diff options
authorDima Ryazanov <>2015-08-12 19:34:31 -0700
committerPekka Paalanen <>2015-08-14 10:14:05 +0300
commitfb7e13021730d0a5516ecbd3712ea4235e05d24d (patch)
parent441f9bb144efd561f0ac4bc4e672acc9703b5126 (diff)
client: require WAYLAND_DISPLAY to be set
Although defaulting to wayland-0 seems convenient, it has an undesirable side effect: clients may unintentionally connect to the wrong compositor. Generally, it's safer to fail instead. Here's a real example: In Fedora 22, Gtk+ prefers Wayland over X11, though the default session is still a normal X11 Gnome session. When you launch a Gtk+ app, it will try Wayland, fail, then try X11, and succesfully start up. That works fine. Now suppose you launch Weston while running the Gnome session. Suddenly, all of the Gtk+ apps launched from Gnome will show up inside Weston instead. That's unexpected. There's also no good way to prevent that from happening (other than perhaps setting WAYLAND_DISPLAY to an invalid value when launching an app). Not using wayland-0 as the default will solve that problem: an app launched from the X11 Gnome session will use the X11 backend regardless of whether there's a wayland compositor running at the same time. Everything else should work as before. The compositor already sets the WAYLAND_DISPLAY when starting the session, so the lack of the default value should not make a difference to the user. Signed-off-by: Dima Ryazanov <> Acked-by: Pekka Paalanen <> Acked-by: Giulio Camuffo <> Acked-by: Daniel Stone <> Acked-by: Jasper St. Pierre <> Reviewed-by: Ryo Munakata <> [Pekka: dropped the wayland-server.c hunk, adjusted summary] Signed-off-by: Pekka Paalanen <>
3 files changed, 12 insertions, 11 deletions
diff --git a/doc/man/wl_display_connect.xml b/doc/man/wl_display_connect.xml
index 7e6e05c..ded3cbd 100644
--- a/doc/man/wl_display_connect.xml
+++ b/doc/man/wl_display_connect.xml
@@ -57,9 +57,8 @@
that was previously opened by a Wayland server. The server socket must
be placed in <envar>XDG_RUNTIME_DIR</envar> for this function to
find it. The <varname>name</varname> argument specifies the name of
- the socket or <constant>NULL</constant> to use the default (which is
- <constant>"wayland-0"</constant>). The environment variable
- <envar>WAYLAND_DISPLAY</envar> replaces the default value. If
+ the socket or <constant>NULL</constant> to use the default
+ (which is the value of <envar>WAYLAND_DISPLAY</envar>). If
<envar>WAYLAND_SOCKET</envar> is set, this function behaves like
<function>wl_display_connect_to_fd</function> with the file-descriptor
number taken from the environment variable.</para>
diff --git a/doc/publican/sources/Protocol.xml b/doc/publican/sources/Protocol.xml
index 477063b..9464953 100644
--- a/doc/publican/sources/Protocol.xml
+++ b/doc/publican/sources/Protocol.xml
@@ -60,10 +60,10 @@
<title>Wire Format</title>
The protocol is sent over a UNIX domain stream socket, where the endpoint
- usually is named <systemitem class="service">wayland-0</systemitem>
- (although it can be changed via <emphasis>WAYLAND_DISPLAY</emphasis>
- in the environment). The protocol is message-based. A
- message sent by a client to the server is called request. A message
+ name is determined by the <emphasis>WAYLAND_DISPLAY</emphasis>
+ environment variable. Its value will usually be
+ <systemitem class="service">wayland-0</systemitem>. The protocol is message-based.
+ A message sent by a client to the server is called request. A message
from the server to a client is called event. Every message is
structured as 32-bit words, values are represented in the host's
diff --git a/src/wayland-client.c b/src/wayland-client.c
index 09c594a..ffbca4b 100644
--- a/src/wayland-client.c
+++ b/src/wayland-client.c
@@ -764,8 +764,11 @@ connect_to_socket(const char *name)
if (name == NULL)
name = getenv("WAYLAND_DISPLAY");
- if (name == NULL)
- name = "wayland-0";
+ if (name == NULL) {
+ wl_log("error: WAYLAND_DISPLAY not set in the environment.\n");
+ errno = ENOENT;
+ return -1;
+ }
fd = wl_os_socket_cloexec(PF_LOCAL, SOCK_STREAM, 0);
if (fd < 0)
@@ -869,8 +872,7 @@ wl_display_connect_to_fd(int fd)
* \return A \ref wl_display object or \c NULL on failure
* Connect to the Wayland display named \c name. If \c name is \c NULL,
- * its value will be replaced with the WAYLAND_DISPLAY environment
- * variable if it is set, otherwise display "wayland-0" will be used.
+ * its value will be replaced with the WAYLAND_DISPLAY environment variable.
* \memberof wl_display