What causes "Implement me" in wailsapp/wails?

Replace AddRole(application.Print) with an explicit item wired to your own print logic: Add(NewMenuItem("Print").SetAccelerator("CmdOrCtrl+p").OnClick(func(ctx *application.Context) { ... }))

wailsapp/wails · error

Implement me

Error message

Implement me

What it means

newPrintMenuItem is an unimplemented stub in the Linux GTK3 menu backend. The Role 'Print' dispatches through NewRole (menuitem.go:192-193) to NewPrintMenuItem(), which panics with 'Implement me' at menu-build time, crashing the application on startup. Identical stubs exist in the default GTK4 backend (menuitem_linux.go:337), so both Linux flavors are affected.

Source

Thrown at v3/pkg/application/menuitem_linux_gtk3.go:374

			currentWindow := globalApplication.Window.Current()
			if currentWindow != nil {
				currentWindow.Zoom()
			}
		})
}

func newFullScreenMenuItem() *MenuItem {
	return NewMenuItem("Fullscreen").
		OnClick(func(ctx *Context) {
			currentWindow := globalApplication.Window.Current()
			if currentWindow != nil {
				currentWindow.Fullscreen()
			}
		})
}

func newPrintMenuItem() *MenuItem {
	panic("Implement me")
}

func newPageLayoutMenuItem() *MenuItem {
	panic("Implement me")
}

func newShowAllMenuItem() *MenuItem {
	panic("Implement me")
}

func newBringAllToFrontMenuItem() *MenuItem {
	panic("Implement me")
}

func newNewFileMenuItem() *MenuItem {
	panic("Implement me")
}

View on GitHub (pinned to 0e754b1b40)

Solutions

Replace AddRole(application.Print) with an explicit item wired to your own print logic: Add(NewMenuItem("Print").SetAccelerator("CmdOrCtrl+p").OnClick(func(ctx *application.Context) { ... }))
Restrict the Print role to platforms where it is implemented (check runtime.GOOS before AddRole)
Contribute an implementation of newPrintMenuItem upstream (e.g. invoking the WebKitGTK print dialog via window.Print()) and track it as a GitHub issue

Example fix

// before
fileMenu.AddRole(application.Print)

// after
fileMenu.Add(application.NewMenuItem("Print").
	SetAccelerator("CmdOrCtrl+p").
	OnClick(func(ctx *application.Context) { app.Window.Current().Print() }))

Defensive patterns

Strategy: validation

Validate before calling

var unsupportedOnLinux = map[application.Role]bool{
	application.Print: true, application.PageLayout: true,
	application.NewFile: true, application.Open: true,
	application.Save: true, application.SaveAs: true, application.Revert: true,
	application.Find: true, application.FindAndReplace: true,
	application.FindNext: true, application.FindPrevious: true,
	application.StartSpeaking: true, application.StopSpeaking: true,
	application.ShowAll: true, application.BringAllToFront: true,
	application.Front: true, application.Help: true,
}
func addRole(m *application.Menu, r application.Role) {
	if runtime.GOOS == "linux" && unsupportedOnLinux[r] {
		return
	}
	m.AddRole(r)
}

Try / catch

defer func() {
	if r := recover(); r != nil {
		log.Printf("menu build panic: %v", r)
	}
}()
fileMenu.AddRole(application.Print)

Prevention

Treat the Role enum as macOS-complete but Linux-partial; audit every AddRole against menuitem_linux.go
Wrap menu construction in a recover during development to get a log instead of a crash
Implement app-specific behaviors (print, find) as explicit items from day one

When it happens

Trigger: Calling AddRole(application.Print) or NewPrintMenuItem() in an application running on Linux (with or without -tags gtk3). The panic occurs during menu construction, before the UI shows.

Common situations: Menus written on Windows/macOS where printing roles are expected; v2-to-v3 migrations that keep role-based File menus; test runs on Linux CI for an app developed on another OS.

Related errors

AI-assisted analysis of wailsapp/wails@0e754b1b40 (2026-08-15). Data as JSON: /api/errors/238d0d3c8b714766. Report an issue: GitHub.