Reduce code-duplication of socketpair in WaylandServer

Summary:
WaylandServer creates a socketpair for several Wayland connections. So
far this duplicated code quite a bit.

This change introduces one method to perform the socketpair and the
error checking plus creating the server side ClientConnection from the
pair.

Test Plan: Tests still pass

Reviewers: #kwin, #plasma_on_wayland

Subscribers: plasma-devel, kwin

Tags: #plasma_on_wayland, #kwin

Differential Revision: https://phabricator.kde.org/D3576

wayland_server.cpp

@@ -362,20 +362,32 @@ void WaylandServer::syncOutputsToWayland()
     }
 }
 
-int WaylandServer::createXWaylandConnection()
+WaylandServer::SocketPairConnection WaylandServer::createConnection()
 {
+    SocketPairConnection ret;
     int sx[2];
     if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, sx) < 0) {
         qCWarning(KWIN_CORE) << "Could not create socket";
+        return ret;
+    }
+    ret.connection = m_display->createClient(sx[0]);
+    ret.fd = sx[1];
+    return ret;
+}
+
+int WaylandServer::createXWaylandConnection()
+{
+    const auto socket = createConnection();
+    if (!socket.connection) {
         return -1;
     }
-    m_xwayland.client = m_display->createClient(sx[0]);
+    m_xwayland.client = socket.connection;
     m_xwayland.destroyConnection = connect(m_xwayland.client, &KWayland::Server::ClientConnection::disconnected, this,
         [] {
             qFatal("Xwayland Connection died");
         }
     );
-    return sx[1];
+    return socket.fd;
 }
 
 void WaylandServer::destroyXWaylandConnection()
@@ -394,13 +406,12 @@ void WaylandServer::destroyXWaylandConnection()
 
 int WaylandServer::createInputMethodConnection()
 {
-    int sx[2];
-    if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, sx) < 0) {
-        qCWarning(KWIN_CORE) << "Could not create socket";
+    const auto socket = createConnection();
+    if (!socket.connection) {
         return -1;
     }
-    m_inputMethodServerConnection = m_display->createClient(sx[0]);
-    return sx[1];
+    m_inputMethodServerConnection = socket.connection;
+    return socket.fd;
 }
 
 void WaylandServer::destroyInputMethodConnection()
@@ -414,13 +425,12 @@ void WaylandServer::destroyInputMethodConnection()
 
 int WaylandServer::createXclipboardSyncConnection()
 {
-    int sx[2];
-    if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, sx) < 0) {
-        qCWarning(KWIN_CORE) << "Could not create socket";
+    const auto socket = createConnection();
+    if (!socket.connection) {
         return -1;
     }
-    m_xclipbaordSync.client = m_display->createClient(sx[0]);
-    return sx[1];
+    m_xclipbaordSync.client = socket.connection;
+    return socket.fd;
 }
 
 void WaylandServer::setupX11ClipboardSync()
@@ -460,15 +470,14 @@ void WaylandServer::setupX11ClipboardSync()
 
 void WaylandServer::createInternalConnection()
 {
-    int sx[2];
-    if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, sx) < 0) {
-        qCWarning(KWIN_CORE) << "Could not create socket";
+    const auto socket = createConnection();
+    if (!socket.connection) {
         return;
     }
-    m_internalConnection.server = m_display->createClient(sx[0]);
+    m_internalConnection.server = socket.connection;
     using namespace KWayland::Client;
     m_internalConnection.client = new ConnectionThread();
-    m_internalConnection.client->setSocketFd(sx[1]);
+    m_internalConnection.client->setSocketFd(socket.fd);
     m_internalConnection.clientThread = new QThread;
     m_internalConnection.client->moveToThread(m_internalConnection.clientThread);
     m_internalConnection.clientThread->start();

wayland_server.h

@@ -164,6 +164,25 @@ public:
     void dispatch();
     quint32 createWindowId(KWayland::Server::SurfaceInterface *surface);
 
+    /**
+     * Struct containing information for a created Wayland connection through a
+     * socketpair.
+     **/
+    struct SocketPairConnection {
+        /**
+         * ServerSide Connection
+         **/
+        KWayland::Server::ClientConnection *connection = nullptr;
+        /**
+         * client-side file descriptor for the socket
+         **/
+        int fd = -1;
+    };
+    /**
+     * Creates a Wayland connection using a socket pair.
+     **/
+    SocketPairConnection createConnection();
+
 Q_SIGNALS:
     void shellClientAdded(KWin::ShellClient*);
     void shellClientRemoved(KWin::ShellClient*);