weston: add touchscreen_calibrator option

Add an option to enable the touchscreen calibrator interface. This is a
global on/off toggle, in lack of more fine-grained access restrictions.

As Weston should not hardcode system specifics, the actual permanent
saving of a new calibration is left for a user supplied script or a
program. Usually this script would write an appropriate udev rule to set
LIBINPUT_CALIBRATION_MATRIX for the touch device.

Co-developed by Louis-Francis and Pekka.

v2:
- use syspath instead of devpath

Signed-off-by: Louis-Francis Ratté-Boulianne <lfrb@collabora.com>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
v1 Tested-by: Matt Hoosier <matt.hoosier@gmail.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>

compositor/main.c

@@ -764,6 +764,64 @@ load_modules(struct weston_compositor *ec, const char *modules,
 	return 0;
 }
 
+static int
+save_touch_device_calibration(struct weston_compositor *compositor,
+			      struct weston_touch_device *device,
+			      const struct weston_touch_device_matrix *calibration)
+{
+	struct weston_config_section *s;
+	struct weston_config *config = wet_get_config(compositor);
+	char *helper = NULL;
+	char *helper_cmd = NULL;
+	int ret = -1;
+	int status;
+	const float *m = calibration->m;
+
+	s = weston_config_get_section(config,
+				      "libinput", NULL, NULL);
+
+	weston_config_section_get_string(s, "calibration_helper",
+					 &helper, NULL);
+
+	if (!helper || strlen(helper) == 0) {
+		ret = 0;
+		goto out;
+	}
+
+	if (asprintf(&helper_cmd, "\"%s\" '%s' %f %f %f %f %f %f",
+		     helper, device->syspath,
+		     m[0], m[1], m[2],
+		     m[3], m[4], m[5]) < 0)
+		goto out;
+
+	status = system(helper_cmd);
+	free(helper_cmd);
+
+	if (status < 0) {
+		weston_log("Error: failed to run calibration helper '%s'.\n",
+			   helper);
+		goto out;
+	}
+
+	if (!WIFEXITED(status)) {
+		weston_log("Error: calibration helper '%s' possibly killed.\n",
+			   helper);
+		goto out;
+	}
+
+	if (WEXITSTATUS(status) == 0) {
+		ret = 0;
+	} else {
+		weston_log("Calibration helper '%s' exited with status %d.\n",
+			   helper, WEXITSTATUS(status));
+	}
+
+out:
+	free(helper);
+
+	return ret;
+}
+
 static int
 weston_compositor_init_config(struct weston_compositor *ec,
 			      struct weston_config *config)
@@ -772,7 +830,9 @@ weston_compositor_init_config(struct weston_compositor *ec,
 	struct weston_config_section *s;
 	int repaint_msec;
 	int vt_switching;
+	int cal;
 
+	/* weston.ini [keyboard] */
 	s = weston_config_get_section(config, "keyboard", NULL, NULL);
 	weston_config_section_get_string(s, "keymap_rules",
 					 (char **) &xkb_names.rules, NULL);
@@ -797,6 +857,7 @@ weston_compositor_init_config(struct weston_compositor *ec,
 				       &vt_switching, true);
 	ec->vt_switching = vt_switching;
 
+	/* weston.ini [core] */
 	s = weston_config_get_section(config, "core", NULL, NULL);
 	weston_config_section_get_int(s, "repaint-window", &repaint_msec,
 				      ec->repaint_msec);
@@ -809,6 +870,13 @@ weston_compositor_init_config(struct weston_compositor *ec,
 	weston_log("Output repaint window is %d ms maximum.\n",
 		   ec->repaint_msec);
 
+	/* weston.ini [libinput] */
+	s = weston_config_get_section(config, "libinput", NULL, NULL);
+	weston_config_section_get_bool(s, "touchscreen_calibrator", &cal, 0);
+	if (cal)
+		weston_compositor_enable_touch_calibrator(ec,
+						save_touch_device_calibration);
+
 	return 0;
 }
 

man/weston.ini.man

@@ -200,8 +200,47 @@ Available configuration are:
 .TP 7
 .BI "enable_tap=" true
 enables tap to click on touchpad devices
+.TP 7
+.BI "touchscreen_calibrator=" true
+Advertise the touchscreen calibrator interface to all clients. This is a
+potential denial-of-service attack vector, so it should only be enabled on
+trusted userspace. Boolean, defaults to
+.BR false .
+
+The interface is required for running touchscreen calibrator applications. It
+provides the application raw touch events, bypassing the normal touch handling.
+It also allows the application to upload a new calibration into the compositor.
+
+Even though this option is listed in the libinput section, it does affect all
+Weston configurations regardless of the used backend. If the backend does not
+use libinput, the interface can still be advertised, but it will not list any
+devices.
+.TP 7
+.BI "calibration_helper=" /bin/echo
+An optional calibration helper program to permanently save a new touchscreen
+calibration. String, defaults to unset.
+
+The given program will be executed with seven arguments when a calibrator
+application requests the server to take a new calibration matrix into use.
+The program is executed synchronously and will therefore block Weston for its
+duration. If the program exit status is non-zero, Weston will not apply the
+new calibration. If the helper is unset or the program exit status is zero,
+Weston will use the new calibration immediately.
+
+The program is invoked as:
+.PP
+.RS 10
+.I calibration_helper syspath m1 m2 m3 m4 m5 m6
+.RE
 .RS
 .PP
+.RI "where " syspath
+is the udev sys path for the device and
+.IR m1 "  through " m6
+are the calibration matrix elements in libinput's
+.BR LIBINPUT_CALIBRATION_MATRIX " udev property format."
+The sys path is an absolute path and starts with the sys mount point.
+.RE
 
 .SH "SHELL SECTION"
 The