[PATCH libinput] tablet: use the tilt resolution if we have it

[Peter Hutterer]

A nonzero resolution on the tilt axes is units/rad so we can calculate the
physical min/max based. Uneven min/max ranges are supported.

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 src/evdev-tablet.c | 28 +++++++++++++++++++++-------
 test/tablet.c      | 12 ++++++++----
 2 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/src/evdev-tablet.c b/src/evdev-tablet.c
index 1e5c2cd..226d5bd 100644
--- a/src/evdev-tablet.c
+++ b/src/evdev-tablet.c
@@ -230,17 +230,31 @@ adjust_tilt(const struct input_absinfo *absinfo)
 	double range = absinfo->maximum - absinfo->minimum;
 	double value = (absinfo->value - absinfo->minimum) / range;
 	const int WACOM_MAX_DEGREES = 64;
+	double max_degrees;
+
+	/* If resolution is nonzero, it's in units/radian. But require
+	 * a min/max less/greater than zero so we can assume 0 is the
+	 * center */
+	if (absinfo->resolution != 0 &&
+	    absinfo->maximum > 0 &&
+	    absinfo->minimum < 0) {
+		int range_max = absinfo->value >= 0 ? absinfo->maximum
+						    : -absinfo->minimum;
+
+		max_degrees = 180.0/M_PI * range_max/absinfo->resolution;
+	} else {
+		/* Wacom supports physical [-64, 64] degrees, so map to that by
+		 * default. If other tablets have a different physical range or
+		 * nonzero physical offsets, they need extra treatment
+		 * here.
+		 */
+		max_degrees = WACOM_MAX_DEGREES;
+	}
 
 	/* Map to the (-1, 1) range */
 	value = (value * 2) - 1;
 
-	/* Wacom supports physical [-64, 64] degrees, so map to that by
-	 * default. If other tablets have a different physical range or
-	 * nonzero physical offsets, they need extra treatment
-	 * here.
-	 */
-
-	return value * WACOM_MAX_DEGREES;
+	return value * max_degrees;
 }
 
 static inline int32_t
diff --git a/test/tablet.c b/test/tablet.c
index c5dc892..ad6ac45 100644
--- a/test/tablet.c
+++ b/test/tablet.c
@@ -3298,7 +3298,8 @@ START_TEST(tilt_x)
 	ck_assert_double_ge(tx, -52);
 
 	ty = libinput_event_tablet_tool_get_tilt_y(tev);
-	ck_assert_double_eq(ty, -64);
+	ck_assert_double_ge(ty, -65);
+	ck_assert_double_lt(ty, -63);
 
 	libinput_event_destroy(event);
 
@@ -3320,7 +3321,8 @@ START_TEST(tilt_x)
 		ck_assert_double_le(tx, expected_tx + 2);
 
 		ty = libinput_event_tablet_tool_get_tilt_y(tev);
-		ck_assert_double_eq(ty, -64);
+		ck_assert_double_ge(ty, -65);
+		ck_assert_double_lt(ty, -63);
 
 		libinput_event_destroy(event);
 
@@ -3365,7 +3367,8 @@ START_TEST(tilt_y)
 	ck_assert_double_ge(ty, -52);
 
 	tx = libinput_event_tablet_tool_get_tilt_x(tev);
-	ck_assert_double_eq(tx, -64);
+	ck_assert_double_ge(tx, -65);
+	ck_assert_double_lt(tx, -63);
 
 	libinput_event_destroy(event);
 
@@ -3387,7 +3390,8 @@ START_TEST(tilt_y)
 		ck_assert_double_le(ty, expected_ty + 2);
 
 		tx = libinput_event_tablet_tool_get_tilt_x(tev);
-		ck_assert_double_eq(tx, -64);
+		ck_assert_double_ge(tx, -65);
+		ck_assert_double_lt(tx, -63);
 
 		libinput_event_destroy(event);
 
-- 
2.5.0