PageSize

import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.aspectRatio
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.pager.HorizontalPager
import androidx.compose.foundation.pager.PageSize
import androidx.compose.foundation.pager.PagerState
import androidx.compose.foundation.pager.rememberPagerState
import androidx.compose.material.Text
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.Density
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp

// [PageSize] should be defined as a top level constant in order to avoid unnecessary re-
// creations.
val CustomPageSize =
    object : PageSize {
        override fun Density.calculateMainAxisPageSize(
            availableSpace: Int,
            pageSpacing: Int,
        ): Int {
            // [availableSpace] represents the whole Pager width (in this case), we'd like to
            // have
            // 3 pages per viewport, so we divide it by 3, taking into consideration the start
            // and end spacings.
            return (availableSpace - 2 * pageSpacing) / 3
        }
    }

val state = rememberPagerState { 10 }
HorizontalPager(state = state, modifier = Modifier.fillMaxSize(), pageSize = CustomPageSize) {
    page ->
    Box(
        modifier =
            Modifier.padding(10.dp).background(Color.Blue).fillMaxWidth().aspectRatio(1f),
        contentAlignment = Alignment.Center,
    ) {
        Text(text = page.toString(), fontSize = 32.sp)
    }
}