fix(vulkan): bound the damage split of wl_shm copies to a bounding box

commit: f958185cb8cc55c79ac5f947a2c02975d31f3ab4
author: brice · 14d ago · 2026-10-08 19:49 UTC
parent: d6a3812
signature: GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email

2 files · +36 -1

M internal/adapters/vulkan/shm.go +15 -1


@@ -294,11 +294,25 @@ func (r Renderer) retireShm(s shmSurface) {
294	294		}
295	295		}
296	296
	297	+	// maxDisjointRects bounds the pieces disjointRects cuts the damage into: the
	298	+	// rects come from the client, and each cut can add three pieces.
	299	+	const maxDisjointRects = 64
	300	+
297	301		// disjointRects appends to dst the parts of rects inside a w×h buffer, with
298		-	// no pixel in two of them. It reuses dst's capacity.
	302	+	// no pixel in two of them. Past maxDisjointRects pieces it appends their
	303	+	// bounding box instead: some undamaged pixels are copied again. It reuses
	304	+	// dst's capacity.
299	305		func disjointRects(dst []image.Rectangle, rects []ports.Rect, w, h int) []image.Rectangle {
300	306		bounds := image.Rect(0, 0, w, h)
	307	+	start := len(dst)
301	308		for _, rc := range rects {
	309	+	if len(dst)-start > maxDisjointRects {
	310	+	var box image.Rectangle
	311	+	for _, rc := range rects {
	312	+	box = box.Union(image.Rect(rc.X, rc.Y, rc.X+rc.W, rc.Y+rc.H).Intersect(bounds))
	313	+	}
	314	+	return append(dst[:start], box)
	315	+	}
302	316		pending := len(dst)
303	317		dst = append(dst, image.Rect(rc.X, rc.Y, rc.X+rc.W, rc.Y+rc.H).Intersect(bounds))
304	318		// Cut the new rect by each earlier one; the pieces it leaves are


@@ -294,11 +294,25 @@ func (r Renderer) retireShm(s shmSurface) {
294		}	294		}
295		}	295		}
296			296
			297	+	// maxDisjointRects bounds the pieces disjointRects cuts the damage into: the
			298	+	// rects come from the client, and each cut can add three pieces.
			299	+	const maxDisjointRects = 64
			300	+
297		// disjointRects appends to dst the parts of rects inside a w×h buffer, with	301		// disjointRects appends to dst the parts of rects inside a w×h buffer, with
298	-	// no pixel in two of them. It reuses dst's capacity.	302	+	// no pixel in two of them. Past maxDisjointRects pieces it appends their
			303	+	// bounding box instead: some undamaged pixels are copied again. It reuses
			304	+	// dst's capacity.
299		func disjointRects(dst []image.Rectangle, rects []ports.Rect, w, h int) []image.Rectangle {	305		func disjointRects(dst []image.Rectangle, rects []ports.Rect, w, h int) []image.Rectangle {
300		bounds := image.Rect(0, 0, w, h)	306		bounds := image.Rect(0, 0, w, h)
			307	+	start := len(dst)
301		for _, rc := range rects {	308		for _, rc := range rects {
			309	+	if len(dst)-start > maxDisjointRects {
			310	+	var box image.Rectangle
			311	+	for _, rc := range rects {
			312	+	box = box.Union(image.Rect(rc.X, rc.Y, rc.X+rc.W, rc.Y+rc.H).Intersect(bounds))
			313	+	}
			314	+	return append(dst[:start], box)
			315	+	}
302		pending := len(dst)	316		pending := len(dst)
303		dst = append(dst, image.Rect(rc.X, rc.Y, rc.X+rc.W, rc.Y+rc.H).Intersect(bounds))	317		dst = append(dst, image.Rect(rc.X, rc.Y, rc.X+rc.W, rc.Y+rc.H).Intersect(bounds))
304		// Cut the new rect by each earlier one; the pieces it leaves are	318		// Cut the new rect by each earlier one; the pieces it leaves are

M internal/adapters/vulkan/shm_rects_test.go +21 -0

@@ -1,6 +1,7 @@
1	1		package vulkan
2	2
3	3		import (
	4	+	"image"
4	5		"math/rand"
5	6		"testing"
6	7

@@ -46,6 +47,26 @@ func TestDisjointRectsCoverUnionOnce(t *testing.T) {
46	47		}
47	48		}
48	49
	50	+	// Client damage that would cut into too many pieces falls back to its
	51	+	// bounding box: the work stays bounded and every damaged pixel is copied.
	52	+	func TestDisjointRectsBoundsAdversarialDamage(t *testing.T) {
	53	+	const w, h = 1024, 1024
	54	+	rects := make([]ports.Rect, 128)
	55	+	for i := range rects {
	56	+	rects[i] = ports.Rect{X: i * 3, Y: i * 3, W: w - i*6, H: 4 + i}
	57	+	}
	58	+	got := disjointRects(nil, rects, w, h)
	59	+	if len(got) != 1 {
	60	+	t.Fatalf("%d pieces, want the bounding box", len(got))
	61	+	}
	62	+	for _, rc := range rects {
	63	+	r := image.Rect(rc.X, rc.Y, rc.X+rc.W, rc.Y+rc.H)
	64	+	if !r.In(got[0]) {
	65	+	t.Fatalf("damage %v outside %v", r, got[0])
	66	+	}
	67	+	}
	68	+	}
	69	+
49	70		// With a reused scratch slice the helper allocates nothing.
50	71		func TestDisjointRectsNoAllocs(t *testing.T) {
51	72		rects := []ports.Rect{{X: 0, Y: 0, W: 10, H: 10}, {X: 5, Y: 5, W: 10, H: 10}, {X: 2, Y: 8, W: 4, H: 4}}

@@ -1,6 +1,7 @@
1	package vulkan	1		package vulkan
2		2
3	import (	3		import (
		4	+	"image"
4	"math/rand"	5		"math/rand"
5	"testing"	6		"testing"
6		7

@@ -46,6 +47,26 @@ func TestDisjointRectsCoverUnionOnce(t *testing.T) {
46	}	47		}
47	}	48		}
48		49
		50	+	// Client damage that would cut into too many pieces falls back to its
		51	+	// bounding box: the work stays bounded and every damaged pixel is copied.
		52	+	func TestDisjointRectsBoundsAdversarialDamage(t *testing.T) {
		53	+	const w, h = 1024, 1024
		54	+	rects := make([]ports.Rect, 128)
		55	+	for i := range rects {
		56	+	rects[i] = ports.Rect{X: i * 3, Y: i * 3, W: w - i*6, H: 4 + i}
		57	+	}
		58	+	got := disjointRects(nil, rects, w, h)
		59	+	if len(got) != 1 {
		60	+	t.Fatalf("%d pieces, want the bounding box", len(got))
		61	+	}
		62	+	for _, rc := range rects {
		63	+	r := image.Rect(rc.X, rc.Y, rc.X+rc.W, rc.Y+rc.H)
		64	+	if !r.In(got[0]) {
		65	+	t.Fatalf("damage %v outside %v", r, got[0])
		66	+	}
		67	+	}
		68	+	}
		69	+
49	// With a reused scratch slice the helper allocates nothing.	70		// With a reused scratch slice the helper allocates nothing.
50	func TestDisjointRectsNoAllocs(t *testing.T) {	71		func TestDisjointRectsNoAllocs(t *testing.T) {
51	rects := []ports.Rect{{X: 0, Y: 0, W: 10, H: 10}, {X: 5, Y: 5, W: 10, H: 10}, {X: 2, Y: 8, W: 4, H: 4}}	72		rects := []ports.Rect{{X: 0, Y: 0, W: 10, H: 10}, {X: 5, Y: 5, W: 10, H: 10}, {X: 2, Y: 8, W: 4, H: 4}}