akapplication.h

/*
    SPDX-FileCopyrightText: 2008 Volker Krause <vkrause@kde.org>
 
    SPDX-License-Identifier: LGPL-2.0-or-later
*/
 
#pragma once
 
#include <QCommandLineParser>
#include <QDBusConnection>
#include <QDBusError>
#include <QLoggingCategory>
#include <QObject>
 
#include <memory>
 
class QCoreApplication;
class QApplication;
class QGuiApplication;
 
/**
 * D-Bus session bus monitoring and command line handling.
 */
class AkApplicationBase : public QObject
{
    Q_OBJECT
public:
    ~AkApplicationBase() override;
    void parseCommandLine();
    void setDescription(const QString &desc);
 
    void addCommandLineOptions(const QCommandLineOption &option);
    void addPositionalCommandLineOption(const QString &name, const QString &description = QString(), const QString &syntax = QString());
    const QCommandLineParser &commandLineArguments() const
    {
        return mCmdLineParser;
    }
 
    void printUsage() const;
 
    /** Returns the AkApplication instance */
    static AkApplicationBase *instance();
 
    /** Forward to Q[Core]Application for convenience. */
    int exec();
 
protected:
    AkApplicationBase(std::unique_ptr<QCoreApplication> app, const QLoggingCategory &loggingCategory);
    void init();
 
    std::unique_ptr<QCoreApplication> mApp;
 
private Q_SLOTS:
    void pollSessionBus() const;
 
private:
    QString mInstanceId;
    const QLoggingCategory &mLoggingCategory;
    static AkApplicationBase *sInstance;
 
    QCommandLineParser mCmdLineParser;
};
 
template<typename T>
class AkApplicationImpl : public AkApplicationBase
{
public:
    AkApplicationImpl(int &argc, char **argv, const QLoggingCategory &loggingCategory = *QLoggingCategory::defaultCategory())
        : AkApplicationBase(std::make_unique<T>(argc, argv), loggingCategory)
    {
        init();
    }
};
 
template<typename T>
class AkUniqueApplicationImpl : public AkApplicationBase
{
public:
    AkUniqueApplicationImpl(int &argc, char **argv, const QString &serviceName, const QLoggingCategory &loggingCategory = *QLoggingCategory::defaultCategory())
        : AkApplicationBase(std::make_unique<T>(argc, argv), loggingCategory)
    {
        registerUniqueServiceOrTerminate(serviceName, loggingCategory);
        init();
    }
 
private:
    void registerUniqueServiceOrTerminate(const QString &serviceName, const QLoggingCategory &log)
    {
        auto bus = QDBusConnection::sessionBus();
        if (!bus.isConnected()) {
            qCCritical(log, "Session bus not found. Is DBus running?");
            exit(1);
        }
 
        if (!bus.registerService(serviceName)) {
            // We couldn't register. Most likely, it's already running.
            const QString lastError = bus.lastError().message();
            if (lastError.isEmpty()) {
                qCInfo(log, "Service %s already registered, terminating now.", qUtf8Printable(serviceName));
                exit(0); // already running, so it's OK. Terminate now.
            } else {
                qCCritical(log, "Unable to register service as %s due to an error: %s", qUtf8Printable(serviceName), qUtf8Printable(lastError));
                exit(1); // :(
            }
        }
    }
};
 
/**
 * Returns the contents of @p name environment variable if it is defined,
 * or @p defaultValue otherwise.
 */
QString akGetEnv(const char *name, const QString &defaultValue = QString());
 
using AkCoreApplication = AkApplicationImpl<QCoreApplication>;
using AkApplication = AkApplicationImpl<QApplication>;
using AkGuiApplication = AkApplicationImpl<QGuiApplication>;
using AkUniqueGuiApplication = AkUniqueApplicationImpl<QGuiApplication>;