wlroots/util/transform.c

#include <wlr/util/transform.h>

enum wl_output_transform wlr_output_transform_invert(
		enum wl_output_transform tr) {
	if ((tr & WL_OUTPUT_TRANSFORM_90) && !(tr & WL_OUTPUT_TRANSFORM_FLIPPED)) {
		tr ^= WL_OUTPUT_TRANSFORM_180;
	}
	return tr;
}

enum wl_output_transform wlr_output_transform_compose(
		enum wl_output_transform tr_a, enum wl_output_transform tr_b) {
	uint32_t flipped = (tr_a ^ tr_b) & WL_OUTPUT_TRANSFORM_FLIPPED;
	uint32_t rotation_mask = WL_OUTPUT_TRANSFORM_90 | WL_OUTPUT_TRANSFORM_180;
	uint32_t rotated;
	if (tr_b & WL_OUTPUT_TRANSFORM_FLIPPED) {
		// When a rotation of k degrees is followed by a flip, the
		// equivalent transform is a flip followed by a rotation of
		// -k degrees.
		rotated = (tr_b - tr_a) & rotation_mask;
	} else {
		rotated = (tr_a + tr_b) & rotation_mask;
	}
	return flipped | rotated;
}