Make startplasma more flexible so it can be leveraged by plasma mobile

Summary:
Allows specifying the shell through an environment variable.
Allows forwarding command line arguments to kwin_wayland, since the arguments we
use on plasma phone are slightly different.

Test Plan: Builds, still starts

Reviewers: #plasma, bshah, mart, davidedmundson

Reviewed By: #plasma, bshah, mart, davidedmundson

Subscribers: broulik, mart, alexeymin, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D25750

shell/main.cpp

@@ -90,7 +90,7 @@ int main(int argc, char *argv[])
 
     KSharedConfig::Ptr startupConf = KSharedConfig::openConfig(QStringLiteral("plasmashellrc"));
     KConfigGroup startupConfGroup(startupConf, "Shell");
-    const QString defaultShell = startupConfGroup.readEntry("ShellPackage", "org.kde.plasma.desktop");
+    const QString defaultShell = startupConfGroup.readEntry("ShellPackage", qEnvironmentVariable("PLASMA_DEFAULT_SHELL", "org.kde.plasma.desktop"));
 
     bool replace = false;
     {

startkde/startplasma-wayland.cpp

@@ -23,7 +23,7 @@
 #include <QDBusConnection>
 #include <QDBusInterface>
 
-int main(int /*argc*/, char** /*argv*/)
+int main(int argc, char** argv)
 {
     createConfigDirectory();
     setupCursor(true);
@@ -82,7 +82,16 @@ int main(int /*argc*/, char** /*argv*/)
         return 1;
     }
 
-    runSync(QStringLiteral(KWIN_WAYLAND_BIN_PATH), { QStringLiteral("--xwayland"), QStringLiteral("--libinput"), QStringLiteral("--exit-with-session=" CMAKE_INSTALL_FULL_LIBEXECDIR "/startplasma-waylandsession") });
+    QStringList args;
+    if (argc > 1) {
+        args.reserve(argc);
+        for (int i = 1; i < argc; ++i) {
+            args << QString::fromLocal8Bit(argv[i]);
+        }
+    } else {
+        args = QStringList { QStringLiteral("--xwayland"), QStringLiteral("--libinput"), QStringLiteral("--exit-with-session=" CMAKE_INSTALL_FULL_LIBEXECDIR "/startplasma-waylandsession") };
+    }
+    runSync(QStringLiteral(KWIN_WAYLAND_BIN_PATH), args);
 
     out << "startplasmacompositor: Shutting down...\n";
     cleanupPlasmaEnvironment();