[wayland] A backend can mark whether it is ready

Replaces the functionality of the WaylandBackend and makes it available
to all backends by providing the functionality directly in
AbstractBackend. By default a backend is not ready and the implementation
must call setReady(true) to indicate that setup has finished
successfully. The compositor won't start till the backend indicates that
it is ready.

abstract_backend.cpp

@@ -298,4 +298,13 @@ void AbstractBackend::repaint(const QRect &rect)
     Compositor::self()->addRepaint(rect);
 }
 
+void AbstractBackend::setReady(bool ready)
+{
+    if (m_ready == ready) {
+        return;
+    }
+    m_ready = ready;
+    emit readyChanged(m_ready);
+}
+
 }

abstract_backend.h

@@ -57,6 +57,9 @@ public:
     bool handlesOutputs() const {
         return m_handlesOutputs;
     }
+    bool isReady() const {
+        return m_ready;
+    }
 
     void pointerMotion(const QPointF &position, quint32 time);
     void pointerButtonPressed(quint32 button, quint32 time);
@@ -75,6 +78,7 @@ public:
 
 Q_SIGNALS:
     void cursorChanged();
+    void readyChanged(bool);
 
 protected:
     explicit AbstractBackend(QObject *parent = nullptr);
@@ -85,6 +89,7 @@ protected:
         m_handlesOutputs = true;
     }
     void repaint(const QRect &rect);
+    void setReady(bool ready);
 
 private Q_SLOTS:
     void installThemeCursor(quint32 id, const QPoint &hotspot);
@@ -99,6 +104,7 @@ private:
     } m_cursor;
     WaylandCursorTheme *m_cursorTheme = nullptr;
     bool m_handlesOutputs = false;
+    bool m_ready = false;
 };
 
 }

backends/drm/drm_backend.cpp

@@ -232,6 +232,7 @@ void DrmBackend::openDrm()
             m_udevMonitor->enable();
         }
     }
+    setReady(true);
 
     initCursor();
 }

backends/fbdev/fb_backend.cpp

@@ -92,6 +92,7 @@ void FramebufferBackend::openFrameBuffer()
     }
     m_fd = fd;
     queryScreenInfo();
+    setReady(true);
     emit screensQueried();
 }
 

backends/wayland/wayland_backend.cpp

@@ -458,7 +458,7 @@ void WaylandBackend::initConnection()
         Qt::QueuedConnection);
     connect(m_connectionThreadObject, &ConnectionThread::connectionDied, this,
         [this]() {
-            m_ready = false;
+            setReady(false);
             emit systemCompositorDied();
             m_seat.reset();
             m_shm->destroy();
@@ -581,16 +581,7 @@ void WaylandBackend::checkBackendReady()
         return;
     }
     disconnect(this, &WaylandBackend::shellSurfaceSizeChanged, this, &WaylandBackend::checkBackendReady);
-    m_ready = true;
-    emit backendReady();
-}
-
-void WaylandBackend::connectNotify(const QMetaMethod &signal)
-{
-    if (m_ready && signal == QMetaMethod::fromSignal(&WaylandBackend::backendReady)) {
-        // backend is already ready, let's emit the signal
-        signal.invoke(this, Qt::QueuedConnection);
-    }
+    setReady(true);
 }
 
 Screens *WaylandBackend::createScreens(QObject *parent)

backends/wayland/wayland_backend.h

@@ -150,13 +150,9 @@ public:
     OpenGLBackend *createOpenGLBackend() override;
     QPainterBackend *createQPainterBackend() override;
 
-protected:
-    void connectNotify(const QMetaMethod &signal) override;
-
 Q_SIGNALS:
     void shellSurfaceSizeChanged(const QSize &size);
     void systemCompositorDied();
-    void backendReady();
     void outputsChanged();
     void connectionFailed();
 private:
@@ -179,7 +175,6 @@ private:
     KWayland::Client::FullscreenShell *m_fullscreenShell;
     KWayland::Client::SubCompositor *m_subCompositor;
     WaylandCursor *m_cursor;
-    bool m_ready = false;
 };
 
 inline

backends/x11/x11windowed_backend.cpp

@@ -77,6 +77,7 @@ X11WindowedBackend::X11WindowedBackend(const QByteArray &display, const QSize &s
         XRenderUtils::init(m_connection, m_screen->root);
         createWindow();
         startEventReading();
+        setReady(true);
     }
 }
 

composite.cpp

@@ -38,7 +38,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "compositingprefs.h"
 #include "xcbutils.h"
 #if HAVE_WAYLAND
-#include "backends/wayland/wayland_backend.h"
+#include "abstract_backend.h"
 #include "wayland_server.h"
 #endif
 #include "decorations/decoratedclient.h"
@@ -119,12 +119,18 @@ Compositor::Compositor(QObject* workspace)
     connect(&m_unusedSupportPropertyTimer, SIGNAL(timeout()), SLOT(deleteUnusedSupportProperties()));
 #if HAVE_WAYLAND
     if (kwinApp()->operationMode() != Application::OperationModeX11) {
-        if (Wayland::WaylandBackend *w = dynamic_cast<Wayland::WaylandBackend *>(waylandServer()->backend())) {
-            connect(w, &Wayland::WaylandBackend::systemCompositorDied, this, &Compositor::finish);
-            connect(w, &Wayland::WaylandBackend::backendReady, this, &Compositor::setup);
-        } else {
+        if (waylandServer()->backend()->isReady()) {
             QMetaObject::invokeMethod(this, "setup", Qt::QueuedConnection);
         }
+        connect(waylandServer()->backend(), &AbstractBackend::readyChanged, this,
+            [this] (bool ready) {
+                if (ready) {
+                    setup();
+                } else {
+                    finish();
+                }
+            }, Qt::QueuedConnection
+        );
     } else
 #endif