[PATCH libinput 06/11] util: add a couple of 3x3 matrix helper functions

[Peter Hutterer]

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 src/libinput-util.h | 100 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 test/misc.c         |  78 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 178 insertions(+)

diff --git a/src/libinput-util.h b/src/libinput-util.h
index 5d366b0..925b86e 100644
--- a/src/libinput-util.h
+++ b/src/libinput-util.h
@@ -25,6 +25,7 @@
 
 #include <unistd.h>
 #include <math.h>
+#include <string.h>
 
 #include "libinput.h"
 
@@ -179,4 +180,103 @@ long_set_bit_state(unsigned long *array, int bit, int state)
 		long_clear_bit(array, bit);
 }
 
+struct matrix {
+	float val[3][3]; /* [row][col] */
+};
+
+static inline void
+matrix_init_identity(struct matrix *m)
+{
+	memset(m, 0, sizeof(*m));
+	m->val[0][0] = 1;
+	m->val[1][1] = 1;
+	m->val[2][2] = 1;
+}
+
+static inline void
+matrix_from_farray6(struct matrix *m, const float values[6])
+{
+	matrix_init_identity(m);
+	m->val[0][0] = values[0];
+	m->val[0][1] = values[1];
+	m->val[0][2] = values[2];
+	m->val[1][0] = values[3];
+	m->val[1][1] = values[4];
+	m->val[1][2] = values[5];
+}
+
+static inline void
+matrix_init_scale(struct matrix *m, float sx, float sy)
+{
+	matrix_init_identity(m);
+	m->val[0][0] = sx;
+	m->val[1][1] = sy;
+}
+
+static inline void
+matrix_init_translate(struct matrix *m, float x, float y)
+{
+	matrix_init_identity(m);
+	m->val[0][2] = x;
+	m->val[1][2] = y;
+}
+
+static inline int
+matrix_is_identity(struct matrix *m)
+{
+	return (m->val[0][0] == 1 &&
+		m->val[0][1] == 0 &&
+		m->val[0][2] == 0 &&
+		m->val[1][0] == 0 &&
+		m->val[1][1] == 1 &&
+		m->val[1][2] == 0 &&
+		m->val[2][0] == 0 &&
+		m->val[2][1] == 0 &&
+		m->val[2][2] == 1);
+}
+
+static inline void
+matrix_mult(struct matrix *dest,
+	    const struct matrix *m1,
+	    const struct matrix *m2)
+{
+	struct matrix m;
+	int row, col, i;
+
+	for (row = 0; row < 3; row++) {
+		for (col = 0; col < 3; col++) {
+			double v = 0;
+			for (i = 0; i < 3; i++) {
+				v += m1->val[row][i] * m2->val[i][col];
+			}
+			m.val[row][col] = v;
+		}
+	}
+
+	memcpy(dest, &m, sizeof(m));
+}
+
+static inline void
+matrix_mult_vec(struct matrix *m, int *x, int *y)
+{
+	int tx, ty;
+
+	tx = *x * m->val[0][0] + *y * m->val[0][1] + m->val[0][2];
+	ty = *x * m->val[1][0] + *y * m->val[1][1] + m->val[1][2];
+
+	*x = tx;
+	*y = ty;
+}
+
+static inline void
+matrix_to_farray6(const struct matrix *m, float out[6])
+{
+	out[0] = m->val[0][0];
+	out[1] = m->val[0][1];
+	out[2] = m->val[0][2];
+	out[3] = m->val[1][0];
+	out[4] = m->val[1][1];
+	out[5] = m->val[1][2];
+}
+
 #endif /* LIBINPUT_UTIL_H */
diff --git a/test/misc.c b/test/misc.c
index 983c3f9..1512180 100644
--- a/test/misc.c
+++ b/test/misc.c
@@ -431,6 +431,83 @@ START_TEST(config_status_string)
 }
 END_TEST
 
+START_TEST(matrix_helpers)
+{
+	struct matrix m1, m2, m3;
+	float f[6] = { 1, 2, 3, 4, 5, 6 };
+	int x, y;
+	int row, col;
+
+	matrix_init_identity(&m1);
+
+	for (row = 0; row < 3; row++) {
+		for (col = 0; col < 3; col++) {
+			ck_assert_int_eq(m1.val[row][col],
+					 (row == col) ? 1 : 0);
+		}
+	}
+	ck_assert(matrix_is_identity(&m1));
+
+	matrix_from_farray6(&m2, f);
+	ck_assert_int_eq(m2.val[0][0], 1);
+	ck_assert_int_eq(m2.val[0][1], 2);
+	ck_assert_int_eq(m2.val[0][2], 3);
+	ck_assert_int_eq(m2.val[1][0], 4);
+	ck_assert_int_eq(m2.val[1][1], 5);
+	ck_assert_int_eq(m2.val[1][2], 6);
+	ck_assert_int_eq(m2.val[2][0], 0);
+	ck_assert_int_eq(m2.val[2][1], 0);
+	ck_assert_int_eq(m2.val[2][2], 1);
+
+	x = 100;
+	y = 5;
+	matrix_mult_vec(&m1, &x, &y);
+	ck_assert_int_eq(x, 100);
+	ck_assert_int_eq(y, 5);
+
+	matrix_mult(&m3, &m1, &m1);
+	ck_assert(matrix_is_identity(&m3));
+
+	matrix_init_scale(&m2, 2, 4);
+	ck_assert_int_eq(m2.val[0][0], 2);
+	ck_assert_int_eq(m2.val[0][1], 0);
+	ck_assert_int_eq(m2.val[0][2], 0);
+	ck_assert_int_eq(m2.val[1][0], 0);
+	ck_assert_int_eq(m2.val[1][1], 4);
+	ck_assert_int_eq(m2.val[1][2], 0);
+	ck_assert_int_eq(m2.val[2][0], 0);
+	ck_assert_int_eq(m2.val[2][1], 0);
+	ck_assert_int_eq(m2.val[2][2], 1);
+
+	matrix_mult_vec(&m2, &x, &y);
+	ck_assert_int_eq(x, 200);
+	ck_assert_int_eq(y, 20);
+
+	matrix_init_translate(&m2, 10, 100);
+	ck_assert_int_eq(m2.val[0][0], 1);
+	ck_assert_int_eq(m2.val[0][1], 0);
+	ck_assert_int_eq(m2.val[0][2], 10);
+	ck_assert_int_eq(m2.val[1][0], 0);
+	ck_assert_int_eq(m2.val[1][1], 1);
+	ck_assert_int_eq(m2.val[1][2], 100);
+	ck_assert_int_eq(m2.val[2][0], 0);
+	ck_assert_int_eq(m2.val[2][1], 0);
+	ck_assert_int_eq(m2.val[2][2], 1);
+
+	matrix_mult_vec(&m2, &x, &y);
+	ck_assert_int_eq(x, 210);
+	ck_assert_int_eq(y, 120);
+
+	matrix_to_farray6(&m2, f);
+	ck_assert_int_eq(f[0], 1);
+	ck_assert_int_eq(f[1], 0);
+	ck_assert_int_eq(f[2], 10);
+	ck_assert_int_eq(f[3], 0);
+	ck_assert_int_eq(f[4], 1);
+	ck_assert_int_eq(f[5], 100);
+}
+END_TEST
+
 int main (int argc, char **argv) {
 	litest_add_no_device("events:conversion", event_conversion_device_notify);
 	litest_add_no_device("events:conversion", event_conversion_pointer);
@@ -441,5 +518,6 @@ int main (int argc, char **argv) {
 	litest_add("device:id", device_ids, LITEST_ANY, LITEST_ANY);
 	litest_add_no_device("config:status string", config_status_string);
 
+	litest_add_no_device("misc:matrix", matrix_helpers);
 	return litest_run(argc, argv);
 }
-- 
1.9.3