xwayland: Make xinerama index -> Output mapping more robust with fractional scaling

xdg-output-v1 uses the fractional geometry, so also use it when mapping
a xinerama screen index to an Output.

autotests/integration/CMakeLists.txt

@@ -131,6 +131,7 @@ integrationTest(NAME testXwaylandServerRestart SRCS xwaylandserver_restart_test.
 integrationTest(NAME testFakeInput SRCS fakeinput_test.cpp)
 integrationTest(NAME testSecurityContext SRCS security_context_test.cpp)
 integrationTest(NAME testStickyKeys SRCS sticky_keys_test.cpp)
+integrationTest(NAME testXinerama SRCS xinerama_test.cpp)
 
 qt_add_dbus_interfaces(DBUS_SRCS ${CMAKE_BINARY_DIR}/src/org.kde.kwin.VirtualKeyboard.xml)
 integrationTest(NAME testVirtualKeyboardDBus SRCS test_virtualkeyboard_dbus.cpp ${DBUS_SRCS})

autotests/integration/xinerama_test.cpp

@@ -0,0 +1,65 @@
+/*
+    SPDX-FileCopyrightText: 2024 Vlad Zahorodnii <vlad.zahorodnii@kde.org>
+
+    SPDX-License-Identifier: GPL-2.0-or-later
+*/
+
+#include "kwin_wayland_test.h"
+
+#include "core/output.h"
+#include "wayland_server.h"
+#include "workspace.h"
+
+namespace KWin
+{
+
+static const QString s_socketName = QStringLiteral("wayland_test_kwin_xinerama-0");
+
+class XineramaTest : public QObject
+{
+    Q_OBJECT
+
+private Q_SLOTS:
+    void initTestCase();
+    void indexToOutput();
+};
+
+void XineramaTest::initTestCase()
+{
+    QSignalSpy applicationStartedSpy(kwinApp(), &Application::started);
+    QVERIFY(waylandServer()->init(s_socketName));
+    kwinApp()->start();
+    QVERIFY(applicationStartedSpy.wait());
+}
+
+void XineramaTest::indexToOutput()
+{
+    Test::setOutputConfig({
+        Test::OutputInfo{
+            .geometry = QRect(0, 0, 1280, 1024),
+            .scale = 1.5,
+        },
+        Test::OutputInfo{
+            .geometry = QRect(1280, 0, 1280, 1024),
+            .scale = 1.5,
+        },
+    });
+    kwinApp()->setXwaylandScale(1.5);
+
+    // Start Xwayland
+    Test::XcbConnectionPtr c = Test::createX11Connection();
+    QVERIFY(!xcb_connection_has_error(c.get()));
+
+    const auto outputs = workspace()->outputs();
+    QCOMPARE(workspace()->xineramaIndexToOutput(0), outputs.at(0));
+    QCOMPARE(workspace()->xineramaIndexToOutput(1), outputs.at(1));
+
+    workspace()->setOutputOrder({outputs[1], outputs[0]});
+    QCOMPARE(workspace()->xineramaIndexToOutput(0), outputs.at(1));
+    QCOMPARE(workspace()->xineramaIndexToOutput(1), outputs.at(0));
+}
+
+} // namespace KWin
+
+WAYLANDTEST_MAIN(KWin::XineramaTest)
+#include "xinerama_test.moc"

src/wayland/xdgoutput_v1.cpp

@@ -108,8 +108,8 @@ XdgOutputV1Interface::XdgOutputV1Interface(OutputInterface *output)
 
     name = handle->name();
     description = handle->description();
-    pos = handle->geometry().topLeft();
-    size = handle->geometry().size();
+    pos = handle->fractionalGeometry().topLeft();
+    size = handle->fractionalGeometry().size();
 
     connect(handle, &Output::geometryChanged, this, &XdgOutputV1Interface::update);
 }

src/workspace.cpp

@@ -2518,7 +2518,7 @@ Output *Workspace::xineramaIndexToOutput(int index) const
     const QRect needle(infos[index].x_org, infos[index].y_org, infos[index].width, infos[index].height);
 
     for (Output *output : std::as_const(m_outputs)) {
-        if (Xcb::toXNative(output->geometry()) == needle) {
+        if (Xcb::toXNative(output->fractionalGeometry()) == needle) {
             return output;
         }
     }