Add configuration option for no input device.

As it has been discussed in the past [1], running Weston
without any input device at launch might be beneficial for
some use cases.

Certainly, it's best for the vast majority of users (and
the project) to require an input device to be present, as
to avoid frustration and hassle, but for those brave souls
that so prefer, this patch lets them run without any input
device at all.

This introduces a simple configuration in weston.ini:
  [core]
  require-input=true

True is the default, so no behavioral change is introduced.

[1] https://lists.freedesktop.org/archives/wayland-devel/2015-November/025193.html

Signed-off-by: Daniel Díaz <daniel.diaz@linaro.org>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Daniel Stone <daniels@collabora.com>

compositor/main.c

@@ -1738,6 +1738,7 @@ int main(int argc, char *argv[])
 	struct wl_listener primary_client_destroyed;
 	struct weston_seat *seat;
 	struct wet_compositor user_data;
+	int require_input;
 
 	const struct weston_option core_options[] = {
 		{ WESTON_OPTION_STRING, "backend", 'B', &backend },
@@ -1822,6 +1823,10 @@ int main(int argc, char *argv[])
 	if (weston_compositor_init_config(ec, config) < 0)
 		goto out;
 
+	weston_config_section_get_bool(section, "require-input",
+				       &require_input, true);
+	ec->require_input = require_input;
+
 	if (load_backend(ec, backend, &argc, argv, config) < 0) {
 		weston_log("fatal: failed to create compositor backend\n");
 		goto out;

libweston/compositor.h

@@ -830,6 +830,10 @@ struct weston_compositor {
 
 	void *user_data;
 	void (*exit)(struct weston_compositor *c);
+
+	/* Whether to let the compositor run without any input device. */
+	bool require_input;
+
 };
 
 struct weston_buffer {

libweston/libinput-seat.c

@@ -259,6 +259,12 @@ udev_input_enable(struct udev_input *input)
 			devices_found = 1;
 	}
 
+	if (devices_found == 0 && !c->require_input) {
+		weston_log("warning: no input devices found, but none required "
+			   "as per configuration.\n");
+		return 0;
+	}
+
 	if (devices_found == 0) {
 		weston_log(
 			"warning: no input devices on entering Weston. "

man/weston.ini.man

@@ -168,6 +168,11 @@ time, the one specified in the command-line will be used. On the other
 hand, if none of these sets the value, default idle timeout will be
 set to 300 seconds.
 .RS
+.PP
+.RE
+.TP 7
+.BI "require-input=" true
+require an input device for launch
 
 .SH "LIBINPUT SECTION"
 The

weston.ini.in

@@ -2,6 +2,7 @@
 #modules=xwayland.so,cms-colord.so
 #shell=desktop-shell.so
 #gbm-format=xrgb2101010
+#require-input=true
 
 [shell]
 background-image=/usr/share/backgrounds/gnome/Aqua.jpg