Merge "Extract AwaitFirstLayoutModifier and apply it to LazyStaggeredGrid" into androidx-main

ShikaSD · Gerrit Code Review · commit 37f86e324ba0 · 2023-05-05T13:38:57.000Z
diff --git a/compose/foundation/foundation/src/androidAndroidTest/kotlin/androidx/compose/foundation/lazy/staggeredgrid/LazyStaggeredGridTest.kt b/compose/foundation/foundation/src/androidAndroidTest/kotlin/androidx/compose/foundation/lazy/staggeredgrid/LazyStaggeredGridTest.kt
@@ -22,10 +22,12 @@ import androidx.compose.foundation.border
 import androidx.compose.foundation.gestures.Orientation
 import androidx.compose.foundation.gestures.scrollBy
 import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.BoxWithConstraints
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.lazy.list.setContentWithTestViewConfiguration
 import androidx.compose.foundation.text.BasicText
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateListOf
 import androidx.compose.runtime.mutableStateOf
@@ -1934,4 +1936,60 @@ class LazyStaggeredGridTest(
         rule.onNodeWithTag("1")
             .assertAxisBounds(DpOffset(itemSizeDp, itemSizeDp * 2), DpSize(itemSizeDp, itemSizeDp))
     }
+
+    @Test
+    fun scrollDuringMeasure() {
+        rule.setContent {
+            BoxWithConstraints {
+                val state = rememberLazyStaggeredGridState()
+                LazyStaggeredGrid(
+                    lanes = 1,
+                    state = state,
+                    modifier = Modifier.axisSize(
+                        crossAxis = itemSizeDp * 2,
+                        mainAxis = itemSizeDp * 5
+                    ),
+                ) {
+                    items(20) {
+                        Spacer(
+                            modifier = Modifier.mainAxisSize(itemSizeDp).testTag(it.toString())
+                        )
+                    }
+                }
+                LaunchedEffect(state) {
+                    state.scrollToItem(10)
+                }
+            }
+        }
+
+        rule.onNodeWithTag("10")
+            .assertStartPositionInRootIsEqualTo(0.dp)
+    }
+
+    @Test
+    fun scrollInLaunchedEffect() {
+        rule.setContent {
+            val state = rememberLazyStaggeredGridState()
+            LazyStaggeredGrid(
+                lanes = 1,
+                state = state,
+                modifier = Modifier.axisSize(
+                    crossAxis = itemSizeDp * 2,
+                    mainAxis = itemSizeDp * 5
+                ),
+            ) {
+                items(20) {
+                    Spacer(
+                        modifier = Modifier.mainAxisSize(itemSizeDp).testTag(it.toString())
+                    )
+                }
+            }
+            LaunchedEffect(state) {
+                state.scrollToItem(10)
+            }
+        }
+
+        rule.onNodeWithTag("10")
+            .assertStartPositionInRootIsEqualTo(0.dp)
+    }
 }
diff --git a/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/LazyListState.kt b/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/LazyListState.kt
@@ -23,9 +23,10 @@ import androidx.compose.foundation.gestures.ScrollScope
 import androidx.compose.foundation.gestures.ScrollableState
 import androidx.compose.foundation.interaction.InteractionSource
 import androidx.compose.foundation.interaction.MutableInteractionSource
+import androidx.compose.foundation.lazy.layout.AwaitFirstLayoutModifier
 import androidx.compose.foundation.lazy.layout.LazyLayoutBeyondBoundsInfo
-import androidx.compose.foundation.lazy.layout.LazyLayoutPrefetchState
 import androidx.compose.foundation.lazy.layout.LazyLayoutPinnedItemList
+import androidx.compose.foundation.lazy.layout.LazyLayoutPrefetchState
 import androidx.compose.foundation.lazy.layout.animateScrollToItem
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.Stable
@@ -35,16 +36,11 @@ import androidx.compose.runtime.saveable.Saver
 import androidx.compose.runtime.saveable.listSaver
 import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
-import androidx.compose.ui.layout.LayoutCoordinates
-import androidx.compose.ui.layout.OnGloballyPositionedModifier
 import androidx.compose.ui.layout.Remeasurement
 import androidx.compose.ui.layout.RemeasurementModifier
 import androidx.compose.ui.unit.Constraints
 import androidx.compose.ui.unit.Density
 import androidx.compose.ui.unit.IntSize
-import kotlin.coroutines.Continuation
-import kotlin.coroutines.resume
-import kotlin.coroutines.suspendCoroutine
 import kotlin.math.abs
 
 /**
@@ -436,25 +432,4 @@ private object EmptyLazyListLayoutInfo : LazyListLayoutInfo {
     override val beforeContentPadding = 0
     override val afterContentPadding = 0
     override val mainAxisItemSpacing = 0
-}
-
-internal class AwaitFirstLayoutModifier : OnGloballyPositionedModifier {
-    private var wasPositioned = false
-    private var continuation: Continuation<Unit>? = null
-
-    suspend fun waitForFirstLayout() {
-        if (!wasPositioned) {
-            val oldContinuation = continuation
-            suspendCoroutine<Unit> { continuation = it }
-            oldContinuation?.resume(Unit)
-        }
-    }
-
-    override fun onGloballyPositioned(coordinates: LayoutCoordinates) {
-        if (!wasPositioned) {
-            wasPositioned = true
-            continuation?.resume(Unit)
-            continuation = null
-        }
-    }
 }
diff --git a/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/grid/LazyGridState.kt b/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/grid/LazyGridState.kt
@@ -23,7 +23,7 @@ import androidx.compose.foundation.gestures.ScrollScope
 import androidx.compose.foundation.gestures.ScrollableState
 import androidx.compose.foundation.interaction.InteractionSource
 import androidx.compose.foundation.interaction.MutableInteractionSource
-import androidx.compose.foundation.lazy.AwaitFirstLayoutModifier
+import androidx.compose.foundation.lazy.layout.AwaitFirstLayoutModifier
 import androidx.compose.foundation.lazy.layout.LazyLayoutBeyondBoundsInfo
 import androidx.compose.foundation.lazy.layout.LazyLayoutPrefetchState
 import androidx.compose.foundation.lazy.layout.LazyLayoutPinnedItemList
diff --git a/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/layout/AwaitFirstLayoutModifier.kt b/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/layout/AwaitFirstLayoutModifier.kt
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * 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 androidx.compose.foundation.lazy.layout
+
+import androidx.compose.ui.layout.LayoutCoordinates
+import androidx.compose.ui.layout.OnGloballyPositionedModifier
+import kotlin.coroutines.Continuation
+import kotlin.coroutines.resume
+import kotlin.coroutines.suspendCoroutine
+
+/**
+ * Internal modifier which allows to delay some interactions (e.g. scroll) until layout is ready.
+ */
+internal class AwaitFirstLayoutModifier : OnGloballyPositionedModifier {
+    private var wasPositioned = false
+    private var continuation: Continuation<Unit>? = null
+
+    suspend fun waitForFirstLayout() {
+        if (!wasPositioned) {
+            val oldContinuation = continuation
+            suspendCoroutine { continuation = it }
+            oldContinuation?.resume(Unit)
+        }
+    }
+
+    override fun onGloballyPositioned(coordinates: LayoutCoordinates) {
+        if (!wasPositioned) {
+            wasPositioned = true
+            continuation?.resume(Unit)
+            continuation = null
+        }
+    }
+}
diff --git a/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/staggeredgrid/LazyStaggeredGrid.kt b/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/staggeredgrid/LazyStaggeredGrid.kt
@@ -81,6 +81,7 @@ internal fun LazyStaggeredGrid(
     LazyLayout(
         modifier = modifier
             .then(state.remeasurementModifier)
+            .then(state.awaitLayoutModifier)
             .lazyLayoutSemantics(
                 itemProvider = itemProvider,
                 state = semanticState,
diff --git a/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/staggeredgrid/LazyStaggeredGridState.kt b/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/staggeredgrid/LazyStaggeredGridState.kt
@@ -22,6 +22,7 @@ import androidx.compose.foundation.gestures.ScrollScope
 import androidx.compose.foundation.gestures.ScrollableState
 import androidx.compose.foundation.interaction.InteractionSource
 import androidx.compose.foundation.interaction.MutableInteractionSource
+import androidx.compose.foundation.lazy.layout.AwaitFirstLayoutModifier
 import androidx.compose.foundation.lazy.layout.LazyAnimateScrollScope
 import androidx.compose.foundation.lazy.layout.LazyLayoutBeyondBoundsInfo
 import androidx.compose.foundation.lazy.layout.LazyLayoutItemProvider
@@ -166,6 +167,12 @@ class LazyStaggeredGridState private constructor(
         }
     }
 
+    /**
+     * Provides a modifier which allows to delay some interactions (e.g. scroll)
+     * until layout is ready.
+     */
+    internal val awaitLayoutModifier = AwaitFirstLayoutModifier()
+
     internal val beyondBoundsInfo = LazyLayoutBeyondBoundsInfo()
 
     /**
@@ -228,6 +235,7 @@ class LazyStaggeredGridState private constructor(
         scrollPriority: MutatePriority,
         block: suspend ScrollScope.() -> Unit
     ) {
+        awaitLayoutModifier.waitForFirstLayout()
         scrollableState.scroll(scrollPriority, block)
     }
 
diff --git a/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/pager/PagerState.kt b/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/pager/PagerState.kt
@@ -27,7 +27,7 @@ import androidx.compose.foundation.gestures.ScrollableState
 import androidx.compose.foundation.gestures.animateScrollBy
 import androidx.compose.foundation.interaction.InteractionSource
 import androidx.compose.foundation.interaction.MutableInteractionSource
-import androidx.compose.foundation.lazy.AwaitFirstLayoutModifier
+import androidx.compose.foundation.lazy.layout.AwaitFirstLayoutModifier
 import androidx.compose.foundation.lazy.layout.LazyLayoutBeyondBoundsInfo
 import androidx.compose.foundation.lazy.layout.LazyLayoutPinnedItemList
 import androidx.compose.foundation.lazy.layout.LazyLayoutPrefetchState
