[client] Create GUI windows on demand and destroy them on close

The main and Settings windows were created at startup and kept alive hidden on
close, so an idle tray held two webview processes for surfaces the user may
never open. Both are now built on first show and destroyed on close, which
takes the idle footprint on macOS from ~160 MB to ~74 MB.

The WindowManager owns creation: it rebuilds the main window on the next show
and hands out live pointers, since a stored one goes stale. Every show is
deferred until the frontend reports it has rendered, so a freshly created
window is never on screen empty, with a timeout so a frontend that never
reports cannot strand a window hidden.

client/ui/services/windowmanager.go

@@ -8,6 +8,7 @@ import (
 	"sync"
 	"time"
 
+	log "github.com/sirupsen/logrus"
 	"github.com/wailsapp/wails/v3/pkg/application"
 	"github.com/wailsapp/wails/v3/pkg/events"
 
@@ -29,6 +30,10 @@ const EventBrowserLoginCancel = "browser-login:cancel"
 // EventSettingsOpen tells the mounted settings window which tab to show.
 const EventSettingsOpen = "netbird:settings:open"
 
+const EventWindowPainted = "netbird:window-painted"
+
+const paintedFallback = 2 * time.Second
+
 var WindowBackgroundColour = application.NewRGB(24, 26, 29) // bg-nb-gray-950
 
 // WindowHeight is shared by the main and Settings windows.
@@ -94,9 +99,6 @@ func DialogWindowOptions(name, title, url string, linuxIcon []byte) application.
 	}
 }
 
-// WindowManager owns the auxiliary windows (main is created in main.go). Settings is created
-// eagerly and hidden on close to keep React state; the rest are created on open, destroyed on
-// close, so the macOS dock-reopen handler finds no hidden window to resurrect.
 type WindowManager struct {
 	app               *application.App
 	mainWindow        *application.WebviewWindow
@@ -112,15 +114,29 @@ type WindowManager struct {
 	// hiddenForLogin holds windows hidden while the BrowserLogin popup is open, restored on close.
 	hiddenForLogin []application.Window
 	mu             sync.Mutex
+	newMain        func() *application.WebviewWindow
+	ready          map[uint]bool
+	showPending    map[uint]bool
+	pendingTab     map[uint]string
+	fallbackTimers map[uint]*time.Timer
 	// recenterOnShow is set only on the minimal-WM/XEmbed path, where the WM neither centers nor
 	// restores position; nil on full desktops so re-centering can't fight a user-moved window.
 	recenterOnShow func() bool
 }
 
-// NewWindowManager wires the manager to the main app; translator/prefs may be nil (tests). The
-// Settings window is created here (hidden) so the first OpenSettings is instant.
 func NewWindowManager(app *application.App, mainWindow *application.WebviewWindow, translator ErrorTranslator, prefs LanguagePreference, linuxIcon []byte) *WindowManager {
-	s := &WindowManager{app: app, mainWindow: mainWindow, translator: translator, prefs: prefs, linuxIcon: linuxIcon}
+	s := &WindowManager{
+		app:            app,
+		mainWindow:     mainWindow,
+		translator:     translator,
+		prefs:          prefs,
+		linuxIcon:      linuxIcon,
+		ready:          map[uint]bool{},
+		showPending:    map[uint]bool{},
+		pendingTab:     map[uint]string{},
+		fallbackTimers: map[uint]*time.Timer{},
+	}
+	s.watchPainted()
 	// Re-title live windows on language flip. Wired internally so the binding generator
 	// doesn't try to expose the interface param.
 	if sub, ok := prefs.(LanguageSubscriber); ok && sub != nil {
@@ -136,7 +152,11 @@ func NewWindowManager(app *application.App, mainWindow *application.WebviewWindo
 			}
 		}()
 	}
-	s.settings = app.Window.NewWithOptions(application.WebviewWindowOptions{
+	return s
+}
+
+func (s *WindowManager) newSettingsWindow() *application.WebviewWindow {
+	w := s.app.Window.NewWithOptions(application.WebviewWindowOptions{
 		Name:                "settings",
 		Title:               s.title("window.title.settings"),
 		Width:               900,
@@ -150,18 +170,15 @@ func NewWindowManager(app *application.App, mainWindow *application.WebviewWindo
 		URL:                 "/#/settings",
 		Mac:                 AppleMacOSAppearanceOptions(),
 		Windows:             MicrosoftWindowsAppearanceOptions(),
-		Linux:               LinuxAppearanceOptions(linuxIcon),
+		Linux:               LinuxAppearanceOptions(s.linuxIcon),
 	})
-	// Hide (not destroy) on close to keep React state; reset to General for a flash-free reopen.
-	s.settings.RegisterHook(events.Common.WindowClosing, func(e *application.WindowEvent) {
-		if ShuttingDown() {
-			return
-		}
-		e.Cancel()
-		s.app.Event.Emit(EventSettingsOpen, "general")
-		s.settings.Hide()
+	w.RegisterHook(events.Common.WindowClosing, func(_ *application.WindowEvent) {
+		s.mu.Lock()
+		s.settings = nil
+		s.forgetWindowLocked(w)
+		s.mu.Unlock()
 	})
-	return s
+	return w
 }
 
 // OpenSettings shows the settings window on tab (empty → General), switching tab via
@@ -171,11 +188,23 @@ func (s *WindowManager) OpenSettings(tab string) {
 	if target == "" {
 		target = "general"
 	}
-	s.app.Event.Emit(EventSettingsOpen, target)
-	s.settings.Show()
-	s.settings.Focus()
-	// Re-center (minimal-WM only; see centerWhenReady).
-	s.centerWhenReady(s.settings)
+
+	s.mu.Lock()
+	fresh := s.settings == nil
+	if fresh {
+		s.settings = s.newSettingsWindow()
+		s.armReady(s.settings)
+	}
+	w := s.settings
+	if fresh {
+		s.pendingTab[w.ID()] = target
+	}
+	s.mu.Unlock()
+
+	if !fresh {
+		s.app.Event.Emit(EventSettingsOpen, target)
+	}
+	s.showWhenReady(w)
 }
 
 // OpenBrowserLogin shows the SSO popup, creating it on first use.
@@ -440,13 +469,150 @@ func (s *WindowManager) OpenMain() {
 // ShowMain brings the main window forward (re-centering on minimal WMs). The single entry
 // point every surface (tray, SIGUSR1, welcome) should use so centering applies uniformly.
 func (s *WindowManager) ShowMain() {
-	if s.mainWindow == nil {
+	s.showWhenReady(s.MainWindow())
+}
+
+func (s *WindowManager) MainWindow() *application.WebviewWindow {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.mainWindow == nil && s.newMain != nil {
+		s.mainWindow = s.newMain()
+		s.armReady(s.mainWindow)
+	}
+	return s.mainWindow
+}
+
+func (s *WindowManager) armReady(w *application.WebviewWindow) {
+	if w == nil {
 		return
 	}
-	s.mainWindow.Show()
-	s.mainWindow.Focus()
-	// Re-center (minimal-WM only; see centerWhenReady).
-	s.centerWhenReady(s.mainWindow)
+	w.RegisterHook(events.Common.WindowRuntimeReady, func(_ *application.WindowEvent) {
+		timer := time.AfterFunc(paintedFallback, func() {
+			log.Warnf("window %q never reported a first render, showing it anyway", w.Name())
+			s.markReady(w)
+		})
+		s.mu.Lock()
+		s.fallbackTimers[w.ID()] = timer
+		s.mu.Unlock()
+	})
+}
+
+func (s *WindowManager) watchPainted() {
+	s.app.Event.On(EventWindowPainted, func(e *application.CustomEvent) {
+		if w := s.windowByName(e.Sender); w != nil {
+			s.markReady(w)
+		}
+	})
+}
+
+func (s *WindowManager) forgetWindowLocked(w *application.WebviewWindow) {
+	if w == nil {
+		return
+	}
+
+	id := w.ID()
+	if timer := s.fallbackTimers[id]; timer != nil {
+		timer.Stop()
+	}
+	delete(s.fallbackTimers, id)
+	delete(s.ready, id)
+	delete(s.showPending, id)
+	delete(s.pendingTab, id)
+
+	kept := s.hiddenForLogin[:0]
+	for _, hidden := range s.hiddenForLogin {
+		if hidden != application.Window(w) {
+			kept = append(kept, hidden)
+		}
+	}
+	s.hiddenForLogin = kept
+}
+
+func (s *WindowManager) windowByName(name string) *application.WebviewWindow {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	switch name {
+	case "main":
+		return s.mainWindow
+	case "settings":
+		return s.settings
+	default:
+		return nil
+	}
+}
+
+func (s *WindowManager) markReady(w *application.WebviewWindow) {
+	id := w.ID()
+	s.mu.Lock()
+	already := s.ready[id]
+	s.ready[id] = true
+	wanted := s.showPending[id]
+	tab, hasTab := s.pendingTab[id]
+	if timer := s.fallbackTimers[id]; timer != nil {
+		timer.Stop()
+		delete(s.fallbackTimers, id)
+	}
+	delete(s.showPending, id)
+	delete(s.pendingTab, id)
+	s.mu.Unlock()
+
+	if already {
+		return
+	}
+
+	if hasTab {
+		s.app.Event.Emit(EventSettingsOpen, tab)
+	}
+
+	if wanted {
+		s.showNow(w)
+	}
+}
+
+func (s *WindowManager) showWhenReady(w *application.WebviewWindow) {
+	if w == nil {
+		return
+	}
+
+	id := w.ID()
+	s.mu.Lock()
+	ready := s.ready[id]
+	if !ready {
+		s.showPending[id] = true
+	}
+	s.mu.Unlock()
+
+	if ready {
+		s.showNow(w)
+	}
+}
+
+func (s *WindowManager) showNow(w *application.WebviewWindow) {
+	w.Show()
+	w.Focus()
+	s.centerWhenReady(w)
+}
+
+func (s *WindowManager) ShowMainAt(url string) {
+	w := s.MainWindow()
+	if w == nil {
+		return
+	}
+	w.SetURL(url)
+	s.showWhenReady(w)
+}
+
+func (s *WindowManager) SetMainFactory(f func() *application.WebviewWindow) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.newMain = f
+}
+
+func (s *WindowManager) ForgetMain() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.forgetWindowLocked(s.mainWindow)
+	s.mainWindow = nil
 }
 
 // SetRecenterOnShow installs the recenterOnShow predicate (see the field).