DroidDeck/docs/compose-previews.md

Compose previews

Select the debug build variant in Android Studio, then open a preview file under app/src/debug/java/com/droiddeck/launcher/ and choose Split or Design. Build the project after syncing Gradle. Previews call the production composables; there is no separate mock UI to keep in sync.

File	Coverage
ui/LauncherPreviews.kt	Steam home, runtime missing/downloading, populated/empty library, game details, desktop, emulator, Android apps, Store, Updates, alternate theme
ui/SettingsPreviews.kt	All four Setup tabs, all six Steam settings tabs, desktop settings, controller/mapping, performance, shared settings widgets
ui/RuntimePreviews.kt	Proton installed/empty/downloading, components/loading, GPU drivers and driver downloads
ui/SessionPreviews.kt	Every session drawer page, loading/starting/error screens, PC keyboard, HUD, cursor
ui/DialogPreviews.kt	Add/edit app, confirmation, custom resolution, ROM folder, environment variables, Windows components, display chooser, wireless ADB, process-limit help
files/FilePreviews.kt	File manager grid/list/empty/favorites, file/folder pickers, properties

@DroidDeckPreviews shows handheld landscape (960×540 dp), compact landscape (480×360 dp), portrait (400×700 dp), and larger text. The Paper theme has a separate launcher preview. Dimensions are Android layout units, not physical display pixels.

Edit the real UI components to adjust layouts. Edit PreviewData.kt for sample screen state and callbacks, and FilePreviews.kt for file metadata. Add a preview for each new screen or materially different state. Add its entry to PreviewCases.kt or filePreviewCases so it is covered by the render check.

Preview fixtures and tooling are debug-only. PreviewHost supplies the production theme, inspection mode, and inert navigation/file-picker owners. Inspection paths skip automatic runtime, directory, device, and network operations and settle entrance animations so content is visible immediately. File manager mutation commands are disabled in inspection mode. Previews are for layout and local UI interaction; they do not validate installation, pairing, launching, or controller input latency.

The native game surface, Termux terminal, on-screen gamepad, and second-screen View controls are outside this Compose preview set. Their surrounding Compose menus are covered. These components still need device validation.

Run the preview render smoke checks:

./gradlew app:testDebugUnitTest --tests '*PreviewRenderTest'

The checks use Robolectric native graphics with an ordinary Application, render the same 68 preview entry points at handheld, compact, and portrait sizes, reject empty/solid-color output, and write PNGs to app/build/preview-renders/. This catches composition/render errors without starting the Linux runtime. Android Studio uses Layoutlib, so the smoke check complements Studio preview validation rather than replacing it.