %2").arg(QString::number(sym, 16))
-                                                    .arg(codec->toUnicode(chars));
-#endif
-    return QString::fromUtf8(chars).at(0).unicode();
-}
-
-static inline int fromBase8(const char *s, const char *end)
-{
-    int result = 0;
-    while (*s && s != end) {
-        if (*s < '0' || *s > '7')
-            return 0;
-        result *= 8;
-        result += *s - '0';
-        ++s;
-    }
-    return result;
-}
-
-static inline int fromBase16(const char *s, const char *end)
-{
-    int result = 0;
-    while (*s && s != end) {
-        result *= 16;
-        if (*s >= '0' && *s <= '9')
-            result += *s - '0';
-        else if (*s >= 'a' && *s <= 'f')
-            result += *s - 'a' + 10;
-        else if (*s >= 'A' && *s <= 'F')
-            result += *s - 'A' + 10;
-        else
-            return 0;
-        ++s;
-    }
-    return result;
-}
-
-void TableGenerator::parseKeySequence(char *line)
-{
-    // we are interested in the lines with the following format:
-    // <Multi_key> <numbersign> <S> : "♬"   U266c # BEAMED SIXTEENTH NOTE
-    char *keysEnd = strchr(line, ':');
-    if (!keysEnd)
-        return;
-
-    QComposeTableElement elem;
-    // find the composed value - strings may be direct text encoded in the locale
-    // for which the compose file is to be used, or an escaped octal or hexadecimal
-    // character code. Octal codes are specified as "\123" and hexadecimal codes as "\0x123a".
-    char *composeValue = strchr(keysEnd, '"');
-    if (!composeValue)
-        return;
-    ++composeValue;
-
-    char *composeValueEnd = strchr(composeValue, '"');
-    if (!composeValueEnd)
-        return;
-
-    // if composed value is a quotation mark adjust the end pointer
-    if (composeValueEnd[1] == '"')
-        ++composeValueEnd;
-
-    if (*composeValue == '\\' && composeValue[1] >= '0' && composeValue[1] <= '9') {
-        // handle octal and hex code values
-        char detectBase = composeValue[2];
-        if (detectBase == 'x') {
-            // hexadecimal character code
-            elem.value = keysymToUtf8(fromBase16(composeValue + 3, composeValueEnd));
-        } else {
-            // octal character code
-            elem.value = keysymToUtf8(fromBase8(composeValue + 1, composeValueEnd));
-        }
-    } else {
-        // handle direct text encoded in the locale
-        if (*composeValue == '\\')
-            ++composeValue;
-        elem.value = QString::fromLocal8Bit(composeValue, composeValueEnd - composeValue).at(0).unicode();
-        ++composeValue;
-    }
-
-#ifdef DEBUG_GENERATOR
-    // find the comment
-    elem.comment = QString::fromLocal8Bit(composeValueEnd + 1).trimmed();
-#endif
-
-    // find the key sequence and convert to X11 keysym
-    char *k = line;
-    const char *kend = keysEnd;
-
-    for (int i = 0; i < QT_KEYSEQUENCE_MAX_LEN; i++) {
-        // find the next pair of angle brackets and get the contents within
-        while (k < kend && *k != '<')
-            ++k;
-        char *sym = ++k;
-        while (k < kend && *k != '>')
-            ++k;
-        *k = '\0';
-        if (k < kend) {
-            elem.keys[i] = xkb_keysym_from_name(sym, (xkb_keysym_flags)0);
-            if (elem.keys[i] == XKB_KEY_NoSymbol) {
-                if (!strcmp(sym, "dead_inverted_breve"))
-                    elem.keys[i] = XKB_KEY_dead_invertedbreve;
-                else if (!strcmp(sym, "dead_double_grave"))
-                    elem.keys[i] = XKB_KEY_dead_doublegrave;
-#ifdef DEBUG_GENERATOR
-                else
-                    qWarning() << QString("Qt Warning - invalid keysym: %1").arg(sym);
-#endif
-            }
-        } else {
-            elem.keys[i] = 0;
-        }
-    }
-    m_composeTable.append(elem);
-}
-
-void TableGenerator::printComposeTable() const
-{
-#ifdef DEBUG_GENERATOR
-# ifndef QT_NO_DEBUG_STREAM
-    if (m_composeTable.isEmpty())
-        return;
-
-    QDebug ds = qDebug() << "output:\n";
-    ds.nospace();
-    const int tableSize = m_composeTable.size();
-    for (int i = 0; i < tableSize; ++i) {
-        const QComposeTableElement &elem = m_composeTable.at(i);
-        ds << "{ {";
-        for (int j = 0; j < QT_KEYSEQUENCE_MAX_LEN; j++) {
-            ds << hex << showbase << elem.keys[j] << ", ";
-        }
-        ds << "}, " << hex << showbase << elem.value << ", \"\" }, // " << elem.comment << " \n";
-    }
-# endif
-#endif
-}
-
-void TableGenerator::orderComposeTable()
-{
-    // Stable-sorting to ensure that the item that appeared before the other in the
-    // original container will still appear first after the sort. This property is
-    // needed to handle the cases when user re-defines already defined key sequence
-    std::stable_sort(m_composeTable.begin(), m_composeTable.end(), ByKeys());
-}
-
diff --git a/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.h b/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.h
deleted file mode 100644
index 4f58358f4e..0000000000
--- a/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.h
+++ /dev/null
@@ -1,145 +0,0 @@
-/****************************************************************************
-**
-** Copyright (C) 2016 The Qt Company Ltd.
-** Contact: https://www.qt.io/licensing/
-**
-** This file is part of the plugins of the Qt Toolkit.
-**
-** $QT_BEGIN_LICENSE:LGPL$
-** 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 Lesser General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU Lesser
-** General Public License version 3 as published by the Free Software
-** Foundation and appearing in the file LICENSE.LGPL3 included in the
-** packaging of this file. Please review the following information to
-** ensure the GNU Lesser General Public License version 3 requirements
-** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
-**
-** GNU General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU
-** General Public License version 2.0 or (at your option) the GNU General
-** Public license version 3 or any later version approved by the KDE Free
-** Qt Foundation. The licenses are as published by the Free Software
-** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
-** 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-2.0.html and
-** https://www.gnu.org/licenses/gpl-3.0.html.
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-#ifndef QTABLEGENERATOR_H
-#define QTABLEGENERATOR_H
-
-#include <QtCore/QVector>
-#include <QtCore/QFile>
-#include <QtCore/QMap>
-#include <QtCore/QString>
-
-#include <algorithm>
-
-static Q_CONSTEXPR int QT_KEYSEQUENCE_MAX_LEN = 6;
-
-//#define DEBUG_GENERATOR
-
-/* Whenever QComposeTableElement gets modified supportedCacheVersion
- from qtablegenerator.cpp must be bumped. */
-struct QComposeTableElement {
-    uint keys[QT_KEYSEQUENCE_MAX_LEN];
-    uint value;
-#ifdef DEBUG_GENERATOR
-    QString comment;
-#endif
-};
-
-#ifndef DEBUG_GENERATOR
-QT_BEGIN_NAMESPACE
-Q_DECLARE_TYPEINFO(QComposeTableElement, Q_PRIMITIVE_TYPE);
-QT_END_NAMESPACE
-#endif
-
-struct ByKeys
-{
-    using uint_array = uint[QT_KEYSEQUENCE_MAX_LEN];
-    using result_type = bool;
-
-    bool operator()(const uint_array &lhs, const uint_array &rhs) const Q_DECL_NOTHROW
-    {
-        return std::lexicographical_compare(lhs, lhs + QT_KEYSEQUENCE_MAX_LEN,
-                                            rhs, rhs + QT_KEYSEQUENCE_MAX_LEN);
-    }
-
-    bool operator()(const uint_array &lhs, const QComposeTableElement &rhs) const Q_DECL_NOTHROW
-    {
-        return operator()(lhs, rhs.keys);
-    }
-
-    bool operator()(const QComposeTableElement &lhs, const uint_array &rhs) const Q_DECL_NOTHROW
-    {
-        return operator()(lhs.keys, rhs);
-    }
-
-    bool operator()(const QComposeTableElement &lhs, const QComposeTableElement &rhs) const Q_DECL_NOTHROW
-    {
-        return operator()(lhs.keys, rhs.keys);
-    }
-};
-
-class TableGenerator
-{
-
-public:
-    enum TableState
-    {
-        UnsupportedLocale,
-        EmptyTable,
-        UnknownSystemComposeDir,
-        MissingComposeFile,
-        NoErrors
-    };
-
-    TableGenerator();
-    ~TableGenerator();
-
-    void parseComposeFile(QFile *composeFile);
-    void printComposeTable() const;
-    void orderComposeTable();
-
-    QVector<QComposeTableElement> composeTable() const;
-    TableState tableState() const { return m_state; }
-
-protected:
-    bool processFile(const QString &composeFileName);
-    void parseKeySequence(char *line);
-    void parseIncludeInstruction(QString line);
-
-    QString findComposeFile();
-    bool findSystemComposeDir();
-    QString systemComposeDir();
-    QString composeTableForLocale();
-
-    ushort keysymToUtf8(quint32 sym);
-
-    QString readLocaleMappings(const QByteArray &locale);
-    QByteArray readLocaleAliases(const QByteArray &locale);
-    void initPossibleLocations();
-    bool cleanState() const { return m_state == NoErrors; }
-    QString locale() const;
-
-private:
-      QVector<QComposeTableElement> m_composeTable;
-      TableState m_state;
-      QString m_systemComposeDir;
-      QList<QString> m_possibleLocations;
-};
-
-#endif // QTABLEGENERATOR_H
diff --git a/src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontext.cpp b/src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontext.cpp
index 81a730232c..6b9687c22d 100644
--- a/src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontext.cpp
+++ b/src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontext.cpp
@@ -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.
@@ -36,131 +36,100 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-
 #include "qcomposeplatforminputcontext.h"
 
 #include <QtCore/QCoreApplication>
 #include <QtGui/QKeyEvent>
-#include <QtCore/QDebug>
 
-#include <algorithm>
+#include <locale.h>
 
 QT_BEGIN_NAMESPACE
 
-//#define DEBUG_COMPOSING
+Q_LOGGING_CATEGORY(lcXkbCompose, "qt.xkb.compose")
 
-static const int ignoreKeys[] = {
-    Qt::Key_Shift,
-    Qt::Key_Control,
-    Qt::Key_Meta,
-    Qt::Key_Alt,
-    Qt::Key_CapsLock,
-    Qt::Key_Super_L,
-    Qt::Key_Super_R,
-    Qt::Key_Hyper_L,
-    Qt::Key_Hyper_R,
-    Qt::Key_Mode_switch
-};
+QComposeInputContext::QComposeInputContext()
+{
+    setObjectName(QStringLiteral("QComposeInputContext"));
+    qCDebug(lcXkbCompose, "using xkb compose input context");
+}
 
-static const int composingKeys[] = {
-    Qt::Key_Multi_key,
-    Qt::Key_Dead_Grave,
-    Qt::Key_Dead_Acute,
-    Qt::Key_Dead_Circumflex,
-    Qt::Key_Dead_Tilde,
-    Qt::Key_Dead_Macron,
-    Qt::Key_Dead_Breve,
-    Qt::Key_Dead_Abovedot,
-    Qt::Key_Dead_Diaeresis,
-    Qt::Key_Dead_Abovering,
-    Qt::Key_Dead_Doubleacute,
-    Qt::Key_Dead_Caron,
-    Qt::Key_Dead_Cedilla,
-    Qt::Key_Dead_Ogonek,
-    Qt::Key_Dead_Iota,
-    Qt::Key_Dead_Voiced_Sound,
-    Qt::Key_Dead_Semivoiced_Sound,
-    Qt::Key_Dead_Belowdot,
-    Qt::Key_Dead_Hook,
-    Qt::Key_Dead_Horn,
-    Qt::Key_Dead_Stroke,
-    Qt::Key_Dead_Abovecomma,
-    Qt::Key_Dead_Abovereversedcomma,
-    Qt::Key_Dead_Doublegrave,
-    Qt::Key_Dead_Belowring,
-    Qt::Key_Dead_Belowmacron,
-    Qt::Key_Dead_Belowcircumflex,
-    Qt::Key_Dead_Belowtilde,
-    Qt::Key_Dead_Belowbreve,
-    Qt::Key_Dead_Belowdiaeresis,
-    Qt::Key_Dead_Invertedbreve,
-    Qt::Key_Dead_Belowcomma,
-    Qt::Key_Dead_Currency,
-    Qt::Key_Dead_a,
-    Qt::Key_Dead_A,
-    Qt::Key_Dead_e,
-    Qt::Key_Dead_E,
-    Qt::Key_Dead_i,
-    Qt::Key_Dead_I,
-    Qt::Key_Dead_o,
-    Qt::Key_Dead_O,
-    Qt::Key_Dead_u,
-    Qt::Key_Dead_U,
-    Qt::Key_Dead_Small_Schwa,
-    Qt::Key_Dead_Capital_Schwa,
-    Qt::Key_Dead_Greek,
-    Qt::Key_Dead_Lowline,
-    Qt::Key_Dead_Aboveverticalline,
-    Qt::Key_Dead_Belowverticalline,
-    Qt::Key_Dead_Longsolidusoverlay
-};
+QComposeInputContext::~QComposeInputContext()
+{
+    xkb_compose_state_unref(m_composeState);
+    xkb_compose_table_unref(m_composeTable);
+}
 
-QComposeInputContext::QComposeInputContext()
-    : m_tableState(TableGenerator::EmptyTable)
-    , m_compositionTableInitialized(false)
+void QComposeInputContext::ensureInitialized()
 {
-    clearComposeBuffer();
+    if (m_initialized)
+        return;
+
+    if (!m_XkbContext) {
+        qCWarning(lcXkbCompose) << "error: xkb context has not been set on" << metaObject()->className();
+        return;
+    }
+
+    m_initialized = true;
+    const char *const locale = setlocale(LC_CTYPE, "");
+    qCDebug(lcXkbCompose) << "detected locale (LC_CTYPE):" << locale;
+
+    m_composeTable = xkb_compose_table_new_from_locale(m_XkbContext, locale, XKB_COMPOSE_COMPILE_NO_FLAGS);
+    if (m_composeTable)
+        m_composeState = xkb_compose_state_new(m_composeTable, XKB_COMPOSE_STATE_NO_FLAGS);
+
+    if (!m_composeTable) {
+        qCWarning(lcXkbCompose, "failed to create compose table");
+        return;
+    }
+    if (!m_composeState) {
+        qCWarning(lcXkbCompose, "failed to create compose state");
+        return;
+    }
 }
 
 bool QComposeInputContext::filterEvent(const QEvent *event)
 {
-    const QKeyEvent *keyEvent = (const QKeyEvent *)event;
-    // should pass only the key presses
-    if (keyEvent->type() != QEvent::KeyPress) {
+    auto keyEvent = static_cast<const QKeyEvent *>(event);
+    if (keyEvent->type() != QEvent::KeyPress)
         return false;
-    }
 
-    // if there were errors when generating the compose table input
-    // context should not try to filter anything, simply return false
-    if (m_compositionTableInitialized && (m_tableState & TableGenerator::NoErrors) != TableGenerator::NoErrors)
+    if (!inputMethodAccepted())
         return false;
 
-    int keyval = keyEvent->key();
-    int keysym = 0;
+    // lazy initialization - we don't want to do this on an app startup
+    ensureInitialized();
 
-    if (ignoreKey(keyval))
+    if (!m_composeTable || !m_composeState)
         return false;
 
-    if (!composeKey(keyval) && keyEvent->text().isEmpty())
-        return false;
+    xkb_compose_state_feed(m_composeState, keyEvent->nativeVirtualKey());
 
-    keysym = keyEvent->nativeVirtualKey();
+    switch (xkb_compose_state_get_status(m_composeState)) {
+    case XKB_COMPOSE_COMPOSING:
+        return true;
+    case XKB_COMPOSE_CANCELLED:
+        reset();
+        return false;
+    case XKB_COMPOSE_COMPOSED:
+    {
+        const int size = xkb_compose_state_get_utf8(m_composeState, nullptr, 0);
+        QVarLengthArray<char, 32> buffer(size + 1);
+        xkb_compose_state_get_utf8(m_composeState, buffer.data(), buffer.size());
+        QString composedText = QString::fromUtf8(buffer.constData());
 
-    int nCompose = 0;
-    while (nCompose < QT_KEYSEQUENCE_MAX_LEN && m_composeBuffer[nCompose] != 0)
-        nCompose++;
+        QInputMethodEvent event;
+        event.setCommitString(composedText);
+        QCoreApplication::sendEvent(m_focusObject, &event);
 
-    if (nCompose == QT_KEYSEQUENCE_MAX_LEN) {
         reset();
-        nCompose = 0;
-    }
-
-    m_composeBuffer[nCompose] = keysym;
-    // check sequence
-    if (checkComposeTable())
         return true;
-
-    return false;
+    }
+    case XKB_COMPOSE_NOTHING:
+        return false;
+    default:
+        Q_UNREACHABLE();
+        return false;
+    }
 }
 
 bool QComposeInputContext::isValid() const
@@ -175,7 +144,8 @@ void QComposeInputContext::setFocusObject(QObject *object)
 
 void QComposeInputContext::reset()
 {
-    clearComposeBuffer();
+    if (m_composeState)
+        xkb_compose_state_reset(m_composeState);
 }
 
 void QComposeInputContext::update(Qt::InputMethodQueries q)
@@ -183,125 +153,4 @@ void QComposeInputContext::update(Qt::InputMethodQueries q)
     QPlatformInputContext::update(q);
 }
 
-static bool isDuplicate(const QComposeTableElement &lhs, const QComposeTableElement &rhs)
-{
-    return std::equal(lhs.keys, lhs.keys + QT_KEYSEQUENCE_MAX_LEN,
-                      QT_MAKE_CHECKED_ARRAY_ITERATOR(rhs.keys, QT_KEYSEQUENCE_MAX_LEN));
-}
-
-bool QComposeInputContext::checkComposeTable()
-{
-    if (!m_compositionTableInitialized) {
-        TableGenerator reader;
-        m_tableState = reader.tableState();
-
-        m_compositionTableInitialized = true;
-        if ((m_tableState & TableGenerator::NoErrors) == TableGenerator::NoErrors) {
-            m_composeTable = reader.composeTable();
-        } else {
-#ifdef DEBUG_COMPOSING
-            qDebug( "### FAILED_PARSING ###" );
-#endif
-            // if we have errors, don' try to look things up anyways.
-            reset();
-            return false;
-        }
-    }
-    Q_ASSERT(!m_composeTable.isEmpty());
-    QVector<QComposeTableElement>::const_iterator it =
-            std::lower_bound(m_composeTable.constBegin(), m_composeTable.constEnd(), m_composeBuffer, ByKeys());
-
-    // prevent dereferencing an 'end' iterator, which would result in a crash
-    if (it == m_composeTable.constEnd())
-        it -= 1;
-
-    QComposeTableElement elem = *it;
-    // would be nicer if qLowerBound had API that tells if the item was actually found
-    if (m_composeBuffer[0] != elem.keys[0]) {
-#ifdef DEBUG_COMPOSING
-        qDebug( "### no match ###" );
-#endif
-        reset();
-        return false;
-    }
-    // check if compose buffer is matched
-    for (int i=0; i < QT_KEYSEQUENCE_MAX_LEN; i++) {
-
-        // check if partial match
-        if (m_composeBuffer[i] == 0 && elem.keys[i]) {
-#ifdef DEBUG_COMPOSING
-            qDebug("### partial match ###");
-#endif
-            return true;
-        }
-
-        if (m_composeBuffer[i] != elem.keys[i]) {
-#ifdef DEBUG_COMPOSING
-            qDebug("### different entry ###");
-#endif
-            reset();
-            return i != 0;
-        }
-    }
-#ifdef DEBUG_COMPOSING
-    qDebug("### match exactly ###");
-#endif
-
-    // check if the key sequence is overwriten - see the comment in
-    // TableGenerator::orderComposeTable()
-    int next = 1;
-    do {
-        // if we are at the end of the table, then we have nothing to do here
-        if (it + next != m_composeTable.constEnd()) {
-            QComposeTableElement nextElem = *(it + next);
-            if (isDuplicate(elem, nextElem)) {
-                elem = nextElem;
-                next++;
-                continue;
-            } else {
-                break;
-            }
-        }
-        break;
-    } while (true);
-
-    commitText(elem.value);
-    reset();
-
-    return true;
-}
-
-void QComposeInputContext::commitText(uint character) const
-{
-    QInputMethodEvent event;
-    event.setCommitString(QChar(character));
-    QCoreApplication::sendEvent(m_focusObject, &event);
-}
-
-bool QComposeInputContext::ignoreKey(int keyval) const
-{
-    for (uint i = 0; i < (sizeof(ignoreKeys) / sizeof(ignoreKeys[0])); i++)
-        if (keyval == ignoreKeys[i])
-            return true;
-
-    return false;
-}
-
-bool QComposeInputContext::composeKey(int keyval) const
-{
-    for (uint i = 0; i < (sizeof(composingKeys) / sizeof(composingKeys[0])); i++)
-        if (keyval == composingKeys[i])
-            return true;
-
-    return false;
-}
-
-void QComposeInputContext::clearComposeBuffer()
-{
-    for (uint i=0; i < (sizeof(m_composeBuffer) / sizeof(int)); i++)
-        m_composeBuffer[i] = 0;
-}
-
-QComposeInputContext::~QComposeInputContext() {}
-
 QT_END_NAMESPACE
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
diff --git a/src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontextmain.cpp b/src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontextmain.cpp
index 6b33df65b9..d062d4fd6a 100644
--- a/src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontextmain.cpp
+++ b/src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontextmain.cpp
@@ -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.
@@ -61,7 +61,7 @@ QComposeInputContext *QComposePlatformInputContextPlugin::create(const QString &
     if (system.compare(system, QLatin1String("compose"), Qt::CaseInsensitive) == 0
             || system.compare(system, QLatin1String("xim"), Qt::CaseInsensitive) == 0)
         return new QComposeInputContext;
-    return 0;
+    return nullptr;
 }
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/xcb/qxcbintegration.cpp b/src/plugins/platforms/xcb/qxcbintegration.cpp
index ed9e87a036..a70c7db923 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.cpp
+++ b/src/plugins/platforms/xcb/qxcbintegration.cpp
@@ -357,6 +357,8 @@ void QXcbIntegration::initialize()
     m_inputContext.reset(QPlatformInputContextFactory::create(icStr));
     if (!m_inputContext && icStr != defaultInputContext && icStr != QLatin1String("none"))
         m_inputContext.reset(QPlatformInputContextFactory::create(defaultInputContext));
+
+    defaultConnection()->keyboard()->initialize();
 }
 
 void QXcbIntegration::moveToScreen(QWindow *window, int screen)
diff --git a/src/plugins/platforms/xcb/qxcbkeyboard.cpp b/src/plugins/platforms/xcb/qxcbkeyboard.cpp
index 6eb31d67bd..d0e02ecdd1 100644
--- a/src/plugins/platforms/xcb/qxcbkeyboard.cpp
+++ b/src/plugins/platforms/xcb/qxcbkeyboard.cpp
@@ -565,6 +565,12 @@ QXcbKeyboard::~QXcbKeyboard()
         xcb_key_symbols_free(m_key_symbols);
 }
 
+void QXcbKeyboard::initialize()
+{
+    auto inputContext = QGuiApplicationPrivate::platformIntegration()->inputContext();
+    QXkbCommon::setXkbContext(inputContext, m_xkbContext.get());
+}
+
 void QXcbKeyboard::selectEvents()
 {
 #if QT_CONFIG(xkb)
diff --git a/src/plugins/platforms/xcb/qxcbkeyboard.h b/src/plugins/platforms/xcb/qxcbkeyboard.h
index 75071d045f..e35c82ad24 100644
--- a/src/plugins/platforms/xcb/qxcbkeyboard.h
+++ b/src/plugins/platforms/xcb/qxcbkeyboard.h
@@ -63,6 +63,7 @@ public:
 
     ~QXcbKeyboard();
 
+    void initialize();
     void selectEvents();
 
     void handleKeyPressEvent(const xcb_key_press_event_t *event);
diff --git a/tests/auto/other/other.pro b/tests/auto/other/other.pro
index a720860288..378750472d 100644
--- a/tests/auto/other/other.pro
+++ b/tests/auto/other/other.pro
@@ -67,3 +67,8 @@ winrt|!qtHaveModule(gui)|!qtConfig(accessibility): SUBDIRS -= qaccessibility
 
 android: SUBDIRS += \
     android
+
+qtConfig(xkbcommon): {
+    SUBDIRS += \
+        xkbkeyboard
+}
diff --git a/tests/auto/other/xkbkeyboard/tst_xkbkeyboard.cpp b/tests/auto/other/xkbkeyboard/tst_xkbkeyboard.cpp
new file mode 100644
index 0000000000..65364eddf4
--- /dev/null
+++ b/tests/auto/other/xkbkeyboard/tst_xkbkeyboard.cpp
@@ -0,0 +1,60 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** 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.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtCore>
+#include <QtGui>
+#include <QtTest>
+
+#include <qpa/qplatforminputcontextfactory_p.h>
+#include <qpa/qplatforminputcontext.h>
+
+class tst_XkbKeyboard : public QObject
+{
+    Q_OBJECT
+private slots:
+    void verifyComposeInputContextInterface();
+};
+
+void tst_XkbKeyboard::verifyComposeInputContextInterface()
+{
+    QPlatformInputContext *inputContext = QPlatformInputContextFactory::create(QStringLiteral("compose"));
+    QVERIFY(inputContext);
+
+    const char *const inputContextClassName = "QComposeInputContext";
+    const char *const normalizedSignature = "setXkbContext(xkb_context*)";
+
+    QVERIFY(inputContext->objectName() == QLatin1String(inputContextClassName));
+
+    int methodIndex = inputContext->metaObject()->indexOfMethod(normalizedSignature);
+    QMetaMethod method = inputContext->metaObject()->method(methodIndex);
+    Q_ASSERT(method.isValid());
+}
+
+QTEST_MAIN(tst_XkbKeyboard)
+#include "tst_xkbkeyboard.moc"
+
diff --git a/tests/auto/other/xkbkeyboard/xkbkeyboard.pro b/tests/auto/other/xkbkeyboard/xkbkeyboard.pro
new file mode 100644
index 0000000000..17396ee475
--- /dev/null
+++ b/tests/auto/other/xkbkeyboard/xkbkeyboard.pro
@@ -0,0 +1,7 @@
+CONFIG += testcase
+TARGET = tst_xkbkeyboard
+
+SOURCES += tst_xkbkeyboard.cpp
+
+QT = core-private gui-private testlib
+