Skill: Compose Multiplatform (CMP) UI

Description

Guidelines for building shared UI, adaptive layouts, and handling strings/resources in Meshtastic-Android. The codebase uses Material 3 Adaptive.

1. UI Components & Layouts

• Material 3 / Adaptive: Use currentWindowAdaptiveInfo(supportLargeAndXLargeWidth = true) to support Large (1200dp) and XL (1600dp) breakpoints. Investigate 3-pane "Power User" scenes using Navigation 3 Scenes and draggable dividers for desktopApp/tablets.
• Dialogs & Alerts: Use centralized components like AlertHost(alertManager) from core:ui/commonMain. Do NOT trigger alerts inline or duplicate alert logic. Use SharedDialogs(uiViewModel) for general popups.
• Placeholders: Use PlaceholderScreen(name) from core:ui/commonMain for unimplemented desktopApp/JVM features.
• Theme Picker: Use ThemePickerDialog from feature:settings/commonMain.
• Platform Implementations: Inject platform-specific behavior (e.g., Map providers) via CompositionLocal from the androidApp or desktopApp shells. Do not tightly couple Google Maps dependencies to commonMain; the MapLibre surfaces live in :feature:map-maplibre, not in a core module.

2. Strings & Resources

• Multiplatform Resources: MUST use core:resources (e.g., stringResource(Res.string.your_key)). Never use hardcoded strings.
• ViewModels/Coroutines: Use the asynchronous getStringSuspend(Res.string.your_key). NEVER use blocking getString() in a coroutine context.
• Formatting Constraints: CMP stringResource only supports %N$s (string) and %N$d (integer).
  • No Float formatting: Formats like %N$.1f pass through unsubstituted. Pre-format in Kotlin using NumberFormatter.format(value, decimalPlaces) from core:common and pass as a string argument (%N$s):

    val formatted = NumberFormatter.format(batteryLevel, 1) // "73.5"
    stringResource(Res.string.battery_percent, formatted)   // uses %1$s
    

  • Percent Literals: Use bare % (not %%) for literal percent signs in CMP-consumed strings.

String Formatting Decision Tree

Choose the right tool for the job:

Scenario	Tool	Example
Metric display (temp, voltage, %, signal)	MetricFormatter.*	MetricFormatter.temperature(25.0f, isFahrenheit) → "77.0°F"
Simple number + unit	NumberFormatter + interpolation	"${NumberFormatter.format(val, 1)} dB"
Localized template from strings.xml	stringResource(Res.string.key, preFormattedArgs)	stringResource(Res.string.battery, formatted)
Non-composable template (notifications, plain functions)	formatString(template, args)	formatString(template, label, value)
Hex formatting	formatString	formatString("!%08x", nodeNum)
Date/time	DateFormatter	DateFormatter.format(instant)

Rules:

1. NEVER use %.Nf in strings.xml — CMP cannot substitute them. Use %N$s and pre-format floats.
2. Prefer MetricFormatter over scattered formatString("%.1f°C", temp) calls.
3. formatString (pure Kotlin) is a pure-Kotlin commonMain implementation for: hex formats, multi-arg templates fetched at runtime, and chart axis formatters. Located in core:common Formatter.kt.
4. NumberFormatter always uses . as decimal separator — intentional for mesh networking precision.

• Workflow to Add a String:
  1. Add to core/resources/src/commonMain/composeResources/values/strings.xml.
  2. Run python3 scripts/sort-strings.py — keeps the file sorted and regenerates strings-index.txt.
  3. Use the generated org.meshtastic.core.resources.<key> symbol.
  4. Validate UI presentation.

3. Tooling & Capabilities

• Image Loading: Use libs.coil (Coil Compose) in feature modules. Configuration/Networking for Coil (coil-network-ktor3) happens strictly in the androidApp and desktopApp host modules.
• QR Codes: Use rememberQrCodePainter from core:ui/commonMain powered by qrcode-kotlin. No ZXing or Android Bitmap APIs in shared code.

4. Compose Previews

• Preview in commonMain: CMP 1.11+ supports @Preview in commonMain via compose-multiplatform-ui-tooling-preview. Place preview functions alongside their composables.
• Import: Use androidx.compose.ui.tooling.preview.Preview. The JetBrains-prefixed import (org.jetbrains.compose.ui.tooling.preview.Preview) is deprecated.

5. Dialog & State Patterns

• Dialog State Preservation: Use rememberSaveable for dialog state (search queries, selected tabs, expanded flags) to preserve across configuration changes. Boolean and String types are auto-saveable — no custom Saver needed.

6. Driving the running desktop app

CMP 1.12+ ships an MCP server inside Compose Hot Reload; .mcp.json registers it as compose-hot-reload (:desktopApp:hotMcpServer). With ./gradlew :desktopApp:hotRun running, it drives the live app — inspect, input and reload without a rebuild.

• Tools: status, reload, await_reload, get_semantic_tree, click, type_text, scroll, get_logs, get_ui_error, take_screenshot.
• Poll status until connected: true before anything else — the server accepts requests before the app has connected to it.
• get_semantic_tree is the assertion surface: roles, text, selected/focused, available actions and bounds. click addresses nodes by nodeId taken from that tree. Prefer it over take_screenshot, whose output depends on the host renderer.
• reload after editing sources applies the change into the running app; use await_reload instead when the app was started with --auto.

Reference Anchors

• Shared Strings: core/resources/src/commonMain/composeResources/values/strings.xml
• Platform abstraction contract: core/ui/src/commonMain/kotlin/org/meshtastic/core/ui/util/MapViewProvider.kt
• Provider wiring: androidApp/src/main/kotlin/org/meshtastic/app/MainActivity.kt