matrix: move to util/

wlr_matrix is not a standalone type like other headers in types/,
it's more of an internal utility. Move it to the appropriate place.

util/matrix.c

@@ -0,0 +1,142 @@
+#include <string.h>
+#include <wayland-server-protocol.h>
+#include <wlr/types/wlr_output.h>
+#include <wlr/util/box.h>
+#include "util/matrix.h"
+
+void wlr_matrix_identity(float mat[static 9]) {
+	static const float identity[9] = {
+		1.0f, 0.0f, 0.0f,
+		0.0f, 1.0f, 0.0f,
+		0.0f, 0.0f, 1.0f,
+	};
+	memcpy(mat, identity, sizeof(identity));
+}
+
+void wlr_matrix_multiply(float mat[static 9], const float a[static 9],
+		const float b[static 9]) {
+	float product[9];
+
+	product[0] = a[0]*b[0] + a[1]*b[3] + a[2]*b[6];
+	product[1] = a[0]*b[1] + a[1]*b[4] + a[2]*b[7];
+	product[2] = a[0]*b[2] + a[1]*b[5] + a[2]*b[8];
+
+	product[3] = a[3]*b[0] + a[4]*b[3] + a[5]*b[6];
+	product[4] = a[3]*b[1] + a[4]*b[4] + a[5]*b[7];
+	product[5] = a[3]*b[2] + a[4]*b[5] + a[5]*b[8];
+
+	product[6] = a[6]*b[0] + a[7]*b[3] + a[8]*b[6];
+	product[7] = a[6]*b[1] + a[7]*b[4] + a[8]*b[7];
+	product[8] = a[6]*b[2] + a[7]*b[5] + a[8]*b[8];
+
+	memcpy(mat, product, sizeof(product));
+}
+
+void wlr_matrix_translate(float mat[static 9], float x, float y) {
+	float translate[9] = {
+		1.0f, 0.0f, x,
+		0.0f, 1.0f, y,
+		0.0f, 0.0f, 1.0f,
+	};
+	wlr_matrix_multiply(mat, mat, translate);
+}
+
+void wlr_matrix_scale(float mat[static 9], float x, float y) {
+	float scale[9] = {
+		x,    0.0f, 0.0f,
+		0.0f, y,    0.0f,
+		0.0f, 0.0f, 1.0f,
+	};
+	wlr_matrix_multiply(mat, mat, scale);
+}
+
+static const float transforms[][9] = {
+	[WL_OUTPUT_TRANSFORM_NORMAL] = {
+		1.0f, 0.0f, 0.0f,
+		0.0f, 1.0f, 0.0f,
+		0.0f, 0.0f, 1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_90] = {
+		0.0f, 1.0f, 0.0f,
+		-1.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_180] = {
+		-1.0f, 0.0f, 0.0f,
+		0.0f, -1.0f, 0.0f,
+		0.0f, 0.0f, 1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_270] = {
+		0.0f, -1.0f, 0.0f,
+		1.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_FLIPPED] = {
+		-1.0f, 0.0f, 0.0f,
+		0.0f, 1.0f, 0.0f,
+		0.0f, 0.0f, 1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_FLIPPED_90] = {
+		0.0f, 1.0f, 0.0f,
+		1.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_FLIPPED_180] = {
+		1.0f, 0.0f, 0.0f,
+		0.0f, -1.0f, 0.0f,
+		0.0f, 0.0f, 1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_FLIPPED_270] = {
+		0.0f, -1.0f, 0.0f,
+		-1.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 1.0f,
+	},
+};
+
+void wlr_matrix_transform(float mat[static 9],
+		enum wl_output_transform transform) {
+	wlr_matrix_multiply(mat, mat, transforms[transform]);
+}
+
+void matrix_projection(float mat[static 9], int width, int height,
+		enum wl_output_transform transform) {
+	memset(mat, 0, sizeof(*mat) * 9);
+
+	const float *t = transforms[transform];
+	float x = 2.0f / width;
+	float y = 2.0f / height;
+
+	// Rotation + reflection
+	mat[0] = x * t[0];
+	mat[1] = x * t[1];
+	mat[3] = y * -t[3];
+	mat[4] = y * -t[4];
+
+	// Translation
+	mat[2] = -copysign(1.0f, mat[0] + mat[1]);
+	mat[5] = -copysign(1.0f, mat[3] + mat[4]);
+
+	// Identity
+	mat[8] = 1.0f;
+}
+
+void wlr_matrix_project_box(float mat[static 9], const struct wlr_box *box,
+		enum wl_output_transform transform, const float projection[static 9]) {
+	int x = box->x;
+	int y = box->y;
+	int width = box->width;
+	int height = box->height;
+
+	wlr_matrix_identity(mat);
+	wlr_matrix_translate(mat, x, y);
+
+	wlr_matrix_scale(mat, width, height);
+
+	if (transform != WL_OUTPUT_TRANSFORM_NORMAL) {
+		wlr_matrix_translate(mat, 0.5, 0.5);
+		wlr_matrix_transform(mat, transform);
+		wlr_matrix_translate(mat, -0.5, -0.5);
+	}
+
+	wlr_matrix_multiply(mat, projection, mat);
+}

util/meson.build

@@ -5,6 +5,7 @@ wlr_files += files(
 	'env.c',
 	'global.c',
 	'log.c',
+	'matrix.c',
 	'rect_union.c',
 	'region.c',
 	'set.c',