Reconnect Pipewire on Failure

Our connection to pipewire can go down if the pipewire service restarts, it's on us to tear down and reconnect.
To ensure Streams can tear down on their own properly, this patch leaves existing streams with a defunct connection
and creates a new connection for new streams, sharing the connection between them.

This also implicitly fixes the case for distributions without working socket activation.

BUG: 483137

src/plugins/screencast/pipewirecore.cpp

@@ -48,6 +48,7 @@ void PipeWireCore::onCoreError(void *data, uint32_t id, int seq, int res, const
     qCWarning(KWIN_SCREENCAST) << "PipeWire remote error: " << message;
     if (id == PW_ID_CORE && res == -EPIPE) {
         PipeWireCore *pw = static_cast<PipeWireCore *>(data);
+        pw->m_valid = false;
         Q_EMIT pw->pipewireFailed(QString::fromUtf8(message));
     }
 }
@@ -91,9 +92,15 @@ bool PipeWireCore::init()
     }
 
     pw_core_add_listener(pwCore, &coreListener, &pwCoreEvents, this);
+    m_valid = true;
     return true;
 }
 
+bool PipeWireCore::isValid() const
+{
+    return m_valid;
+}
+
 } // namespace KWin
 
 #include "moc_pipewirecore.cpp"

src/plugins/screencast/pipewirecore.h

@@ -28,6 +28,7 @@ public:
     ~PipeWireCore();
 
     bool init();
+    bool isValid() const;
 
     static std::shared_ptr<PipeWireCore> self();
 
@@ -41,6 +42,9 @@ public:
 
 Q_SIGNALS:
     void pipewireFailed(const QString &message);
+
+private:
+    bool m_valid = false;
 };
 
 } // namespace KWin

src/plugins/screencast/screencastmanager.cpp

@@ -27,9 +27,9 @@ namespace KWin
 
 ScreencastManager::ScreencastManager()
     : m_screencast(new ScreencastV1Interface(waylandServer()->display(), this))
-    , m_core(new PipeWireCore)
 {
-    m_core->init();
+    getPipewireConnection();
+
     connect(m_screencast, &ScreencastV1Interface::windowScreencastRequested, this, &ScreencastManager::streamWindow);
     connect(m_screencast, &ScreencastV1Interface::outputScreencastRequested, this, &ScreencastManager::streamWaylandOutput);
     connect(m_screencast, &ScreencastV1Interface::virtualOutputScreencastRequested, this, &ScreencastManager::streamVirtualOutput);
@@ -46,7 +46,7 @@ void ScreencastManager::streamWindow(ScreencastStreamV1Interface *waylandStream,
         return;
     }
 
-    auto stream = new ScreenCastStream(new WindowScreenCastSource(window), m_core, this);
+    auto stream = new ScreenCastStream(new WindowScreenCastSource(window), getPipewireConnection(), this);
     stream->setObjectName(window->desktopFileName());
     stream->setCursorMode(mode, 1, window->clientGeometry());
 
@@ -88,7 +88,7 @@ void ScreencastManager::streamOutput(ScreencastStreamV1Interface *waylandStream,
         return;
     }
 
-    auto stream = new ScreenCastStream(new OutputScreenCastSource(streamOutput), m_core, this);
+    auto stream = new ScreenCastStream(new OutputScreenCastSource(streamOutput), getPipewireConnection(), this);
     stream->setObjectName(streamOutput->name());
     stream->setCursorMode(mode, streamOutput->scale(), streamOutput->geometry());
 
@@ -112,7 +112,7 @@ void ScreencastManager::streamRegion(ScreencastStreamV1Interface *waylandStream,
     }
 
     auto source = new RegionScreenCastSource(geometry, scale);
-    auto stream = new ScreenCastStream(source, m_core, this);
+    auto stream = new ScreenCastStream(source, getPipewireConnection(), this);
     stream->setObjectName(rectToString(geometry));
     stream->setCursorMode(mode, scale, geometry);
 
@@ -135,6 +135,20 @@ void ScreencastManager::integrateStreams(ScreencastStreamV1Interface *waylandStr
     }
 }
 
+std::shared_ptr<PipeWireCore> ScreencastManager::getPipewireConnection()
+{
+    if (m_pipewireConnectionCache && m_pipewireConnectionCache->isValid()) {
+        return m_pipewireConnectionCache;
+    } else {
+        std::shared_ptr<PipeWireCore> pipeWireCore = std::make_shared<PipeWireCore>();
+        if (pipeWireCore->init()) {
+            m_pipewireConnectionCache = pipeWireCore;
+        }
+        // return a valid object even if init fails
+        return pipeWireCore;
+    }
+}
+
 } // namespace KWin
 
 #include "moc_screencastmanager.cpp"

src/plugins/screencast/screencastmanager.h

@@ -46,8 +46,10 @@ private:
 
     void integrateStreams(ScreencastStreamV1Interface *waylandStream, ScreenCastStream *stream);
 
+    std::shared_ptr<PipeWireCore> getPipewireConnection();
+
     ScreencastV1Interface *m_screencast;
-    std::shared_ptr<PipeWireCore> m_core;
+    std::shared_ptr<PipeWireCore> m_pipewireConnectionCache;
 };
 
 } // namespace KWin