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-rw-r--r--util/meson.build2
-rw-r--r--util/transform.c25
2 files changed, 26 insertions, 1 deletions
diff --git a/util/meson.build b/util/meson.build
index 5af2254f..053e2c5e 100644
--- a/util/meson.build
+++ b/util/meson.build
@@ -11,6 +11,6 @@ wlr_files += files(
'shm.c',
'time.c',
'token.c',
+ 'transform.c',
'utf8.c',
)
-
diff --git a/util/transform.c b/util/transform.c
new file mode 100644
index 00000000..4cc725fd
--- /dev/null
+++ b/util/transform.c
@@ -0,0 +1,25 @@
+#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;
+}