[PATCH v2 weston] libinput: normalize WL_CALIBRATION before passing it to libinput

[Peter Hutterer]

WL_CALIBRATION, introduced in weston-1.1, requires the translation component
of the calibration matrix to be in screen coordinates. libinput does not have
access to this and it's not a very generic way to do this anyway. So with
the libinput backend, WL_CALIBRATION support is currently broken (#82742).
This cannot be fixed in libinput without changing its API for this specific
use-case.

This patch lets weston take care of WL_CALIBRATION. It takes the original
format and normalizes it before passing it to libinput. This way libinput
still does the coordinate transformation, weston just needs to provide the
initial configuration.

Note that this needs an updated libinput, otherwise libinput will try to
transform coordinates as well.
---
Changes to v1:
- fix copy/paste error assigning height to the screen width

https://bugs.freedesktop.org/show_bug.cgi?id=82742 has positive test results
so we don't break exisint setups with WL_CALIBRATION set.

Can be merged once libinput 0.6 is released.

 configure.ac          |  2 +-
 src/libinput-device.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index bc5c88a..fb19fb2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -160,7 +160,7 @@ AC_ARG_ENABLE(libinput-backend, [  --disable-libinput-backend],,
 AM_CONDITIONAL([ENABLE_LIBINPUT_BACKEND], [test x$enable_libinput_backend = xyes])
 if test x$enable_libinput_backend = xyes; then
   AC_DEFINE([BUILD_LIBINPUT_BACKEND], [1], [Build the libinput input device backend])
-  PKG_CHECK_MODULES(LIBINPUT_BACKEND, [libinput >= 0.5.0])
+  PKG_CHECK_MODULES(LIBINPUT_BACKEND, [libinput >= 0.6.0])
 fi
 
 
diff --git a/src/libinput-device.c b/src/libinput-device.c
index 6e50eeb..fded34c 100644
--- a/src/libinput-device.c
+++ b/src/libinput-device.c
@@ -282,6 +282,90 @@ notify_output_destroy(struct wl_listener *listener, void *data)
 	}
 }
 
+/**
+ * The WL_CALIBRATION property requires a pixel-specific matrix to be
+ * applied after scaling device coordinates to screen coordinates. libinput
+ * can't do that, so we need to convert the calibration to the normalized
+ * format libinput expects.
+ */
+static void
+evdev_device_set_calibration(struct evdev_device *device)
+{
+	struct udev *udev;
+	struct udev_device *udev_device = NULL;
+	const char *sysname = libinput_device_get_sysname(device->device);
+	const char *calibration_values;
+	uint32_t width, height;
+	float calibration[6];
+	enum libinput_config_status status;
+
+	if (!device->output)
+		return;
+
+	width = device->output->width;
+	height = device->output->height;
+	if (width == 0 || height == 0)
+		return;
+
+	/* If libinput has a pre-set calibration matrix, don't override it */
+	if (!libinput_device_config_calibration_has_matrix(device->device) ||
+	    libinput_device_config_calibration_get_default_matrix(
+							  device->device,
+							  calibration) != 0)
+		return;
+
+	udev = udev_new();
+	if (!udev)
+		return;
+
+	udev_device = udev_device_new_from_subsystem_sysname(udev,
+							     "input",
+							     sysname);
+	if (!udev_device)
+		goto out;
+
+	calibration_values =
+	udev_device_get_property_value(udev_device,
+				       "WL_CALIBRATION");
+
+	if (!calibration_values || sscanf(calibration_values,
+					  "%f %f %f %f %f %f",
+					  &calibration[0],
+					  &calibration[1],
+					  &calibration[2],
+					  &calibration[3],
+					  &calibration[4],
+					  &calibration[5]) != 6)
+		goto out;
+
+	weston_log("Applying calibration: %f %f %f %f %f %f "
+		   "(normalized %f %f)\n",
+		    calibration[0],
+		    calibration[1],
+		    calibration[2],
+		    calibration[3],
+		    calibration[4],
+		    calibration[5],
+		    calibration[2]/width,
+		    calibration[5]/height);
+
+	/* normalize to a format libinput can use. There is a chance of
+	   this being wrong if the width/height don't match the device
+	   width/height but I'm not sure how to fix that */
+	calibration[2] /= width;
+	calibration[5] /= height;
+
+	status = libinput_device_config_calibration_set_matrix(device->device,
+							       calibration);
+	if (status != LIBINPUT_CONFIG_STATUS_SUCCESS)
+		weston_log("Failed to apply calibration.\n");
+
+out:
+	if (udev_device)
+		udev_device_unref(udev_device);
+	udev_unref(udev);
+}
+
 void
 evdev_device_set_output(struct evdev_device *device,
 			struct weston_output *output)
@@ -295,6 +379,7 @@ evdev_device_set_output(struct evdev_device *device,
 	device->output_destroy_listener.notify = notify_output_destroy;
 	wl_signal_add(&output->destroy_signal,
 		      &device->output_destroy_listener);
+	evdev_device_set_calibration(device);
 }
 
 static void
@@ -318,6 +403,8 @@ configure_device(struct evdev_device *device)
 		libinput_device_config_tap_set_enabled(device->device,
 						       enable_tap);
 	}
+
+	evdev_device_set_calibration(device);
 }
 
 struct evdev_device *
-- 
1.9.3