[startkde] Move ksplash loading to handle new kwin_wayland

KSplash is changed to read which theme to use directly. It's already
linking config and it already loads the default shared config implicitly
so we weren't saving anything having it done by the launcher.

On X11 ksplash is still managed by startplasma-x11 as we can do it
straight away.

For wayland we need to wait till kwin is up so this is done either by
plasma-session or systemd. For systemd the unit is started explicitly so
we can parse the config file, but after the target starting kwin is
started so that the "After=" line works correctly.

ksplash/ksplashqml/CMakeLists.txt

@@ -23,3 +23,4 @@ target_link_libraries(ksplashqml
 install(TARGETS ksplashqml ${KDE_INSTALL_TARGETS_DEFAULT_ARGS})
 install(FILES org.kde.KSplash.xml DESTINATION ${KDE_INSTALL_DBUSINTERFACEDIR})
 
+ecm_install_configured_files(INPUT plasma-ksplash.service.in @ONLY DESTINATION  ${SYSTEMD_USER_UNIT_INSTALL_DIR})

ksplash/ksplashqml/plasma-ksplash.service.in

@@ -0,0 +1,10 @@
+[Unit]
+Description=Splash screen shown during boot
+PartOf=graphical-session.target
+After=plasma-kwin_wayland.service
+
+[Service]
+ExecStart=@CMAKE_INSTALL_FULL_BINDIR@/ksplashqml
+Type=oneshot
+Slice=background.slice
+TimeoutSec=40sec

ksplash/ksplashqml/splashapp.cpp

@@ -18,6 +18,10 @@
 
 #include <KQuickAddons/QtQuickSettings>
 #include <KWindowSystem>
+
+#include <KConfigGroup>
+#include <KSharedConfig>
+
 #include <LayerShellQt/Shell>
 
 #define TEST_STEP_INTERVAL 2000
@@ -53,6 +57,12 @@ SplashApp::SplashApp(int &argc, char **argv)
     m_testing = parser.isSet(QStringLiteral("test"));
     m_window = parser.isSet(QStringLiteral("window"));
     m_theme = parser.positionalArguments().value(0);
+    if (m_theme.isEmpty()) {
+        KConfigGroup ksplashCfg = KSharedConfig::openConfig()->group("KSplash");
+        if (ksplashCfg.readEntry("Engine", QStringLiteral("KSplashQML")) == QLatin1String("KSplashQML")) {
+            m_theme = ksplashCfg.readEntry("Theme", QStringLiteral("Breeze"));
+        }
+    }
 
     QDBusConnection dbus = QDBusConnection::sessionBus();
     dbus.registerObject(QStringLiteral("/KSplash"), this, QDBusConnection::ExportScriptableSlots);

startkde/plasma-session/startup.cpp

@@ -174,7 +174,7 @@ Startup::Startup(QObject *parent)
         // the splashscreen and progress indicator
         KConfigGroup ksplashCfg = cfg.group("KSplash");
         if (ksplashCfg.readEntry("Engine", QStringLiteral("KSplashQML")) == QLatin1String("KSplashQML")) {
-            QProcess::startDetached(QStringLiteral("ksplashqml"), {ksplashCfg.readEntry("Theme", QStringLiteral("Breeze"))});
+            QProcess::startDetached(QStringLiteral("ksplashqml"), {});
         }
         // FIXME 1: this code path is missing setupFontDpi() after X has started. Move to kcminit?
         // FIXME 2: the systemd path has no concept of kslpash

startkde/startplasma.cpp

@@ -540,6 +540,21 @@ bool useSystemdBoot()
     return hasSystemdService(QStringLiteral("xdg-desktop-autostart.target"));
 }
 
+void startKSplashViaSystemd()
+{
+    const KConfig cfg(QStringLiteral("ksplashrc"));
+    // the splashscreen and progress indicator
+    KConfigGroup ksplashCfg = cfg.group("KSplash");
+    if (ksplashCfg.readEntry("Engine", QStringLiteral("KSplashQML")) == QLatin1String("KSplashQML")) {
+        auto msg = QDBusMessage::createMethodCall(QStringLiteral("org.freedesktop.systemd1"),
+                                                  QStringLiteral("/org/freedesktop/systemd1"),
+                                                  QStringLiteral("org.freedesktop.systemd1.Manager"),
+                                                  QStringLiteral("StartUnit"));
+        msg << QStringLiteral("plasma-ksplash.service") << QStringLiteral("fail");
+        QDBusReply<QDBusObjectPath> reply = QDBusConnection::sessionBus().call(msg);
+    }
+}
+
 bool startPlasmaSession(bool wayland)
 {
     resetSystemdFailedUnits();
@@ -628,6 +643,9 @@ bool startPlasmaSession(bool wayland)
         } else {
             playStartupSound(&e);
         }
+        if (wayland) {
+            startKSplashViaSystemd();
+        }
     }
     if (rc) {
         QObject::connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit, &e, &QEventLoop::quit);