Stop configuring the max width and height in YogaUIView

CHANGELOG.md

@@ -13,6 +13,7 @@ Fixed:
 - Don't measure the height of `RedwoodUIView` as zero when measured with `sizeThatFits()` or `intrinsicContentSize()`. We had been using `UIStackView` which doesn't support these functions.
 - Correctly signal `RedwoodUIView` size changes of to callers who measure it with `intrinsicContentSize()`.
 - The Redwood Gradle plugin is now compatible with Gradle 9.1.
+- Don't incorrectly size items to 0 when using the `Flex()` modifier on a `Wrap` container.
 
 
 ## [0.18.0] - 2025-08-01

redwood-layout-shared-test/src/commonMain/kotlin/app/cash/redwood/layout/AbstractFlexContainerTest.kt

@@ -1089,6 +1089,43 @@ abstract class AbstractFlexContainerTest<T : Any> {
 
     snapshotter(row.value).snapshot()
   }
+
+  /**
+   * We had a bug where putting `flex(1.0)` on a child of a column with `height(Constraint.Wrap)`
+   * would cause that child to get a height of 0.
+   *
+   * https://github.com/cashapp/redwood/issues/2753
+   */
+  @Test
+  fun testFlexOnChildOfWrappingColumn() {
+    val root = row().apply {
+      width(Constraint.Fill)
+      height(Constraint.Fill)
+    }
+
+    val fixedSize = row().apply {
+      width(Constraint.Fill)
+      height(Constraint.Fill)
+      modifier = SizeImpl(width = 300.dp, height = 500.dp)
+    }.also {
+      root.children.insert(0, it)
+    }
+
+    val column = column().apply {
+      width(Constraint.Fill)
+    }.also {
+      fixedSize.children.insert(0, it)
+    }
+
+    widgetFactory.text("hello").apply {
+      modifier = FlexImpl(1.0)
+      bgColor(Blue)
+    }.also {
+      column.children.insert(0, it)
+    }
+
+    snapshotter(root.value).snapshot()
+  }
 }
 
 interface TestFlexContainer<T : Any> :

redwood-layout-uiview/src/commonMain/kotlin/app/cash/redwood/layout/uiview/UIViewMeasureCallback.kt

@@ -23,6 +23,8 @@ import kotlinx.cinterop.CValue
 import kotlinx.cinterop.useContents
 import platform.CoreGraphics.CGSize
 import platform.CoreGraphics.CGSizeMake
+import platform.UIKit.UILayoutPriorityDefaultLow
+import platform.UIKit.UILayoutPriorityRequired
 import platform.UIKit.UIView
 import platform.UIKit.UIViewNoIntrinsicMetric
 
@@ -44,15 +46,18 @@ internal object UIViewMeasureCallback : MeasureCallback {
       else -> height.toDouble()
     }
 
-    // The default implementation of sizeThatFits: returns the existing size of
-    // the view. That means that if we want to layout an empty UIView, which
-    // already has a frame set, its measured size should be CGSizeZero, but
-    // UIKit returns the existing size. See https://github.com/facebook/yoga/issues/606
-    // for more information.
+    // The default implementation of sizeThatFits: returns the existing size of the view. That means
+    // that if we want to layout an empty UIView, which already has a frame set, its measured size
+    // should be CGSizeZero, but UIKit returns the existing size. For more information, see
+    // https://github.com/facebook/yoga/issues/606
     val sizeThatFits = if (view.isMemberOfClass(UIView.`class`()) && view.typedSubviews.isEmpty()) {
       Size(0f, 0f)
     } else {
-      view.sizeThatFits(CGSizeMake(constrainedWidth, constrainedHeight)).toSize()
+      view.systemLayoutSizeFittingSize(
+        targetSize = CGSizeMake(constrainedWidth, constrainedHeight),
+        withHorizontalFittingPriority = widthMode.toFittingPriority(),
+        verticalFittingPriority = heightMode.toFittingPriority(),
+      ).toSize()
     }
 
     return Size(
@@ -65,3 +70,8 @@ internal object UIViewMeasureCallback : MeasureCallback {
 private fun CValue<CGSize>.toSize() = useContents {
   Size(width.toFloat(), height.toFloat())
 }
+
+private fun MeasureMode.toFittingPriority() = when (this) {
+  MeasureMode.Exactly -> UILayoutPriorityRequired
+  else -> UILayoutPriorityDefaultLow
+}

redwood-layout-uiview/src/commonMain/kotlin/app/cash/redwood/layout/uiview/YogaUIView.kt

@@ -21,6 +21,8 @@ import platform.CoreGraphics.CGRectMake
 import platform.CoreGraphics.CGRectZero
 import platform.CoreGraphics.CGSize
 import platform.CoreGraphics.CGSizeMake
+import platform.UIKit.UILayoutPriority
+import platform.UIKit.UILayoutPriorityRequired
 import platform.UIKit.UIScrollView
 import platform.UIKit.UIScrollViewContentInsetAdjustmentBehavior.UIScrollViewContentInsetAdjustmentNever
 import platform.UIKit.UIScrollViewDelegateProtocol
@@ -94,19 +96,36 @@ internal class YogaUIView : UIScrollView(cValue { CGRectZero }), UIScrollViewDel
   override fun intrinsicContentSize(): CValue<CGSize> {
     return calculateLayout(
       width = fillWidth.toYogaWithWidthConstraint(),
-      maxWidth = fillWidth.toYoga(),
       height = fillHeight.toYogaWithWidthConstraint(),
-      maxHeight = fillHeight.toYoga(),
     )
   }
 
   override fun sizeThatFits(size: CValue<CGSize>): CValue<CGSize> {
     return size.useContents<CGSize, CValue<CGSize>> {
       calculateLayout(
         width = width.toYogaWithWidthConstraint(),
-        maxWidth = width.toYoga(),
         height = height.toYogaWithHeightConstraint(),
-        maxHeight = height.toYoga(),
+      )
+    }
+  }
+
+  override fun systemLayoutSizeFittingSize(
+    targetSize: CValue<CGSize>,
+    withHorizontalFittingPriority: UILayoutPriority,
+    verticalFittingPriority: UILayoutPriority,
+  ): CValue<CGSize> {
+    return targetSize.useContents<CGSize, CValue<CGSize>> {
+      calculateLayout(
+        width = when {
+          withHorizontalFittingPriority == UILayoutPriorityRequired -> width.toYoga()
+          widthConstraint == Constraint.Fill -> width.toYoga()
+          else -> Size.UNDEFINED
+        },
+        height = when {
+          verticalFittingPriority == UILayoutPriorityRequired -> height.toYoga()
+          heightConstraint == Constraint.Fill -> height.toYoga()
+          else -> Size.UNDEFINED
+        },
       )
     }
   }
@@ -160,14 +179,12 @@ internal class YogaUIView : UIScrollView(cValue { CGRectZero }), UIScrollViewDel
 
   private fun calculateLayout(
     width: Float = Size.UNDEFINED,
-    maxWidth: Float = Size.UNDEFINED,
     height: Float = Size.UNDEFINED,
-    maxHeight: Float = Size.UNDEFINED,
   ): CValue<CGSize> {
     rootNode.requestedWidth = width
-    rootNode.requestedMaxWidth = maxWidth
+    rootNode.requestedMaxWidth = Size.UNDEFINED
     rootNode.requestedHeight = height
-    rootNode.requestedMaxHeight = maxHeight
+    rootNode.requestedMaxHeight = Size.UNDEFINED
 
     rootNode.measureOnly(Size.UNDEFINED, Size.UNDEFINED)