[wayland] Introduce an additional --exit-with-session command line arg

This is similar to the applications to start. That is the value of the
command line argument is interpreted as a command to start.
The difference is that when this application exits, KWin will also quit.
The argument is so to say interpreted as a session.

Reviewed-By: Bhushan Shah

main_wayland.cpp

@@ -214,6 +214,14 @@ void ApplicationWayland::continueStartupWithX()
     }
 
     m_environment.insert(QStringLiteral("DISPLAY"), QString::fromUtf8(qgetenv("DISPLAY")));
+    // start session
+    if (!m_sessionArgument.isEmpty()) {
+        QProcess *p = new QProcess(this);
+        p->setProcessEnvironment(m_environment);
+        auto finishedSignal = static_cast<void (QProcess::*)(int, QProcess::ExitStatus)>(&QProcess::finished);
+        connect(p, finishedSignal, this, &ApplicationWayland::quit);
+        p->start(m_sessionArgument);
+    }
     // start the applications passed to us as command line arguments
     if (!m_applicationsToStart.isEmpty()) {
         for (const QString &application: m_applicationsToStart) {
@@ -513,6 +521,11 @@ int main(int argc, char * argv[])
                                           i18n("Starts the session in locked mode."));
     parser.addOption(screenLockerOption);
 
+    QCommandLineOption exitWithSessionOption(QStringLiteral("exit-with-session"),
+                                             i18n("Exit after the session application, which is started by KWin, closed."),
+                                             QStringLiteral("/path/to/session"));
+    parser.addOption(exitWithSessionOption);
+
     parser.addPositionalArgument(QStringLiteral("applications"),
                                  i18n("Applications to start once Wayland and Xwayland server are started"),
                                  QStringLiteral("[/path/to/application...]"));
@@ -527,6 +540,10 @@ int main(int argc, char * argv[])
         return 0;
     }
 
+    if (parser.isSet(exitWithSessionOption)) {
+        a.setSessionArgument(parser.value(exitWithSessionOption));
+    }
+
 #if HAVE_INPUT
     KWin::Application::setUseLibinput(parser.isSet(libinputOption));
 #endif

main_wayland.h

@@ -46,6 +46,9 @@ public:
     void setProcessStartupEnvironment(const QProcessEnvironment &environment) {
         m_environment = environment;
     }
+    void setSessionArgument(const QString &session) {
+        m_sessionArgument = session;
+    }
 
     QProcessEnvironment processStartupEnvironment() const override {
         return m_environment;
@@ -68,6 +71,7 @@ private:
     QProcess *m_xwaylandProcess = nullptr;
     QMetaObject::Connection m_xwaylandFailConnection;
     QProcessEnvironment m_environment;
+    QString m_sessionArgument;
 };
 
 }