libinput: deprecate WL_CALIBRATION

The udev property WL_CALIBRATION is an old way of giving Weston a
touchscreen calibration matrix. It is Weston-specific.

The recommended way of setting up a calibration is to use the udev
property LIBINPUT_CALIBRATION_MATRIX, which libinput will load
automatically and therefore applies to all libinput using display
servers and applications.

The syntax of WL_CALIBRATION and LIBINPUT_CALIBRATION_MATRIX is
different as well: WL_CALIBRATION uses pixels as the translation part
units, which makes the values depend on the output resolution.
LIBINPUT_CALIBRATION_MATRIX on the other hand uses normalized units.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>

libweston/libinput-device.c

@@ -500,6 +500,13 @@ evdev_device_set_calibration(struct evdev_device *device)
 		udev_device_get_property_value(udev_device,
 					       "WL_CALIBRATION");
 
+	if (calibration_values) {
+		weston_log("Warning: input device %s has WL_CALIBRATION property set. "
+			   "Support for it will be removed in the future. "
+			   "Please use LIBINPUT_CALIBRATION_MATRIX instead.\n",
+			   sysname);
+	}
+
 	if (!calibration_values || sscanf(calibration_values,
 					  "%f %f %f %f %f %f",
 					  &calibration[0],