:
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            MyApplicationTheme {
                // A surface container using the 'background' color from the theme
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colorScheme.background
                ) {
                    /* コンテンツ */
                }
            }
        }
    }
	    :

@Composable
@NonRestartableComposable
fun Surface(
    modifier: Modifier = Modifier,
    shape: Shape = RectangleShape,
    color: Color = MaterialTheme.colorScheme.surface,
    contentColor: Color = contentColorFor(color),
    tonalElevation: Dp = 0.dp,
    shadowElevation: Dp = 0.dp,
    border: BorderStroke? = null,
    content: @Composable () -> Unit
)

val _primasy = MaterialTheme.colorScheme.primary
val _onPrimasy = MaterialTheme.colorScheme.onPrimary
val _secondary = MaterialTheme.colorScheme.secondary
val _tertiary = MaterialTheme.colorScheme.tertiary
val _background = MaterialTheme.colorScheme.background
val _error = MaterialTheme.colorScheme.error
val _surface = MaterialTheme.colorScheme.surface
    :
	:

@Composable
@NonRestartableComposable
fun Surface(
    ...
    color: Color = MaterialTheme.colorScheme.surface,
    contentColor: Color = contentColorFor(color),	// 対になる色を返す
    tonalElevation: Dp = 0.dp,
    ...
) {
    val absoluteElevation = LocalAbsoluteTonalElevation.current + tonalElevation
    CompositionLocalProvider(	// スコープの指定
        LocalContentColor provides contentColor,
        LocalAbsoluteTonalElevation provides absoluteElevation
    ) {
        Box(...) {		// 　↑
            content()	// CompositionLocal変数のスコープ範囲
        }				// 　↓
    }
}

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            MyApplicationTheme {
                // A surface container using the 'background' color from the theme
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colorScheme.background
                ) {
                    Text(text = "Hello World !!", fontSize = 32.sp)
                }
            }
        }
    }
}

@Composable
fun Text(
    text: String,
    modifier: Modifier = Modifier,
    color: Color = Color.Unspecified,
    ...,
    style: TextStyle = LocalTextStyle.current
) {

    val textColor = color.takeOrElse {
        style.color.takeOrElse {
            LocalContentColor.current
        }
    }
    // NOTE(text-perf-review): It might be worthwhile writing a bespoke merge implementation that
    // will avoid reallocating if all of the options here are the defaults
    val mergedStyle = style.merge(
        TextStyle(
            color = textColor,
            ...
        )
    )
    BasicText(
        text,
        modifier,
        mergedStyle,
        onTextLayout,
        overflow,
        softWrap,
        maxLines,
    )
}