MetaWayland: install an X io error handler

This way can detect X disconnections correctly, crash with a core
dump and reset the tty.

https://bugzilla.gnome.org/show_bug.cgi?id=706962

src/core/display.c

@@ -75,6 +75,8 @@
 #include <string.h>
 #include <unistd.h>
 
+#include "meta-xwayland-private.h"
+
 #define GRAB_OP_IS_WINDOW_SWITCH(g)                     \
         (g == META_GRAB_OP_KEYBOARD_TABBING_NORMAL  ||  \
          g == META_GRAB_OP_KEYBOARD_TABBING_DOCK    ||  \
@@ -516,6 +518,9 @@ meta_display_open (void)
       return FALSE;
     }
 
+  if (meta_is_wayland_compositor ())
+    meta_xwayland_complete_init ();
+
   if (meta_is_syncing ())
     XSynchronize (xdisplay, True);
   

src/wayland/meta-xwayland-private.h

@@ -27,6 +27,9 @@
 gboolean
 meta_xwayland_start (MetaWaylandCompositor *compositor);
 
+void
+meta_xwayland_complete_init (void);
+
 void
 meta_xwayland_stop (MetaWaylandCompositor *compositor);
 

src/wayland/meta-xwayland.c

@@ -301,6 +301,14 @@ xserver_died (GPid     pid,
     }
 }
 
+static int
+x_io_error (Display *display)
+{
+  g_error ("Connection to xwayland lost");
+
+  return 0;
+}
+
 gboolean
 meta_xwayland_start (MetaWaylandCompositor *compositor)
 {
@@ -425,6 +433,18 @@ meta_xwayland_start (MetaWaylandCompositor *compositor)
   return TRUE;
 }
 
+/* To be called right after connecting */
+void
+meta_xwayland_complete_init (void)
+{
+  /* We install an X IO error handler in addition to the child watch,
+     because after Xlib connects our child watch may not be called soon
+     enough, and therefore we won't crash when X exits (and most important
+     we won't reset the tty).
+  */
+  XSetIOErrorHandler (x_io_error);
+}
+
 void
 meta_xwayland_stop (MetaWaylandCompositor *compositor)
 {