[PATCH wayland] RFC: Require WAYLAND_DISPLAY to be set instead of using wayland-0 as the default
Dima Ryazanov
dima at gmail.com
Mon May 25 01:12:15 PDT 2015
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 <dima at gmail.com>
---
doc/man/wl_display_connect.xml | 5 ++---
doc/publican/sources/Protocol.xml | 8 ++++----
src/wayland-client.c | 10 ++++++----
src/wayland-server.c | 6 +++---
4 files changed, 15 insertions(+), 14 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>
<para>
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
byte-order.
diff --git a/src/wayland-client.c b/src/wayland-client.c
index ed108e1..2e612d0 100644
--- a/src/wayland-client.c
+++ b/src/wayland-client.c
@@ -759,8 +759,11 @@ 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)
@@ -864,8 +867,7 @@ 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
*/
diff --git a/src/wayland-server.c b/src/wayland-server.c
index ecbae68..acb090f 100644
--- a/src/wayland-server.c
+++ b/src/wayland-server.c
@@ -1205,8 +1205,8 @@ wl_display_add_socket_auto(struct wl_display *display)
* connect to Wayland display.
*
* If NULL is passed as name, then it would look for WAYLAND_DISPLAY env
- * variable for the socket name. If WAYLAND_DISPLAY is not set, then default
- * wayland-0 is used.
+ * variable for the socket name. If WAYLAND_DISPLAY is not set, this function
+ * fails and returns -1.
*
* The Unix socket will be created in the directory pointed to by environment
* variable XDG_RUNTIME_DIR. If XDG_RUNTIME_DIR is not set, then this function
@@ -1231,7 +1231,7 @@ wl_display_add_socket(struct wl_display *display, const char *name)
if (name == NULL)
name = getenv("WAYLAND_DISPLAY");
if (name == NULL)
- name = "wayland-0";
+ return -1;
if (wl_socket_init_for_display_name(s, name) < 0) {
wl_socket_destroy(s);
--
2.4.1
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