Lots of Paging tidy-ups

- Removed our hacky items() overload for LazyGridScope - Removed workaround for https://issuetracker.google.com/issues/177245496
chrisbanes · Jul 25, 2023 · 08cea48 · 08cea48
1 parent 40d64b8
commit 08cea48
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diff --git a/common/ui/compose/src/commonMain/kotlin/app/tivi/common/compose/EntryGrid.kt b/common/ui/compose/src/commonMain/kotlin/app/tivi/common/compose/EntryGrid.kt
@@ -47,6 +47,7 @@ import androidx.compose.ui.input.nestedscroll.nestedScroll
 import androidx.compose.ui.unit.dp
 import app.cash.paging.LoadStateLoading
 import app.cash.paging.compose.LazyPagingItems
+import app.cash.paging.compose.itemKey
 import app.tivi.common.compose.ui.PlaceholderPosterCard
 import app.tivi.common.compose.ui.PosterCard
 import app.tivi.common.compose.ui.RefreshButton
@@ -130,7 +131,6 @@ fun <E : Entry> EntryGrid(
             val gutter = Layout.gutter
 
             LazyVerticalGrid(
-                state = rememberLazyGridState(lazyPagingItems.itemCount == 0),
                 columns = GridCells.Fixed((columns / 1.5).roundToInt()),
                 contentPadding = paddingValues +
                     PaddingValues(horizontal = bodyMargin, vertical = gutter),
@@ -143,9 +143,10 @@ fun <E : Entry> EntryGrid(
                     .fillMaxHeight(),
             ) {
                 items(
-                    items = lazyPagingItems,
-                    key = { it.show.id },
-                ) { entry ->
+                    count = lazyPagingItems.itemCount,
+                    key = lazyPagingItems.itemKey { it.show.id },
+                ) { index ->
+                    val entry = lazyPagingItems[index]
                     val mod = Modifier
                         .animateItemPlacement()
                         .aspectRatio(2 / 3f)

diff --git a/common/ui/compose/src/commonMain/kotlin/app/tivi/common/compose/LazyList.kt b/common/ui/compose/src/commonMain/kotlin/app/tivi/common/compose/LazyList.kt
@@ -5,28 +5,16 @@
 
 package app.tivi.common.compose
 
-import androidx.compose.foundation.layout.Box
-import androidx.compose.foundation.layout.PaddingValues
-import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
-import androidx.compose.foundation.layout.calculateEndPadding
-import androidx.compose.foundation.layout.calculateStartPadding
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
-import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.layout.width
-import androidx.compose.foundation.lazy.LazyItemScope
 import androidx.compose.foundation.lazy.LazyListScope
 import androidx.compose.foundation.lazy.grid.GridItemSpan
 import androidx.compose.foundation.lazy.grid.LazyGridItemScope
-import androidx.compose.foundation.lazy.grid.LazyGridItemSpanScope
 import androidx.compose.foundation.lazy.grid.LazyGridScope
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.platform.LocalLayoutDirection
 import androidx.compose.ui.unit.Dp
-import androidx.compose.ui.unit.dp
-import app.cash.paging.compose.LazyPagingItems
 
 inline fun LazyListScope.itemSpacer(height: Dp) {
     item {
@@ -68,44 +56,6 @@ inline fun LazyGridScope.itemSpacer(height: Dp) {
     }
 }
 
-fun <T : Any> LazyGridScope.items(
-    items: LazyPagingItems<T>,
-    key: ((item: T) -> Any)? = null,
-    span: (LazyGridItemSpanScope.(item: T) -> GridItemSpan)? = null,
-    contentType: (item: T) -> Any? = { null },
-    itemContent: @Composable LazyGridItemScope.(item: T?) -> Unit,
-) {
-    items(
-        count = items.itemCount,
-        span = { index ->
-            val item = items.peek(index)
-            when {
-                item != null && span != null -> span(item)
-                else -> GridItemSpan(1)
-            }
-        },
-        contentType = { index ->
-            items.peek(index)?.let { contentType(it) }
-        },
-        key = if (key == null) {
-            null
-        } else {
-            { index ->
-                val item = items.peek(index)
-                if (item == null) {
-                    PagingPlaceholderKey(index)
-                } else {
-                    key(item)
-                }
-            }
-        },
-    ) { index ->
-        itemContent(items[index])
-    }
-}
-
-internal data class PagingPlaceholderKey(private val index: Int)
-
 inline fun LazyGridScope.fullSpanItem(
     key: Any? = null,
     contentType: Any? = null,
@@ -118,55 +68,3 @@ inline fun LazyGridScope.fullSpanItem(
         content = content,
     )
 }
-
-/**
- * Displays a 'fake' grid using [LazyColumn]'s DSL. It's fake in that we just we add individual
- * column items, with a inner fake row.
- */
-fun <T : Any> LazyListScope.itemsInGrid(
-    items: List<T>,
-    columns: Int,
-    contentPadding: PaddingValues = PaddingValues(),
-    horizontalItemPadding: Dp = 0.dp,
-    verticalItemPadding: Dp = 0.dp,
-    itemContent: @Composable LazyItemScope.(T) -> Unit,
-) {
-    val rows = when {
-        items.size % columns == 0 -> items.size / columns
-        else -> (items.size / columns) + 1
-    }
-
-    for (row in 0 until rows) {
-        if (row == 0) itemSpacer(contentPadding.calculateTopPadding())
-
-        item {
-            val layoutDirection = LocalLayoutDirection.current
-            Row(
-                modifier = Modifier
-                    .fillMaxWidth()
-                    .padding(
-                        start = contentPadding.calculateStartPadding(layoutDirection),
-                        end = contentPadding.calculateEndPadding(layoutDirection),
-                    ),
-            ) {
-                for (column in 0 until columns) {
-                    Box(modifier = Modifier.weight(1f)) {
-                        val index = (row * columns) + column
-                        if (index < items.size) {
-                            itemContent(items[index])
-                        }
-                    }
-                    if (column < columns - 1) {
-                        Spacer(modifier = Modifier.width(horizontalItemPadding))
-                    }
-                }
-            }
-        }
-
-        if (row < rows - 1) {
-            itemSpacer(verticalItemPadding)
-        } else {
-            itemSpacer(contentPadding.calculateBottomPadding())
-        }
-    }
-}
diff --git a/common/ui/compose/src/commonMain/kotlin/app/tivi/common/compose/LazyPagingExtensions.kt b/common/ui/compose/src/commonMain/kotlin/app/tivi/common/compose/LazyPagingExtensions.kt
@@ -1,14 +1,18 @@
 // Copyright 2021, Google LLC, Christopher Banes and the Tivi project contributors
 // SPDX-License-Identifier: Apache-2.0
 
+@file:Suppress("USELESS_IS_CHECK", "CAST_NEVER_SUCCEEDS")
+
 package app.tivi.common.compose
 
-import androidx.compose.foundation.lazy.LazyListState
-import androidx.compose.foundation.lazy.grid.LazyGridState
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.remember
 import app.cash.paging.CombinedLoadStates
 import app.cash.paging.LoadStateError
+import app.cash.paging.PagingData
+import app.cash.paging.cachedIn
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.Flow
 
 fun CombinedLoadStates.appendErrorOrNull(): UiMessage? {
     return (append.takeIf { it is LoadStateError } as? LoadStateError)
@@ -25,35 +29,7 @@ fun CombinedLoadStates.refreshErrorOrNull(): UiMessage? {
         ?.let { UiMessage(it.error) }
 }
 
-/*
- * The following are workarounds for https://issuetracker.google.com/issues/177245496.
- *
- * Due to the way which paging loads data, it will always result in an initial empty state,
- * and then the loaded items. That conflicts with the way which rememberLazyListState() and
- * friends store their state, as they rely on the items being present at the time of
- * (Android) state restoration. To workaround this, we use a different LazyListState while the
- * lazy paging items are empty, and then switcheroo to the standard state once we know we have the
- * items available.
- */
-
-@Composable
-fun rememberLazyListState(empty: Boolean = false): LazyListState {
-    return if (empty) {
-        // Return a different state instance
-        remember { LazyListState(0, 0) }
-    } else {
-        // Return restored state
-        androidx.compose.foundation.lazy.rememberLazyListState()
-    }
-}
-
 @Composable
-fun rememberLazyGridState(empty: Boolean = false): LazyGridState {
-    return if (empty) {
-        // Return a different state instance
-        remember { LazyGridState(0, 0) }
-    } else {
-        // Return restored state
-        androidx.compose.foundation.lazy.grid.rememberLazyGridState()
-    }
-}
+inline fun <T : Any> Flow<PagingData<T>>.rememberCachedPagingFlow(
+    scope: CoroutineScope = rememberCoroutineScope(),
+): Flow<PagingData<T>> = remember(this, scope) { cachedIn(scope) }
diff --git a/ui/library/src/commonMain/kotlin/app/tivi/home/library/Library.kt b/ui/library/src/commonMain/kotlin/app/tivi/home/library/Library.kt
@@ -62,15 +62,14 @@ import androidx.compose.ui.text.input.TextFieldValue
 import androidx.compose.ui.unit.dp
 import app.cash.paging.LoadStateLoading
 import app.cash.paging.compose.LazyPagingItems
+import app.cash.paging.compose.itemKey
 import app.tivi.common.compose.Layout
 import app.tivi.common.compose.LocalStrings
 import app.tivi.common.compose.LocalTiviDateFormatter
 import app.tivi.common.compose.LocalTiviTextCreator
 import app.tivi.common.compose.bodyWidth
 import app.tivi.common.compose.fullSpanItem
-import app.tivi.common.compose.items
 import app.tivi.common.compose.rememberCoroutineScope
-import app.tivi.common.compose.rememberLazyGridState
 import app.tivi.common.compose.rememberTiviFlingBehavior
 import app.tivi.common.compose.ui.EmptyContent
 import app.tivi.common.compose.ui.PosterCard
@@ -254,7 +253,6 @@ private fun LibraryGrid(
     var filterExpanded by remember { mutableStateOf(false) }
 
     LazyVerticalGrid(
-        state = rememberLazyGridState(lazyPagingItems.itemCount == 0),
         columns = GridCells.Fixed(columns / 4),
         flingBehavior = rememberTiviFlingBehavior(),
         contentPadding = paddingValues + PaddingValues(
@@ -355,9 +353,10 @@ private fun LibraryGrid(
         }
 
         items(
-            items = lazyPagingItems,
-            key = { it.show.id },
-        ) { entry ->
+            count = state.items.itemCount,
+            key = state.items.itemKey { it.show.id },
+        ) { index ->
+            val entry = state.items[index]
             if (entry != null) {
                 LibraryItem(
                     show = entry.show,

diff --git a/ui/library/src/commonMain/kotlin/app/tivi/home/library/LibraryPresenter.kt b/ui/library/src/commonMain/kotlin/app/tivi/home/library/LibraryPresenter.kt
@@ -15,6 +15,7 @@ import app.cash.paging.PagingConfig
 import app.cash.paging.compose.collectAsLazyPagingItems
 import app.tivi.common.compose.UiMessage
 import app.tivi.common.compose.UiMessageManager
+import app.tivi.common.compose.rememberCachedPagingFlow
 import app.tivi.common.compose.rememberCoroutineScope
 import app.tivi.data.models.SortOption
 import app.tivi.data.traktauth.TraktAuthState
@@ -70,7 +71,9 @@ class LibraryPresenter(
         val scope = rememberCoroutineScope()
         val uiMessageManager = remember { UiMessageManager() }
 
-        val items = observePagedLibraryShows.flow.collectAsLazyPagingItems()
+        val items = observePagedLibraryShows.flow
+            .rememberCachedPagingFlow(scope)
+            .collectAsLazyPagingItems()
 
         var filter by remember { mutableStateOf<String?>(null) }
         var sort by remember { mutableStateOf(SortOption.LAST_WATCHED) }

diff --git a/ui/popular/src/commonMain/kotlin/app/tivi/home/popular/PopularShowsPresenter.kt b/ui/popular/src/commonMain/kotlin/app/tivi/home/popular/PopularShowsPresenter.kt
@@ -7,6 +7,7 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import app.cash.paging.PagingConfig
 import app.cash.paging.compose.collectAsLazyPagingItems
+import app.tivi.common.compose.rememberCachedPagingFlow
 import app.tivi.domain.observers.ObservePagedPopularShows
 import app.tivi.screens.PopularShowsScreen
 import app.tivi.screens.ShowDetailsScreen
@@ -39,7 +40,9 @@ class PopularShowsPresenter(
 
     @Composable
     override fun present(): PopularShowsUiState {
-        val items = pagingInteractor.flow.collectAsLazyPagingItems()
+        val items = pagingInteractor.flow
+            .rememberCachedPagingFlow()
+            .collectAsLazyPagingItems()
 
         LaunchedEffect(Unit) {
             pagingInteractor(ObservePagedPopularShows.Params(PAGING_CONFIG))

diff --git a/ui/recommended/src/commonMain/kotlin/app/tivi/home/recommended/RecommendedShowsPresenter.kt b/ui/recommended/src/commonMain/kotlin/app/tivi/home/recommended/RecommendedShowsPresenter.kt
@@ -7,6 +7,7 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import app.cash.paging.PagingConfig
 import app.cash.paging.compose.collectAsLazyPagingItems
+import app.tivi.common.compose.rememberCachedPagingFlow
 import app.tivi.domain.observers.ObservePagedRecommendedShows
 import app.tivi.screens.RecommendedShowsScreen
 import app.tivi.screens.ShowDetailsScreen
@@ -39,7 +40,9 @@ class RecommendedShowsPresenter(
 
     @Composable
     override fun present(): RecommendedShowsUiState {
-        val items = pagingInteractor.flow.collectAsLazyPagingItems()
+        val items = pagingInteractor.flow
+            .rememberCachedPagingFlow()
+            .collectAsLazyPagingItems()
 
         LaunchedEffect(Unit) {
             pagingInteractor(ObservePagedRecommendedShows.Params(PAGING_CONFIG))

diff --git a/ui/trending/src/commonMain/kotlin/app/tivi/home/trending/TrendingShowsPresenter.kt b/ui/trending/src/commonMain/kotlin/app/tivi/home/trending/TrendingShowsPresenter.kt
@@ -7,6 +7,7 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import app.cash.paging.PagingConfig
 import app.cash.paging.compose.collectAsLazyPagingItems
+import app.tivi.common.compose.rememberCachedPagingFlow
 import app.tivi.domain.observers.ObservePagedTrendingShows
 import app.tivi.screens.ShowDetailsScreen
 import app.tivi.screens.TrendingShowsScreen
@@ -39,7 +40,9 @@ class TrendingShowsPresenter(
 
     @Composable
     override fun present(): TrendingShowsUiState {
-        val items = pagingInteractor.flow.collectAsLazyPagingItems()
+        val items = pagingInteractor.flow
+            .rememberCachedPagingFlow()
+            .collectAsLazyPagingItems()
 
         LaunchedEffect(Unit) {
             pagingInteractor(ObservePagedTrendingShows.Params(PAGING_CONFIG))

diff --git a/ui/upnext/src/commonMain/kotlin/app/tivi/home/upnext/UpNext.kt b/ui/upnext/src/commonMain/kotlin/app/tivi/home/upnext/UpNext.kt
@@ -58,14 +58,13 @@ import androidx.compose.ui.input.nestedscroll.nestedScroll
 import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.unit.dp
 import app.cash.paging.LoadStateLoading
+import app.cash.paging.compose.itemKey
 import app.tivi.common.compose.Layout
 import app.tivi.common.compose.LocalStrings
 import app.tivi.common.compose.LocalTiviTextCreator
 import app.tivi.common.compose.bodyWidth
 import app.tivi.common.compose.fullSpanItem
-import app.tivi.common.compose.items
 import app.tivi.common.compose.rememberCoroutineScope
-import app.tivi.common.compose.rememberLazyGridState
 import app.tivi.common.compose.rememberTiviFlingBehavior
 import app.tivi.common.compose.ui.AsyncImage
 import app.tivi.common.compose.ui.EmptyContent
@@ -217,7 +216,6 @@ internal fun UpNext(
             val gutter = Layout.gutter
 
             LazyVerticalGrid(
-                state = rememberLazyGridState(state.items.itemCount == 0),
                 columns = GridCells.Fixed(columns / 4),
                 contentPadding = paddingValues + PaddingValues(
                     horizontal = (bodyMargin - 8.dp).coerceAtLeast(0.dp),
@@ -258,9 +256,10 @@ internal fun UpNext(
                 }
 
                 items(
-                    items = state.items,
-                    key = { it.show.id },
-                ) { entry ->
+                    count = state.items.itemCount,
+                    key = state.items.itemKey { it.show.id },
+                ) { index ->
+                    val entry = state.items[index]
                     if (entry != null) {
                         SwipeUpNextItem(
                             onSwipe = { openTrackEpisode(entry.episode.id) },

diff --git a/ui/upnext/src/commonMain/kotlin/app/tivi/home/upnext/UpNextPresenter.kt b/ui/upnext/src/commonMain/kotlin/app/tivi/home/upnext/UpNextPresenter.kt
@@ -15,6 +15,7 @@ import app.cash.paging.PagingConfig
 import app.cash.paging.compose.collectAsLazyPagingItems
 import app.tivi.common.compose.UiMessage
 import app.tivi.common.compose.UiMessageManager
+import app.tivi.common.compose.rememberCachedPagingFlow
 import app.tivi.common.compose.rememberCoroutineScope
 import app.tivi.data.models.SortOption
 import app.tivi.data.traktauth.TraktAuthState
@@ -73,7 +74,9 @@ class UpNextPresenter(
 
         val uiMessageManager = remember { UiMessageManager() }
 
-        val items = observePagedUpNextShows.flow.collectAsLazyPagingItems()
+        val items = observePagedUpNextShows.flow
+            .rememberCachedPagingFlow(scope)
+            .collectAsLazyPagingItems()
 
         var sort by remember { mutableStateOf(SortOption.LAST_WATCHED) }