sna: Only reduce damage addition to a region operation if clean

Some paths bypass operating upon the region as they do not have an
YX-banded set of boxes and so prefer to defer the costly construction of
the region till later. As a result, we have to be careful not to
overwrite any existing information if we do operate on the region after
setting the dirty boxes.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=50744
Reported-by: Zdenek Kabelac <zdenek.kabelac@gmail.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 3 insertions, 8 deletions

diff --git a/src/sna/sna_damage.c b/src/sna/sna_damage.c
index 1ea9e3c0..6149be7f 100644
--- a/src/sna/sna_damage.c
+++ b/src/sna/sna_damage.c
@@ -574,14 +574,9 @@ static struct sna_damage *__sna_damage_add_box(struct sna_damage *damage,
 		break;
 	}
 
-	switch (REGION_NUM_RECTS(&damage->region)) {
-	case 0:
-		pixman_region_init_rects(&damage->region, box, 1);
-		damage->extents = *box;
-		return damage;
-	case 1:
+	if (REGION_NUM_RECTS(&damage->region) <= 1) {
 		_pixman_region_union_box(&damage->region, box);
-		damage->extents = damage->region.extents;
+		damage_union(damage, box);
 		return damage;
 	}
 
@@ -616,7 +611,7 @@ inline static struct sna_damage *__sna_damage_add(struct sna_damage *damage,
 
 	if (REGION_NUM_RECTS(&damage->region) <= 1) {
 		pixman_region_union(&damage->region, &damage->region, region);
-		damage->extents = damage->region.extents;
+		damage_union(damage, &region->extents);
 		return damage;
 	}