diff --git a/autotests/integration/activation_test.cpp b/autotests/integration/activation_test.cpp
index 949c100fa9..e61ad435df 100644
--- a/autotests/integration/activation_test.cpp
+++ b/autotests/integration/activation_test.cpp
@@ -49,9 +49,8 @@ void ActivationTest::initTestCase()
     qRegisterMetaType<Window *>();
 
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
@@ -524,7 +523,6 @@ void ActivationTest::stackScreensHorizontally()
     QMetaObject::invokeMethod(kwinApp()->outputBackend(),
                               "setVirtualOutputs",
                               Qt::DirectConnection,
-                              Q_ARG(int, screenGeometries.count()),
                               Q_ARG(QVector<QRect>, screenGeometries),
                               Q_ARG(QVector<int>, screenScales));
 }
@@ -547,7 +545,6 @@ void ActivationTest::stackScreensVertically()
     QMetaObject::invokeMethod(kwinApp()->outputBackend(),
                               "setVirtualOutputs",
                               Qt::DirectConnection,
-                              Q_ARG(int, screenGeometries.count()),
                               Q_ARG(QVector<QRect>, screenGeometries),
                               Q_ARG(QVector<int>, screenScales));
 }
diff --git a/autotests/integration/activities_test.cpp b/autotests/integration/activities_test.cpp
index f8df5b62a7..bef20c35cb 100644
--- a/autotests/integration/activities_test.cpp
+++ b/autotests/integration/activities_test.cpp
@@ -49,9 +49,8 @@ void ActivitiesTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::Deleted *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setUseKActivities(true);
     kwinApp()->start();
diff --git a/autotests/integration/dbus_interface_test.cpp b/autotests/integration/dbus_interface_test.cpp
index 9ae6ca9966..9755d4e262 100644
--- a/autotests/integration/dbus_interface_test.cpp
+++ b/autotests/integration/dbus_interface_test.cpp
@@ -58,8 +58,8 @@ void TestDbusInterface::initTestCase()
     qRegisterMetaType<KWin::Window *>();
 
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/debug_console_test.cpp b/autotests/integration/debug_console_test.cpp
index 5048a259d3..93e5f1e95f 100644
--- a/autotests/integration/debug_console_test.cpp
+++ b/autotests/integration/debug_console_test.cpp
@@ -50,9 +50,8 @@ void DebugConsoleTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::InternalWindow *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/decoration_input_test.cpp b/autotests/integration/decoration_input_test.cpp
index 0a923777a0..83d9c747d4 100644
--- a/autotests/integration/decoration_input_test.cpp
+++ b/autotests/integration/decoration_input_test.cpp
@@ -121,9 +121,8 @@ void DecorationInputTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::InternalWindow *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     // change some options
     KSharedConfig::Ptr config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
diff --git a/autotests/integration/desktop_window_x11_test.cpp b/autotests/integration/desktop_window_x11_test.cpp
index c631605e96..ee550cb94e 100644
--- a/autotests/integration/desktop_window_x11_test.cpp
+++ b/autotests/integration/desktop_window_x11_test.cpp
@@ -44,9 +44,8 @@ void X11DesktopWindowTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::Deleted *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/dont_crash_aurorae_destroy_deco.cpp b/autotests/integration/dont_crash_aurorae_destroy_deco.cpp
index 8119bc944e..545ce56040 100644
--- a/autotests/integration/dont_crash_aurorae_destroy_deco.cpp
+++ b/autotests/integration/dont_crash_aurorae_destroy_deco.cpp
@@ -43,9 +43,8 @@ void DontCrashAuroraeDestroyDecoTest::initTestCase()
     qputenv("XDG_DATA_DIRS", QCoreApplication::applicationDirPath().toUtf8());
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     KSharedConfig::Ptr config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     config->group("org.kde.kdecoration2").writeEntry("library", "org.kde.kwin.aurorae");
diff --git a/autotests/integration/dont_crash_cancel_animation.cpp b/autotests/integration/dont_crash_cancel_animation.cpp
index 2ddce0680c..e051904506 100644
--- a/autotests/integration/dont_crash_cancel_animation.cpp
+++ b/autotests/integration/dont_crash_cancel_animation.cpp
@@ -45,8 +45,8 @@ void DontCrashCancelAnimationFromAnimationEndedTest::initTestCase()
 {
     qRegisterMetaType<KWin::Deleted *>();
     qRegisterMetaType<KWin::Window *>();
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
     kwinApp()->start();
     QVERIFY(Compositor::self());
     QSignalSpy compositorToggledSpy(Compositor::self(), &Compositor::compositingToggled);
diff --git a/autotests/integration/dont_crash_empty_deco.cpp b/autotests/integration/dont_crash_empty_deco.cpp
index e7d35bc141..1ec7285916 100644
--- a/autotests/integration/dont_crash_empty_deco.cpp
+++ b/autotests/integration/dont_crash_empty_deco.cpp
@@ -40,9 +40,8 @@ void DontCrashEmptyDecorationTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     // this test needs to enforce OpenGL compositing to get into the crashy condition
     qputenv("KWIN_COMPOSE", QByteArrayLiteral("O2"));
diff --git a/autotests/integration/dont_crash_glxgears.cpp b/autotests/integration/dont_crash_glxgears.cpp
index 1865237e19..cc1136f813 100644
--- a/autotests/integration/dont_crash_glxgears.cpp
+++ b/autotests/integration/dont_crash_glxgears.cpp
@@ -34,8 +34,8 @@ void DontCrashGlxgearsTest::initTestCase()
 {
     qRegisterMetaType<KWin::Deleted *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
 }
diff --git a/autotests/integration/dont_crash_no_border.cpp b/autotests/integration/dont_crash_no_border.cpp
index ec8399a2f5..18cd911b74 100644
--- a/autotests/integration/dont_crash_no_border.cpp
+++ b/autotests/integration/dont_crash_no_border.cpp
@@ -44,9 +44,8 @@ void DontCrashNoBorder::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     KSharedConfig::Ptr config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     config->group("org.kde.kdecoration2").writeEntry("NoPlugin", true);
diff --git a/autotests/integration/dont_crash_reinitialize_compositor.cpp b/autotests/integration/dont_crash_reinitialize_compositor.cpp
index e3a3422bac..6015bdc710 100644
--- a/autotests/integration/dont_crash_reinitialize_compositor.cpp
+++ b/autotests/integration/dont_crash_reinitialize_compositor.cpp
@@ -47,9 +47,8 @@ void DontCrashReinitializeCompositorTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::Deleted *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     KConfigGroup plugins(config, QStringLiteral("Plugins"));
diff --git a/autotests/integration/dont_crash_useractions_menu.cpp b/autotests/integration/dont_crash_useractions_menu.cpp
index 82130e9167..ab55a57937 100644
--- a/autotests/integration/dont_crash_useractions_menu.cpp
+++ b/autotests/integration/dont_crash_useractions_menu.cpp
@@ -47,9 +47,8 @@ void TestDontCrashUseractionsMenu::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     // force style to breeze as that's the one which triggered the crash
     QVERIFY(kwinApp()->setStyle(QStringLiteral("breeze")));
diff --git a/autotests/integration/effects/desktop_switching_animation_test.cpp b/autotests/integration/effects/desktop_switching_animation_test.cpp
index d65917d566..f34298c9ae 100644
--- a/autotests/integration/effects/desktop_switching_animation_test.cpp
+++ b/autotests/integration/effects/desktop_switching_animation_test.cpp
@@ -44,9 +44,8 @@ void DesktopSwitchingAnimationTest::initTestCase()
 
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     KConfigGroup plugins(config, QStringLiteral("Plugins"));
diff --git a/autotests/integration/effects/maximize_animation_test.cpp b/autotests/integration/effects/maximize_animation_test.cpp
index 3336d7e7f2..1aea0e111f 100644
--- a/autotests/integration/effects/maximize_animation_test.cpp
+++ b/autotests/integration/effects/maximize_animation_test.cpp
@@ -42,9 +42,8 @@ void MaximizeAnimationTest::initTestCase()
 
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     KConfigGroup plugins(config, QStringLiteral("Plugins"));
diff --git a/autotests/integration/effects/minimize_animation_test.cpp b/autotests/integration/effects/minimize_animation_test.cpp
index 6bd564499d..1dc47e6602 100644
--- a/autotests/integration/effects/minimize_animation_test.cpp
+++ b/autotests/integration/effects/minimize_animation_test.cpp
@@ -45,9 +45,8 @@ void MinimizeAnimationTest::initTestCase()
 
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     KConfigGroup plugins(config, QStringLiteral("Plugins"));
diff --git a/autotests/integration/effects/popup_open_close_animation_test.cpp b/autotests/integration/effects/popup_open_close_animation_test.cpp
index 872a2ee38c..2755cd6a54 100644
--- a/autotests/integration/effects/popup_open_close_animation_test.cpp
+++ b/autotests/integration/effects/popup_open_close_animation_test.cpp
@@ -51,9 +51,8 @@ void PopupOpenCloseAnimationTest::initTestCase()
     qRegisterMetaType<KWin::Deleted *>();
     qRegisterMetaType<KWin::InternalWindow *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     KConfigGroup plugins(config, QStringLiteral("Plugins"));
diff --git a/autotests/integration/effects/scripted_effects_test.cpp b/autotests/integration/effects/scripted_effects_test.cpp
index 8bea912c4f..f27e748c62 100644
--- a/autotests/integration/effects/scripted_effects_test.cpp
+++ b/autotests/integration/effects/scripted_effects_test.cpp
@@ -130,9 +130,8 @@ void ScriptedEffectsTest::initTestCase()
     qRegisterMetaType<KWin::Deleted *>();
     qRegisterMetaType<KWin::Effect *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 1));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024)));
 
     // disable all effects - we don't want to have it interact with the rendering
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
diff --git a/autotests/integration/effects/slidingpopups_test.cpp b/autotests/integration/effects/slidingpopups_test.cpp
index 0719b8b9e4..543973a345 100644
--- a/autotests/integration/effects/slidingpopups_test.cpp
+++ b/autotests/integration/effects/slidingpopups_test.cpp
@@ -52,9 +52,8 @@ void SlidingPopupsTest::initTestCase()
     qRegisterMetaType<KWin::Deleted *>();
     qRegisterMetaType<KWin::Effect *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     // disable all effects - we don't want to have it interact with the rendering
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
diff --git a/autotests/integration/effects/toplevel_open_close_animation_test.cpp b/autotests/integration/effects/toplevel_open_close_animation_test.cpp
index b91e44b257..c2cd3c85d5 100644
--- a/autotests/integration/effects/toplevel_open_close_animation_test.cpp
+++ b/autotests/integration/effects/toplevel_open_close_animation_test.cpp
@@ -47,9 +47,8 @@ void ToplevelOpenCloseAnimationTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::Deleted *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     KConfigGroup plugins(config, QStringLiteral("Plugins"));
diff --git a/autotests/integration/effects/translucency_test.cpp b/autotests/integration/effects/translucency_test.cpp
index 195e320d15..af4c0c34de 100644
--- a/autotests/integration/effects/translucency_test.cpp
+++ b/autotests/integration/effects/translucency_test.cpp
@@ -46,9 +46,8 @@ void TranslucencyTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::Effect *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     // disable all effects - we don't want to have it interact with the rendering
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
diff --git a/autotests/integration/effects/wobbly_shade_test.cpp b/autotests/integration/effects/wobbly_shade_test.cpp
index 214a0bfd8c..914a81a96b 100644
--- a/autotests/integration/effects/wobbly_shade_test.cpp
+++ b/autotests/integration/effects/wobbly_shade_test.cpp
@@ -47,9 +47,8 @@ void WobblyWindowsShadeTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::Effect *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     // disable all effects - we don't want to have it interact with the rendering
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
diff --git a/autotests/integration/generic_scene_opengl_test.cpp b/autotests/integration/generic_scene_opengl_test.cpp
index 6029c176a6..b61743dc38 100644
--- a/autotests/integration/generic_scene_opengl_test.cpp
+++ b/autotests/integration/generic_scene_opengl_test.cpp
@@ -40,9 +40,8 @@ void GenericSceneOpenGLTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     // disable all effects - we don't want to have it interact with the rendering
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
diff --git a/autotests/integration/globalshortcuts_test.cpp b/autotests/integration/globalshortcuts_test.cpp
index b56c35c898..93a9a64881 100644
--- a/autotests/integration/globalshortcuts_test.cpp
+++ b/autotests/integration/globalshortcuts_test.cpp
@@ -60,9 +60,8 @@ void GlobalShortcutsTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::InternalWindow *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
     qputenv("KWIN_XKB_DEFAULT_KEYMAP", "1");
diff --git a/autotests/integration/idle_inhibition_test.cpp b/autotests/integration/idle_inhibition_test.cpp
index c04e1f706b..43d7977324 100644
--- a/autotests/integration/idle_inhibition_test.cpp
+++ b/autotests/integration/idle_inhibition_test.cpp
@@ -40,9 +40,8 @@ void TestIdleInhibition::initTestCase()
     qRegisterMetaType<KWin::Window *>();
 
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/input_stacking_order.cpp b/autotests/integration/input_stacking_order.cpp
index b535ccfde0..7857b0c16b 100644
--- a/autotests/integration/input_stacking_order.cpp
+++ b/autotests/integration/input_stacking_order.cpp
@@ -50,9 +50,8 @@ void InputStackingOrderTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::Deleted *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/inputmethod_test.cpp b/autotests/integration/inputmethod_test.cpp
index 92c4a6e4da..0e8d9e3eeb 100644
--- a/autotests/integration/inputmethod_test.cpp
+++ b/autotests/integration/inputmethod_test.cpp
@@ -84,9 +84,8 @@ void InputMethodTest::initTestCase()
     qRegisterMetaType<KWayland::Client::Output *>();
 
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     static_cast<WaylandTestApplication *>(kwinApp())->setInputMethodServerToStart("internal");
     kwinApp()->start();
diff --git a/autotests/integration/internal_window.cpp b/autotests/integration/internal_window.cpp
index 687dc85af4..7e013a717d 100644
--- a/autotests/integration/internal_window.cpp
+++ b/autotests/integration/internal_window.cpp
@@ -174,9 +174,8 @@ void InternalWindowTest::initTestCase()
     qRegisterMetaType<KWin::Deleted *>();
     qRegisterMetaType<KWin::InternalWindow *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
 
     kwinApp()->start();
@@ -638,7 +637,6 @@ void InternalWindowTest::testPopup()
 void InternalWindowTest::testScale()
 {
     QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection,
-                              Q_ARG(int, 2),
                               Q_ARG(QVector<QRect>, QVector<QRect>({QRect(0, 0, 1280, 1024), QRect(1280 / 2, 0, 1280, 1024)})),
                               Q_ARG(QVector<int>, QVector<int>({2, 2})));
 
diff --git a/autotests/integration/keyboard_layout_test.cpp b/autotests/integration/keyboard_layout_test.cpp
index bdc0509848..d24c84448b 100644
--- a/autotests/integration/keyboard_layout_test.cpp
+++ b/autotests/integration/keyboard_layout_test.cpp
@@ -132,9 +132,8 @@ void KeyboardLayoutTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
     kwinApp()->setKxkbConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
diff --git a/autotests/integration/keymap_creation_failure_test.cpp b/autotests/integration/keymap_creation_failure_test.cpp
index 5709b74cc1..26464269e8 100644
--- a/autotests/integration/keymap_creation_failure_test.cpp
+++ b/autotests/integration/keymap_creation_failure_test.cpp
@@ -48,8 +48,8 @@ void KeymapCreationFailureTest::initTestCase()
 
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
     kwinApp()->setKxkbConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
diff --git a/autotests/integration/kwinbindings_test.cpp b/autotests/integration/kwinbindings_test.cpp
index 20968452c4..5a4440bcd2 100644
--- a/autotests/integration/kwinbindings_test.cpp
+++ b/autotests/integration/kwinbindings_test.cpp
@@ -46,8 +46,8 @@ void KWinBindingsTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
 
diff --git a/autotests/integration/layershellv1window_test.cpp b/autotests/integration/layershellv1window_test.cpp
index ac6318927e..8d247b371d 100644
--- a/autotests/integration/layershellv1window_test.cpp
+++ b/autotests/integration/layershellv1window_test.cpp
@@ -54,9 +54,8 @@ private Q_SLOTS:
 void LayerShellV1WindowTest::initTestCase()
 {
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/lockscreen.cpp b/autotests/integration/lockscreen.cpp
index c27b589ff7..793ebab0ee 100644
--- a/autotests/integration/lockscreen.cpp
+++ b/autotests/integration/lockscreen.cpp
@@ -178,9 +178,8 @@ void LockScreenTest::initTestCase()
     qRegisterMetaType<KWin::ElectricBorder>("ElectricBorder");
 
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     qputenv("KWIN_COMPOSE", QByteArrayLiteral("O2"));
     kwinApp()->start();
diff --git a/autotests/integration/maximize_test.cpp b/autotests/integration/maximize_test.cpp
index cdbc503b17..6db9f8252c 100644
--- a/autotests/integration/maximize_test.cpp
+++ b/autotests/integration/maximize_test.cpp
@@ -48,9 +48,8 @@ void TestMaximized::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
 
diff --git a/autotests/integration/modifier_only_shortcut_test.cpp b/autotests/integration/modifier_only_shortcut_test.cpp
index 30023b6c53..7823aee588 100644
--- a/autotests/integration/modifier_only_shortcut_test.cpp
+++ b/autotests/integration/modifier_only_shortcut_test.cpp
@@ -82,8 +82,8 @@ void Target::shortcut()
 void ModifierOnlyShortcutTest::initTestCase()
 {
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
     qputenv("KWIN_XKB_DEFAULT_KEYMAP", "1");
diff --git a/autotests/integration/move_resize_window_test.cpp b/autotests/integration/move_resize_window_test.cpp
index 19cec522d5..31bc49cc64 100644
--- a/autotests/integration/move_resize_window_test.cpp
+++ b/autotests/integration/move_resize_window_test.cpp
@@ -82,9 +82,8 @@ void MoveResizeWindowTest::initTestCase()
     qRegisterMetaType<KWin::Deleted *>();
     qRegisterMetaType<KWin::MaximizeMode>("MaximizeMode");
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 1));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024)));
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
     const auto outputs = workspace()->outputs();
diff --git a/autotests/integration/nightcolor_test.cpp b/autotests/integration/nightcolor_test.cpp
index 271ba0fa43..52dec18c0e 100644
--- a/autotests/integration/nightcolor_test.cpp
+++ b/autotests/integration/nightcolor_test.cpp
@@ -34,9 +34,8 @@ private Q_SLOTS:
 void NightColorTest::initTestCase()
 {
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
 
diff --git a/autotests/integration/no_global_shortcuts_test.cpp b/autotests/integration/no_global_shortcuts_test.cpp
index 72c7710243..ada09088f7 100644
--- a/autotests/integration/no_global_shortcuts_test.cpp
+++ b/autotests/integration/no_global_shortcuts_test.cpp
@@ -90,8 +90,8 @@ void NoGlobalShortcutsTest::initTestCase()
 {
     qRegisterMetaType<KWin::ElectricBorder>("ElectricBorder");
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName, KWin::WaylandServer::InitializationFlag::NoGlobalShortcuts));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
     qputenv("KWIN_XKB_DEFAULT_KEYMAP", "1");
diff --git a/autotests/integration/outputchanges_test.cpp b/autotests/integration/outputchanges_test.cpp
index d40f382f40..9ba023607c 100644
--- a/autotests/integration/outputchanges_test.cpp
+++ b/autotests/integration/outputchanges_test.cpp
@@ -50,9 +50,8 @@ void OutputChangesTest::initTestCase()
     qRegisterMetaType<Window *>();
 
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
@@ -64,7 +63,7 @@ void OutputChangesTest::initTestCase()
 
 void OutputChangesTest::init()
 {
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
     QVERIFY(Test::setupWaylandConnection());
 
     workspace()->setActiveOutput(QPoint(640, 512));
diff --git a/autotests/integration/placement_test.cpp b/autotests/integration/placement_test.cpp
index ace57574b6..b4fd2aa306 100644
--- a/autotests/integration/placement_test.cpp
+++ b/autotests/integration/placement_test.cpp
@@ -79,9 +79,8 @@ void TestPlacement::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
 
diff --git a/autotests/integration/plasma_surface_test.cpp b/autotests/integration/plasma_surface_test.cpp
index fc8653d15f..b70564b9f9 100644
--- a/autotests/integration/plasma_surface_test.cpp
+++ b/autotests/integration/plasma_surface_test.cpp
@@ -60,9 +60,8 @@ void PlasmaSurfaceTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 1));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
@@ -197,7 +196,6 @@ void PlasmaSurfaceTest::testOSDPlacement()
     const QVector<QRect> geometries{QRect(0, 0, 1280, 1024), QRect(1280, 0, 1280, 1024)};
     QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs",
                               Qt::DirectConnection,
-                              Q_ARG(int, 2),
                               Q_ARG(QVector<QRect>, geometries));
     const auto outputs = workspace()->outputs();
     QCOMPARE(outputs.count(), 2);
diff --git a/autotests/integration/plasmawindow_test.cpp b/autotests/integration/plasmawindow_test.cpp
index d6b868c166..087646743c 100644
--- a/autotests/integration/plasmawindow_test.cpp
+++ b/autotests/integration/plasmawindow_test.cpp
@@ -58,9 +58,8 @@ void PlasmaWindowTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/platformcursor.cpp b/autotests/integration/platformcursor.cpp
index 5d869320e9..552f8b5193 100644
--- a/autotests/integration/platformcursor.cpp
+++ b/autotests/integration/platformcursor.cpp
@@ -28,9 +28,8 @@ private Q_SLOTS:
 void PlatformCursorTest::initTestCase()
 {
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/pointer_constraints_test.cpp b/autotests/integration/pointer_constraints_test.cpp
index da9bdf1d6c..f9cd920d2b 100644
--- a/autotests/integration/pointer_constraints_test.cpp
+++ b/autotests/integration/pointer_constraints_test.cpp
@@ -58,9 +58,8 @@ void TestPointerConstraints::initTestCase()
     qRegisterMetaType<PointerFunc>();
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     // set custom config which disables the OnScreenNotification
     KSharedConfig::Ptr config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
diff --git a/autotests/integration/pointer_input.cpp b/autotests/integration/pointer_input.cpp
index d61b68db82..5066b25189 100644
--- a/autotests/integration/pointer_input.cpp
+++ b/autotests/integration/pointer_input.cpp
@@ -134,9 +134,8 @@ void PointerInputTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::Deleted *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
 
@@ -378,7 +377,6 @@ void PointerInputTest::testUpdateFocusAfterScreenChange()
     // now let's remove the screen containing the cursor
     QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs",
                               Qt::DirectConnection,
-                              Q_ARG(int, 1),
                               Q_ARG(QVector<QRect>, QVector<QRect>{QRect(0, 0, 1280, 1024)}));
     QCOMPARE(workspace()->outputs().count(), 1);
 
@@ -590,7 +588,7 @@ void PointerInputTest::testModifierClickUnrestrictedFullscreenMove()
 {
     // this test ensures that Meta+mouse button press triggers unrestricted move for fullscreen windows
     if (workspace()->outputs().size() < 2) {
-        QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+        QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
     }
 
     // first modify the config for this run
@@ -1564,10 +1562,7 @@ void PointerInputTest::testConfineToScreenGeometry()
         QRect(1280, 0, 1280, 1024),
         QRect(2560, 0, 1280, 1024),
         QRect(1280, 1024, 1280, 1024)};
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs",
-                              Qt::DirectConnection,
-                              Q_ARG(int, geometries.count()),
-                              Q_ARG(QVector<QRect>, geometries));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, geometries));
 
     const auto outputs = workspace()->outputs();
     QCOMPARE(outputs.count(), geometries.count());
diff --git a/autotests/integration/quick_tiling_test.cpp b/autotests/integration/quick_tiling_test.cpp
index edcf3248a9..efbdfe2444 100644
--- a/autotests/integration/quick_tiling_test.cpp
+++ b/autotests/integration/quick_tiling_test.cpp
@@ -83,9 +83,8 @@ void QuickTilingTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::MaximizeMode>("MaximizeMode");
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     // set custom config which disables the Outline
     KSharedConfig::Ptr config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
diff --git a/autotests/integration/screen_changes_test.cpp b/autotests/integration/screen_changes_test.cpp
index 92de7dda4b..652bcb4298 100644
--- a/autotests/integration/screen_changes_test.cpp
+++ b/autotests/integration/screen_changes_test.cpp
@@ -36,9 +36,8 @@ private Q_SLOTS:
 void ScreenChangesTest::initTestCase()
 {
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 1));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
@@ -85,7 +84,6 @@ void ScreenChangesTest::testScreenAddRemove()
     const QVector<QRect> geometries{QRect(0, 0, 1280, 1024), QRect(1280, 0, 1280, 1024)};
     QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs",
                               Qt::DirectConnection,
-                              Q_ARG(int, 2),
                               Q_ARG(QVector<QRect>, geometries));
     auto outputs = workspace()->outputs();
     QCOMPARE(outputs.count(), 2);
@@ -152,7 +150,6 @@ void ScreenChangesTest::testScreenAddRemove()
     const QVector<QRect> geometries2{QRect(0, 0, 1280, 1024)};
     QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs",
                               Qt::DirectConnection,
-                              Q_ARG(int, 1),
                               Q_ARG(QVector<QRect>, geometries2));
     outputs = workspace()->outputs();
     QCOMPARE(outputs.count(), 1);
diff --git a/autotests/integration/screenedge_client_show_test.cpp b/autotests/integration/screenedge_client_show_test.cpp
index ffd1a60273..0d9bf3f278 100644
--- a/autotests/integration/screenedge_client_show_test.cpp
+++ b/autotests/integration/screenedge_client_show_test.cpp
@@ -43,9 +43,8 @@ void ScreenEdgeClientShowTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::Deleted *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     // set custom config which disable touch edge
     KSharedConfig::Ptr config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
diff --git a/autotests/integration/screenedges_test.cpp b/autotests/integration/screenedges_test.cpp
index 20cb29937f..9e59154fbd 100644
--- a/autotests/integration/screenedges_test.cpp
+++ b/autotests/integration/screenedges_test.cpp
@@ -70,9 +70,8 @@ void ScreenEdgesTest::initTestCase()
     qRegisterMetaType<KWin::ElectricBorder>("ElectricBorder");
 
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 1));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024)));
 
     // Disable effects, in particular present windows, which reserves a screen edge.
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
diff --git a/autotests/integration/screens_test.cpp b/autotests/integration/screens_test.cpp
index cc1a8d0326..57e99907ee 100644
--- a/autotests/integration/screens_test.cpp
+++ b/autotests/integration/screens_test.cpp
@@ -43,9 +43,8 @@ void ScreensTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
 
@@ -85,7 +84,7 @@ void ScreensTest::cleanup()
     workspace()->slotReconfigure();
 
     // Reset the screen layout of the test environment.
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 }
 
 void ScreensTest::testCurrent_data()
@@ -132,8 +131,7 @@ void ScreensTest::testCurrentWithFollowsMouse()
     workspace()->slotReconfigure();
 
     QFETCH(QVector<QRect>, geometries);
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection,
-                              Q_ARG(int, geometries.count()), Q_ARG(QVector<QRect>, geometries));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, geometries));
 
     QFETCH(QPoint, cursorPos);
     KWin::Cursors::self()->mouse()->setPos(cursorPos);
@@ -158,8 +156,7 @@ void ScreensTest::testCurrentPoint_data()
 void ScreensTest::testCurrentPoint()
 {
     QFETCH(QVector<QRect>, geometries);
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection,
-                              Q_ARG(int, geometries.count()), Q_ARG(QVector<QRect>, geometries));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, geometries));
 
     // Disable "active screen follows mouse"
     auto group = kwinApp()->config()->group("Windows");
diff --git a/autotests/integration/scripting/minimizeall_test.cpp b/autotests/integration/scripting/minimizeall_test.cpp
index 1ebc0d7bb4..a49062f309 100644
--- a/autotests/integration/scripting/minimizeall_test.cpp
+++ b/autotests/integration/scripting/minimizeall_test.cpp
@@ -46,9 +46,8 @@ void MinimizeAllScriptTest::initTestCase()
     qRegisterMetaType<Window *>();
 
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/scripting/screenedge_test.cpp b/autotests/integration/scripting/screenedge_test.cpp
index 0378630113..5f1c28dd6a 100644
--- a/autotests/integration/scripting/screenedge_test.cpp
+++ b/autotests/integration/scripting/screenedge_test.cpp
@@ -49,9 +49,8 @@ private:
 void ScreenEdgeTest::initTestCase()
 {
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 1));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024)));
 
     // empty config to have defaults
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
diff --git a/autotests/integration/shade_test.cpp b/autotests/integration/shade_test.cpp
index 7fdb26ddac..23111b43c6 100644
--- a/autotests/integration/shade_test.cpp
+++ b/autotests/integration/shade_test.cpp
@@ -39,9 +39,8 @@ void ShadeTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/showing_desktop_test.cpp b/autotests/integration/showing_desktop_test.cpp
index 091f8841d8..5e4ec63c6e 100644
--- a/autotests/integration/showing_desktop_test.cpp
+++ b/autotests/integration/showing_desktop_test.cpp
@@ -36,8 +36,8 @@ void ShowingDesktopTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/stacking_order_test.cpp b/autotests/integration/stacking_order_test.cpp
index e6297fb804..19d3810191 100644
--- a/autotests/integration/stacking_order_test.cpp
+++ b/autotests/integration/stacking_order_test.cpp
@@ -56,8 +56,8 @@ void StackingOrderTest::initTestCase()
     qRegisterMetaType<KWin::Deleted *>();
 
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
 
diff --git a/autotests/integration/struts_test.cpp b/autotests/integration/struts_test.cpp
index be3b176015..0f9ac26fd3 100644
--- a/autotests/integration/struts_test.cpp
+++ b/autotests/integration/struts_test.cpp
@@ -62,9 +62,8 @@ void StrutsTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::Deleted *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     // set custom config which disables the Outline
     KSharedConfig::Ptr config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
@@ -680,7 +679,6 @@ void StrutsTest::test363804()
     const QVector<QRect> geometries{QRect(0, 0, 1920, 1080), QRect(554, 1080, 1366, 768)};
     QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs",
                               Qt::DirectConnection,
-                              Q_ARG(int, 2),
                               Q_ARG(QVector<QRect>, geometries));
     QCOMPARE(workspace()->geometry(), QRect(0, 0, 1920, 1848));
 
@@ -762,7 +760,6 @@ void StrutsTest::testLeftScreenSmallerBottomAligned()
     const QVector<QRect> geometries{QRect(0, 282, 1366, 768), QRect(1366, 0, 1680, 1050)};
     QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs",
                               Qt::DirectConnection,
-                              Q_ARG(int, 2),
                               Q_ARG(QVector<QRect>, geometries));
     QCOMPARE(workspace()->geometry(), QRect(0, 0, 3046, 1050));
 
@@ -876,7 +873,6 @@ void StrutsTest::testWindowMoveWithPanelBetweenScreens()
     const QVector<QRect> geometries{QRect(0, 282, 1366, 768), QRect(1366, 0, 1680, 1050)};
     QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs",
                               Qt::DirectConnection,
-                              Q_ARG(int, 2),
                               Q_ARG(QVector<QRect>, geometries));
     QCOMPARE(workspace()->geometry(), QRect(0, 0, 3046, 1050));
 
diff --git a/autotests/integration/tabbox_test.cpp b/autotests/integration/tabbox_test.cpp
index f838930fab..de54759170 100644
--- a/autotests/integration/tabbox_test.cpp
+++ b/autotests/integration/tabbox_test.cpp
@@ -42,9 +42,8 @@ void TabBoxTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     KSharedConfigPtr c = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     c->group("TabBox").writeEntry("ShowTabBox", false);
diff --git a/autotests/integration/test_virtualkeyboard_dbus.cpp b/autotests/integration/test_virtualkeyboard_dbus.cpp
index b689fb8418..e2b07a345f 100644
--- a/autotests/integration/test_virtualkeyboard_dbus.cpp
+++ b/autotests/integration/test_virtualkeyboard_dbus.cpp
@@ -44,9 +44,8 @@ void VirtualKeyboardDBusTest::initTestCase()
 {
     QDBusConnection::sessionBus().registerService(QStringLiteral("org.kde.kwin.testvirtualkeyboard"));
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     static_cast<WaylandTestApplication *>(kwinApp())->setInputMethodServerToStart("internal");
     kwinApp()->start();
diff --git a/autotests/integration/touch_input_test.cpp b/autotests/integration/touch_input_test.cpp
index 84b8e80816..cfb13c6356 100644
--- a/autotests/integration/touch_input_test.cpp
+++ b/autotests/integration/touch_input_test.cpp
@@ -54,9 +54,8 @@ void TouchInputTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/transient_placement.cpp b/autotests/integration/transient_placement.cpp
index 3b9387102d..2309173793 100644
--- a/autotests/integration/transient_placement.cpp
+++ b/autotests/integration/transient_placement.cpp
@@ -62,9 +62,8 @@ void TransientPlacementTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/virtual_desktop_test.cpp b/autotests/integration/virtual_desktop_test.cpp
index 728bd9a8e1..ca9497fe7d 100644
--- a/autotests/integration/virtual_desktop_test.cpp
+++ b/autotests/integration/virtual_desktop_test.cpp
@@ -39,8 +39,8 @@ void VirtualDesktopTest::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
     qputenv("KWIN_XKB_DEFAULT_KEYMAP", "1");
diff --git a/autotests/integration/window_rules_test.cpp b/autotests/integration/window_rules_test.cpp
index b2b43721f3..2a7fc520ad 100644
--- a/autotests/integration/window_rules_test.cpp
+++ b/autotests/integration/window_rules_test.cpp
@@ -43,9 +43,8 @@ void WindowRuleTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::Deleted *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/window_selection_test.cpp b/autotests/integration/window_selection_test.cpp
index d94c9d5b0b..05846b064d 100644
--- a/autotests/integration/window_selection_test.cpp
+++ b/autotests/integration/window_selection_test.cpp
@@ -54,9 +54,8 @@ void TestWindowSelection::initTestCase()
 {
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
     qputenv("XKB_DEFAULT_RULES", "evdev");
 
     kwinApp()->start();
diff --git a/autotests/integration/x11_window_test.cpp b/autotests/integration/x11_window_test.cpp
index 4d4f570233..66379ee638 100644
--- a/autotests/integration/x11_window_test.cpp
+++ b/autotests/integration/x11_window_test.cpp
@@ -65,8 +65,8 @@ void X11WindowTest::initTestCase()
     qRegisterMetaType<KWin::Deleted *>();
     qRegisterMetaType<KWin::Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024)));
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
 
     kwinApp()->start();
diff --git a/autotests/integration/xdgshellwindow_rules_test.cpp b/autotests/integration/xdgshellwindow_rules_test.cpp
index 298acc4772..1c3fcf516c 100644
--- a/autotests/integration/xdgshellwindow_rules_test.cpp
+++ b/autotests/integration/xdgshellwindow_rules_test.cpp
@@ -178,9 +178,8 @@ void TestXdgShellWindowRules::initTestCase()
     qRegisterMetaType<KWin::Window *>();
 
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/xdgshellwindow_test.cpp b/autotests/integration/xdgshellwindow_test.cpp
index c931300b37..70716e4943 100644
--- a/autotests/integration/xdgshellwindow_test.cpp
+++ b/autotests/integration/xdgshellwindow_test.cpp
@@ -166,9 +166,8 @@ void TestXdgShellWindow::initTestCase()
     qRegisterMetaType<KWayland::Client::Output *>();
 
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/xwayland_input_test.cpp b/autotests/integration/xwayland_input_test.cpp
index fad98ec91f..183dbf5500 100644
--- a/autotests/integration/xwayland_input_test.cpp
+++ b/autotests/integration/xwayland_input_test.cpp
@@ -42,9 +42,8 @@ void XWaylandInputTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<KWin::Deleted *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/xwayland_selections_test.cpp b/autotests/integration/xwayland_selections_test.cpp
index c3af600f01..8cc67df9bd 100644
--- a/autotests/integration/xwayland_selections_test.cpp
+++ b/autotests/integration/xwayland_selections_test.cpp
@@ -50,11 +50,10 @@ void XwaylandSelectionsTest::initTestCase()
     qRegisterMetaType<KWin::Window *>();
     qRegisterMetaType<QProcess::ExitStatus>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     //    QSignalSpy clipboardSyncDevicedCreated{waylandServer(), &WaylandServer::xclipboardSyncDataDeviceCreated};
     //    QVERIFY(clipboardSyncDevicedCreated.isValid());
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());
diff --git a/autotests/integration/xwaylandserver_crash_test.cpp b/autotests/integration/xwaylandserver_crash_test.cpp
index 77807d128b..a72767e5d9 100644
--- a/autotests/integration/xwaylandserver_crash_test.cpp
+++ b/autotests/integration/xwaylandserver_crash_test.cpp
@@ -47,9 +47,8 @@ void XwaylandServerCrashTest::initTestCase()
     qRegisterMetaType<Unmanaged *>();
     qRegisterMetaType<X11Window *>();
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     KSharedConfig::Ptr config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     KConfigGroup xwaylandGroup = config->group("Xwayland");
diff --git a/autotests/integration/xwaylandserver_restart_test.cpp b/autotests/integration/xwaylandserver_restart_test.cpp
index 8e8163e99b..95c5037762 100644
--- a/autotests/integration/xwaylandserver_restart_test.cpp
+++ b/autotests/integration/xwaylandserver_restart_test.cpp
@@ -43,9 +43,8 @@ private Q_SLOTS:
 void XwaylandServerRestartTest::initTestCase()
 {
     QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
-    kwinApp()->outputBackend()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName));
-    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(int, 2));
+    QMetaObject::invokeMethod(kwinApp()->outputBackend(), "setVirtualOutputs", Qt::DirectConnection, Q_ARG(QVector<QRect>, QVector<QRect>() << QRect(0, 0, 1280, 1024) << QRect(1280, 0, 1280, 1024)));
 
     KSharedConfig::Ptr config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     KConfigGroup xwaylandGroup = config->group("Xwayland");
diff --git a/src/backends/virtual/virtual_backend.cpp b/src/backends/virtual/virtual_backend.cpp
index 1b19be4eb5..53f415d405 100644
--- a/src/backends/virtual/virtual_backend.cpp
+++ b/src/backends/virtual/virtual_backend.cpp
@@ -66,23 +66,15 @@ Outputs VirtualBackend::outputs() const
     return m_outputs;
 }
 
-void VirtualBackend::setVirtualOutputs(int count, QVector<QRect> geometries, QVector<int> scales)
+void VirtualBackend::setVirtualOutputs(const QVector<QRect> &geometries, QVector<int> scales)
 {
-    Q_ASSERT(geometries.size() == 0 || geometries.size() == count);
-    Q_ASSERT(scales.size() == 0 || scales.size() == count);
+    Q_ASSERT(scales.size() == 0 || scales.size() == geometries.size());
 
     const QVector<VirtualOutput *> removed = m_outputs;
 
-    int sumWidth = 0;
-    for (int i = 0; i < count; i++) {
+    for (int i = 0; i < geometries.size(); i++) {
         VirtualOutput *vo = new VirtualOutput(this);
-        if (geometries.size()) {
-            const QRect geo = geometries.at(i);
-            vo->init(geo.topLeft(), geo.size());
-        } else {
-            vo->init(QPoint(sumWidth, 0), initialWindowSize());
-            sumWidth += initialWindowSize().width();
-        }
+        vo->init(geometries[i].topLeft(), geometries[i].size());
         if (scales.size()) {
             vo->updateScale(scales.at(i));
         }
diff --git a/src/backends/virtual/virtual_backend.h b/src/backends/virtual/virtual_backend.h
index b0e44878ea..3d1cd0268e 100644
--- a/src/backends/virtual/virtual_backend.h
+++ b/src/backends/virtual/virtual_backend.h
@@ -41,7 +41,7 @@ public:
     std::unique_ptr<QPainterBackend> createQPainterBackend() override;
     std::unique_ptr<OpenGLBackend> createOpenGLBackend() override;
 
-    Q_INVOKABLE void setVirtualOutputs(int count, QVector<QRect> geometries = QVector<QRect>(), QVector<int> scales = QVector<int>());
+    Q_INVOKABLE void setVirtualOutputs(const QVector<QRect> &geometries, QVector<int> scales = QVector<int>());
 
     Outputs outputs() const override;