then 叠加修饰符功能的作用

val reusableModifier = Modifier
    .fillMaxWidth()
    .background(Color.Red)
    .padding(12.dp)

// Append to your reusableModifier
reusableModifier.clickable { /*...*/ }

// Append your reusableModifier
otherModifier.then(reusableModifier)

https://developer.aliyun.com/article/1409449

Compose 类型稳定性注解：@Stable & @Immutable

• 主动测量
  SubcomposeLayout

import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.layout.SubcomposeLayout

@Composable
fun DynamicContent() {
    SubcomposeLayout { constraints ->
        val placeable = subcompose("MyDynamicComponent") {
            // 动态创建或更新子组件
            Box(modifier = Modifier.fillMaxSize()) {
                // 子组件内容
            }
        }.first().measure(constraints)

        layout(placeable.width, placeable.height) {
            placeable.placeRelative(0, 0)
        }
    }
}

以上先测量宽高再布局