Make flatpak portal support to be used also by Snap applications

Snap now uses xdg-desktop-portal for portal support. Add check for apps
running in Snap and make them use portals by default. We also should be
using different name for the platform theme used by sandboxed apps.

Change-Id: Ibaa35b7549b3d94775d7edb937f729a300d071b6
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

7 files changed, 890 insertions, 0 deletions

diff --git a/src/plugins/platformthemes/xdgdesktopportal/main.cpp b/src/plugins/platformthemes/xdgdesktopportal/main.cpp
new file mode 100644
index 0000000000..64a03d479f
--- /dev/null
+++ b/src/plugins/platformthemes/xdgdesktopportal/main.cpp
@@ -0,0 +1,67 @@
+/****************************************************************************
+**
+** Copyright (C) 2017-2018 Red Hat, Inc
+** 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 <qpa/qplatformthemeplugin.h>
+#include "qxdgdesktopportaltheme.h"
+
+QT_BEGIN_NAMESPACE
+
+class QXdgDesktopPortalThemePlugin : public QPlatformThemePlugin
+{
+   Q_OBJECT
+   Q_PLUGIN_METADATA(IID QPlatformThemeFactoryInterface_iid FILE "xdgdesktopportal.json")
+
+public:
+    QPlatformTheme *create(const QString &key, const QStringList &params) override;
+};
+
+QPlatformTheme *QXdgDesktopPortalThemePlugin::create(const QString &key, const QStringList &params)
+{
+    Q_UNUSED(params);
+    if (!key.compare(QLatin1String("xdgdesktopportal"), Qt::CaseInsensitive) ||
+        !key.compare(QLatin1String("flatpak"), Qt::CaseInsensitive) ||
+        !key.compare(QLatin1String("snap"), Qt::CaseInsensitive))
+        return new QXdgDesktopPortalTheme;
+
+    return nullptr;
+}
+
+QT_END_NAMESPACE
+
+#include "main.moc"
diff --git a/src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportalfiledialog.cpp b/src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportalfiledialog.cpp
new file mode 100644
index 0000000000..cda267d24b
--- /dev/null
+++ b/src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportalfiledialog.cpp
@@ -0,0 +1,407 @@
+/****************************************************************************
+**
+** Copyright (C) 2017-2018 Red Hat, Inc
+** 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 "qxdgdesktopportalfiledialog_p.h"
+
+#include <QtCore/qeventloop.h>
+
+#include <QtDBus/QtDBus>
+#include <QDBusConnection>
+#include <QDBusMessage>
+#include <QDBusPendingCall>
+#include <QDBusPendingCallWatcher>
+#include <QDBusPendingReply>
+
+#include <QMetaType>
+#include <QMimeType>
+#include <QMimeDatabase>
+#include <QRandomGenerator>
+#include <QWindow>
+
+QT_BEGIN_NAMESPACE
+
+QDBusArgument &operator <<(QDBusArgument &arg, const QXdgDesktopPortalFileDialog::FilterCondition &filterCondition)
+{
+    arg.beginStructure();
+    arg << filterCondition.type << filterCondition.pattern;
+    arg.endStructure();
+    return arg;
+}
+
+const QDBusArgument &operator >>(const QDBusArgument &arg, QXdgDesktopPortalFileDialog::FilterCondition &filterCondition)
+{
+    uint type;
+    QString filterPattern;
+    arg.beginStructure();
+    arg >> type >> filterPattern;
+    filterCondition.type = (QXdgDesktopPortalFileDialog::ConditionType)type;
+    filterCondition.pattern = filterPattern;
+    arg.endStructure();
+
+    return arg;
+}
+
+QDBusArgument &operator <<(QDBusArgument &arg, const QXdgDesktopPortalFileDialog::Filter filter)
+{
+    arg.beginStructure();
+    arg << filter.name << filter.filterConditions;
+    arg.endStructure();
+    return arg;
+}
+
+const QDBusArgument &operator >>(const QDBusArgument &arg, QXdgDesktopPortalFileDialog::Filter &filter)
+{
+    QString name;
+    QXdgDesktopPortalFileDialog::FilterConditionList filterConditions;
+    arg.beginStructure();
+    arg >> name >> filterConditions;
+    filter.name = name;
+    filter.filterConditions = filterConditions;
+    arg.endStructure();
+
+    return arg;
+}
+
+class QXdgDesktopPortalFileDialogPrivate
+{
+public:
+    QXdgDesktopPortalFileDialogPrivate(QPlatformFileDialogHelper *nativeFileDialog)
+        : nativeFileDialog(nativeFileDialog)
+    { }
+
+    WId winId = 0;
+    bool modal = false;
+    bool multipleFiles = false;
+    bool saveFile = false;
+    QString acceptLabel;
+    QString directory;
+    QString title;
+    QStringList nameFilters;
+    QStringList mimeTypesFilters;
+    QStringList selectedFiles;
+    QPlatformFileDialogHelper *nativeFileDialog = nullptr;
+};
+
+QXdgDesktopPortalFileDialog::QXdgDesktopPortalFileDialog(QPlatformFileDialogHelper *nativeFileDialog)
+    : QPlatformFileDialogHelper()
+    , d_ptr(new QXdgDesktopPortalFileDialogPrivate(nativeFileDialog))
+{
+    Q_D(QXdgDesktopPortalFileDialog);
+
+    if (d->nativeFileDialog) {
+        connect(d->nativeFileDialog, SIGNAL(accept()), this, SIGNAL(accept()));
+        connect(d->nativeFileDialog, SIGNAL(reject()), this, SIGNAL(reject()));
+    }
+}
+
+QXdgDesktopPortalFileDialog::~QXdgDesktopPortalFileDialog()
+{
+}
+
+void QXdgDesktopPortalFileDialog::initializeDialog()
+{
+    Q_D(QXdgDesktopPortalFileDialog);
+
+    if (d->nativeFileDialog)
+        d->nativeFileDialog->setOptions(options());
+
+    if (options()->fileMode() == QFileDialogOptions::ExistingFiles)
+        d->multipleFiles = true;
+
+    if (options()->isLabelExplicitlySet(QFileDialogOptions::Accept))
+        d->acceptLabel = options()->labelText(QFileDialogOptions::Accept);
+
+    if (!options()->windowTitle().isEmpty())
+        d->title = options()->windowTitle();
+
+    if (options()->acceptMode() == QFileDialogOptions::AcceptSave)
+        d->saveFile = true;
+
+    if (!options()->nameFilters().isEmpty())
+        d->nameFilters = options()->nameFilters();
+
+    if (!options()->mimeTypeFilters().isEmpty())
+        d->mimeTypesFilters = options()->mimeTypeFilters();
+
+    setDirectory(options()->initialDirectory());
+}
+
+void QXdgDesktopPortalFileDialog::openPortal()
+{
+    Q_D(const QXdgDesktopPortalFileDialog);
+
+    QDBusMessage message = QDBusMessage::createMethodCall(QLatin1String("org.freedesktop.portal.Desktop"),
+                                                          QLatin1String("/org/freedesktop/portal/desktop"),
+                                                          QLatin1String("org.freedesktop.portal.FileChooser"),
+                                                          d->saveFile ? QLatin1String("SaveFile") : QLatin1String("OpenFile"));
+    QString parentWindowId = QLatin1String("x11:") + QString::number(d->winId);
+
+    QVariantMap options;
+    if (!d->acceptLabel.isEmpty())
+        options.insert(QLatin1String("accept_label"), d->acceptLabel);
+
+    options.insert(QLatin1String("modal"), d->modal);
+    options.insert(QLatin1String("multiple"), d->multipleFiles);
+
+    if (d->saveFile) {
+        if (!d->directory.isEmpty())
+            options.insert(QLatin1String("current_folder"), d->directory.toLatin1());
+
+        if (!d->selectedFiles.isEmpty())
+            options.insert(QLatin1String("current_file"), d->selectedFiles.first().toLatin1());
+    }
+
+    // Insert filters
+    qDBusRegisterMetaType<FilterCondition>();
+    qDBusRegisterMetaType<FilterConditionList>();
+    qDBusRegisterMetaType<Filter>();
+    qDBusRegisterMetaType<FilterList>();
+
+    FilterList filterList;
+
+    if (!d->mimeTypesFilters.isEmpty()) {
+        for (const QString &mimeTypefilter : d->mimeTypesFilters) {
+            QMimeDatabase mimeDatabase;
+            QMimeType mimeType = mimeDatabase.mimeTypeForName(mimeTypefilter);
+
+            // Creates e.g. (1, "image/png")
+            FilterCondition filterCondition;
+            filterCondition.type = MimeType;
+            filterCondition.pattern = mimeTypefilter;
+
+            // Creates e.g. [((1, "image/png"))]
+            FilterConditionList filterConditions;
+            filterConditions << filterCondition;
+
+            // Creates e.g. [("Images", [((1, "image/png"))])]
+            Filter filter;
+            filter.name = mimeType.comment();
+            filter.filterConditions = filterConditions;
+
+            filterList << filter;
+        }
+    } else if (!d->nameFilters.isEmpty()) {
+        for (const QString &filter : d->nameFilters) {
+            // Do parsing:
+            // Supported format is ("Images (*.png *.jpg)")
+            QRegularExpression regexp(QPlatformFileDialogHelper::filterRegExp);
+            QRegularExpressionMatch match = regexp.match(filter);
+            if (match.hasMatch()) {
+                QString userVisibleName = match.captured(1);
+                QStringList filterStrings = match.captured(2).split(QLatin1Char(' '), QString::SkipEmptyParts);
+
+                FilterConditionList filterConditions;
+                for (const QString &filterString : filterStrings) {
+                    FilterCondition filterCondition;
+                    filterCondition.type = GlobalPattern;
+                    filterCondition.pattern = filterString;
+                    filterConditions << filterCondition;
+                }
+
+                Filter filter;
+                filter.name = userVisibleName;
+                filter.filterConditions = filterConditions;
+
+                filterList << filter;
+            }
+        }
+    }
+
+    if (!filterList.isEmpty())
+        options.insert(QLatin1String("filters"), QVariant::fromValue(filterList));
+
+    options.insert(QLatin1String("handle_token"), QStringLiteral("qt%1").arg(QRandomGenerator::global()->generate()));
+
+    // TODO choices a(ssa(ss)s)
+    // List of serialized combo boxes to add to the file chooser.
+
+    message << parentWindowId << d->title << options;
+
+    QDBusPendingCall pendingCall = QDBusConnection::sessionBus().asyncCall(message);
+    QDBusPendingCallWatcher *watcher = new QDBusPendingCallWatcher(pendingCall);
+    connect(watcher, &QDBusPendingCallWatcher::finished, this, [this] (QDBusPendingCallWatcher *watcher) {
+        QDBusPendingReply<QDBusObjectPath> reply = *watcher;
+        if (reply.isError()) {
+            Q_EMIT reject();
+        } else {
+            QDBusConnection::sessionBus().connect(nullptr,
+                                                  reply.value().path(),
+                                                  QLatin1String("org.freedesktop.portal.Request"),
+                                                  QLatin1String("Response"),
+                                                  this,
+                                                  SLOT(gotResponse(uint,QVariantMap)));
+        }
+    });
+}
+
+bool QXdgDesktopPortalFileDialog::defaultNameFilterDisables() const
+{
+    return false;
+}
+
+void QXdgDesktopPortalFileDialog::setDirectory(const QUrl &directory)
+{
+    Q_D(QXdgDesktopPortalFileDialog);
+
+    if (d->nativeFileDialog) {
+        d->nativeFileDialog->setOptions(options());
+        d->nativeFileDialog->setDirectory(directory);
+    }
+
+    d->directory = directory.path();
+}
+
+QUrl QXdgDesktopPortalFileDialog::directory() const
+{
+    Q_D(const QXdgDesktopPortalFileDialog);
+
+    if (d->nativeFileDialog && (options()->fileMode() == QFileDialogOptions::Directory || options()->fileMode() == QFileDialogOptions::DirectoryOnly))
+        return d->nativeFileDialog->directory();
+
+    return d->directory;
+}
+
+void QXdgDesktopPortalFileDialog::selectFile(const QUrl &filename)
+{
+    Q_D(QXdgDesktopPortalFileDialog);
+
+    if (d->nativeFileDialog) {
+        d->nativeFileDialog->setOptions(options());
+        d->nativeFileDialog->selectFile(filename);
+    }
+
+    d->selectedFiles << filename.path();
+}
+
+QList<QUrl> QXdgDesktopPortalFileDialog::selectedFiles() const
+{
+    Q_D(const QXdgDesktopPortalFileDialog);
+
+    if (d->nativeFileDialog && (options()->fileMode() == QFileDialogOptions::Directory || options()->fileMode() == QFileDialogOptions::DirectoryOnly))
+        return d->nativeFileDialog->selectedFiles();
+
+    QList<QUrl> files;
+    for (const QString &file : d->selectedFiles) {
+        files << QUrl(file);
+    }
+    return files;
+}
+
+void QXdgDesktopPortalFileDialog::setFilter()
+{
+    Q_D(QXdgDesktopPortalFileDialog);
+
+    if (d->nativeFileDialog) {
+        d->nativeFileDialog->setOptions(options());
+        d->nativeFileDialog->setFilter();
+    }
+}
+
+void QXdgDesktopPortalFileDialog::selectNameFilter(const QString &filter)
+{
+    Q_D(QXdgDesktopPortalFileDialog);
+
+    if (d->nativeFileDialog) {
+        d->nativeFileDialog->setOptions(options());
+        d->nativeFileDialog->selectNameFilter(filter);
+    }
+}
+
+QString QXdgDesktopPortalFileDialog::selectedNameFilter() const
+{
+    // TODO
+    return QString();
+}
+
+void QXdgDesktopPortalFileDialog::exec()
+{
+    Q_D(QXdgDesktopPortalFileDialog);
+
+    if (d->nativeFileDialog && (options()->fileMode() == QFileDialogOptions::Directory || options()->fileMode() == QFileDialogOptions::DirectoryOnly)) {
+        d->nativeFileDialog->exec();
+        return;
+    }
+
+    // HACK we have to avoid returning until we emit that the dialog was accepted or rejected
+    QEventLoop loop;
+    loop.connect(this, SIGNAL(accept()), SLOT(quit()));
+    loop.connect(this, SIGNAL(reject()), SLOT(quit()));
+    loop.exec();
+}
+
+void QXdgDesktopPortalFileDialog::hide()
+{
+    Q_D(QXdgDesktopPortalFileDialog);
+
+    if (d->nativeFileDialog)
+        d->nativeFileDialog->hide();
+}
+
+bool QXdgDesktopPortalFileDialog::show(Qt::WindowFlags windowFlags, Qt::WindowModality windowModality, QWindow *parent)
+{
+    Q_D(QXdgDesktopPortalFileDialog);
+
+    initializeDialog();
+
+    d->modal = windowModality != Qt::NonModal;
+    d->winId = parent ? parent->winId() : 0;
+
+    if (d->nativeFileDialog && (options()->fileMode() == QFileDialogOptions::Directory || options()->fileMode() == QFileDialogOptions::DirectoryOnly))
+        return d->nativeFileDialog->show(windowFlags, windowModality, parent);
+
+    openPortal();
+
+    return true;
+}
+
+void QXdgDesktopPortalFileDialog::gotResponse(uint response, const QVariantMap &results)
+{
+    Q_D(QXdgDesktopPortalFileDialog);
+
+    if (!response) {
+        if (results.contains(QLatin1String("uris")))
+            d->selectedFiles = results.value(QLatin1String("uris")).toStringList();
+
+        Q_EMIT accept();
+    } else {
+        Q_EMIT reject();
+    }
+}
+
+QT_END_NAMESPACE
diff --git a/src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportalfiledialog_p.h b/src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportalfiledialog_p.h
new file mode 100644
index 0000000000..c1f1a2c005
--- /dev/null
+++ b/src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportalfiledialog_p.h
@@ -0,0 +1,106 @@
+/****************************************************************************
+**
+** Copyright (C) 2017-2018 Red Hat, Inc
+** 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 QXDGDESKTOPPORTALFILEDIALOG_P_H
+#define QXDGDESKTOPPORTALFILEDIALOG_P_H
+
+#include <qpa/qplatformdialoghelper.h>
+#include <QVector>
+
+QT_BEGIN_NAMESPACE
+
+class QXdgDesktopPortalFileDialogPrivate;
+
+class QXdgDesktopPortalFileDialog : public QPlatformFileDialogHelper
+{
+    Q_OBJECT
+    Q_DECLARE_PRIVATE(QXdgDesktopPortalFileDialog)
+public:
+    enum ConditionType : uint {
+        GlobalPattern = 0,
+        MimeType = 1
+    };
+    // Filters a(sa(us))
+    // Example: [('Images', [(0, '*.ico'), (1, 'image/png')]), ('Text', [(0, '*.txt')])]
+    struct FilterCondition {
+        ConditionType type;
+        QString pattern; // E.g. '*ico' or 'image/png'
+    };
+    typedef QVector<FilterCondition> FilterConditionList;
+
+    struct Filter {
+        QString name; // E.g. 'Images' or 'Text
+        FilterConditionList filterConditions;; // E.g. [(0, '*.ico'), (1, 'image/png')] or [(0, '*.txt')]
+    };
+    typedef QVector<Filter> FilterList;
+
+    QXdgDesktopPortalFileDialog(QPlatformFileDialogHelper *nativeFileDialog = nullptr);
+    ~QXdgDesktopPortalFileDialog();
+
+    bool defaultNameFilterDisables() const override;
+    QUrl directory() const override;
+    void setDirectory(const QUrl &directory) override;
+    void selectFile(const QUrl &filename) override;
+    QList<QUrl> selectedFiles() const override;
+    void setFilter() override;
+    void selectNameFilter(const QString &filter) override;
+    QString selectedNameFilter() const override;
+
+    void exec() override;
+    bool show(Qt::WindowFlags windowFlags, Qt::WindowModality windowModality, QWindow *parent) override;
+    void hide() override;
+
+private Q_SLOTS:
+    void gotResponse(uint response, const QVariantMap &results);
+
+private:
+    void initializeDialog();
+    void openPortal();
+
+    QScopedPointer<QXdgDesktopPortalFileDialogPrivate> d_ptr;
+};
+
+QT_END_NAMESPACE
+
+Q_DECLARE_METATYPE(QXdgDesktopPortalFileDialog::FilterCondition);
+Q_DECLARE_METATYPE(QXdgDesktopPortalFileDialog::FilterConditionList);
+Q_DECLARE_METATYPE(QXdgDesktopPortalFileDialog::Filter);
+Q_DECLARE_METATYPE(QXdgDesktopPortalFileDialog::FilterList);
+
+#endif // QXDGDESKTOPPORTALFILEDIALOG_P_H
+
diff --git a/src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportaltheme.cpp b/src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportaltheme.cpp
new file mode 100644
index 0000000000..f07ca3f098
--- /dev/null
+++ b/src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportaltheme.cpp
@@ -0,0 +1,200 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 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 "qxdgdesktopportaltheme.h"
+#include "qxdgdesktopportalfiledialog_p.h"
+
+#include <private/qguiapplication_p.h>
+#include <qpa/qplatformtheme_p.h>
+#include <qpa/qplatformthemefactory_p.h>
+#include <qpa/qplatformintegration.h>
+
+QT_BEGIN_NAMESPACE
+
+class QXdgDesktopPortalThemePrivate : public QPlatformThemePrivate
+{
+public:
+    QXdgDesktopPortalThemePrivate()
+        : QPlatformThemePrivate()
+    { }
+
+    ~QXdgDesktopPortalThemePrivate()
+    {
+        delete baseTheme;
+    }
+
+    QPlatformTheme *baseTheme;
+};
+
+QXdgDesktopPortalTheme::QXdgDesktopPortalTheme()
+    : d_ptr(new QXdgDesktopPortalThemePrivate)
+{
+    Q_D(QXdgDesktopPortalTheme);
+
+    QStringList themeNames;
+    themeNames += QGuiApplicationPrivate::platform_integration->themeNames();
+    // 1) Look for a theme plugin.
+    for (const QString &themeName : qAsConst(themeNames)) {
+        d->baseTheme = QPlatformThemeFactory::create(themeName, nullptr);
+        if (d->baseTheme)
+            break;
+    }
+
+    // 2) If no theme plugin was found ask the platform integration to
+    // create a theme
+    if (!d->baseTheme) {
+        for (const QString &themeName : qAsConst(themeNames)) {
+            d->baseTheme = QGuiApplicationPrivate::platform_integration->createPlatformTheme(themeName);
+            if (d->baseTheme)
+                break;
+        }
+        // No error message; not having a theme plugin is allowed.
+    }
+
+    // 3) Fall back on the built-in "null" platform theme.
+    if (!d->baseTheme)
+        d->baseTheme = new QPlatformTheme;
+}
+
+QPlatformMenuItem* QXdgDesktopPortalTheme::createPlatformMenuItem() const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->createPlatformMenuItem();
+}
+
+QPlatformMenu* QXdgDesktopPortalTheme::createPlatformMenu() const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->createPlatformMenu();
+}
+
+QPlatformMenuBar* QXdgDesktopPortalTheme::createPlatformMenuBar() const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->createPlatformMenuBar();
+}
+
+void QXdgDesktopPortalTheme::showPlatformMenuBar()
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->showPlatformMenuBar();
+}
+
+bool QXdgDesktopPortalTheme::usePlatformNativeDialog(DialogType type) const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+
+    if (type == FileDialog)
+        return true;
+
+    return d->baseTheme->usePlatformNativeDialog(type);
+}
+
+QPlatformDialogHelper* QXdgDesktopPortalTheme::createPlatformDialogHelper(DialogType type) const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+
+    if (type == FileDialog) {
+        if (d->baseTheme->usePlatformNativeDialog(type))
+            return new QXdgDesktopPortalFileDialog(static_cast<QPlatformFileDialogHelper*>(d->baseTheme->createPlatformDialogHelper(type)));
+
+        return new QXdgDesktopPortalFileDialog;
+    }
+
+    return d->baseTheme->createPlatformDialogHelper(type);
+}
+
+#ifndef QT_NO_SYSTEMTRAYICON
+QPlatformSystemTrayIcon* QXdgDesktopPortalTheme::createPlatformSystemTrayIcon() const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->createPlatformSystemTrayIcon();
+}
+#endif
+
+const QPalette *QXdgDesktopPortalTheme::palette(Palette type) const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->palette(type);
+}
+
+const QFont* QXdgDesktopPortalTheme::font(Font type) const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->font(type);
+}
+
+QVariant QXdgDesktopPortalTheme::themeHint(ThemeHint hint) const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->themeHint(hint);
+}
+
+QPixmap QXdgDesktopPortalTheme::standardPixmap(StandardPixmap sp, const QSizeF &size) const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->standardPixmap(sp, size);
+}
+
+QIcon QXdgDesktopPortalTheme::fileIcon(const QFileInfo &fileInfo,
+                              QPlatformTheme::IconOptions iconOptions) const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->fileIcon(fileInfo, iconOptions);
+}
+
+QIconEngine * QXdgDesktopPortalTheme::createIconEngine(const QString &iconName) const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->createIconEngine(iconName);
+}
+
+QList<QKeySequence> QXdgDesktopPortalTheme::keyBindings(QKeySequence::StandardKey key) const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->keyBindings(key);
+}
+
+QString QXdgDesktopPortalTheme::standardButtonText(int button) const
+{
+    Q_D(const QXdgDesktopPortalTheme);
+    return d->baseTheme->standardButtonText(button);
+}
+
+QT_END_NAMESPACE
diff --git a/src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportaltheme.h b/src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportaltheme.h
new file mode 100644
index 0000000000..b72e676419
--- /dev/null
+++ b/src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportaltheme.h
@@ -0,0 +1,90 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 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 QXDGDESKTOPPORTALTHEME_H
+#define QXDGDESKTOPPORTALTHEME_H
+
+#include <qpa/qplatformtheme.h>
+
+QT_BEGIN_NAMESPACE
+
+class QXdgDesktopPortalThemePrivate;
+
+class QXdgDesktopPortalTheme : public QPlatformTheme
+{
+    Q_DECLARE_PRIVATE(QXdgDesktopPortalTheme)
+public:
+    QXdgDesktopPortalTheme();
+
+    QPlatformMenuItem *createPlatformMenuItem() const override;
+    QPlatformMenu *createPlatformMenu() const override;
+    QPlatformMenuBar *createPlatformMenuBar() const override;
+    void showPlatformMenuBar() override;
+
+    bool usePlatformNativeDialog(DialogType type) const override;
+    QPlatformDialogHelper *createPlatformDialogHelper(DialogType type) const override;
+
+#ifndef QT_NO_SYSTEMTRAYICON
+    QPlatformSystemTrayIcon *createPlatformSystemTrayIcon() const override;
+#endif
+
+    const QPalette *palette(Palette type = SystemPalette) const override;
+
+    const QFont *font(Font type = SystemFont) const override;
+
+    QVariant themeHint(ThemeHint hint) const override;
+
+    QPixmap standardPixmap(StandardPixmap sp, const QSizeF &size) const override;
+    QIcon fileIcon(const QFileInfo &fileInfo,
+                   QPlatformTheme::IconOptions iconOptions = 0) const override;
+
+    QIconEngine *createIconEngine(const QString &iconName) const override;
+
+    QList<QKeySequence> keyBindings(QKeySequence::StandardKey key) const override;
+
+    QString standardButtonText(int button) const override;
+
+private:
+    QScopedPointer<QXdgDesktopPortalThemePrivate> d_ptr;
+    Q_DISABLE_COPY(QXdgDesktopPortalTheme)
+};
+
+QT_END_NAMESPACE
+
+#endif // QXDGDESKTOPPORTALTHEME_H
diff --git a/src/plugins/platformthemes/xdgdesktopportal/xdgdesktopportal.json b/src/plugins/platformthemes/xdgdesktopportal/xdgdesktopportal.json
new file mode 100644
index 0000000000..c69062d9a1
--- /dev/null
+++ b/src/plugins/platformthemes/xdgdesktopportal/xdgdesktopportal.json
@@ -0,0 +1,3 @@
+{
+    "Keys": [ "xdgdesktopportal", "flatpak", "snap" ]
+}
diff --git a/src/plugins/platformthemes/xdgdesktopportal/xdgdesktopportal.pro b/src/plugins/platformthemes/xdgdesktopportal/xdgdesktopportal.pro
new file mode 100644
index 0000000000..0a71484cf9
--- /dev/null
+++ b/src/plugins/platformthemes/xdgdesktopportal/xdgdesktopportal.pro
@@ -0,0 +1,17 @@
+TARGET = qxdgdesktopportal
+
+PLUGIN_TYPE = platformthemes
+PLUGIN_EXTENDS = -
+PLUGIN_CLASS_NAME = QXdgDesktopPortalThemePlugin
+load(qt_plugin)
+
+QT += core-private dbus gui-private theme_support-private
+
+HEADERS += \
+        qxdgdesktopportaltheme.h \
+        qxdgdesktopportalfiledialog_p.h
+
+SOURCES += \
+        main.cpp \
+        qxdgdesktopportaltheme.cpp \
+        qxdgdesktopportalfiledialog.cpp