Keyboard Layout plugin: bring back async DBus API

Sync DBus API is more clean and precise for this plugin needs.
But we have demand of async API to not block main plasmashell thread.

components/keyboardlayout/keyboardlayout.cpp

 /*
- * Copyright (C) 2014  Daniel Vratil <dvratil@redhat.com>
- * Copyright (C) 2019  David Edmundson <davidedmundson@kde.org>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2.1 of the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
- *
+ * SPDX-FileCopyrightText: 2014 Daniel Vrátil <dvratil@redhat.com>
+ * SPDX-FileCopyrightText: 2019 David Edmundson <davidedmundson@kde.org>
+ * SPDX-FileCopyrightText: 2020 Andrey Butirsky <butirsky@gmail.com>
+ * SPDX-License-Identifier: LGPL-2.1-or-later
  */
 
 #include "keyboardlayout.h"
@@ -23,6 +10,23 @@
 
 #include <QDBusInterface>
 
+template<>
+void KeyboardLayout::requestDBusData<KeyboardLayout::CurrentLayout>()
+{ if (mIface) requestDBusData(mIface->getCurrentLayout(), mCurrentLayout, &KeyboardLayout::currentLayoutChanged); }
+
+template<>
+void KeyboardLayout::requestDBusData<KeyboardLayout::CurrentLayoutDisplayName>()
+{ if (mIface) requestDBusData(mIface->getLayoutDisplayName(mCurrentLayout), mCurrentLayoutDisplayName, &KeyboardLayout::currentLayoutDisplayNameChanged); }
+
+template<>
+void KeyboardLayout::requestDBusData<KeyboardLayout::CurrentLayoutShortName>()
+{ if (mIface) requestDBusData(mIface->getCurrentLayoutShortName(), mCurrentLayoutShortName, &KeyboardLayout::currentLayoutShortNameChanged); }
+
+template<>
+void KeyboardLayout::requestDBusData<KeyboardLayout::Layouts>()
+{ if (mIface) requestDBusData(mIface->getLayoutsList(), mLayouts, &KeyboardLayout::layoutsChanged); }
+
+
 KeyboardLayout::KeyboardLayout(QObject* parent)
     : QObject(parent)
     , mIface(nullptr)
@@ -41,9 +45,12 @@ KeyboardLayout::KeyboardLayout(QObject* parent)
             this, &KeyboardLayout::onCurrentLayoutChanged);
     connect(mIface, &OrgKdeKeyboardLayoutsInterface::layoutListChanged,
             this, &KeyboardLayout::onLayoutListChanged);
+    connect(this, &KeyboardLayout::currentLayoutChanged,
+            this, &KeyboardLayout::requestDBusData<CurrentLayoutDisplayName>);
 
-    mCurrentLayout = callDBus(mIface->getCurrentLayout());
-    mLayouts = callDBus(mIface->getLayoutsList());
+    requestDBusData<CurrentLayout>();
+    requestDBusData<CurrentLayoutShortName>();
+    requestDBusData<Layouts>();
 }
 
 KeyboardLayout::~KeyboardLayout()
@@ -53,30 +60,19 @@ KeyboardLayout::~KeyboardLayout()
 void KeyboardLayout::onCurrentLayoutChanged(const QString &newLayout)
 {
     mCurrentLayout = newLayout;
-    Q_EMIT currentLayoutChanged();
-}
-
-void KeyboardLayout::onLayoutListChanged()
-{
-    if (mIface) {
-        mLayouts = callDBus(mIface->getLayoutsList());
-        Q_EMIT layoutsChanged();
-    }
-}
 
-QString KeyboardLayout::currentLayoutShortName() const
-{
-    return mIface ? callDBus(mIface->getCurrentLayoutShortName()) : QString();
+    requestDBusData<CurrentLayoutShortName>();
+    requestDBusData<CurrentLayoutDisplayName>();
 }
 
-QString KeyboardLayout::currentLayoutDisplayName() const
+void KeyboardLayout::onLayoutListChanged()
 {
-    return mIface ? callDBus(mIface->getLayoutDisplayName(mCurrentLayout)) : QString();
+    requestDBusData<CurrentLayout>();
+    requestDBusData<CurrentLayoutShortName>();
+    requestDBusData<Layouts>();
 }
 
 void KeyboardLayout::setCurrentLayout(const QString &layout)
 {
-    if (mIface) {
-        mIface->setLayout(layout);
-    }
+    if (mIface) mIface->setLayout(layout);
 }

components/keyboardlayout/keyboardlayout.h

@@ -20,15 +20,16 @@ class KeyboardLayout : public QObject
 
     Q_PROPERTY(QString currentLayout
                MEMBER mCurrentLayout
-               WRITE setCurrentLayout)
+               WRITE setCurrentLayout
+               NOTIFY currentLayoutChanged)
 
     Q_PROPERTY(QString currentLayoutDisplayName
-               READ currentLayoutDisplayName
-               NOTIFY currentLayoutChanged)
+               MEMBER mCurrentLayoutDisplayName
+               NOTIFY currentLayoutDisplayNameChanged)
 
     Q_PROPERTY(QString currentLayoutShortName
-               READ currentLayoutShortName
-               NOTIFY currentLayoutChanged)
+               MEMBER mCurrentLayoutShortName
+               NOTIFY currentLayoutShortNameChanged)
 
     Q_PROPERTY(QStringList layouts
                MEMBER mLayouts
@@ -40,34 +41,47 @@ public:
 
 Q_SIGNALS:
     void currentLayoutChanged();
+    void currentLayoutDisplayNameChanged();
+    void currentLayoutShortNameChanged();
     void layoutsChanged();
 
 private:
-    void onCurrentLayoutChanged(const QString &newLayout);
-    void onLayoutListChanged();
-
-    QString currentLayoutShortName() const;
-    QString currentLayoutDisplayName() const;
     void setCurrentLayout(const QString &layout);
 
+    enum DBusData {CurrentLayout, CurrentLayoutDisplayName, CurrentLayoutShortName, Layouts};
+
     template<class T>
-    static T callDBus(QDBusPendingReply<T> pendingReply);
+    void requestDBusData(QDBusPendingReply<T> pendingReply, T &out, void (KeyboardLayout::*notify)());
+    template<DBusData>
+    inline void requestDBusData();
+
+    void onCurrentLayoutChanged(const QString &newLayout);
+    void onLayoutListChanged();
 
     QStringList mLayouts;
     QString mCurrentLayout;
+    QString mCurrentLayoutDisplayName;
+    QString mCurrentLayoutShortName;
     OrgKdeKeyboardLayoutsInterface *mIface;
 };
 
 template<class T>
-T KeyboardLayout::callDBus(QDBusPendingReply<T> pendingReply)
+void KeyboardLayout::requestDBusData(QDBusPendingReply<T> pendingReply, T &out, void (KeyboardLayout::*notify)())
 {
-    pendingReply.waitForFinished();
-    if (pendingReply.isError()) {
-        qCWarning(KEYBOARD_LAYOUT) << pendingReply.error().message();
-        return {};
-    } else {
-        return pendingReply.value();
-    }
+    const QDBusPendingCallWatcher * const watcher = new QDBusPendingCallWatcher(pendingReply, this);
+    connect(watcher, &QDBusPendingCallWatcher::finished, this,
+        [this, &out, notify](QDBusPendingCallWatcher *watcher)
+        {
+            QDBusPendingReply<T> reply = *watcher;
+            if (reply.isError()) {
+                qCWarning(KEYBOARD_LAYOUT) << reply.error().message();
+            } else {
+                out = reply.value();
+                emit (this->*notify)();
+            }
+            watcher->deleteLater();
+        }
+    );
 }
 
 #endif // KEYBOARDLAYOUT_H