DirectLoadingStrategy is just for testing

redwood-lazylayout-compose/api/redwood-lazylayout-compose.api

@@ -52,8 +52,8 @@ public final class app/cash/redwood/lazylayout/compose/RefreshableLazyListKt {
 public final class app/cash/redwood/lazylayout/compose/ScrollOptimizedLoadingStrategy : app/cash/redwood/lazylayout/compose/LoadingStrategy {
 	public static final field $stable I
 	public fun <init> ()V
-	public fun <init> (IIIIZ)V
-	public synthetic fun <init> (IIIIZILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public fun <init> (IIII)V
+	public synthetic fun <init> (IIIIILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public fun getFirstIndex ()I
 	public final fun getLastIndex ()I
 	public final fun getProgrammaticScrollIndex ()Lapp/cash/redwood/lazylayout/api/ScrollItemIndex;

redwood-lazylayout-compose/api/redwood-lazylayout-compose.klib.api

@@ -25,7 +25,7 @@ abstract interface app.cash.redwood.lazylayout.compose/LoadingStrategy { // app.
 }
 
 final class app.cash.redwood.lazylayout.compose/ScrollOptimizedLoadingStrategy : app.cash.redwood.lazylayout.compose/LoadingStrategy { // app.cash.redwood.lazylayout.compose/ScrollOptimizedLoadingStrategy|null[0]
-    constructor <init>(kotlin/Int = ..., kotlin/Int = ..., kotlin/Int = ..., kotlin/Int = ..., kotlin/Boolean = ...) // app.cash.redwood.lazylayout.compose/ScrollOptimizedLoadingStrategy.<init>|<init>(kotlin.Int;kotlin.Int;kotlin.Int;kotlin.Int;kotlin.Boolean){}[0]
+    constructor <init>(kotlin/Int = ..., kotlin/Int = ..., kotlin/Int = ..., kotlin/Int = ...) // app.cash.redwood.lazylayout.compose/ScrollOptimizedLoadingStrategy.<init>|<init>(kotlin.Int;kotlin.Int;kotlin.Int;kotlin.Int){}[0]
 
     final var firstIndex // app.cash.redwood.lazylayout.compose/ScrollOptimizedLoadingStrategy.firstIndex|{}firstIndex[0]
         final fun <get-firstIndex>(): kotlin/Int // app.cash.redwood.lazylayout.compose/ScrollOptimizedLoadingStrategy.firstIndex.<get-firstIndex>|<get-firstIndex>(){}[0]

redwood-lazylayout-compose/src/commonMain/kotlin/app/cash/redwood/lazylayout/compose/ScrollOptimizedLoadingStrategy.kt

@@ -42,7 +42,6 @@ public class ScrollOptimizedLoadingStrategy(
   private val scrollInProgressPreloadItemCount: Int = SCROLL_IN_PROGRESS_PRELOAD_ITEM_COUNT,
   private val primaryPreloadItemCount: Int = PRIMARY_PRELOAD_ITEM_COUNT,
   private val secondaryPreloadItemCount: Int = SECONDARY_PRELOAD_ITEM_COUNT,
-  private val preloadItems: Boolean = true,
 ) : LoadingStrategy {
   /**
    * Update this to trigger a programmatic scroll. This may be updated multiple times, including
@@ -92,11 +91,6 @@ public class ScrollOptimizedLoadingStrategy(
 
     // Expand the range depending on scroll direction.
     when {
-      // Ignore preloads.
-      !preloadItems -> {
-        // No-op
-      }
-
       isScrollingDown -> {
         begin -= scrollInProgressPreloadItemCount
         end += primaryPreloadItemCount

redwood-lazylayout-compose/src/commonTest/kotlin/app/cash/redwood/lazylayout/compose/LazyListTest.kt

@@ -116,9 +116,7 @@ class LazyListTest {
     TestSchemaTester {
       var index5ComposeCount = 0
       setContent {
-        val lazyListState = rememberLazyListState(
-          ScrollOptimizedLoadingStrategy(preloadItems = false),
-        )
+        val lazyListState = rememberLazyListState(DirectLoadingStrategy())
         LazyColumn(
           state = lazyListState,
           placeholder = { Text("Placeholder") },
@@ -149,21 +147,12 @@ class LazyListTest {
       awaitSnapshot()
       assertThat(index5ComposeCount).isEqualTo(1)
 
-      // Even when it's scrolled off-screen.
+      // It isn't recomposed when it's out of the loaded range.
       lazyList.onViewportChanged(6, 10)
       awaitSnapshot()
       assertThat(index5ComposeCount).isEqualTo(1)
 
-      // The item at index 5 remains composed because (6, 10) is contiguous with (4, 8).
-      lazyList.onViewportChanged(4, 8)
-      awaitSnapshot()
-      assertThat(index5ComposeCount).isEqualTo(1)
-
-      // Scrolling to a non-contiguous range causes a recomposition.
-      lazyList.onViewportChanged(9, 13)
-      awaitSnapshot()
-      assertThat(index5ComposeCount).isEqualTo(1)
-
+      // When it's scrolled back into range, it's recomposed.
       lazyList.onViewportChanged(4, 8)
       awaitSnapshot()
       assertThat(index5ComposeCount).isEqualTo(2)

redwood-lazylayout-testing/api/redwood-lazylayout-testing.api

@@ -1,3 +1,11 @@
+public final class app/cash/redwood/lazylayout/compose/DirectLoadingStrategy : app/cash/redwood/lazylayout/compose/LoadingStrategy {
+	public fun <init> ()V
+	public fun getFirstIndex ()I
+	public fun loadRange (I)Lkotlin/ranges/IntRange;
+	public fun onUserScroll (II)V
+	public fun scrollTo (I)V
+}
+
 public final class app/cash/redwood/lazylayout/testing/LazyListValue : app/cash/redwood/testing/WidgetValue {
 	public synthetic fun <init> (Lapp/cash/redwood/Modifier;ZLkotlin/jvm/functions/Function2;IIIILapp/cash/redwood/ui/Margin;ILapp/cash/redwood/lazylayout/api/ScrollItemIndex;Ljava/util/List;Ljava/util/List;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public synthetic fun <init> (Lapp/cash/redwood/Modifier;ZLkotlin/jvm/functions/Function2;IIIILapp/cash/redwood/ui/Margin;ILapp/cash/redwood/lazylayout/api/ScrollItemIndex;Ljava/util/List;Ljava/util/List;Lkotlin/jvm/internal/DefaultConstructorMarker;)V

redwood-lazylayout-testing/api/redwood-lazylayout-testing.klib.api

@@ -6,6 +6,17 @@
 // - Show declarations: true
 
 // Library unique name: <app.cash.redwood:redwood-lazylayout-testing>
+final class app.cash.redwood.lazylayout.compose/DirectLoadingStrategy : app.cash.redwood.lazylayout.compose/LoadingStrategy { // app.cash.redwood.lazylayout.compose/DirectLoadingStrategy|null[0]
+    constructor <init>() // app.cash.redwood.lazylayout.compose/DirectLoadingStrategy.<init>|<init>(){}[0]
+
+    final val firstIndex // app.cash.redwood.lazylayout.compose/DirectLoadingStrategy.firstIndex|{}firstIndex[0]
+        final fun <get-firstIndex>(): kotlin/Int // app.cash.redwood.lazylayout.compose/DirectLoadingStrategy.firstIndex.<get-firstIndex>|<get-firstIndex>(){}[0]
+
+    final fun loadRange(kotlin/Int): kotlin.ranges/IntRange // app.cash.redwood.lazylayout.compose/DirectLoadingStrategy.loadRange|loadRange(kotlin.Int){}[0]
+    final fun onUserScroll(kotlin/Int, kotlin/Int) // app.cash.redwood.lazylayout.compose/DirectLoadingStrategy.onUserScroll|onUserScroll(kotlin.Int;kotlin.Int){}[0]
+    final fun scrollTo(kotlin/Int) // app.cash.redwood.lazylayout.compose/DirectLoadingStrategy.scrollTo|scrollTo(kotlin.Int){}[0]
+}
+
 final class app.cash.redwood.lazylayout.testing/LazyListValue : app.cash.redwood.testing/WidgetValue { // app.cash.redwood.lazylayout.testing/LazyListValue|null[0]
     constructor <init>(app.cash.redwood/Modifier = ..., kotlin/Boolean, kotlin/Function2<kotlin/Int, kotlin/Int, kotlin/Unit>, kotlin/Int, kotlin/Int, app.cash.redwood.layout.api/Constraint, app.cash.redwood.layout.api/Constraint, app.cash.redwood.ui/Margin, app.cash.redwood.layout.api/CrossAxisAlignment, app.cash.redwood.lazylayout.api/ScrollItemIndex, kotlin.collections/List<app.cash.redwood.testing/WidgetValue> = ..., kotlin.collections/List<app.cash.redwood.testing/WidgetValue> = ...) // app.cash.redwood.lazylayout.testing/LazyListValue.<init>|<init>(app.cash.redwood.Modifier;kotlin.Boolean;kotlin.Function2<kotlin.Int,kotlin.Int,kotlin.Unit>;kotlin.Int;kotlin.Int;app.cash.redwood.layout.api.Constraint;app.cash.redwood.layout.api.Constraint;app.cash.redwood.ui.Margin;app.cash.redwood.layout.api.CrossAxisAlignment;app.cash.redwood.lazylayout.api.ScrollItemIndex;kotlin.collections.List<app.cash.redwood.testing.WidgetValue>;kotlin.collections.List<app.cash.redwood.testing.WidgetValue>){}[0]
 

redwood-lazylayout-testing/build.gradle

@@ -11,6 +11,7 @@ kotlin {
   sourceSets {
     commonMain {
       dependencies {
+        api projects.redwoodLazylayoutCompose
         api projects.redwoodLazylayoutWidget
       }
     }

redwood-lazylayout-testing/src/commonMain/kotlin/app/cash/redwood/lazylayout/compose/DirectLoadingStrategy.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2024 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package app.cash.redwood.lazylayout.compose
+
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
+
+/**
+ * A loading strategy that's appropriate for tests because it's simple and predictable.
+ *
+ * This is not suitable for production use it must show a placeholder before an item is loaded.
+ */
+public class DirectLoadingStrategy : LoadingStrategy {
+  private var loadRange: IntRange by mutableStateOf(0..0)
+
+  public override val firstIndex: Int
+    get() = loadRange.first
+
+  override fun scrollTo(firstIndex: Int) {
+    require(firstIndex >= 0)
+    loadRange = firstIndex..firstIndex + (loadRange.last - loadRange.first)
+  }
+
+  override fun onUserScroll(firstIndex: Int, lastIndex: Int) {
+    loadRange = firstIndex..lastIndex
+  }
+
+  override fun loadRange(itemCount: Int): IntRange =
+    loadRange.first.coerceIn(0, itemCount - 1)..loadRange.last.coerceIn(0, itemCount - 1)
+}