From 69a13a779d49629be6a9209d82afca40794df1a9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Gr=C3=A4=C3=9Flin?= <mgraesslin@kde.org>
Date: Wed, 25 Feb 2015 14:15:32 +0100
Subject: [PATCH] [kwin_wayland] Start Xwayland through socket file descriptor

Creates a socketpair in WaylandServer and creates a ClientConnection for
Xwayland. The created file descriptor is passed to Xwayland through the
WAYLAND_SOCKET env variable.
---
 main_wayland.cpp   | 22 ++++++++++++++++++----
 wayland_server.cpp | 15 +++++++++++++++
 wayland_server.h   |  7 +++++++
 3 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/main_wayland.cpp b/main_wayland.cpp
index 0931ff9ac8..d5babeef04 100644
--- a/main_wayland.cpp
+++ b/main_wayland.cpp
@@ -56,7 +56,7 @@ static void sighandler(int)
     QApplication::exit();
 }
 
-static int startXServer(const QByteArray &waylandSocket, int wmFd);
+static int startXServer(int waylandSocket, int wmFd);
 static void readDisplay(int pipe);
 
 //************************************
@@ -115,8 +115,15 @@ void ApplicationWayland::continueStartupWithScreens()
         return;
     }
 
+    const int fd = waylandServer()->createXWaylandConnection();
+    if (fd == -1) {
+        std::cerr << "FATAL ERROR: failed to open socket for Xwayland" << std::endl;
+        exit(1);
+        return;
+    }
+
     m_xcbConnectionFd = sx[0];
-    const int xDisplayPipe = startXServer(WaylandServer::self()->display()->socketName().toUtf8(), sx[1]);
+    const int xDisplayPipe = startXServer(fd, sx[1]);
     QFutureWatcher<void> *watcher = new QFutureWatcher<void>(this);
     QObject::connect(watcher, &QFutureWatcher<void>::finished, this, &ApplicationWayland::continueStartupWithX, Qt::QueuedConnection);
     QObject::connect(watcher, &QFutureWatcher<void>::finished, watcher, &QFutureWatcher<void>::deleteLater, Qt::QueuedConnection);
@@ -214,7 +221,7 @@ void ApplicationWayland::createX11Connection()
  * Starts the Xwayland-Server.
  * The new process is started by forking into it.
  **/
-static int startXServer(const QByteArray &waylandSocket, int wmFd)
+static int startXServer(int waylandSocket, int wmFd)
 {
     int pipeFds[2];
     if (pipe(pipeFds) != 0) {
@@ -237,7 +244,14 @@ static int startXServer(const QByteArray &waylandSocket, int wmFd)
             return -1;
         }
         sprintf(wmfdbuf, "%d", fd);
-        qputenv("WAYLAND_DISPLAY", waylandSocket.isEmpty() ? QByteArrayLiteral("wayland-0") : waylandSocket);
+
+        int wlfd = dup(waylandSocket);
+        if (wlfd < 0) {
+            std::cerr << "FATAL ERROR: failed to open socket for Xwayland" << std::endl;
+            exit(20);
+            return -1;
+        }
+        qputenv("WAYLAND_SOCKET", QByteArray::number(wlfd));
         execlp("Xwayland", "Xwayland", "-displayfd", fdbuf, "-rootless", "-wm", wmfdbuf, (char *)0);
         close(pipeFds[1]);
         exit(20);
diff --git a/wayland_server.cpp b/wayland_server.cpp
index 6bb59751f3..37f1257920 100644
--- a/wayland_server.cpp
+++ b/wayland_server.cpp
@@ -28,6 +28,10 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <KWayland/Server/seat_interface.h>
 #include <KWayland/Server/shell_interface.h>
 
+// system
+#include <sys/types.h>
+#include <sys/socket.h>
+
 using namespace KWayland::Server;
 
 namespace KWin
@@ -87,4 +91,15 @@ void WaylandServer::initOutputs()
     }
 }
 
+int WaylandServer::createXWaylandConnection()
+{
+    int sx[2];
+    if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, sx) < 0) {
+        qCWarning(KWIN_CORE) << "Could not create socket";
+        return -1;
+    }
+    m_xwaylandConnection = m_display->createClient(sx[0]);
+    return sx[1];
+}
+
 }
diff --git a/wayland_server.h b/wayland_server.h
index 68399d97d0..a4e1b14c54 100644
--- a/wayland_server.h
+++ b/wayland_server.h
@@ -28,6 +28,7 @@ namespace KWayland
 {
 namespace Server
 {
+class ClientConnection;
 class CompositorInterface;
 class Display;
 class ShellInterface;
@@ -60,11 +61,17 @@ public:
         return m_shell;
     }
 
+    /**
+     * @returns file descriptor for Xwayland to connect to.
+     **/
+    int createXWaylandConnection();
+
 private:
     KWayland::Server::Display *m_display = nullptr;
     KWayland::Server::CompositorInterface *m_compositor = nullptr;
     KWayland::Server::SeatInterface *m_seat = nullptr;
     KWayland::Server::ShellInterface *m_shell = nullptr;
+    KWayland::Server::ClientConnection *m_xwaylandConnection = nullptr;
     KWIN_SINGLETON(WaylandServer)
 };