sna: Fix checking the dirty boxes

I forgot how insane the data structure for the list of dirty boxes
attached to the damage is. It is neither a simple list, nor does not store
the count of boxes within each chunk.

Fixes regression from
commit 9026bb954646c0425360c2236e26c79d097142cd [2.21.11]
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Jun 28 15:59:17 2013 +0100

    sna: Inspect the dirty boxes when querying whether damage contains a rectangle

A side effect is that we now make sure that there is an upper bound to
the amount of searching we do for the no-reduce fast path.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=66430
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

2 files changed, 21 insertions, 23 deletions

diff --git a/src/intel_list.h b/src/intel_list.h
index cfaa1ad3..de0b6837 100644
--- a/src/intel_list.h
+++ b/src/intel_list.h
@@ -264,7 +264,7 @@ static inline void list_move_tail(struct list *list, struct list *head)
  * @return True if the list contains one or more elements or False otherwise.
  */
 static inline bool
-list_is_empty(struct list *head)
+list_is_empty(const struct list *head)
 {
     return head->next == head;
 }
diff --git a/src/sna/sna_damage.c b/src/sna/sna_damage.c
index d2a876db..30cc83b3 100644
--- a/src/sna/sna_damage.c
+++ b/src/sna/sna_damage.c
@@ -1341,46 +1341,44 @@ static bool box_overlaps(const BoxRec *a, const BoxRec *b)
 bool _sna_damage_contains_box__no_reduce(const struct sna_damage *damage,
 					 const BoxRec *box)
 {
-	struct sna_damage_box *iter;
-	int ret;
+	int n, count;
+	BoxPtr b;
 
 	assert(damage && damage->mode != DAMAGE_ALL);
 	if (!box_contains(&damage->extents, box))
 		return false;
 
-	ret = pixman_region_contains_rectangle(&damage->region, (BoxPtr)box);
+	n = pixman_region_contains_rectangle(&damage->region, (BoxPtr)box);
 	if (!damage->dirty)
-		return ret == PIXMAN_REGION_IN;
+		return n == PIXMAN_REGION_IN;
 
 	if (damage->mode == DAMAGE_ADD) {
-		if (ret == PIXMAN_REGION_IN)
+		if (n == PIXMAN_REGION_IN)
 			return true;
 
-		list_for_each_entry(iter, &damage->embedded_box.list, list) {
-			BoxPtr b;
-			int n;
+		count = damage->embedded_box.size;
+		if (list_is_empty(&damage->embedded_box.list))
+			count -= damage->remain;
 
-			b = (BoxPtr)(iter + 1);
-			for (n = 0; n < iter->size; n++) {
-				if (box_contains(&b[n], box))
-					return true;
-			}
+		b = damage->embedded_box.box;
+		for (n = 0; n < count; n++) {
+			if (box_contains(&b[n], box))
+				return true;
 		}
 
 		return false;
 	} else {
-		if (ret != PIXMAN_REGION_IN)
+		if (n != PIXMAN_REGION_IN)
 			return false;
 
-		list_for_each_entry(iter, &damage->embedded_box.list, list) {
-			BoxPtr b;
-			int n;
+		if (!list_is_empty(&damage->embedded_box.list))
+			return false;
 
-			b = (BoxPtr)(iter + 1);
-			for (n = 0; n < iter->size; n++) {
-				if (box_overlaps(&b[n], box))
-					return false;
-			}
+		count = damage->embedded_box.size - damage->remain;
+		b = damage->embedded_box.box;
+		for (n = 0; n < count; n++) {
+			if (box_overlaps(&b[n], box))
+				return false;
 		}
 
 		return true;