fix(wayland): sum relative pointer deltas when collapsing queued motions

commit: a589526e41b1148ba827652728db82a8139f29b6
author: brice · 27d ago · 2026-09-26 14:24 UTC
parent: bc84cb3
signature: GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email

2 files · +13 -5

M internal/adapters/wayland/commands_test.go +5 -4


@@ -12,16 +12,17 @@ import (
12	12
13	13		func TestDrainCommandsCollapsesMotion(t *testing.T) {
14	14		cmds := make(chan ports.ClientCommand, 16)
15		-	cmds <- ports.PointerMotionTo{ID: 1, X: 2}
16		-	cmds <- ports.PointerMotionTo{ID: 1, X: 3}
	15	+	cmds <- ports.PointerMotionTo{ID: 1, X: 2, DX: 0.25, UnaccelDX: 0.5}
	16	+	cmds <- ports.PointerMotionTo{ID: 1, X: 3, DX: 0.25, DY: -0.5, UnaccelDX: 0.5, UnaccelDY: -1}
17	17		cmds <- ports.PointerButtonTo{ID: 1, Button: 272, Pressed: true}
18	18		cmds <- ports.PointerMotionTo{ID: 1, X: 4}
19	19		cmds <- ports.PointerFocus{ID: 2}
20	20		cmds <- ports.PointerMotionTo{ID: 2, X: 5}
21	21		cmds <- ports.PointerMotionTo{ID: 2, X: 6}
22		-	batch, open := drainCommands(ports.PointerMotionTo{ID: 1, X: 1}, cmds)
	22	+	batch, open := drainCommands(ports.PointerMotionTo{ID: 1, X: 1, DX: 0.25, UnaccelDX: 0.5}, cmds)
23	23		want := []ports.ClientCommand{
24		-	ports.PointerMotionTo{ID: 1, X: 3},
	24	+	// Slow motions add up: none of the sub-pixel deltas is lost.
	25	+	ports.PointerMotionTo{ID: 1, X: 3, DX: 0.75, DY: -0.5, UnaccelDX: 1.5, UnaccelDY: -1},
25	26		ports.PointerButtonTo{ID: 1, Button: 272, Pressed: true},
26	27		ports.PointerMotionTo{ID: 1, X: 4},
27	28		ports.PointerFocus{ID: 2},

 func TestDrainCommandsCollapsesMotion(t *testing.T) {
 	cmds := make(chan ports.ClientCommand, 16)
-	cmds <- ports.PointerMotionTo{ID: 1, X: 2}
+	cmds <- ports.PointerMotionTo{ID: 1, X: 2, DX: 0.25, UnaccelDX: 0.5}
-	cmds <- ports.PointerMotionTo{ID: 1, X: 3}
+	cmds <- ports.PointerMotionTo{ID: 1, X: 3, DX: 0.25, DY: -0.5, UnaccelDX: 0.5, UnaccelDY: -1}
 	cmds <- ports.PointerButtonTo{ID: 1, Button: 272, Pressed: true}
 	cmds <- ports.PointerMotionTo{ID: 1, X: 4}
 	cmds <- ports.PointerFocus{ID: 2}
 	cmds <- ports.PointerMotionTo{ID: 2, X: 5}
 	cmds <- ports.PointerMotionTo{ID: 2, X: 6}
-	batch, open := drainCommands(ports.PointerMotionTo{ID: 1, X: 1}, cmds)
+	batch, open := drainCommands(ports.PointerMotionTo{ID: 1, X: 1, DX: 0.25, UnaccelDX: 0.5}, cmds)
 	want := []ports.ClientCommand{
-		ports.PointerMotionTo{ID: 1, X: 3},
+		// Slow motions add up: none of the sub-pixel deltas is lost.
+		ports.PointerMotionTo{ID: 1, X: 3, DX: 0.75, DY: -0.5, UnaccelDX: 1.5, UnaccelDY: -1},
 		ports.PointerButtonTo{ID: 1, Button: 272, Pressed: true},
 		ports.PointerMotionTo{ID: 1, X: 4},
 		ports.PointerFocus{ID: 2},

M internal/adapters/wayland/server.go +8 -1


@@ -432,7 +432,8 @@ func (s *Server) forwardContents(ctx context.Context) {
432	432		const maxCommandBatch = 256
433	433
434	434		// drainCommands returns first plus the commands already queued, with runs of
435		-	// pointer motion for the same window collapsed into the latest one. open is
	435	+	// pointer motion for the same window collapsed into the latest one, their
	436	+	// relative deltas summed. open is
436	437		// false once the channel is closed.
437	438		func drainCommands(first ports.ClientCommand, cmds <-chan ports.ClientCommand) (batch []ports.ClientCommand, open bool) {
438	439		batch = append(batch, first)

@@ -444,6 +445,12 @@ func drainCommands(first ports.ClientCommand, cmds <-chan ports.ClientCommand) (
444	445		}
445	446		if m, isMotion := c.(ports.PointerMotionTo); isMotion {
446	447		if last, lastMotion := batch[len(batch)-1].(ports.PointerMotionTo); lastMotion && last.ID == m.ID {
	448	+	// The position is the latest; relative deltas add up so
	449	+	// locked pointers (games) lose no movement.
	450	+	m.DX += last.DX
	451	+	m.DY += last.DY
	452	+	m.UnaccelDX += last.UnaccelDX
	453	+	m.UnaccelDY += last.UnaccelDY
447	454		batch[len(batch)-1] = m
448	455		continue
449	456		}

 const maxCommandBatch = 256
 // drainCommands returns first plus the commands already queued, with runs of
-// pointer motion for the same window collapsed into the latest one. open is
+// pointer motion for the same window collapsed into the latest one, their
+// relative deltas summed. open is
 // false once the channel is closed.
 func drainCommands(first ports.ClientCommand, cmds <-chan ports.ClientCommand) (batch []ports.ClientCommand, open bool) {
 	batch = append(batch, first)
 			}
 			if m, isMotion := c.(ports.PointerMotionTo); isMotion {
 				if last, lastMotion := batch[len(batch)-1].(ports.PointerMotionTo); lastMotion && last.ID == m.ID {
+					// The position is the latest; relative deltas add up so
+					// locked pointers (games) lose no movement.
+					m.DX += last.DX
+					m.DY += last.DY
+					m.UnaccelDX += last.UnaccelDX
+					m.UnaccelDY += last.UnaccelDY
 					batch[len(batch)-1] = m
 					continue
 				}