Multiple Windows

Multi-Window Applications

Wails v3 provides native multi-window support for creating settings windows, document windows, tool palettes, and inspector windows. Track windows, enable communication between them, and manage their lifecycle with simple, consistent APIs.

Main + Settings Window

package main

import "github.com/wailsapp/wails/v3/pkg/application"

type App struct {
    app            *application.Application
    mainWindow     *application.WebviewWindow
    settingsWindow *application.WebviewWindow
}

func main() {
    app := &App{}

    app.app = application.New(application.Options{
        Name: "Multi-Window App",
    })

    // Create main window
    app.mainWindow = app.app.Window.NewWithOptions(application.WebviewWindowOptions{
        Name:   "main",
        Title:  "Main Application",
        Width:  1200,
        Height: 800,
    })

    // Create settings window (hidden initially)
    app.settingsWindow = app.app.Window.NewWithOptions(application.WebviewWindowOptions{
        Name:   "settings",
        Title:  "Settings",
        Width:  600,
        Height: 400,
        Hidden: true,
    })

    app.app.Run()
}

// Show settings from main window
func (a *App) ShowSettings() {
    if a.settingsWindow != nil {
        a.settingsWindow.Show()
        a.settingsWindow.SetFocus()
    }
}

Key points:

• Main window always visible
• Settings window created but hidden
• Show settings on demand
• Reuse same window (don’t create multiple)

Window Tracking

Get All Windows

windows := app.Window.GetAll()
fmt.Printf("Total windows: %d\n", len(windows))

for _, window := range windows {
    fmt.Printf("- %s (ID: %d)\n", window.Name(), window.ID())
}

Find Specific Window

// By name
settings := app.GetWindowByName("settings")
if settings != nil {
    settings.Show()
}

// By ID
window := app.GetWindowByID(123)

// Current (focused) window
current := app.Window.Current()

Window Registry Pattern

Track windows in your application:

type WindowManager struct {
    windows map[string]*application.WebviewWindow
    mu      sync.RWMutex
}

func (wm *WindowManager) Register(name string, window *application.WebviewWindow) {
    wm.mu.Lock()
    defer wm.mu.Unlock()
    wm.windows[name] = window
}

func (wm *WindowManager) Get(name string) *application.WebviewWindow {
    wm.mu.RLock()
    defer wm.mu.RUnlock()
    return wm.windows[name]
}

func (wm *WindowManager) Remove(name string) {
    wm.mu.Lock()
    defer wm.mu.Unlock()
    delete(wm.windows, name)
}

Window Communication

Using Events

Windows communicate via the event system:

// In main window - emit event
app.Event.Emit("settings-changed", map[string]interface{}{
    "theme": "dark",
    "fontSize": 14,
})

// In settings window - listen for event
app.Event.On("settings-changed", func(event *application.WailsEvent) {
    data := event.Data.(map[string]interface{})
    theme := data["theme"].(string)
    fontSize := data["fontSize"].(int)

    // Update UI
    updateSettings(theme, fontSize)
})

Shared State Pattern

Use a shared state manager:

type AppState struct {
    theme    string
    fontSize int
    mu       sync.RWMutex
}

var state = &AppState{
    theme:    "light",
    fontSize: 12,
}

func (s *AppState) SetTheme(theme string) {
    s.mu.Lock()
    s.theme = theme
    s.mu.Unlock()

    // Notify all windows
    app.Event.Emit("theme-changed", theme)
}

func (s *AppState) GetTheme() string {
    s.mu.RLock()
    defer s.mu.RUnlock()
    return s.theme
}

Window-to-Window Messages

Send messages between specific windows:

// Get target window
targetWindow := app.GetWindowByName("preview")

// Emit event to specific window
targetWindow.EmitEvent("update-preview", previewData)

Common Patterns

Pattern 1: Singleton Windows

Ensure only one instance of a window exists:

var settingsWindow *application.WebviewWindow

func ShowSettings(app *application.Application) {
    // Create if doesn't exist
    if settingsWindow == nil {
        settingsWindow = app.Window.NewWithOptions(application.WebviewWindowOptions{
            Name:   "settings",
            Title:  "Settings",
            Width:  600,
            Height: 400,
        })

        // Cleanup on close
        settingsWindow.OnDestroy(func() {
            settingsWindow = nil
        })
    }

    // Show and focus
    settingsWindow.Show()
    settingsWindow.SetFocus()
}

Pattern 2: Document Windows

Multiple instances of the same window type:

type DocumentWindow struct {
    window   *application.WebviewWindow
    filePath string
    modified bool
}

var documents = make(map[string]*DocumentWindow)

func OpenDocument(app *application.Application, filePath string) {
    // Check if already open
    if doc, exists := documents[filePath]; exists {
        doc.window.Show()
        doc.window.SetFocus()
        return
    }

    // Create new document window
    window := app.Window.NewWithOptions(application.WebviewWindowOptions{
        Title:  filepath.Base(filePath),
        Width:  800,
        Height: 600,
    })

    doc := &DocumentWindow{
        window:   window,
        filePath: filePath,
        modified: false,
    }

    documents[filePath] = doc

    // Cleanup on close
    window.OnDestroy(func() {
        delete(documents, filePath)
    })

    // Load document
    loadDocument(window, filePath)
}

Pattern 3: Tool Palettes

Floating windows that stay on top:

func CreateToolPalette(app *application.Application) *application.WebviewWindow {
    palette := app.Window.NewWithOptions(application.WebviewWindowOptions{
        Name:        "tools",
        Title:       "Tools",
        Width:       200,
        Height:      400,
        AlwaysOnTop: true,
        Resizable:   false,
    })

    return palette
}

Pattern 4: Modal dialogs (macOS only)

Child windows that block parent:

func ShowModaldialog(parent *application.WebviewWindow, title string) {
    dialog := app.Window.NewWithOptions(application.WebviewWindowOptions{
        Title:       title,
        Width:       400,
        Height:      200,
        Parent:      parent,
        AlwaysOnTop: true,
        Resizable:   false,
    })

    parent.AttachModal(dialog)
}

Pattern 5: Inspector/Preview Windows

Linked windows that update together:

type EditorApp struct {
    editor  *application.WebviewWindow
    preview *application.WebviewWindow
}

func (e *EditorApp) UpdatePreview(content string) {
    if e.preview != nil && e.preview.IsVisible() {
        e.preview.EmitEvent("content-changed", content)
    }
}

func (e *EditorApp) TogglePreview() {
    if e.preview == nil {
        e.preview = app.Window.NewWithOptions(application.WebviewWindowOptions{
            Name:   "preview",
            Title:  "Preview",
            Width:  600,
            Height: 800,
        })

        e.preview.OnDestroy(func() {
            e.preview = nil
        })
    }

    if e.preview.IsVisible() {
        e.preview.Hide()
    } else {
        e.preview.Show()
    }
}

Parent-Child Relationships

Creating Child Windows

childWindow := app.Window.NewWithOptions(application.WebviewWindowOptions{
    Title:  "Child Window",
})

parentWindow.AttachModal(childWindow)

Behaviour:

• Child stays above parent
• Child moves with parent
• Child blocks interaction to parent

Platform support:

macOS	Windows	Linux
✅	❌	❌

Modal Behaviour

Create modal-like behaviour:

func ShowModaldialog(parent *application.WebviewWindow, title string) {
    dialog := app.Window.NewWithOptions(application.WebviewWindowOptions{
        Title:       title,
        Width:       400,
        Height:      200,
    })

    parent.AttachModal(dialog)
}

Window Lifecycle Management

Creation Callbacks

Be notified when windows are created:

app.OnWindowCreation(func(window *application.WebviewWindow) {
    fmt.Printf("Window created: %s\n", window.Name())

    // Configure all new windows
    window.SetMinSize(400, 300)
})

Destruction Callbacks

Cleanup when windows are destroyed:

window.OnDestroy(func() {
    fmt.Printf("Window %s destroyed\n", window.Name())

    // Cleanup resources
    cleanup(window.ID())

    // Remove from tracking
    removeFromRegistry(window.Name())
})

Application Quit Behaviour

Control when application quits:

app := application.New(application.Options{
    Mac: application.MacOptions{
        // Don't quit when last window closes
        ApplicationShouldTerminateAfterLastWindowClosed: false,
    },
})

Use cases:

• System tray applications
• Background services
• Menu bar applications (macOS)

Memory Management

Preventing Leaks

Always clean up window references:

var windows = make(map[string]*application.WebviewWindow)

func CreateWindow(name string) {
    window := app.Window.New()
    windows[name] = window

    // IMPORTANT: Clean up on destroy
    window.OnDestroy(func() {
        delete(windows, name)
    })
}

Closing vs Destroying

// Close - triggers OnClose, can be cancelled
window.Close()

// Destroy - immediate, cannot be cancelled
window.Destroy()

Best practice: Use Close() for user-initiated closes, Destroy() for cleanup.

Resource Cleanup

type ManagedWindow struct {
    window     *application.WebviewWindow
    resources  []io.Closer
}

func (mw *ManagedWindow) Destroy() {
    // Close all resources
    for _, resource := range mw.resources {
        resource.Close()
    }

    // Destroy window
    mw.window.Destroy()
}

Advanced Patterns

Window Pool

Reuse windows instead of creating new ones:

type WindowPool struct {
    available []*application.WebviewWindow
    inUse     map[uint]*application.WebviewWindow
    mu        sync.Mutex
}

func (wp *WindowPool) Acquire() *application.WebviewWindow {
    wp.mu.Lock()
    defer wp.mu.Unlock()

    // Reuse available window
    if len(wp.available) > 0 {
        window := wp.available[0]
        wp.available = wp.available[1:]
        wp.inUse[window.ID()] = window
        return window
    }

    // Create new window
    window := app.Window.New()
    wp.inUse[window.ID()] = window
    return window
}

func (wp *WindowPool) Release(window *application.WebviewWindow) {
    wp.mu.Lock()
    defer wp.mu.Unlock()

    delete(wp.inUse, window.ID())
    window.Hide()
    wp.available = append(wp.available, window)
}

Window Groups

Manage related windows together:

type WindowGroup struct {
    name    string
    windows []*application.WebviewWindow
}

func (wg *WindowGroup) Add(window *application.WebviewWindow) {
    wg.windows = append(wg.windows, window)
}

func (wg *WindowGroup) ShowAll() {
    for _, window := range wg.windows {
        window.Show()
    }
}

func (wg *WindowGroup) HideAll() {
    for _, window := range wg.windows {
        window.Hide()
    }
}

func (wg *WindowGroup) CloseAll() {
    for _, window := range wg.windows {
        window.Close()
    }
}

Workspace Management

Save and restore window layouts:

type WindowLayout struct {
    Windows []WindowState `json:"windows"`
}

type WindowState struct {
    Name   string `json:"name"`
    X      int    `json:"x"`
    Y      int    `json:"y"`
    Width  int    `json:"width"`
    Height int    `json:"height"`
}

func SaveLayout() *WindowLayout {
    layout := &WindowLayout{}

    for _, window := range app.Window.GetAll() {
        x, y := window.Position()
        width, height := window.Size()

        layout.Windows = append(layout.Windows, WindowState{
            Name:   window.Name(),
            X:      x,
            Y:      y,
            Width:  width,
            Height: height,
        })
    }

    return layout
}

func RestoreLayout(layout *WindowLayout) {
    for _, state := range layout.Windows {
        window := app.GetWindowByName(state.Name)
        if window != nil {
            window.SetPosition(state.X, state.Y)
            window.SetSize(state.Width, state.Height)
        }
    }
}

Complete Example

Here’s a production-ready multi-window application:

package main

import (
    "encoding/json"
    "os"
    "sync"
    "github.com/wailsapp/wails/v3/pkg/application"
)

type MultiWindowApp struct {
    app     *application.Application
    windows map[string]*application.WebviewWindow
    mu      sync.RWMutex
}

func main() {
    mwa := &MultiWindowApp{
        windows: make(map[string]*application.WebviewWindow),
    }

    mwa.app = application.New(application.Options{
        Name: "Multi-Window Application",
        Mac: application.MacOptions{
            ApplicationShouldTerminateAfterLastWindowClosed: false,
        },
    })

    // Create main window
    mwa.CreateMainWindow()

    // Load saved layout
    mwa.LoadLayout()

    mwa.app.Run()
}

func (mwa *MultiWindowApp) CreateMainWindow() {
    window := mwa.app.Window.NewWithOptions(application.WebviewWindowOptions{
        Name:   "main",
        Title:  "Main Application",
        Width:  1200,
        Height: 800,
    })

    mwa.RegisterWindow("main", window)
}

func (mwa *MultiWindowApp) ShowSettings() {
    if window := mwa.GetWindow("settings"); window != nil {
        window.Show()
        window.SetFocus()
        return
    }

    window := mwa.app.Window.NewWithOptions(application.WebviewWindowOptions{
        Name:   "settings",
        Title:  "Settings",
        Width:  600,
        Height: 400,
    })

    mwa.RegisterWindow("settings", window)
}

func (mwa *MultiWindowApp) OpenDocument(path string) {
    name := "doc-" + path

    if window := mwa.GetWindow(name); window != nil {
        window.Show()
        window.SetFocus()
        return
    }

    window := mwa.app.Window.NewWithOptions(application.WebviewWindowOptions{
        Name:  name,
        Title: path,
        Width: 800,
        Height: 600,
    })

    mwa.RegisterWindow(name, window)
}

func (mwa *MultiWindowApp) RegisterWindow(name string, window *application.WebviewWindow) {
    mwa.mu.Lock()
    mwa.windows[name] = window
    mwa.mu.Unlock()

    window.OnDestroy(func() {
        mwa.UnregisterWindow(name)
    })
}

func (mwa *MultiWindowApp) UnregisterWindow(name string) {
    mwa.mu.Lock()
    delete(mwa.windows, name)
    mwa.mu.Unlock()
}

func (mwa *MultiWindowApp) GetWindow(name string) *application.WebviewWindow {
    mwa.mu.RLock()
    defer mwa.mu.RUnlock()
    return mwa.windows[name]
}

func (mwa *MultiWindowApp) SaveLayout() {
    layout := make(map[string]WindowState)

    mwa.mu.RLock()
    for name, window := range mwa.windows {
        x, y := window.Position()
        width, height := window.Size()

        layout[name] = WindowState{
            X:      x,
            Y:      y,
            Width:  width,
            Height: height,
        }
    }
    mwa.mu.RUnlock()

    data, _ := json.Marshal(layout)
    os.WriteFile("layout.json", data, 0644)
}

func (mwa *MultiWindowApp) LoadLayout() {
    data, err := os.ReadFile("layout.json")
    if err != nil {
        return
    }

    var layout map[string]WindowState
    if err := json.Unmarshal(data, &layout); err != nil {
        return
    }

    for name, state := range layout {
        if window := mwa.GetWindow(name); window != nil {
            window.SetPosition(state.X, state.Y)
            window.SetSize(state.Width, state.Height)
        }
    }
}

type WindowState struct {
    X      int `json:"x"`
    Y      int `json:"y"`
    Width  int `json:"width"`
    Height int `json:"height"`
}

Best Practices

✅ Do

• Track windows - Keep references for easy access
• Clean up on destroy - Prevent memory leaks
• Use events for communication - Decoupled architecture
• Reuse windows - Don’t create duplicates
• Save/restore layouts - Better UX
• Handle window close - Confirm before closing with unsaved data

❌ Don’t

• Don’t create unlimited windows - Memory and performance issues
• Don’t forget to clean up - Memory leaks
• Don’t use global variables carelessly - Thread-safety issues
• Don’t block window creation - Create asynchronously if needed
• Don’t ignore platform differences - Test on all platforms

Next Steps

• Window Basics - Learn the fundamentals of window management
• Window Events - Handle window lifecycle events
• Events System - Deep dive into the event system
• Frameless Windows - Create custom window chrome

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Questions? Ask in Discord or check the multi-window example.