[gtk+] wayland: require WAYLAND_DISPLAY be set to open wayland display

[Ray Strode <halfline src gnome org>]

commit 35489f5d31b20a390b45803d760f965391d0b57f
Author: Ray Strode <rstrode redhat com>
Date:   Fri Aug 14 10:23:31 2015 -0400

    wayland: require WAYLAND_DISPLAY be set to open wayland display
    
    The wayland client libraries now require WAYLAND_DISPLAY be set
    to use them.
    
    See:
    
    http://cgit.freedesktop.org/wayland/wayland/commit/?id=fb7e13021730d0a5516ecbd3712ea4235e05d24d
    
    This commit makes _gdk_wayland_display_open bail early if
    WAYLAND_DISPLAY is unset, just as it does for XDG_RUNTIME_DIR.

 gdk/wayland/gdkdisplay-wayland.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/gdk/wayland/gdkdisplay-wayland.c b/gdk/wayland/gdkdisplay-wayland.c
index 149200d..b2fad08 100644
--- a/gdk/wayland/gdkdisplay-wayland.c
+++ b/gdk/wayland/gdkdisplay-wayland.c
@@ -431,13 +431,16 @@ _gdk_wayland_display_open (const gchar *display_name)
 
   GDK_NOTE (MISC, g_message ("opening display %s", display_name ? display_name : ""));
 
-  /* If this variable is unset then wayland initialisation will surely
+  /* If these variables are unset then wayland initialisation will surely
    * fail, logging a fatal error in the process.  Save ourselves from
    * that.
    */
   if (g_getenv ("XDG_RUNTIME_DIR") == NULL)
     return NULL;
 
+  if (g_getenv ("WAYLAND_DISPLAY") == NULL)
+    return NULL;
+
   wl_log_set_handler_client (log_handler);
 
   wl_display = wl_display_connect (display_name);