Add option to use wl_display_add_socket_auto

Summary:
If automaticSocketNaming is enabled, it will use wl_display_add_socket_auto
to allocate the next free socket. The resulting name can be retrieved using
socketName after a successful start afterwards.

Test Plan: Ran the new autotest, passes. kwin_wayland still uses the old behaviour.

Reviewers: #kwin, #plasma, romangg

Reviewed By: #kwin, #plasma, romangg

Subscribers: davidedmundson, zzag, romangg, kde-frameworks-devel

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D17122

src/wayland/autotests/server/test_display.cpp

@@ -43,6 +43,7 @@ private Q_SLOTS:
     void testClientConnection();
     void testConnectNoSocket();
     void testOutputManagement();
+    void testAutoSocketName();
 };
 
 void TestWaylandServerDisplay::testSocketName()
@@ -215,6 +216,29 @@ void TestWaylandServerDisplay::testOutputManagement()
     QVERIFY(kwin->isValid());
 }
 
+void TestWaylandServerDisplay::testAutoSocketName()
+{
+    QTemporaryDir runtimeDir;
+    QVERIFY(runtimeDir.isValid());
+    QVERIFY(qputenv("XDG_RUNTIME_DIR", runtimeDir.path().toUtf8()));
+
+    Display display0;
+    display0.setAutomaticSocketNaming(true);
+    QSignalSpy socketNameChangedSpy0(&display0, SIGNAL(socketNameChanged(QString)));
+    display0.start();
+    QVERIFY(display0.isRunning());
+    QCOMPARE(socketNameChangedSpy0.count(), 0);
+    QCOMPARE(display0.socketName(), QStringLiteral("wayland-0"));
+
+    Display display1;
+    display1.setAutomaticSocketNaming(true);
+    QSignalSpy socketNameChangedSpy1(&display1, SIGNAL(socketNameChanged(QString)));
+    display1.start();
+    QVERIFY(display1.isRunning());
+    QCOMPARE(socketNameChangedSpy1.count(), 1);
+    QCOMPARE(display1.socketName(), QStringLiteral("wayland-1"));
+}
+
 
 QTEST_GUILESS_MAIN(TestWaylandServerDisplay)
 #include "test_display.moc"

src/wayland/display.cpp

@@ -84,6 +84,7 @@ public:
     wl_event_loop *loop = nullptr;
     QString socketName = QStringLiteral("wayland-0");
     bool running = false;
+    bool automaticSocketNaming = false;
     QList<OutputInterface*> outputs;
     QList<OutputDeviceInterface*> outputdevices;
     QVector<SeatInterface*> seats;
@@ -161,13 +162,39 @@ QString Display::socketName() const
     return d->socketName;
 }
 
+void Display::setAutomaticSocketNaming(bool automaticSocketNaming)
+{
+    if (d->automaticSocketNaming == automaticSocketNaming) {
+        return;
+    }
+    d->automaticSocketNaming = automaticSocketNaming;
+    emit automaticSocketNamingChanged(automaticSocketNaming);
+}
+
+bool Display::automaticSocketNaming() const
+{
+    return d->automaticSocketNaming;
+}
+
 void Display::start(StartMode mode)
 {
     Q_ASSERT(!d->running);
     Q_ASSERT(!d->display);
     d->display = wl_display_create();
     if (mode == StartMode::ConnectToSocket) {
-        if (wl_display_add_socket(d->display, qPrintable(d->socketName)) != 0) {
+        if (d->automaticSocketNaming) {
+            const char *socket = wl_display_add_socket_auto(d->display);
+            if (socket == nullptr) {
+                qCWarning(KWAYLAND_SERVER) << "Failed to create Wayland socket";
+                return;
+            }
+
+            const QString newEffectiveSocketName = QString::fromUtf8(socket);
+            if (d->socketName != newEffectiveSocketName) {
+                d->socketName = newEffectiveSocketName;
+                emit socketNameChanged(d->socketName);
+            }
+        } else if (wl_display_add_socket(d->display, qPrintable(d->socketName)) != 0) {
             qCWarning(KWAYLAND_SERVER) << "Failed to create Wayland socket";
             return;
         }

src/wayland/display.h

@@ -100,14 +100,28 @@ class KWAYLANDSERVER_EXPORT Display : public QObject
 {
     Q_OBJECT
     Q_PROPERTY(QString socketName READ socketName WRITE setSocketName NOTIFY socketNameChanged)
+    Q_PROPERTY(bool automaticSocketNaming READ automaticSocketNaming WRITE setAutomaticSocketNaming NOTIFY automaticSocketNamingChanged)
     Q_PROPERTY(bool running READ isRunning NOTIFY runningChanged)
 public:
     explicit Display(QObject *parent = nullptr);
     virtual ~Display();
 
+    /**
+     * Sets the basename of the socket to @p name. If @p name is empty, it will use
+     * wl_display_add_socket_auto to get a free socket with a filename "wayland-%d".
+     **/
     void setSocketName(const QString &name);
     QString socketName() const;
 
+    /**
+     * If automaticSocketNaming is true, the manually set socketName is ignored
+     * and it will use wl_display_add_socket_auto on start to get a free socket with
+     * a filename "wayland-%d" instead. The effective socket is written into socketName.
+     * @since 5.55
+     **/
+    void setAutomaticSocketNaming(bool automaticSocketNaming);
+    bool automaticSocketNaming() const;
+
     quint32 serial();
     quint32 nextSerial();
 
@@ -316,6 +330,7 @@ public:
 
 Q_SIGNALS:
     void socketNameChanged(const QString&);
+    void automaticSocketNamingChanged(bool);
     void runningChanged(bool);
     void aboutToTerminate();
     void clientConnected(KWayland::Server::ClientConnection*);