Fix initial TUI sizing and align two-row sparklines

7 files changed, 137 insertions, 39 deletions

diff --git a/internal/tui/common/viewport.go b/internal/tui/common/viewport.go
new file mode 100644
index 0000000..e1729db
--- /dev/null
+++ b/internal/tui/common/viewport.go
@@ -0,0 +1,38 @@
+package common
+
+import (
+	"os"
+
+	xterm "github.com/charmbracelet/x/term"
+)
+
+const (
+	defaultViewportWidth  = 80
+	defaultViewportHeight = 24
+)
+
+// EffectiveViewport returns a usable terminal viewport size. Missing or invalid
+// dimensions are resolved from the active terminal when possible.
+func EffectiveViewport(width, height int) (int, int) {
+	if width > 0 && height > 0 {
+		return width, height
+	}
+
+	termWidth, termHeight, err := xterm.GetSize(os.Stdout.Fd())
+	if err == nil {
+		if width <= 0 && termWidth > 0 {
+			width = termWidth
+		}
+		if height <= 0 && termHeight > 0 {
+			height = termHeight
+		}
+	}
+
+	if width <= 0 {
+		width = defaultViewportWidth
+	}
+	if height <= 0 {
+		height = defaultViewportHeight
+	}
+	return width, height
+}
diff --git a/internal/tui/dashboard/histogram.go b/internal/tui/dashboard/histogram.go
index 1e68a7b..47942fe 100644
--- a/internal/tui/dashboard/histogram.go
+++ b/internal/tui/dashboard/histogram.go
@@ -15,7 +15,7 @@ func renderLatencyTab(snap *statsengine.Snapshot, width, height int) string {
 	}
 
 	hist := renderHistogram(snap.LatencyHistogram, "Latency Histogram", width, height)
-	spark := common.PanelStyle.Render("Latency sparkline: " + renderSparkline(snap.LatencySeriesNs(), sparklineWidth(width)))
+	spark := common.PanelStyle.Render(renderLabeledSparkline("Latency sparkline:", snap.LatencySeriesNs(), sparklineWidth(width)))
 	return strings.Join([]string{hist, spark}, "\n")
 }
 
@@ -25,7 +25,7 @@ func renderGapsTab(snap *statsengine.Snapshot, width, height int) string {
 	}
 
 	hist := renderHistogram(snap.GapHistogram, "Gap Histogram", width, height)
-	spark := common.PanelStyle.Render("Gap sparkline: " + renderSparkline(snap.GapSeriesNs(), sparklineWidth(width)))
+	spark := common.PanelStyle.Render(renderLabeledSparkline("Gap sparkline:", snap.GapSeriesNs(), sparklineWidth(width)))
 	return strings.Join([]string{hist, spark}, "\n")
 }
 
diff --git a/internal/tui/dashboard/model.go b/internal/tui/dashboard/model.go
index 78da351..56e1980 100644
--- a/internal/tui/dashboard/model.go
+++ b/internal/tui/dashboard/model.go
@@ -241,10 +241,12 @@ func (m *Model) SetStreamSource(source *eventstream.RingBuffer) {
 
 // View renders the tab bar, active tab scaffold, and help bar.
 func (m Model) View() string {
+	width, height := common.EffectiveViewport(m.width, m.height)
+
 	var b strings.Builder
-	b.WriteString(renderTabBar(m.activeTab, m.width))
+	b.WriteString(renderTabBar(m.activeTab, width))
 	b.WriteString("\n")
-	b.WriteString(renderActiveTab(m.activeTab, m.latest, &m.streamModel, m.width, m.height, m.syscallsOffset, m.filesOffset, m.processesOffset))
+	b.WriteString(renderActiveTab(m.activeTab, m.latest, &m.streamModel, width, height, m.syscallsOffset, m.filesOffset, m.processesOffset))
 	b.WriteString("\n")
 	b.WriteString(common.HighlightStyle.Render("Press ? for help"))
 	b.WriteString("\n")
diff --git a/internal/tui/dashboard/overview.go b/internal/tui/dashboard/overview.go
index 9feafab..7cbc7fe 100644
--- a/internal/tui/dashboard/overview.go
+++ b/internal/tui/dashboard/overview.go
@@ -29,9 +29,9 @@ func renderOverview(snap *statsengine.Snapshot, width, height int) string {
 		trendWithArrow(snap.ThroughputTrend),
 	)
 
-	latencySpark := "Latency: " + renderSparkline(snap.LatencySeriesNs(), sparklineWidth(width))
-	gapSpark := "Gap: " + renderSparkline(snap.GapSeriesNs(), sparklineWidth(width))
-	throughputSpark := "Throughput: " + renderSparkline(snap.ThroughputSeriesB(), sparklineWidth(width))
+	latencySpark := renderLabeledSparkline("Latency:", snap.LatencySeriesNs(), sparklineWidth(width))
+	gapSpark := renderLabeledSparkline("Gap:", snap.GapSeriesNs(), sparklineWidth(width))
+	throughputSpark := renderLabeledSparkline("Throughput:", snap.ThroughputSeriesB(), sparklineWidth(width))
 	topSyscalls := "Top syscalls: " + summarizeTopSyscalls(snap)
 	topFiles := "Top files: " + summarizeTopFiles(snap)
 	topProcesses := "Top processes: " + summarizeTopProcesses(snap)
diff --git a/internal/tui/dashboard/sparkline.go b/internal/tui/dashboard/sparkline.go
index 9c1f2c4..b94d84f 100644
--- a/internal/tui/dashboard/sparkline.go
+++ b/internal/tui/dashboard/sparkline.go
@@ -1,8 +1,9 @@
 package dashboard
 
 import "math"
+import "strings"
 
-var sparkChars = []rune("▁▂▃▄▅▆▇█")
+var sparkRowChars = []rune(" ▁▂▃▄▅▆▇█")
 
 func renderSparkline(data []float64, width int) string {
 	if len(data) == 0 || width <= 0 {
@@ -11,27 +12,51 @@ func renderSparkline(data []float64, width int) string {
 
 	samples := sampleForWidth(data, width)
 	min, max := minMax(samples)
-	line := ""
 	if min == max {
-		line = repeatRune('▄', len(samples))
-		return line + "\n" + line
+		top := repeatRune(' ', len(samples))
+		bottom := repeatRune('█', len(samples))
+		return top + "\n" + bottom
 	}
 
-	out := make([]rune, len(samples))
-	scale := float64(len(sparkChars) - 1)
+	top := make([]rune, len(samples))
+	bottom := make([]rune, len(samples))
+	scale := 16.0
 	denom := max - min
 	for i, value := range samples {
-		idx := int(math.Round((value - min) / denom * scale))
-		if idx < 0 {
-			idx = 0
+		level := int(math.Round((value - min) / denom * scale))
+		if level < 0 {
+			level = 0
 		}
-		if idx >= len(sparkChars) {
-			idx = len(sparkChars) - 1
+		if level > 16 {
+			level = 16
 		}
-		out[i] = sparkChars[idx]
+
+		topLevel := level - 8
+		if topLevel < 0 {
+			topLevel = 0
+		}
+		bottomLevel := level
+		if bottomLevel > 8 {
+			bottomLevel = 8
+		}
+
+		top[i] = sparkRowChars[topLevel]
+		bottom[i] = sparkRowChars[bottomLevel]
+	}
+	return string(top) + "\n" + string(bottom)
+}
+
+func renderLabeledSparkline(label string, data []float64, width int) string {
+	spark := renderSparkline(data, width)
+	if spark == "" {
+		return label
+	}
+	lines := strings.Split(spark, "\n")
+	if len(lines) == 1 {
+		return label + " " + lines[0]
 	}
-	line = string(out)
-	return line + "\n" + line
+	pad := repeatRune(' ', len([]rune(label))+1)
+	return label + " " + lines[0] + "\n" + pad + lines[1]
 }
 
 func sampleForWidth(data []float64, width int) []float64 {
diff --git a/internal/tui/dashboard/sparkline_test.go b/internal/tui/dashboard/sparkline_test.go
index d39d145..97dac03 100644
--- a/internal/tui/dashboard/sparkline_test.go
+++ b/internal/tui/dashboard/sparkline_test.go
@@ -16,28 +16,50 @@ func TestRenderSparklineEmptyOrInvalidWidth(t *testing.T) {
 
 func TestRenderSparklineSingleValue(t *testing.T) {
 	got := renderSparkline([]float64{10}, 8)
-	if got != "▄" {
-		t.Fatalf("expected single mid-bar rune, got %q", got)
+	if got != " \n█" {
+		t.Fatalf("expected two-line constant sparkline, got %q", got)
 	}
 }
 
 func TestRenderSparklineAllEqualValues(t *testing.T) {
 	got := renderSparkline([]float64{5, 5, 5, 5}, 4)
-	if got != "▄▄▄▄" {
-		t.Fatalf("expected flat sparkline, got %q", got)
+	if got != "    \n████" {
+		t.Fatalf("expected two-line flat sparkline, got %q", got)
 	}
 }
 
 func TestRenderSparklineRespectsWidthTruncation(t *testing.T) {
 	got := renderSparkline([]float64{1, 2, 3, 4, 5, 6, 7, 8}, 4)
-	if len([]rune(got)) != 4 {
-		t.Fatalf("expected 4 runes, got %q", got)
+	lines := strings.Split(got, "\n")
+	if len(lines) != 2 {
+		t.Fatalf("expected 2 lines, got %q", got)
+	}
+	if len([]rune(lines[0])) != 4 || len([]rune(lines[1])) != 4 {
+		t.Fatalf("expected 4 runes per line, got %q", got)
 	}
 }
 
 func TestRenderSparklineSpansLowToHigh(t *testing.T) {
 	got := renderSparkline([]float64{0, 10}, 2)
-	if !strings.Contains(got, "▁") || !strings.Contains(got, "█") {
-		t.Fatalf("expected low/high bars, got %q", got)
+	lines := strings.Split(got, "\n")
+	if len(lines) != 2 {
+		t.Fatalf("expected 2 lines, got %q", got)
+	}
+	if !strings.Contains(got, "█") {
+		t.Fatalf("expected high bar, got %q", got)
+	}
+}
+
+func TestRenderLabeledSparklineAlignsSecondRow(t *testing.T) {
+	got := renderLabeledSparkline("Latency:", []float64{0, 10}, 2)
+	lines := strings.Split(got, "\n")
+	if len(lines) != 2 {
+		t.Fatalf("expected 2 lines, got %q", got)
+	}
+	if !strings.HasPrefix(lines[0], "Latency: ") {
+		t.Fatalf("expected label prefix on first row, got %q", lines[0])
+	}
+	if !strings.HasPrefix(lines[1], "         ") {
+		t.Fatalf("expected padding on second row to align sparkline, got %q", lines[1])
 	}
 }
diff --git a/internal/tui/tui.go b/internal/tui/tui.go
index 7e77a81..5aff6a2 100644
--- a/internal/tui/tui.go
+++ b/internal/tui/tui.go
@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"ior/internal/flags"
 	"ior/internal/statsengine"
+	common "ior/internal/tui/common"
 	dashboardui "ior/internal/tui/dashboard"
 	"ior/internal/tui/eventstream"
 	tuiexport "ior/internal/tui/export"
@@ -144,10 +145,18 @@ func NewModel(initialPID int, startTrace TraceStarter) Model {
 
 // Init initializes the active child model and optional tracing startup command.
 func (m Model) Init() tea.Cmd {
+	sizeCmd := initialWindowSizeCmd()
 	if m.screen == ScreenDashboard && m.attaching {
-		return tea.Batch(m.spin.Tick, m.beginTraceCmd())
+		return tea.Batch(sizeCmd, tea.WindowSize(), m.spin.Tick, m.beginTraceCmd())
+	}
+	return tea.Batch(sizeCmd, tea.WindowSize(), m.pidPicker.Init())
+}
+
+func initialWindowSizeCmd() tea.Cmd {
+	return func() tea.Msg {
+		width, height := common.EffectiveViewport(0, 0)
+		return tea.WindowSizeMsg{Width: width, Height: height}
 	}
-	return m.pidPicker.Init()
 }
 
 // Update routes messages, transitions screens, and manages tracing startup state.
@@ -288,34 +297,36 @@ func (m Model) View() string {
 		return ""
 	}
 
+	width, height := common.EffectiveViewport(m.width, m.height)
+
 	if m.attaching {
 		line := fmt.Sprintf("%s Attaching tracepoints...", m.spin.View())
-		return placeToViewport(m.width, m.height, ScreenStyle.Render(PanelStyle.Render(line)))
+		return placeToViewport(width, height, ScreenStyle.Render(PanelStyle.Render(line)))
 	}
 
 	if m.lastErr != nil {
-		return placeToViewport(m.width, m.height, ScreenStyle.Render(ErrorStyle.Render(m.lastErr.Error())))
+		return placeToViewport(width, height, ScreenStyle.Render(ErrorStyle.Render(m.lastErr.Error())))
 	}
 
 	switch m.screen {
 	case ScreenPIDPicker:
 		base := m.pidPicker.View()
 		if m.exporter.Visible() {
-			return placeToViewport(m.width, m.height, m.exporter.View(m.width, m.height)+"\n"+base)
+			return placeToViewport(width, height, m.exporter.View(width, height)+"\n"+base)
 		}
 		if m.showHelp {
-			return placeToViewport(m.width, m.height, renderHelpOverlay(m.width, m.height, [][]key.Binding{m.keys.PickerShortHelp()})+"\n"+base)
+			return placeToViewport(width, height, renderHelpOverlay(width, height, [][]key.Binding{m.keys.PickerShortHelp()})+"\n"+base)
 		}
-		return placeToViewport(m.width, m.height, base)
+		return placeToViewport(width, height, base)
 	case ScreenDashboard:
 		base := m.dashboard.View()
 		if m.exporter.Visible() {
-			return placeToViewport(m.width, m.height, m.exporter.View(m.width, m.height)+"\n"+base)
+			return placeToViewport(width, height, m.exporter.View(width, height)+"\n"+base)
 		}
 		if m.showHelp {
-			return placeToViewport(m.width, m.height, renderHelpOverlay(m.width, m.height, m.keys.DashboardFullHelp())+"\n"+base)
+			return placeToViewport(width, height, renderHelpOverlay(width, height, m.keys.DashboardFullHelp())+"\n"+base)
 		}
-		return placeToViewport(m.width, m.height, base)
+		return placeToViewport(width, height, base)
 	default:
 		return ""
 	}