task 364: animate flamegraph zoom transitions

2 files changed, 32 insertions, 3 deletions

diff --git a/internal/tui/flamegraph/model.go b/internal/tui/flamegraph/model.go
index c1693b1..8433fea 100644
--- a/internal/tui/flamegraph/model.go
+++ b/internal/tui/flamegraph/model.go
@@ -283,7 +283,7 @@ func (m Model) Paused() bool {
 func (m *Model) SetViewport(width, height int) {
 	m.width = width
 	m.height = height
-	m.rebuildFrames(false)
+	m.rebuildFrames(true)
 }
 
 // SetDarkMode sets the active color theme mode.
@@ -331,7 +331,7 @@ func (m *Model) zoomIn() {
 	m.zoomRoot = target
 	m.zoomPath = selectedPath
 	m.selectedIdx = 0
-	m.rebuildFrames(false)
+	m.rebuildFrames(true)
 }
 
 func (m *Model) zoomUndo() {
@@ -347,7 +347,7 @@ func (m *Model) zoomUndo() {
 		m.zoomRoot = findNodeByPath(m.snapshot, m.zoomPath)
 	}
 	m.selectedIdx = last.previousSelectedIdx
-	m.rebuildFrames(false)
+	m.rebuildFrames(true)
 }
 
 func (m *Model) zoomReset() {
diff --git a/internal/tui/flamegraph/model_test.go b/internal/tui/flamegraph/model_test.go
index 45e0c48..326c2d8 100644
--- a/internal/tui/flamegraph/model_test.go
+++ b/internal/tui/flamegraph/model_test.go
@@ -165,6 +165,35 @@ func TestZoomInUndoResetAndNestedZoom(t *testing.T) {
 	}
 }
 
+func TestZoomTransitionAnimatesToNewLayout(t *testing.T) {
+	m := newZoomModel()
+	pathA := "root" + pathSeparator + "A"
+	preWidth := m.frames[mustFrameIndex(t, m.frames, pathA)].Width
+
+	m.selectedIdx = mustFrameIndex(t, m.frames, pathA)
+	m = pressFlameKey(t, m, tea.KeyPressMsg{Code: tea.KeyEnter})
+	if !m.animating {
+		t.Fatalf("expected zoom-in to start animation")
+	}
+	currentWidth := m.frames[mustFrameIndex(t, m.frames, pathA)].Width
+	targetWidth := m.targetFrames[mustFrameIndex(t, m.targetFrames, pathA)].Width
+	if currentWidth == targetWidth {
+		t.Fatalf("expected intermediate zoom frame width to differ from target (current=%d target=%d, pre=%d)", currentWidth, targetWidth, preWidth)
+	}
+
+	for i := 0; i < 180 && m.animating; i++ {
+		next, _ := m.Update(animTickMsg{})
+		m = next.(Model)
+	}
+	if m.animating {
+		t.Fatalf("expected zoom animation to settle within 180 ticks")
+	}
+	finalWidth := m.frames[mustFrameIndex(t, m.frames, pathA)].Width
+	if finalWidth != targetWidth {
+		t.Fatalf("expected final zoom width %d, got %d", targetWidth, finalWidth)
+	}
+}
+
 func TestSearchLifecycleAndMatchNavigation(t *testing.T) {
 	m := NewModel(nil)
 	m.frames = []tuiFrame{