【QT】Qt Application Manager启动应用源码分析

Qt Application Manager启动应用源码分析

Qt Application Manager（以下简称QTAM）是QT推出的一款应用管理程序，可以把它简单理解成Android的Launcher+SystemUI。但是，QTAM又集成了Wayland功能，并且自身实现了一套Compositor。QTAM以多进程启动情况下（默认），其地位相当于 Launcher+SystemUI+Compositor。
关于QTAM的基本介绍可以参考《Qt Application Manager简介》

启用应用

QTAM作为一款应用管理程序，适用于嵌入式端（如车载）应用。利用QT开发的应用程序只需要简单适配一下QTAM的规范，可以大幅度减少开发一套应用管理程序的成本。同时QTAM支持QML方式。应用管理最基本的功能，是应用的启动。下面基于QTAM 6.2.2版本进行分析。
启动应用的接口ApplicationManager:: startApplication，该接口可以以C++或QML的形式调用（下述摘取了部分源码）

// src\manager-lib\applicationmanager.h
class ApplicationManager : public QAbstractListModel
{
    Q_OBJECT
    Q_CLASSINFO("D-Bus Interface", "io.qt.ApplicationManager")
    Q_CLASSINFO("AM-QmlType", "QtApplicationManager.SystemUI/ApplicationManager 2.0 SINGLETON")
    
public:
	// 通过C++和QML互相调用的方式，QML端也可以调用到该接口。
	// 关于QML调用C++，网上文章比较多可自行百度。
	Q_SCRIPTABLE bool startApplication(const QString &id, const QString &documentUrl = QString());
}

// src\manager-lib\applicationmanager.cpp
bool ApplicationManager::startApplication(const QString &id, const QString &documentUrl)
{
    try {
        return startApplicationInternal(id, documentUrl);
    } catch (const Exception &e) {
        qCWarning(LogSystem) << e.what();
        return false;
    }
}

// src\manager-lib\applicationmanager.cpp
bool ApplicationManager::startApplicationInternal(const QString &appId, const QString &documentUrl,
                                                  const QString &documentMimeType,
                                                  const QString &debugWrapperSpecification,
                                                  const QVector<int> &stdioRedirections)  Q_DECL_NOEXCEPT_EXPR(false)
{
	// 根据appid，获取到应用信息。appid唯一标识应用
    Application *app = fromId(appId);

	// 获取应用的RunTime，Runtime可以理解为应用运行时。QTAM提供多种Runtime，比如NativeRuntime、QML Runtime等。
    AbstractRuntime *runtime = app->currentRuntime();
    auto runtimeManager = runtime ? runtime->manager() : RuntimeFactory::instance()->manager(app->runtimeName());
    if (!runtimeManager)
        throw Exception("No RuntimeManager found for runtime: %1").arg(app->runtimeName());
		
	// 判断QtAM运行的是多进程模式，还是单进程模式（默认为多进程模式，即每个应用以单独的进程启动）
    bool inProcess = runtimeManager->inProcess();

	// 判断当前rimtime的状态。 应用的状态为 StartingUp-> Running -> ShuttingDown -> NotRunning
	// 第一次启动时，这里为NotRunning
    if (runtime) {
        switch (runtime->state()) {
        case Am::StartingUp:
        case Am::Running:
            if (!debugWrapperCommand.isEmpty()) {
                throw Exception("Application %1 is already running - cannot start with debug-wrapper: %2")
                        .arg(app->id(), debugWrapperSpecification);
            }
			
			// documentUrl为应用入口。比如一个QML文件。
            if (!documentUrl.isNull())
                runtime->openDocument(documentUrl, documentMimeType);
            else if (!app->documentUrl().isNull())
                runtime->openDocument(app->documentUrl(), documentMimeType);
			// 激活App
            emitActivated(app);
            return true;

        case Am::ShuttingDown:
            return false;

        case Am::NotRunning:
            break;
        }
    }

	// container指应用运行上下文（Context）
    AbstractContainer *container = nullptr;
    QString containerId;
	
	// 如果是多进程模式
    if (!inProcess) {
        if (d->containerSelectionConfig.isEmpty()) {
			// 默认使用ProcessContainer
            containerId = qSL("process");
        } else {
            // check config file
            for (const auto &it : qAsConst(d->containerSelectionConfig)) {
                const QString &key = it.first;
                const QString &value = it.second;
                bool hasAsterisk = key.contains(qL1C('*'));

                if ((hasAsterisk && key.length() == 1)
                        || (!hasAsterisk && key == app->id())
                        || QRegularExpression(QRegularExpression::wildcardToRegularExpression(key)).match(app->id()).hasMatch()) {
                    containerId = value;
                    break;
                }
            }
        }

        if (d->containerSelectionFunction.isCallable()) {
            QJSValueList args = { QJSValue(app->id()), QJSValue(containerId) };
            containerId = d->containerSelectionFunction.call(args).toString();
        }

        if (!ContainerFactory::instance()->manager(containerId))
            throw Exception("No ContainerManager found for container: %1").arg(containerId);
    }
    bool attachRuntime = false;

    if (!runtime) {
        if (!inProcess) {
		
			// 快启动模式，可以理解为预先启动几个（有上限）的Runtime+Contianer，预先加载了一些资源。
            if (QuickLauncher::instance()) {
              // 该情况比较特殊，不考虑。
            }

            if (!container) {
				// 创建Container
                container = ContainerFactory::instance()->create(containerId, app, stdioRedirections,
                                                                 debugEnvironmentVariables, debugWrapperCommand);
            } else {
                container->setApplication(app);
            }
            if (!container) {
                qCCritical(LogSystem) << "ERROR: Couldn't create Container for Application (" << app->id() <<")!";
                return false;
            }
            if (runtime)
                attachRuntime = true;
        }
        if (!runtime)
            runtime = RuntimeFactory::instance()->create(container, app);

        if (runtime)
            emit internalSignals.newRuntimeCreated(runtime);
    }

    if (!runtime) {
        qCCritical(LogSystem) << "ERROR: Couldn't create Runtime for Application (" << app->id() <<")!";
        return false;
    }

	// 绑定信号与槽。监听应用状态变化。
    connect(runtime, &AbstractRuntime::stateChanged, this, [this, app](Am::RunState newRuntimeState) {
        app->setRunState(newRuntimeState);
        emit applicationRunStateChanged(app->id(), newRuntimeState);
        emitDataChanged(app, QVector<int> { IsRunning, IsStartingUp, IsShuttingDown });
    });

	// 加载应用入口。
    if (!documentUrl.isNull())
        runtime->openDocument(documentUrl, documentMimeType);
    else if (!app->documentUrl().isNull())
        runtime->openDocument(app->documentUrl(), documentMimeType);

	
    if (inProcess) {
		// 如果是单进程模式（以线程方式启动应用）
        bool ok = runtime->start();
        if (ok)
            emitActivated(app);
        else
            runtime->deleteLater();
        return ok;
    } else {
        // We can only start the app when both the container and the windowmanager are ready.
        // Using a state-machine would be one option, but then we would need that state-machine
        // object plus the per-app state. Relying on 2 lambdas is the easier choice for now.

		// 多进程模式下，QTAM需要完成了Compositor初始化，才可以启动应用。
        auto doStartInContainer = [this, app, attachRuntime, runtime]() -> bool {
			// 首次启动应用默认走 runtime->start()
            bool successfullyStarted = attachRuntime ? runtime->attachApplicationToQuickLauncher(app)
                                                     : runtime->start();
            if (successfullyStarted)
                emitActivated(app);
            else
                runtime->deleteLater(); // ~Runtime() will clean app->nonAliased()->m_runtime

            return successfullyStarted;
        };

        auto tryStartInContainer = [container, doStartInContainer]() -> bool {
            if (container->isReady()) {
                // Since the container is already ready, start the app immediately
                return doStartInContainer();
            } else {
                // We postpone the starting of the application to a later point in time,
                // since the container is not ready yet
#  if defined(Q_CC_MSVC)
                qApp->connect(container, &AbstractContainer::ready, doStartInContainer); // MSVC cannot distinguish between static and non-static overloads in lambdas
# else
                connect(container, &AbstractContainer::ready, doStartInContainer);
#endif
                return true;
            }
        };

        if (isWindowManagerCompositorReady()) {
            return tryStartInContainer();
        } else {
            connect(this, &ApplicationManager::windowManagerCompositorReadyChanged, tryStartInContainer);
            return true;
        }
    }
}

上面的代码中，主要就是通过AppID获取应用对象（包含应用信息）、创建应用Runtime、创建应用Container（Context）、加载应用入口（比如QML文件）、调用RunTime启动应用。加载应用入口文件，实际上会调用QML引擎解析QML文件。这里主要关注RunTime如何将应用进程启动。
多进程默认情况下，走NativeRuntime。

// src\manager-lib\nativeruntime.cpp
bool NativeRuntime::start()
{
    // 首次启动时，状态为 Am::NotRunning
    switch (state()) {
    case Am::StartingUp:
    case Am::Running:
        return true;
    case Am::ShuttingDown:
        return false;
    case Am::NotRunning:
        break;
    }

	// 初始化OpenGL配置
    if (m_app)
        openGLConfig = m_app->info()->openGLConfiguration();
    if (openGLConfig.isEmpty())
        openGLConfig = manager()->systemOpenGLConfiguration();
    if (!openGLConfig.isEmpty())
        uiConfig.insert(qSL("opengl"), openGLConfig);
	
	// 获取Icon
    QString iconThemeName = manager()->iconThemeName();
    QStringList iconThemeSearchPaths = manager()->iconThemeSearchPaths();
    if (!iconThemeName.isEmpty())
        uiConfig.insert(qSL("iconThemeName"), iconThemeName);
    if (!iconThemeSearchPaths.isEmpty())
        uiConfig.insert(qSL("iconThemeSearchPaths"), iconThemeSearchPaths);

    QVariantMap config = {
        { qSL("logging"), loggingConfig },
        { qSL("baseDir"), QDir::currentPath() },
        { qSL("runtimeConfiguration"), configuration() },
        { qSL("securityToken"), qL1S(securityToken().toHex()) },
        { qSL("dbus"), dbusConfig }
    };

    if (!m_startedViaLauncher && !m_isQuickLauncher)
        config.insert(qSL("systemProperties"), systemProperties());
    if (!uiConfig.isEmpty())
        config.insert(qSL("ui"), uiConfig);

    QMap<QString, QString> env = {
        { qSL("QT_QPA_PLATFORM"), qSL("wayland") },
        { qSL("QT_IM_MODULE"), QString() },     // Applications should use wayland text input
        { qSL("QT_SCALE_FACTOR"), QString() },  // do not scale wayland clients
        { qSL("AM_CONFIG"), QString::fromUtf8(QtYaml::yamlFromVariantDocuments({ config })) },
        { qSL("QT_WAYLAND_SHELL_INTEGRATION"), qSL("xdg-shell")},
    };

	// 判断DLT（一种日志服务）是否开启。
    if (!Logging::isDltEnabled()) {
        // sadly we still need this, since we need to disable DLT as soon as possible
        env.insert(qSL("AM_NO_DLT_LOGGING"), qSL("1"));
    }


	// 获取环境变量（QT也有自己的一套环境变量）
    for (QMapIterator<QString, QVariant> it(configuration().value(qSL("environmentVariables")).toMap()); it.hasNext(); ) {
        it.next();
        if (!it.key().isEmpty())
            env.insert(it.key(), it.value().toString());
    }


    QStringList args;

    if (!m_startedViaLauncher) {
        args.append(variantToStringList(m_app->runtimeParameters().value(qSL("arguments"))));
		// 获取启动参数
        if (!m_document.isNull())
            args << qSL("--start-argument") << m_document;
		// 如果DLT没有开启的话
        if (!Logging::isDltEnabled())
            args << qSL("--no-dlt-logging");
    } else {
        if (m_isQuickLauncher)
            args << qSL("--quicklaunch");

        args << QString::fromLocal8Bit(ProcessTitle::placeholderArgument);    // must be last argument
    }

    emit signaler()->aboutToStart(this);
	// 调用Container，启动应用
    m_process = m_container->start(args, env, config);

    if (!m_process)
        return false;
	
	// 绑定信号，获得应用状态。
    QObject::connect(m_process, &AbstractContainerProcess::started,
                     this, &NativeRuntime::onProcessStarted);
    QObject::connect(m_process, &AbstractContainerProcess::errorOccured,
                     this, &NativeRuntime::onProcessError);
    QObject::connect(m_process, &AbstractContainerProcess::finished,
                     this, &NativeRuntime::onProcessFinished);
	
	// 到此默认认为应用已经启动。通过上面的三个绑定信号操作，可以更新状态。
    setState(Am::StartingUp);
    return true;
}

Runtime调用Container启动应用，默认情况下走ProcessContainer，这里会调用QProcess创建出应用进程。

// src\manager-lib\processcontainer.cpp
AbstractContainerProcess *ProcessContainer::start(const QStringList &arguments,
                                                  const QMap<QString, QString> &runtimeEnvironment,
                                                  const QVariantMap &amConfig)
{
	// m_program 是 Appman 这个二进制程序。是QTAM提供的用来加载应用的程序。
    if (!QFile::exists(m_program)) {
        qCWarning(LogSystem) << "Program" << m_program << "not found";
        return nullptr;
    }

    // 创建HostProcess，通过它创建出进程。
    HostProcess *process = new HostProcess();
    process->setWorkingDirectory(m_baseDirectory);
    process->setProcessEnvironment(penv);
    process->setStopBeforeExec(configuration().value(qSL("stopBeforeExec")).toBool());
    process->setStdioRedirections(m_stdioRedirections);

    QString command = m_program;
    QStringList args = arguments;

    if (!m_debugWrapperCommand.isEmpty()) {
        auto cmd = DebugWrapper::substituteCommand(m_debugWrapperCommand, m_program, arguments);

        command = cmd.takeFirst();
        args = cmd;
    }
    qCDebug(LogSystem) << "Running command:" << command << "arguments:" << args;
	
	// 实际上，第一个参数是Appman这个二进程程序的路径。
	// 例如： /system/bin/Appman
	// 调用HostProcess启动应用
    process->start(command, args);
    m_process = process;

    setControlGroup(configuration().value(qSL("defaultControlGroup")).toString());
    return process;
}

// src\manager-lib\processcontainer.cpp
void HostProcess::start(const QString &program, const QStringList &arguments)
{
	// 绑定各种状态信号
    connect(m_process, &QProcess::started, this, [this]() {
         // we to cache the pid in order to have it available after the process crashed
        m_pid = m_process->processId();
        emit started();
    });
    connect(m_process, &QProcess::errorOccurred, this, [this](QProcess::ProcessError error) {
        emit errorOccured(static_cast<Am::ProcessError>(error));
    });
    connect(m_process, static_cast<void (QProcess::*)(int,QProcess::ExitStatus)>(&QProcess::finished),
            this, [this](int exitCode, QProcess::ExitStatus exitStatus) {
        emit finished(exitCode, static_cast<Am::ExitStatus>(exitStatus));
    });
    connect(m_process, &QProcess::stateChanged,
            this, [this](QProcess::ProcessState newState) {
        emit stateChanged(static_cast<Am::RunState>(newState));
    });

#if defined(Q_OS_UNIX)
    // make sure that the redirection fds do not have a close-on-exec flag, since we need them
    // in the child process.
    for (int fd : qAsConst(m_stdioRedirections)) {
        if (fd < 0)
            continue;
        int flags = fcntl(fd, F_GETFD);
        if (flags & FD_CLOEXEC)
            fcntl(fd, F_SETFD, flags & ~FD_CLOEXEC);
    }
#endif
	
	//  QProcess *m_process;
	//  调用QProcess的start函数，这个类会根据入参启动进程。
	//  参数Program是 Appman这个二进制程序。
	//  参数arguments作为入参，传给Appman这个二进制程序。
	//  到此应用进程就启动起来了。
    m_process->start(program, arguments);

#if defined(Q_OS_UNIX)
    // we are forked now and the child process has received a copy of all redirected fds
    // now it's time to close our fds, since we don't need them anymore (plus we would block
    // the tty where they originated from)
    for (int fd : qAsConst(m_stdioRedirections)) {
        if (fd >= 0)
            ::close(fd);
    }
#endif
}