Merge pull request #127 from JetBrains/feature/fix_density_change_crash

Fix crash in MeasureAndLayoutDelegate.forceMeasureTheSubtree()
JetBrains · Nov 25, 2021 · ca6db90 · ca6db90
2 parents c9896b9 + 03f1af1
commit ca6db90
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Showing 2 changed files with 48 additions and 4 deletions.
diff --git a/...ui/ui/src/androidAndroidTest/kotlin/androidx/compose/ui/layout/NodesRemeasuredOnceTest.kt b/...ui/ui/src/androidAndroidTest/kotlin/androidx/compose/ui/layout/NodesRemeasuredOnceTest.kt
@@ -119,6 +119,34 @@ class NodesRemeasuredOnceTest {
             assertThat(remeasurements).isEqualTo(2)
         }
     }
+
+    @Test
+    fun remeasuringChildWithExtraLayer_notPlacedChild() {
+        val height = mutableStateOf(10)
+        var remeasurements = 0
+
+        rule.setContent {
+            WrapChild(onMeasured = { actualHeight ->
+                assertThat(actualHeight).isEqualTo(height.value)
+                remeasurements++
+            }) {
+                NotPlaceChild(height) {
+                    WrapChild {
+                        Child(height)
+                    }
+                }
+            }
+        }
+
+        rule.runOnIdle {
+            assertThat(remeasurements).isEqualTo(1)
+            height.value = 20
+        }
+
+        rule.runOnIdle {
+            assertThat(remeasurements).isEqualTo(2)
+        }
+    }
 }
 
 @Composable
@@ -133,6 +161,16 @@ private fun WrapChild(onMeasured: (Int) -> Unit = {}, content: @Composable () ->
     }
 }
 
+@Composable
+private fun NotPlaceChild(height: State<Int>, content: @Composable () -> Unit) {
+    Layout(content = content) { measurables, constraints ->
+        layout(constraints.maxWidth, height.value) {
+            measurables.first()
+                .measure(constraints.copy(minHeight = 0, maxHeight = Constraints.Infinity))
+        }
+    }
+}
+
 @Composable
 private fun Child(height: State<Int>) {
     Layout { _, constraints ->

diff --git a/compose/ui/ui/src/commonMain/kotlin/androidx/compose/ui/node/MeasureAndLayoutDelegate.kt b/compose/ui/ui/src/commonMain/kotlin/androidx/compose/ui/node/MeasureAndLayoutDelegate.kt
@@ -256,6 +256,9 @@ internal class MeasureAndLayoutDelegate(private val root: LayoutNode) {
 
     /**
      * Makes sure the passed [layoutNode] and its subtree is remeasured and has the final sizes.
+     *
+     * The node or some of the nodes in its subtree can still be kept unmeasured if they are
+     * not placed and don't affect the parent size. See [requestRemeasure] for details.
      */
     fun forceMeasureTheSubtree(layoutNode: LayoutNode) {
         // if there is nothing in `relayoutNodes` everything is remeasured.
@@ -273,8 +276,13 @@ internal class MeasureAndLayoutDelegate(private val root: LayoutNode) {
                 remeasureAndRelayoutIfNeeded(child)
             }
 
-            // run recursively for the subtree.
-            forceMeasureTheSubtree(child)
+            // if the child is still in NeedsRemeasure state then this child remeasure wasn't
+            // needed. it can happen for example when this child is not placed and can't affect
+            // the parent size. we can skip the whole subtree.
+            if (child.layoutState != NeedsRemeasure) {
+                // run recursively for the subtree.
+                forceMeasureTheSubtree(child)
+            }
         }
 
         // if the child was resized during the remeasurement it could request a remeasure on
@@ -283,8 +291,6 @@ internal class MeasureAndLayoutDelegate(private val root: LayoutNode) {
         if (layoutNode.layoutState == NeedsRemeasure && relayoutNodes.remove(layoutNode)) {
             remeasureAndRelayoutIfNeeded(layoutNode)
         }
-
-        require(layoutNode.layoutState != NeedsRemeasure)
     }
 
     /**