[PATCH wayland] Require WAYLAND_DISPLAY to be set instead of using wayland-0 as the default
Pekka Paalanen
ppaalanen at gmail.com
Fri Aug 14 00:20:52 PDT 2015
On Wed, 12 Aug 2015 19:34:31 -0700
Dima Ryazanov <dima at gmail.com> wrote:
> 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>
> Acked-by: Pekka Paalanen <ppaalanen at gmail.com>
> Acked-by: Giulio Camuffo <giuliocamuffo at gmail.com>
> Acked-by: Daniel Stone <daniel at fooishbar.org>
> Acked-by: Jasper St. Pierre <jstpierre at mecheye.net>
> ---
> 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 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
> */
Hi,
this patch is Reviewed-by me up to this point, but I don't agree with
the below change to wayland-server.c as part of this patch.
> diff --git a/src/wayland-server.c b/src/wayland-server.c
> index 0f04f66..1ea53f9 100644
> --- a/src/wayland-server.c
> +++ b/src/wayland-server.c
> @@ -1209,8 +1209,8 @@ 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
> @@ -1235,7 +1235,7 @@ 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);
wl_display_add_socket() is used by the server to create a socket. If
the program does not give a name parameter, it's probably ok to try and
default to "wayland-0". I am not sure why WAYLAND_DISPLAY is involved
at all.
Anyway, the essence of this patch is to fix libwayland-client, so this
change to libwayland-server is off-topic anyway and should be
considered separately.
I dropped the hunk to wayland-server.c and committed the rest.
Pushed:
441f9bb..fb7e130 master -> master
Thanks,
pq
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