TransformingLazyColumnAnchorType

value class TransformingLazyColumnAnchorType

import androidx.compose.foundation.layout.PaddingValues
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.runtime.mutableIntStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import androidx.wear.compose.foundation.lazy.TransformingLazyColumn
import androidx.wear.compose.foundation.lazy.TransformingLazyColumnAnchorType
import androidx.wear.compose.foundation.lazy.rememberTransformingLazyColumnState
import androidx.wear.compose.material.Text
import androidx.wear.compose.material3.Button
import androidx.wear.compose.material3.ButtonDefaults
import androidx.wear.compose.material3.SurfaceTransformation
import androidx.wear.compose.material3.lazy.rememberTransformationSpec
import androidx.wear.compose.material3.lazy.transformedHeight

// This sample demonstrates how to use requestAnchorItem to control the expansion direction
// of an item. When the "input_box" Button is clicked, its text content grows, causing its
// intrinsic height to increase. By requesting ItemBottom as the layout anchor immediately
// before the state change, the visual bottom edge of the button remains pinned in place on
// the screen, and the new height expands upwards.
val state = rememberTransformingLazyColumnState()
val transformationSpec = rememberTransformationSpec()

var textLines by remember { mutableIntStateOf(1) }

TransformingLazyColumn(
    state = state,
    contentPadding = PaddingValues(20.dp),
    modifier = Modifier.fillMaxSize(),
) {
    items(3, key = { "item_$it" }) { index ->
        Button(
            onClick = {},
            modifier =
                Modifier.fillMaxWidth()
                    .transformedHeight(this, transformationSpec)
                    .minimumVerticalContentPadding(
                        ButtonDefaults.minimumVerticalListContentPadding
                    ),
            transformation = SurfaceTransformation(transformationSpec),
        ) {
            Text(text = "Item $index")
        }
    }

    // The expanding item
    item(key = "input_box") {
        Button(
            onClick = {
                state.requestAnchorItem(
                    key = "input_box",
                    anchorType = TransformingLazyColumnAnchorType.ItemBottom,
                )
                textLines = if (textLines < 4) textLines + 1 else 1
            },
            modifier = Modifier.fillMaxWidth().transformedHeight(this, transformationSpec),
            transformation = SurfaceTransformation(transformationSpec),
        ) {
            val text = List(textLines) { "Input line ${it + 1}" }.joinToString("\n")
            Text(text = text)
        }
    }

    items(3, key = { "item_${it + 4}" }) { index ->
        Button(
            onClick = {},
            modifier =
                Modifier.fillMaxWidth()
                    .transformedHeight(this, transformationSpec)
                    .minimumVerticalContentPadding(
                        ButtonDefaults.minimumVerticalListContentPadding
                    ),
            transformation = SurfaceTransformation(transformationSpec),
        ) {
            Text(text = "Item ${index + 4}")
        }
    }
}