Add scroll to top button in HomeSongList

app/src/main/kotlin/it/vfsfitvnm/vimusic/ui/components/themed/ScrollToTop.kt

@@ -0,0 +1,101 @@
+package it.vfsfitvnm.vimusic.ui.components.themed
+
+import androidx.compose.animation.AnimatedVisibility
+import androidx.compose.animation.slideInVertically
+import androidx.compose.animation.slideOutVertically
+import androidx.compose.foundation.Image
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.lazy.LazyListState
+import androidx.compose.foundation.lazy.grid.LazyGridState
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.derivedStateOf
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.rotate
+import androidx.compose.ui.graphics.ColorFilter
+import androidx.compose.ui.res.painterResource
+import androidx.compose.ui.unit.dp
+import it.vfsfitvnm.vimusic.LocalPlayerAwarePaddingValues
+import it.vfsfitvnm.vimusic.R
+import it.vfsfitvnm.vimusic.ui.styling.LocalAppearance
+import kotlinx.coroutines.launch
+
+@Composable
+fun ScrollToTop(
+    lazyListState: LazyListState,
+    modifier: Modifier = Modifier,
+) {
+    val showScrollTopButton by remember {
+        derivedStateOf {
+            lazyListState.firstVisibleItemIndex > lazyListState.layoutInfo.visibleItemsInfo.size
+        }
+    }
+
+    ScrollToTop(
+        isVisible = showScrollTopButton,
+        onClick = { lazyListState.animateScrollToItem(0) },
+        modifier = modifier
+    )
+}
+
+@Composable
+fun ScrollToTop(
+    lazyGridState: LazyGridState,
+    modifier: Modifier = Modifier,
+) {
+    val showScrollTopButton by remember {
+        derivedStateOf {
+            lazyGridState.firstVisibleItemIndex > lazyGridState.layoutInfo.visibleItemsInfo.size
+        }
+    }
+
+    ScrollToTop(
+        isVisible = showScrollTopButton,
+        onClick = { lazyGridState.animateScrollToItem(0) },
+        modifier = modifier
+    )
+}
+
+@Composable
+private fun ScrollToTop(
+    isVisible: Boolean,
+    onClick: suspend () -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    AnimatedVisibility(
+        visible = isVisible,
+        enter = slideInVertically { it },
+        exit = slideOutVertically { it },
+        modifier = modifier
+    ) {
+        val coroutineScope = rememberCoroutineScope()
+
+        Box(
+            modifier = Modifier
+                .padding(all = 16.dp)
+                .padding(LocalPlayerAwarePaddingValues.current)
+                .clickable {
+                    coroutineScope.launch {
+                        onClick()
+                    }
+                }
+                .size(32.dp)
+        ) {
+            Image(
+                painter = painterResource(R.drawable.chevron_down),
+                contentDescription = null,
+                colorFilter = ColorFilter.tint(LocalAppearance.current.colorPalette.text),
+                modifier = Modifier
+                    .align(Alignment.Center)
+                    .rotate(180f)
+                    .size(20.dp)
+            )
+        }
+    }
+}

app/src/main/kotlin/it/vfsfitvnm/vimusic/ui/screens/home/HomeSongList.kt

@@ -12,14 +12,17 @@ import androidx.compose.foundation.ExperimentalFoundationApi
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.offset
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.itemsIndexed
+import androidx.compose.foundation.lazy.rememberLazyListState
 import androidx.compose.foundation.text.BasicText
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
@@ -44,6 +47,7 @@ import it.vfsfitvnm.vimusic.models.DetailedSong
 import it.vfsfitvnm.vimusic.savers.DetailedSongListSaver
 import it.vfsfitvnm.vimusic.ui.components.themed.Header
 import it.vfsfitvnm.vimusic.ui.components.themed.InHistoryMediaItemMenu
+import it.vfsfitvnm.vimusic.ui.components.themed.ScrollToTop
 import it.vfsfitvnm.vimusic.ui.styling.Dimensions
 import it.vfsfitvnm.vimusic.ui.styling.LocalAppearance
 import it.vfsfitvnm.vimusic.ui.styling.px
@@ -88,11 +92,16 @@ fun HomeSongList() {
         animationSpec = tween(durationMillis = 400, easing = LinearEasing)
     )
 
-    LazyColumn(
+    val lazyListState = rememberLazyListState()
-        contentPadding = LocalPlayerAwarePaddingValues.current,
+
+    Box(
         modifier = Modifier
             .background(colorPalette.background0)
             .fillMaxSize()
+    ) {
+        LazyColumn(
+            state = lazyListState,
+            contentPadding = LocalPlayerAwarePaddingValues.current,
         ) {
             item(
                 key = "header",
@@ -198,4 +207,12 @@ fun HomeSongList() {
                 )
             }
         }
+
+        ScrollToTop(
+            lazyListState = lazyListState,
+            modifier = Modifier
+                .offset(x = -Dimensions.verticalBarWidth)
+                .align(Alignment.BottomStart)
+        )
+    }
 }