Improve process safety, metrics, and UI fixes

Several improvements and bugfixes across app, metrics, config and UI:

- Prevent sending signals to PID <= 1 on Unix and Windows to avoid killing init/critical processes.
- Add ProcLimit config/CLI flag (default 50) and thread it through collectSnapshot so process collection can be limited.
- Refactor metric panel rendering into buildMetricsSection to remove duplicated layout logic used by View() and computeUsedLines().
- Make GPU collection concurrent with other collectors and compute energy impact after collection; export ComputeEnergyImpact and update backends to use it.
- Handle counter wrap for network and disk deltas via safeDeltaRate/safeDiskDeltaRate and add tests for counter wrap behavior.
- Improve battery parsing to infer charging state from power source when status is absent.
- Export snapshots to the user's home directory with more restrictive file permissions (0600) and stable filename.
- Improve UI: preserve UTF-8 when truncating strings, and warn to stderr and fall back to dark theme when an unknown theme is selected.
- Add Ctrl-C handling to search to cancel collection and quit.

These changes improve robustness (prevent dangerous signals and counter-wrap artifacts), configurability (process limit), and maintainability (layout refactor).

Author: youhide

internal/app/kill_unix.go

@@ -2,7 +2,10 @@
 
 package app
 
-import "syscall"
+import (
+	"fmt"
+	"syscall"
+)
 
 // killSignal represents a signal to send to a process.
 type killSignal int
@@ -13,6 +16,10 @@ const (
 )
 
 // killProcess sends sig to the given PID.
+// Rejects PID <= 1 to prevent killing init or the entire process group.
 func killProcess(pid int, sig killSignal) error {
+	if pid <= 1 {
+		return fmt.Errorf("refusing to signal PID %d", pid)
+	}
 	return syscall.Kill(pid, syscall.Signal(sig))
 }

internal/app/kill_windows.go

@@ -16,7 +16,11 @@ const (
 )
 
 // killProcess terminates the given PID on Windows via taskkill.
+// Rejects PID <= 1 to prevent killing critical system processes.
 func killProcess(pid int, sig killSignal) error {
+	if pid <= 1 {
+		return fmt.Errorf("refusing to signal PID %d", pid)
+	}
 	var cmd *exec.Cmd
 	if sig == signalKill {
 		cmd = exec.Command("taskkill", "/F", "/PID", fmt.Sprint(pid))

internal/app/model.go

@@ -101,7 +101,7 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			ctx, cancel := context.WithTimeout(context.Background(), m.collectionTimeout())
 			m.collectCancel = cancel
 			m.collecting = true
-			cmds = append(cmds, collectSnapshot(ctx, m.sortBy, m.snap, m.processSampleEvery(), metrics.CollectOptions{
+			cmds = append(cmds, collectSnapshot(ctx, m.sortBy, m.snap, m.processSampleEvery(), m.cfg.ProcLimit, metrics.CollectOptions{
 				SkipGPU:  m.cfg.NoGPU,
 				SkipTemp: m.cfg.NoTemp,
 			}))
@@ -217,22 +217,7 @@ func (m Model) View() string {
 	}
 
 	// Render panels at appropriate widths
-	cpuPanel := ui.RenderCPU(m.snap.CPU, colL, m.cpuHistory)
-	gpuPanel := ui.RenderGPU(m.snap.GPU, colR, m.gpuHistory)
-	tempPanel := ui.RenderTemperature(m.snap.Temperature, colR)
-	netPanel := ui.RenderNetwork(m.netDelta, colL)
-	diskPanel := ui.RenderDisk(m.diskDelta, m.snap.Disk, colR)
-
-	// Memory panel width depends on whether GPU is present (left vs right column)
-	var memPanel string
-	if twoCol && gpuPanel != "" {
-		memPanel = ui.RenderMemory(m.snap.Memory, m.snap.Load, colL, m.memHistory)
-	} else if twoCol {
-		// No GPU: memory goes to the right of CPU
-		memPanel = ui.RenderMemory(m.snap.Memory, m.snap.Load, colR, m.memHistory)
-	} else {
-		memPanel = ui.RenderMemory(m.snap.Memory, m.snap.Load, colL, m.memHistory)
-	}
+	metricsSection := m.buildMetricsSection(colL, colR, twoCol)
 
 	// Filter processes and resolve PID-based selection.
 	procs := m.filteredProcesses()
@@ -248,57 +233,6 @@ func (m Model) View() string {
 		TotalProcs:  len(m.snap.Processes),
 	}
 
-	// Build the metric panels section
-	var metricRows []string
-
-	if twoCol {
-		// Two-column layout: pair panels side by side with matched heights
-		// Row 1: CPU | GPU (or Memory if no GPU)
-		if gpuPanel != "" {
-			metricRows = append(metricRows, joinPanelRow(cpuPanel, gpuPanel, colL, colR))
-		} else {
-			metricRows = append(metricRows, joinPanelRow(cpuPanel, memPanel, colL, colR))
-		}
-
-		// Row 2: Memory | Temperature (only if GPU existed in row 1)
-		if gpuPanel != "" {
-			if tempPanel != "" {
-				metricRows = append(metricRows, joinPanelRow(memPanel, tempPanel, colL, colR))
-			} else {
-				metricRows = append(metricRows, memPanel)
-			}
-		} else if tempPanel != "" {
-			metricRows = append(metricRows, tempPanel)
-		}
-
-		// Row 3: Network | Disk
-		if netPanel != "" && diskPanel != "" {
-			metricRows = append(metricRows, joinPanelRow(netPanel, diskPanel, colL, colR))
-		} else if netPanel != "" {
-			metricRows = append(metricRows, netPanel)
-		} else if diskPanel != "" {
-			metricRows = append(metricRows, diskPanel)
-		}
-	} else {
-		// Single-column stacked layout
-		metricRows = append(metricRows, cpuPanel)
-		if gpuPanel != "" {
-			metricRows = append(metricRows, gpuPanel)
-		}
-		metricRows = append(metricRows, memPanel)
-		if tempPanel != "" {
-			metricRows = append(metricRows, tempPanel)
-		}
-		if netPanel != "" {
-			metricRows = append(metricRows, netPanel)
-		}
-		if diskPanel != "" {
-			metricRows = append(metricRows, diskPanel)
-		}
-	}
-
-	metricsSection := lipgloss.JoinVertical(lipgloss.Left, metricRows...)
-
 	// Count lines used by fixed panels to size the process panel.
 	usedLines := strings.Count(header, "\n") + 1
 	usedLines += strings.Count(metricsSection, "\n") + 1
@@ -507,9 +441,6 @@ func (m Model) computeUsedLines() int {
 		w = 80
 	}
 
-	// Header is always 1 line
-	usedLines := 1
-
 	twoCol := w >= 110
 	var colL, colR int
 	if twoCol {
@@ -520,6 +451,20 @@ func (m Model) computeUsedLines() int {
 		colR = w
 	}
 
+	metricsSection := m.buildMetricsSection(colL, colR, twoCol)
+
+	// Header is always 1 line
+	usedLines := 1
+	usedLines += strings.Count(metricsSection, "\n") + 1
+	usedLines += 1 // help bar
+
+	return usedLines
+}
+
+// buildMetricsSection renders all metric panels and joins them into a single string.
+// This is the single source of truth for panel layout, used by both View() and
+// computeUsedLines() to avoid duplication.
+func (m Model) buildMetricsSection(colL, colR int, twoCol bool) string {
 	cpuPanel := ui.RenderCPU(m.snap.CPU, colL, m.cpuHistory)
 	gpuPanel := ui.RenderGPU(m.snap.GPU, colR, m.gpuHistory)
 	tempPanel := ui.RenderTemperature(m.snap.Temperature, colR)
@@ -536,6 +481,7 @@ func (m Model) computeUsedLines() int {
 	}
 
 	var metricRows []string
+
 	if twoCol {
 		if gpuPanel != "" {
 			metricRows = append(metricRows, joinPanelRow(cpuPanel, gpuPanel, colL, colR))
@@ -575,11 +521,7 @@ func (m Model) computeUsedLines() int {
 		}
 	}
 
-	metricsSection := lipgloss.JoinVertical(lipgloss.Left, metricRows...)
-	usedLines += strings.Count(metricsSection, "\n") + 1
-	usedLines += 1 // help bar
-
-	return usedLines
+	return lipgloss.JoinVertical(lipgloss.Left, metricRows...)
 }
 
 // computeProcDataY returns the Y line where process data rows begin on screen.
@@ -591,6 +533,13 @@ func (m Model) computeProcDataY() int {
 
 func (m Model) handleSearchKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 	switch msg.Type {
+	case tea.KeyCtrlC:
+		m.quitting = true
+		if m.collectCancel != nil {
+			m.collectCancel()
+			m.collectCancel = nil
+		}
+		return m, tea.Quit
 	case tea.KeyEscape:
 		m.searching = false
 		m.searchQuery = ""
@@ -724,9 +673,9 @@ func tick(d time.Duration) tea.Cmd {
 	})
 }
 
-func collectSnapshot(ctx context.Context, sortBy metrics.SortField, previous metrics.Snapshot, processSampleEvery time.Duration, opts metrics.CollectOptions) tea.Cmd {
+func collectSnapshot(ctx context.Context, sortBy metrics.SortField, previous metrics.Snapshot, processSampleEvery time.Duration, procLimit int, opts metrics.CollectOptions) tea.Cmd {
 	return func() tea.Msg {
-		snap := metrics.Collect(ctx, 200*time.Millisecond, sortBy, 50, processSampleEvery, previous, opts)
+		snap := metrics.Collect(ctx, 200*time.Millisecond, sortBy, procLimit, processSampleEvery, previous, opts)
 		return snapshotMsg(snap)
 	}
 }
@@ -766,12 +715,18 @@ func (m Model) killSelectedProcess(sig killSignal) string {
 }
 
 func (m Model) exportSnapshot() string {
-	filename := fmt.Sprintf("hideTop_%s.json", m.snap.CollectedAt.Format("20060102_150405"))
+	basename := fmt.Sprintf("hideTop_%s.json", m.snap.CollectedAt.Format("20060102_150405"))
+	// Write to user's home directory for a predictable location.
+	home, err := os.UserHomeDir()
+	if err != nil {
+		home = "."
+	}
+	filename := home + string(os.PathSeparator) + basename
 	data, err := json.MarshalIndent(m.snap, "", "  ")
 	if err != nil {
 		return fmt.Sprintf("export error: %v", err)
 	}
-	if err := os.WriteFile(filename, data, 0o644); err != nil {
+	if err := os.WriteFile(filename, data, 0o600); err != nil {
 		return fmt.Sprintf("export error: %v", err)
 	}
 	return fmt.Sprintf("exported to %s", filename)

internal/config/config.go

@@ -16,6 +16,7 @@ type Config struct {
 	NoGPU           bool
 	NoTemp          bool
 	FilterUsers     []string
+	ProcLimit       int
 }
 
 // DefaultFilterUsers is used when no custom filter is configured.
@@ -29,6 +30,7 @@ type fileConfig struct {
 	NoTemp      bool     `json:"no_temp"`
 	Debug       bool     `json:"debug"`
 	FilterUsers []string `json:"filter_users"`
+	ProcLimit   int      `json:"proc_limit"`
 }
 
 func Parse() Config {
@@ -40,6 +42,7 @@ func Parse() Config {
 	theme := flag.String("theme", "", "color theme (dark, light, dracula, nord, monokai)")
 	noGPU := flag.Bool("no-gpu", false, "disable GPU metrics")
 	noTemp := flag.Bool("no-temp", false, "disable temperature metrics")
+	procLimit := flag.Int("proc-limit", 0, "max number of processes to display (0 = 50)")
 	flag.Parse()
 
 	cfg := Config{
@@ -49,6 +52,7 @@ func Parse() Config {
 		Theme:           *theme,
 		NoGPU:           *noGPU,
 		NoTemp:          *noTemp,
+		ProcLimit:       *procLimit,
 	}
 
 	// Load config file (flags take precedence)
@@ -85,6 +89,14 @@ func Parse() Config {
 		cfg.FilterUsers = DefaultFilterUsers
 	}
 
+	// Apply proc_limit from config file if not set via CLI
+	if fc != nil && cfg.ProcLimit == 0 && fc.ProcLimit > 0 {
+		cfg.ProcLimit = fc.ProcLimit
+	}
+	if cfg.ProcLimit <= 0 {
+		cfg.ProcLimit = 50
+	}
+
 	return cfg
 }
 

internal/metrics/battery.go

@@ -76,11 +76,7 @@ func collectBatteryDarwin(_ context.Context) (BatteryStats, error) {
 
 	s := string(out)
 	stats := BatteryStats{}
-
-	// Parse: "Now drawing from 'Battery Power'" or "'AC Power'"
-	if strings.Contains(s, "'AC Power'") {
-		stats.Charging = true
-	}
+	onAC := strings.Contains(s, "'AC Power'")
 
 	// Parse percentage: "InternalBattery-0 (id=...)	85%; charging; ..."
 	for _, line := range strings.Split(s, "\n") {
@@ -116,6 +112,9 @@ func collectBatteryDarwin(_ context.Context) (BatteryStats, error) {
 		case strings.Contains(lower, "charged"):
 			stats.Status = "Full"
 			stats.Charging = false
+		default:
+			// No explicit status found; infer from power source
+			stats.Charging = onAC
 		}
 		break
 	}

internal/metrics/collector.go

@@ -37,11 +37,15 @@ func Collect(
 	)
 
 	processesDue := shouldCollectProcesses(now, processSampleEvery, sortBy, previous)
-	workers := 5 // cpu, memory, load, network, disk, battery — adjusted below
+
+	// Count workers: cpu + memory + load + network + disk + battery = 6
+	workers := 6
 	if !opts.SkipTemp {
 		workers++
 	}
-	workers++ // battery
+	if !opts.SkipGPU {
+		workers++
+	}
 	if processesDue {
 		workers++
 	} else {
@@ -180,17 +184,27 @@ func Collect(
 		}()
 	}
 
+	if !opts.SkipGPU {
+		go func() {
+			defer wg.Done()
+			g := gpu.Collect(ctx, 0) // cpuTotal not needed for raw GPU metrics
+			mu.Lock()
+			defer mu.Unlock()
+			if g.Available {
+				snap.GPU = &g
+			} else if previous.GPU != nil && previous.GPU.Available {
+				snap.GPU = previous.GPU
+				snap.Status.GPU = staleStatus(errors.New("collector unavailable"))
+			}
+		}()
+	}
+
 	wg.Wait()
 
-	// GPU collection runs after CPU so it can use cpuTotal for energy impact.
-	if !opts.SkipGPU {
-		g := gpu.Collect(ctx, snap.CPU.Total)
-		if g.Available {
-			snap.GPU = &g
-		} else if previous.GPU != nil && previous.GPU.Available {
-			snap.GPU = previous.GPU
-			snap.Status.GPU = staleStatus(errors.New("collector unavailable"))
-		}
+	// Compute energy impact after all metrics are collected, since it
+	// depends on both CPU and GPU utilization.
+	if snap.GPU != nil && snap.GPU.Available {
+		snap.GPU.Energy = gpu.ComputeEnergyImpact(snap.CPU.Total, snap.GPU.Utilization, true, snap.GPU.Thermal)
 	}
 
 	return snap