11 - Multiple windows

Use ui.Run(Program) for one window. Use ui.Application when the process owns multiple windows, a system tray, or an explicit lifecycle.

Basic structure

func main() {
    application := ui.NewApplication()

    counter := ui.NewWindow("counter", ui.NewProgram(
        CounterModel{}, counterUpdate, counterView,
    ), ui.Title("Counter"), ui.Size(400, 300))

    mainWindow := ui.NewWindow("main", ui.NewProgram(
        MainModel{}, mainUpdate, mainView,
    ), ui.Title("Main"), ui.Size(640, 480))

    application.Run(mainWindow)
    _ = counter
}

Application.Open returns true when a new window starts. If the key is already open, it raises the existing window and returns false.

if application.Open(counter) {
    // A new window started.
}
application.Close("counter")

Each window has an independent model instance. Use a full Program initializer when a model contains slices, maps, or pointers that must be freshly allocated for every opening.

Theme and language

Apply changes through the application so they reach the target window's event loop:

application.SetTheme("main", ui.DarkTheme())
application.SetLanguage("main", ui.LanguageChinese)

Do not mutate a window's theme from an arbitrary goroutine.

Window state and actions

ctx.WindowState() reports size, focus, decoration, top-most state, and the current window mode. Program.WindowStateMessage can map native changes to an application message. Application.Perform sends actions such as minimize, maximize, restore, fullscreen, raise, or center.

Close lifecycle

OnWindowCloseRequest handles FlowUI close requests. WindowCloseCancel keeps the window open; WindowCloseKeepAlive closes the native window while keeping the process alive for a tray or background service. Native window manager close events cannot all be intercepted on every platform.

See examples/multi_windows and examples/systray_ui.