Add UIViewBox Implementation

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

@@ -0,0 +1,185 @@
+/*
+ * Copyright (C) 2022 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.layout.uiview
+
+import app.cash.redwood.Modifier
+import app.cash.redwood.layout.api.Constraint
+import app.cash.redwood.layout.api.CrossAxisAlignment
+import app.cash.redwood.layout.modifier.HorizontalAlignment
+import app.cash.redwood.layout.modifier.VerticalAlignment
+import app.cash.redwood.layout.widget.Box
+import app.cash.redwood.ui.Margin
+import app.cash.redwood.widget.UIViewChildren
+import kotlinx.cinterop.CValue
+import kotlinx.cinterop.convert
+import kotlinx.cinterop.readValue
+import kotlinx.cinterop.useContents
+import platform.CoreGraphics.CGFloat
+import platform.CoreGraphics.CGRectMake
+import platform.CoreGraphics.CGRectZero
+import platform.CoreGraphics.CGSize
+import platform.CoreGraphics.CGSizeMake
+import platform.UIKit.UIView
+import platform.darwin.NSInteger
+
+internal class UIViewBox : Box<UIView> {
+  override val value: View = View()
+
+  override var modifier: Modifier = Modifier
+
+  override val children = value.children
+
+  override fun width(width: Constraint) {
+    value.widthConstraint = width
+  }
+
+  override fun height(height: Constraint) {
+    value.heightConstraint = height
+  }
+
+  override fun margin(margin: Margin) {
+  }
+
+  override fun horizontalAlignment(horizontalAlignment: CrossAxisAlignment) {
+    value.horizontalAlignment = horizontalAlignment
+  }
+
+  override fun verticalAlignment(verticalAlignment: CrossAxisAlignment) {
+    value.verticalAlignment = verticalAlignment
+  }
+
+  internal class View() : UIView(CGRectZero.readValue()) {
+    var widthConstraint = Constraint.Wrap
+    var heightConstraint = Constraint.Wrap
+
+    var horizontalAlignment = CrossAxisAlignment.Start
+    var verticalAlignment = CrossAxisAlignment.Start
+
+    val children = UIViewChildren(
+      this,
+      insert = { view, index ->
+        insertSubview(view, index.convert<NSInteger>())
+        view.setNeedsLayout()
+      },
+      remove = { index, count ->
+        val views = Array(count) {
+          typedSubviews[index].also(UIView::removeFromSuperview)
+        }
+        setNeedsLayout()
+        return@UIViewChildren views
+      },
+    )
+
+    override fun layoutSubviews() {
+      super.layoutSubviews()
+
+      children.widgets.forEach {
+        val view = it.value
+        view.sizeToFit()
+        var childWidth: CGFloat = view.frame.useContents { this.size.width }
+        var childHeight: CGFloat = view.frame.useContents { this.size.height }
+
+        // Check for modifier overrides in the children, otherwise default to the Box's alignment values
+        var itemHorizontalAlignment = horizontalAlignment
+        var itemVerticalAlignment = verticalAlignment
+        it.modifier.forEach { childModifier ->
+          when (childModifier) {
+            is HorizontalAlignment -> {
+              itemHorizontalAlignment = childModifier.alignment
+            }
+            is VerticalAlignment -> {
+              itemVerticalAlignment = childModifier.alignment
+            }
+          }
+        }
+
+        // Compute origin and stretch if needed
+        var x: CGFloat = 0.0
+        var y: CGFloat = 0.0
+        when (itemHorizontalAlignment) {
+          CrossAxisAlignment.Stretch -> {
+            x = 0.0
+            childWidth = frame.useContents { this.size.width }
+          }
+          CrossAxisAlignment.Start -> x = 0.0
+          CrossAxisAlignment.Center -> x = (frame.useContents { this.size.width } - childWidth) / 2.0
+          CrossAxisAlignment.End -> x = frame.useContents { this.size.width } - childWidth
+        }
+        when (itemVerticalAlignment) {
+          CrossAxisAlignment.Stretch -> {
+            y = 0.0
+            childHeight = frame.useContents { this.size.height }
+          }
+          CrossAxisAlignment.Start -> y = 0.0
+          CrossAxisAlignment.Center -> y = (frame.useContents { this.size.height } - childHeight) / 2.0
+          CrossAxisAlignment.End -> y = frame.useContents { this.size.height } - childHeight
+        }
+
+        // Position the view
+        view.setFrame(CGRectMake(x, y, childWidth, childHeight))
+      }
+    }
+
+    override fun sizeThatFits(size: CValue<CGSize>): CValue<CGSize> {
+      var width: CGFloat = 0.0
+      var height: CGFloat = 0.0
+
+      // Calculate the size based on Constraint Values
+      when (widthConstraint) {
+        Constraint.Fill -> {
+          when (heightConstraint) {
+            Constraint.Fill -> {
+              width = size.useContents { this.width }
+              height = size.useContents { this.height }
+            }
+            Constraint.Wrap -> {
+              height = size.useContents { this.height }
+
+              width = typedSubviews
+                .map { it.sizeThatFits(size).useContents { this.width } }
+                .max()
+            }
+          }
+        }
+        Constraint.Wrap -> {
+          when (heightConstraint) {
+            Constraint.Fill -> {
+              width = size.useContents { this.width }
+
+              // calculate the height of the biggest item
+              height = typedSubviews
+                .map { it.sizeThatFits(size).useContents { this.height } }
+                .max()
+            }
+            Constraint.Wrap -> {
+              val unconstrainedSizes = typedSubviews
+                .map { it.sizeThatFits(size) }
+
+              width = unconstrainedSizes
+                .map { it.useContents { this.width } }
+                .max()
+
+              height = unconstrainedSizes
+                .map { it.useContents { this.height } }
+                .max()
+            }
+          }
+        }
+      }
+      return CGSizeMake(width, height)
+    }
+  }
+}

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

@@ -25,9 +25,7 @@ import platform.UIKit.UIView
 
 @ObjCName("UIViewRedwoodLayoutWidgetFactory", exact = true)
 public class UIViewRedwoodLayoutWidgetFactory : RedwoodLayoutWidgetFactory<UIView> {
-  override fun Box(): Box<UIView> {
-    TODO("Not yet implemented")
-  }
+  override fun Box(): Box<UIView> = UIViewBox()
   override fun Column(): Column<UIView> = UIViewFlexContainer(FlexDirection.Column)
   override fun Row(): Row<UIView> = UIViewFlexContainer(FlexDirection.Row)
   override fun Spacer(): Spacer<UIView> = UIViewSpacer()

test-app/presenter/src/commonMain/kotlin/com/example/redwood/testing/presenter/BoxSandbox.kt

@@ -30,7 +30,7 @@ import com.example.redwood.testing.compose.Button
 import com.example.redwood.testing.compose.Text
 
 @Composable
-fun BoxSandbox(modifier: Modifier = Modifier) {
+fun BoxSandbox() {
   Column(
     width = Constraint.Fill,
     height = Constraint.Fill,