using System;
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using JetBrains.Annotations;
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using UnityEngine;
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namespace Core.Extensions
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{
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public static class GameObjectExtensions
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{
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/// <summary>
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/// Sets the layer for this game object and all its children
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/// </summary>
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public static void SetLayerRecursively(this GameObject gameObject, int layer)
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{
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gameObject.layer = layer;
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// Non recursive, non allocating traversal
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Transform goTransform = gameObject.transform;
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if (goTransform.childCount > 0)
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{
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WalkHeirarchyAndSetLayer(goTransform, layer);
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}
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}
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/// <summary>
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/// Walks the heirarchy from <paramref name="root"/>, look at all its children and change the layer.
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/// Non-allocating and non-recursive
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/// </summary>
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/// <param name="root">The root object to start our search from</param>
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/// <param name="layer">The layer to set the game object too</param>
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static void WalkHeirarchyAndSetLayer([NotNull] Transform root, int layer)
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{
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if (root.childCount == 0)
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{
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throw new InvalidOperationException("Root transform has no children");
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}
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Transform workingTransform = root.GetChild(0);
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// Work until we get back to the root
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while (workingTransform != root)
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{
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// Change layer
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workingTransform.gameObject.layer = layer;
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// Get children if we have
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if (workingTransform.childCount > 0)
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{
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workingTransform = workingTransform.GetChild(0);
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}
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// No children, look for siblings
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else
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{
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// Set to our sibling
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if (!TryGetNextSibling(ref workingTransform))
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{
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// Otherwise walk up parents and find THEIR next sibling
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workingTransform = workingTransform.parent;
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while (workingTransform != root &&
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!TryGetNextSibling(ref workingTransform))
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{
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workingTransform = workingTransform.parent;
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}
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}
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}
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}
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}
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/// <summary>
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/// Tries to advance to a sibling of <paramref name="transform"/>
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/// </summary>
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/// <param name="transform">The transform whose siblings we're looking for</param>
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/// <returns>True if we had a sibling. <paramref name="transform"/> will now refer to it.</returns>
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static bool TryGetNextSibling([NotNull] ref Transform transform)
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{
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Transform parent = transform.parent;
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int siblingIndex = transform.GetSiblingIndex();
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// Get siblings if we don't have children
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if (parent.childCount > siblingIndex + 1)
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{
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transform = parent.GetChild(siblingIndex + 1);
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return true;
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}
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return false;
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}
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}
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}
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