fix: dispose old buffers in BufferSet.Reset() to prevent marker leaks

BufferSet.Reset() created new Buffer instances without disposing the old
ones, leaving markers and their event listeners on the old CircularList
alive. This adds Buffer.Dispose() and calls it from BufferSet.Reset()
and BufferSet.Dispose() before replacing or releasing buffers.

Fixes #24

Co-authored-by: Ona <no-reply@ona.com>

Author: ona-automations

buffer.go

@@ -574,6 +574,11 @@ func (b *Buffer) ClearAllMarkers() {
 	b.isClearing = false
 }
 
+// Dispose cleans up the buffer by disposing all markers and their event listeners.
+func (b *Buffer) Dispose() {
+	b.ClearAllMarkers()
+}
+
 // AddMarker creates a marker at the given line and registers it for
 // automatic adjustment on trim/insert/delete events.
 func (b *Buffer) AddMarker(y int) *Marker {

buffer_test.go

@@ -438,6 +438,23 @@ func TestBufferClearAllMarkers(t *testing.T) {
 	}
 }
 
+func TestBufferDispose(t *testing.T) {
+	t.Parallel()
+	type Expectation struct {
+		MarkerCount    int
+		MarkerDisposed bool
+	}
+	b := NewBuffer(defaultBufferOpts())
+	b.FillViewportRows(nil)
+	m := b.AddMarker(3)
+	b.Dispose()
+	got := Expectation{MarkerCount: len(b.Markers), MarkerDisposed: m.IsDisposed}
+	expected := Expectation{MarkerCount: 0, MarkerDisposed: true}
+	if diff := cmp.Diff(expected, got); diff != "" {
+		t.Errorf("(-want +got):\n%s", diff)
+	}
+}
+
 func TestBufferGetNullCell(t *testing.T) {
 	t.Parallel()
 	type Expectation struct {

bufferset.go

@@ -35,7 +35,14 @@ func NewBufferSet(cols, rows, scrollback, tabStopWidth int) *BufferSet {
 }
 
 // Reset recreates both buffers and activates the normal buffer.
+// Old buffers are disposed to clean up markers and event listeners.
 func (bs *BufferSet) Reset() {
+	if bs.normal != nil {
+		bs.normal.Dispose()
+	}
+	if bs.alt != nil {
+		bs.alt.Dispose()
+	}
 	bs.normal = NewBuffer(BufferOptions{
 		Cols:          bs.cols,
 		Rows:          bs.rows,
@@ -119,7 +126,13 @@ func (bs *BufferSet) SetupTabStops(startCol int) {
 	bs.alt.SetupTabStops(startCol)
 }
 
-// Dispose cleans up event emitters.
+// Dispose cleans up buffers and event emitters.
 func (bs *BufferSet) Dispose() {
+	if bs.normal != nil {
+		bs.normal.Dispose()
+	}
+	if bs.alt != nil {
+		bs.alt.Dispose()
+	}
 	bs.OnBufferActivateEmitter.Dispose()
 }

bufferset_test.go

@@ -141,6 +141,48 @@ func TestBufferSetReset(t *testing.T) {
 	}
 }
 
+func TestBufferSetResetDisposesOldMarkers(t *testing.T) {
+	t.Parallel()
+	type Expectation struct {
+		NormalMarkerDisposed bool
+		AltMarkerDisposed    bool
+		NewNormalMarkerCount int
+	}
+	bs := NewBufferSet(80, 24, 1000, 8)
+	normalMarker := bs.Normal().AddMarker(0)
+	bs.ActivateAltBuffer(nil)
+	altMarker := bs.Alt().AddMarker(0)
+	bs.Reset()
+	got := Expectation{
+		NormalMarkerDisposed: normalMarker.IsDisposed,
+		AltMarkerDisposed:    altMarker.IsDisposed,
+		NewNormalMarkerCount: len(bs.Normal().Markers),
+	}
+	expected := Expectation{
+		NormalMarkerDisposed: true,
+		AltMarkerDisposed:    true,
+		NewNormalMarkerCount: 0,
+	}
+	if diff := cmp.Diff(expected, got); diff != "" {
+		t.Errorf("(-want +got):\n%s", diff)
+	}
+}
+
+func TestBufferSetDisposeDisposesBufferMarkers(t *testing.T) {
+	t.Parallel()
+	type Expectation struct {
+		MarkerDisposed bool
+	}
+	bs := NewBufferSet(80, 24, 1000, 8)
+	marker := bs.Normal().AddMarker(0)
+	bs.Dispose()
+	got := Expectation{MarkerDisposed: marker.IsDisposed}
+	expected := Expectation{MarkerDisposed: true}
+	if diff := cmp.Diff(expected, got); diff != "" {
+		t.Errorf("(-want +got):\n%s", diff)
+	}
+}
+
 func TestBufferSetResize(t *testing.T) {
 	t.Parallel()
 	type Expectation struct {