fix(client): restore the real cursor when only a predicted cursor moved

commit: f0493e8b37547ae9cfd26afa7fc76a018e3219ab
author: brice · 14d ago · 2026-10-08 08:52 UTC
committer: brice · 14d ago · 2026-10-08 09:31 UTC
parent: fe83619
signature: GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email

2 files · +23 -11

M internal/usecase/client/predictive_echo.go +1 -1


@@ -619,7 +619,7 @@ func (p *echoPredictor) needsTick() bool {
619	619		// scrolls would otherwise move a guess where nothing ever repairs it. The
620	620		// guesses stay pending and render draws them again after the frame.
621	621		func (p *echoPredictor) undraw() []byte {
622		-	if len(p.drawn) == 0 {
	622	+	if len(p.drawn) == 0 && !p.cursorMove {
623	623		return nil
624	624		}
625	625		var out bytes.Buffer


@@ -619,7 +619,7 @@ func (p *echoPredictor) needsTick() bool {
619		// scrolls would otherwise move a guess where nothing ever repairs it. The	619		// scrolls would otherwise move a guess where nothing ever repairs it. The
620		// guesses stay pending and render draws them again after the frame.	620		// guesses stay pending and render draws them again after the frame.
621		func (p *echoPredictor) undraw() []byte {	621		func (p *echoPredictor) undraw() []byte {
622	-	if len(p.drawn) == 0 {	622	+	if len(p.drawn) == 0 && !p.cursorMove {
623		return nil	623		return nil
624		}	624		}
625		var out bytes.Buffer	625		var out bytes.Buffer

M internal/usecase/client/predictive_echo_test.go +22 -10


@@ -141,17 +141,29 @@ func TestEchoPredictorEnterKeepsDrawnGuessesUntilAFrame(t *testing.T) {
141	141
142	142		func TestEchoPredictorUndrawRestoresMirror(t *testing.T) {
143	143		t.Parallel()
144		-	h := newEchoHarness(t, domain.EchoPredictAlways)
145		-	h.warm(100 * time.Millisecond)
146		-	h.confirm()
147		-	if got := h.typed("b"); !bytes.Contains(got, []byte("b")) {
148		-	t.Fatalf("render = %q, want the guess drawn", got)
149		-	}
150		-	if got, want := string(h.p.undraw()), "\x1b[1;4H\x1b[0m \x1b[0m\x1b[1;4H"; got != want {
151		-	t.Fatalf("undraw = %q, want %q", got, want)
	144	+	tests := []struct {
	145	+	name, typed, want string
	146	+	}{
	147	+	{name: "drawn guess", typed: "b", want: "\x1b[1;4H\x1b[0m \x1b[0m\x1b[1;4H"},
	148	+	// A blank guess matches the mirror cell, so only the cursor moved.
	149	+	{name: "cursor-only guess", typed: " ", want: "\x1b[0m\x1b[1;4H"},
152	150		}
153		-	if got := h.p.undraw(); len(got) != 0 {
154		-	t.Fatalf("second undraw = %q, want nothing", got)
	151	+	for _, tt := range tests {
	152	+	t.Run(tt.name, func(t *testing.T) {
	153	+	t.Parallel()
	154	+	h := newEchoHarness(t, domain.EchoPredictAlways)
	155	+	h.warm(100 * time.Millisecond)
	156	+	h.confirm()
	157	+	if got := h.typed(tt.typed); len(got) == 0 {
	158	+	t.Fatal("guess rendered nothing")
	159	+	}
	160	+	if got := string(h.p.undraw()); got != tt.want {
	161	+	t.Fatalf("undraw = %q, want %q", got, tt.want)
	162	+	}
	163	+	if got := h.p.undraw(); len(got) != 0 {
	164	+	t.Fatalf("second undraw = %q, want nothing", got)
	165	+	}
	166	+	})
155	167		}
156	168		}
157	169

 func TestEchoPredictorUndrawRestoresMirror(t *testing.T) {
 	t.Parallel()
-	h := newEchoHarness(t, domain.EchoPredictAlways)
+	tests := []struct {
-	h.warm(100 * time.Millisecond)
+		name, typed, want string
-	h.confirm()
+	}{
-	if got := h.typed("b"); !bytes.Contains(got, []byte("b")) {
+		{name: "drawn guess", typed: "b", want: "\x1b[1;4H\x1b[0m \x1b[0m\x1b[1;4H"},
-		t.Fatalf("render = %q, want the guess drawn", got)
+		// A blank guess matches the mirror cell, so only the cursor moved.
-	}
+		{name: "cursor-only guess", typed: " ", want: "\x1b[0m\x1b[1;4H"},
-	if got, want := string(h.p.undraw()), "\x1b[1;4H\x1b[0m \x1b[0m\x1b[1;4H"; got != want {
-		t.Fatalf("undraw = %q, want %q", got, want)
 	}
-	if got := h.p.undraw(); len(got) != 0 {
+	for _, tt := range tests {
-		t.Fatalf("second undraw = %q, want nothing", got)
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			h := newEchoHarness(t, domain.EchoPredictAlways)
+			h.warm(100 * time.Millisecond)
+			h.confirm()
+			if got := h.typed(tt.typed); len(got) == 0 {
+				t.Fatal("guess rendered nothing")
+			}
+			if got := string(h.p.undraw()); got != tt.want {
+				t.Fatalf("undraw = %q, want %q", got, tt.want)
+			}
+			if got := h.p.undraw(); len(got) != 0 {
+				t.Fatalf("second undraw = %q, want nothing", got)
+			}
+		})
 	}
 }