Desktop & mobile apps

rat start app boots the runtime on a random loopback port and opens a native window onto it. The default build is cgo-free: it launches an installed Chromium browser in app mode (chromeless, throwaway profile). A -tags desktop build swaps in a single-process embedded webview instead. Either way you get a real window with no source changes.

# from your app directory
rat start app

# tune the window in settings.rat
> desktop
title: 'My App'
width: 1100
height: 760
resizable: true

rat build desktop emits one self-contained executable. The default is the cgo-free browser-app window - nothing to install on the target machine beyond an existing browser. Add --webview for the single-process embedded-webview variant (needs a C toolchain at build time and the platform webview runtime: WebView2 on Windows, webkit2gtk on Linux, system WebKit on macOS).

rat build desktop            # cgo-free browser-app window
rat build desktop --webview  # embedded webview (-tags desktop)

rat build apk stages an Android shell, drops in a gomobile-bound library carrying the whole Go runtime + sqlite, embeds your app as assets, and produces an installable .apk - one command from any app directory. The server runs in-process behind a system WebView; routing, reactivity, services, and SSE ride loopback HTTP exactly as on web and desktop. Add --install to push it to a connected device.

rat build apk            # builds <name>.apk
rat build apk --install  # build + adb install to a device

The same source runs everywhere, but sometimes you want a touch-first layout on mobile or a different affordance on desktop. The env global exposes the resolved target for progressive enhancement. Reach for it only for genuine UX differences - the substrate already works on every target without it.

> page
(env.mobile)
    <p> Tap and hold to share.
(env.desktop)
    <p> Right-click for the context menu.