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output: fix output transform compositions 

This change ensures that wlr_output_transform_compose correctly composes
transforms when the first transform includes a rotation and the second
transform includes a flip.
This commit is contained in:
Manuel Stoeckl 2020-02-09 10:24:44 -05:00 committed by Drew DeVault
parent f22a5d1704
commit 2fddec56e8
1 changed files with 10 additions and 2 deletions
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12
types/wlr_output.c
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@ -1118,7 +1118,15 @@ enum wl_output_transform wlr_output_transform_invert(
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 rotated =
(tr_a + tr_b) & (WL_OUTPUT_TRANSFORM_90 | WL_OUTPUT_TRANSFORM_180);
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;
}