Kotlinify ViewGroupDrawingOrderHelper

Summary:
As per title.

Changelog: [Internal]

Reviewed By: javache

Differential Revision: D72566036

fbshipit-source-id: ac3156b247df3818073e31aa44d5c96f62f7b881

Author: fabriziocucci

packages/react-native/ReactAndroid/api/ReactAndroid.api

@@ -4763,13 +4763,13 @@ public final class com/facebook/react/uimanager/ViewDefaults {
 	public static final field NUMBER_OF_LINES I
 }
 
-public class com/facebook/react/uimanager/ViewGroupDrawingOrderHelper {
+public final class com/facebook/react/uimanager/ViewGroupDrawingOrderHelper {
 	public fun <init> (Landroid/view/ViewGroup;)V
-	public fun getChildDrawingOrder (II)I
-	public fun handleAddView (Landroid/view/View;)V
-	public fun handleRemoveView (Landroid/view/View;)V
-	public fun shouldEnableCustomDrawingOrder ()Z
-	public fun update ()V
+	public final fun getChildDrawingOrder (II)I
+	public final fun handleAddView (Landroid/view/View;)V
+	public final fun handleRemoveView (Landroid/view/View;)V
+	public final fun shouldEnableCustomDrawingOrder ()Z
+	public final fun update ()V
 }
 
 public abstract class com/facebook/react/uimanager/ViewGroupManager : com/facebook/react/uimanager/BaseViewManager, com/facebook/react/uimanager/IViewGroupManager {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/ViewGroupDrawingOrderHelper.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.uimanager
+
+import android.view.View
+import android.view.ViewGroup
+import com.facebook.common.logging.FLog
+import com.facebook.react.common.ReactConstants
+
+/** Helper to handle implementing ViewGroups with custom drawing order based on z-index. */
+public class ViewGroupDrawingOrderHelper(private val viewGroup: ViewGroup) {
+  private var numberOfChildrenWithZIndex = 0
+  private var drawingOrderIndices: IntArray? = null
+
+  /**
+   * This should be called every time a view is added to the ViewGroup in [ViewGroup.addView].
+   *
+   * @param view The view that is being added
+   */
+  public fun handleAddView(view: View) {
+    if (ViewGroupManager.getViewZIndex(view) != null) {
+      numberOfChildrenWithZIndex++
+    }
+
+    drawingOrderIndices = null
+  }
+
+  /**
+   * This should be called every time a view is removed from the ViewGroup in [ViewGroup.removeView]
+   * and [ViewGroup.removeViewAt].
+   *
+   * @param view The view that is being removed.
+   */
+  public fun handleRemoveView(view: View?) {
+    if (ViewGroupManager.getViewZIndex(view) != null) {
+      numberOfChildrenWithZIndex--
+    }
+
+    drawingOrderIndices = null
+  }
+
+  /**
+   * If the ViewGroup should enable drawing order. ViewGroups should call
+   * [ViewGroup.setChildrenDrawingOrderEnabled] with the value returned from this method when a view
+   * is added or removed.
+   */
+  public fun shouldEnableCustomDrawingOrder(): Boolean = numberOfChildrenWithZIndex > 0
+
+  /**
+   * The index of the child view that should be drawn. This should be used in
+   * [ViewGroup.getChildDrawingOrder].
+   */
+  public fun getChildDrawingOrder(childCount: Int, index: Int): Int {
+    var currentDrawingOrderIndices = this.drawingOrderIndices
+    if (currentDrawingOrderIndices != null &&
+        (index >= currentDrawingOrderIndices.size ||
+            currentDrawingOrderIndices[index] >= childCount)) {
+      FLog.w(
+          ReactConstants.TAG,
+          "getChildDrawingOrder index out of bounds! Please check any custom view manipulations you" +
+              " may have done. childCount = %d, index = %d",
+          childCount,
+          index)
+      update()
+    }
+
+    if (currentDrawingOrderIndices == null) {
+      val viewsToSort = ArrayList<View>()
+      for (i in 0 until childCount) {
+        viewsToSort.add(viewGroup.getChildAt(i))
+      }
+
+      // Sort the views by zIndex
+      viewsToSort.sortWith(
+          Comparator { view1, view2 ->
+            val view1ZIndex = ViewGroupManager.getViewZIndex(view1) ?: 0
+            val view2ZIndex = ViewGroupManager.getViewZIndex(view2) ?: 0
+            view1ZIndex - view2ZIndex
+          })
+
+      currentDrawingOrderIndices = IntArray(childCount)
+      for (i in 0 until childCount) {
+        val child = viewsToSort[i]
+        currentDrawingOrderIndices[i] = viewGroup.indexOfChild(child)
+      }
+
+      this.drawingOrderIndices = currentDrawingOrderIndices
+    }
+
+    return currentDrawingOrderIndices[index]
+  }
+
+  /** Recheck all children for z-index changes. */
+  public fun update() {
+    numberOfChildrenWithZIndex = 0
+    for (i in 0 until viewGroup.childCount) {
+      val child = viewGroup.getChildAt(i)
+      if (ViewGroupManager.getViewZIndex(child) != null) {
+        numberOfChildrenWithZIndex++
+      }
+    }
+    drawingOrderIndices = null
+  }
+}