object vs compositionLocalOf vs staticCompositionLocalOf.kt

// ==========================================================
// 【DEFINITION AREA】 
// Must be defined at the TOP-LEVEL (Outside of any @Composable)
// ==========================================================

// A. object: A global, immutable box (Constants)
object AppDesignConfig {
    val BrandColor = Color(0xFF6200EE) // Fixed brand color
    val CornerRadius = 12.dp
}

// B. compositionLocalOf: The "Smart" dynamic pipe.
// When the provided value changes, only the parts using '.current' recompose.
val LocalUserStatus = compositionLocalOf { "Guest" }

// C. staticCompositionLocalOf: The "High-speed" static foundation.
// When the value changes, the entire tree below the Provider is reset/recomposed.
val LocalAppThemeColor = staticCompositionLocalOf { Color.Gray }


// ==========================================================
// 【UI IMPLEMENTATION AREA】
// ==========================================================

@Composable
fun AppMainScreen() {
    // State holders for B and C
    var userStatus by remember { mutableStateOf("Guest User") }
    var themeColor by remember { mutableStateOf(Color(0xFF03DAC5)) }

    // Provider Side: This is where we inject the actual values into the Locals
    CompositionLocalProvider(
        LocalUserStatus provides userStatus,
        LocalAppThemeColor provides themeColor
    ) {
        Column(
            modifier = Modifier
                .fillMaxSize()
                .padding(24.dp),
            verticalArrangement = Arrangement.spacedBy(20.dp),
            horizontalAlignment = Alignment.CenterHorizontally
        ) {
            Text("State Sharing Comparison", style = MaterialTheme.typography.headlineMedium)

            // A: Direct access to object (No Provider or .current needed)
            Button(
                onClick = { /* Constant value */ },
                colors = ButtonDefaults.buttonColors(containerColor = AppDesignConfig.BrandColor)
            ) {
                Text("A: Using Object Constant")
            }

            // B: Using compositionLocalOf
            UserInfoCard()

            // C: Using staticCompositionLocalOf
            ThemeColorBox()

            Spacer(modifier = Modifier.height(20.dp))
            HorizontalDivider()

            // Operation Panel
            Text("Update State:", style = MaterialTheme.typography.titleMedium)
            
            Button(onClick = { userStatus = "Logged in: John Doe" }) {
                Text("Update B (User Status)")
            }
            
            Button(onClick = { themeColor = Color.Magenta }) {
                Text("Update C (Theme Color)")
            }
        }
    }
}

@Composable
fun UserInfoCard() {
    // Consuming B: Only this specific function recomposes when userStatus changes
    val status = LocalUserStatus.current
    Card(
        modifier = Modifier.fillMaxWidth(),
        colors = CardDefaults.cardColors(containerColor = Color.LightGray.copy(alpha = 0.2f))
    ) {
        Box(modifier = Modifier.padding(16.dp)) {
            Text("B (compositionLocalOf): $status")
        }
    }
}

@Composable
fun ThemeColorBox() {
    // Consuming C: If themeColor changes, the entire sub-tree is refreshed
    val color = LocalAppThemeColor.current
    Surface(
        color = color,
        modifier = Modifier.size(120.dp),
        shape = MaterialTheme.shapes.medium,
        shadowElevation = 8.dp
    ) {
        Box(contentAlignment = Alignment.Center) {
            Text("C (static)", color = Color.White)
        }
    }
}

object vs compositionLocalOf vs staticCompositionLocalOf: The Ultimate State Sharing Guide
https://android.benigumo.com/20260223/object-vs-compositionlocalof-vs-staticcompositionlocalof/