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Zero Camera

Zero is a minimal camera app for the Light Phone III. It aims to take photos with as little processing as possible.

Tech Stack: Kotlin 2.1.0, Jetpack Compose/Material 3, Camera2 API, Gradle 9.2.1 (Kotlin DSL), Min SDK 29, Target SDK 35

Build Commands

./gradlew assembleDebug          # Build debug APK
./gradlew assembleRelease        # Build release APK (minified)
./gradlew clean assembleDebug    # Clean build
./gradlew build                  # Full build with tests

Lint & Code Style

This project uses ktlint 1.8.0 for code formatting. Always run ktlint before committing.

./gradlew ktlintCheck    # Check for code style violations
./gradlew ktlintFormat   # Auto-fix formatting issues
./gradlew lint           # Run Android lint
./gradlew lintDebug

ktlint Configuration (see .editorconfig):

  • Composable functions MAY use PascalCase (standard Compose convention)
  • Wildcard imports are allowed for Android/Compose packages

Project Structure

app/src/main/java/com/vandam/zero/
├── MainActivity.kt           # Entry point, key event handling
├── CameraViewModel.kt        # UI state management, settings persistence
├── camera/
│   ├── CameraController.kt   # Camera2 API implementation
│   └── GrayscaleConverter.kt # BT.709 grayscale conversion
└── ui/
    ├── CameraScreen.kt       # Main screen composable
    ├── components/
    │   ├── CameraSliders.kt  # Exposure/ISO/Shutter sliders
    │   ├── Crosshair.kt      # Focus indicator
    │   ├── GridOverlay.kt    # Rule of thirds grid
    │   └── ModifierExtensions.kt
    └── theme/
        └── CameraTheme.kt    # Typography, colors, dimensions

Code Style Guidelines

Naming Conventions

Type Convention Example
Composable functions PascalCase CameraScreen(), ExposureSlider()
Regular functions camelCase takePhoto(), formatShutterSpeed()
Classes/Objects PascalCase CameraController, CameraColors
Constants SCREAMING_SNAKE_CASE OUTPUT_FORMAT_JPEG, R_WEIGHT
StateFlow properties camelCase with underscore prefix for private _isCapturing / isCapturing

Compose Best Practices

  1. Composable naming: Use PascalCase for @Composable functions that emit UI
  2. State hoisting: Keep state in ViewModel, pass values and callbacks to composables
  3. Modifier parameter: Always accept modifier: Modifier = Modifier as a parameter
  4. Parameter order: Required params first, then modifier, then optional params, then trailing lambda
  5. Single responsibility: Each composable should emit 0 or 1 layout node
@Composable
fun MyButton(
    text: String,                    // Required
    onClick: () -> Unit,             // Required callback
    modifier: Modifier = Modifier,   // Optional, starts with modifier
    enabled: Boolean = true,         // Other optional params
) { ... }

State Management

  • Use StateFlow for observable state in ViewModel
  • Collect state with collectAsState() in composables
  • Group related state into data classes when practical
  • Private mutable state with public read-only exposure:
private val _isCapturing = MutableStateFlow(false)
val isCapturing: StateFlow<Boolean> = _isCapturing

Import Organisation

Imports are ordered lexicographically by ktlint. Wildcard imports are allowed for Android/Compose packages.

Error Handling

  • Use nullable types with safe calls (?.) for optional operations
  • Log errors with Android Log class: Log.e("Tag", "message")
  • Camera operations should handle CameraAccessException
  • Never crash on permission denial - show appropriate UI

Documentation

  • Use KDoc (/** */) for public APIs and complex functions
  • Document non-obvious parameters and return values

Theme Constants

Use centralized constants from ui/theme/CameraTheme.kt:

CameraColors.background      // Color.Black
CameraColors.onSurface       // Color.White
CameraColors.onSurfaceVariant // Color.White.copy(alpha = 0.7f)
CameraDimens.toolbarWidth    // 60.dp
CameraDimens.crosshairSize   // 80.dp
CameraTypography.toolbarText // 32.sp, ExtraBold
CameraTiming.TOAST_DISPLAY_DURATION_MS  // 2000L