101 lines
3.5 KiB
C#
101 lines
3.5 KiB
C#
using UnityEngine;
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/// <summary>
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/// 全屏背景/遮罩自适应(Cover)：保持原始宽高比，等比放大到覆盖整个根 Canvas，超出部分裁切。
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/// 过覆盖 => 任意宽高比都无缝铺满、且 sizeDelta 永不为 0；对纯色遮罩与艺术背景都正确、不失真。
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/// 仅调整 sizeDelta(表现层)，不改锚点/位置/pivot，不影响居中布局与位移动画。
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/// 16:9 屏下结果等于设计尺寸，与原始逐像素一致。由 UIResolutionAutoFitter 自动附加。
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/// </summary>
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[RequireComponent(typeof(RectTransform))]
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[DisallowMultipleComponent]
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public class UIBackgroundCover : MonoBehaviour
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{
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public float sourceAspect = 16f / 9f;
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private RectTransform rt;
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private RectTransform coverTarget;
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private float lastW = -1f, lastH = -1f;
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private bool aspectResolved;
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// 重入锁：设置 sizeDelta 会同步触发 OnRectTransformDimensionsChange，
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// 若不拦截会无限递归导致 StackOverflow 崩溃。
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private bool _isFitting;
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private void OnEnable()
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{
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rt = GetComponent<RectTransform>();
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ResolveAspectFromInitialSize();
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ResolveTarget();
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Fit(true);
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}
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private void LateUpdate()
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{
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// 每帧检测 coverTarget 实际尺寸变化（而非只看 Screen）：Unity 布局延迟更新，
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// Screen 变化后 CanvasScaler 可能过几帧才把新尺寸写入 rootCanvas.rect。
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// Fit(false) 内部按 lastW/lastH 判重，尺寸未变时零开销，无需额外节流。
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if (coverTarget == null) ResolveTarget();
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if (coverTarget != null)
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{
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float pw = coverTarget.rect.width;
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float ph = coverTarget.rect.height;
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if (!Mathf.Approximately(pw, lastW) || !Mathf.Approximately(ph, lastH))
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{
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Fit(false);
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}
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}
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}
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/// <summary>用元素初始 sizeDelta 推断原始宽高比，避免写死。</summary>
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private void ResolveAspectFromInitialSize()
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{
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if (aspectResolved) return;
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if (rt == null) rt = GetComponent<RectTransform>();
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Vector2 s = rt.sizeDelta;
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if (s.x > 1f && s.y > 1f) sourceAspect = s.x / s.y;
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aspectResolved = true;
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}
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private void OnRectTransformDimensionsChange()
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{
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if (_isFitting) return; // 拦截自身写入触发的递归回调
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Fit(false);
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}
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private void ResolveTarget()
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{
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Canvas canvas = GetComponentInParent<Canvas>();
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if (canvas != null)
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{
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Canvas root = canvas.rootCanvas != null ? canvas.rootCanvas : canvas;
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coverTarget = root.GetComponent<RectTransform>();
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}
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}
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private void Fit(bool force)
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{
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if (_isFitting) return;
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if (rt == null) rt = GetComponent<RectTransform>();
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if (coverTarget == null) ResolveTarget();
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if (coverTarget == null || sourceAspect <= 0f) return;
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float pw = coverTarget.rect.width;
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float ph = coverTarget.rect.height;
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if (pw <= 0f || ph <= 0f) return;
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if (!force && Mathf.Approximately(pw, lastW) && Mathf.Approximately(ph, lastH)) return;
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lastW = pw; lastH = ph;
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float targetAspect = pw / ph;
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float w, h;
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if (targetAspect > sourceAspect) { w = pw; h = pw / sourceAspect; }
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else { h = ph; w = ph * sourceAspect; }
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Vector2 newSize = new Vector2(w, h);
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if (rt.sizeDelta != newSize)
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{
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_isFitting = true;
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rt.sizeDelta = newSize;
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_isFitting = false;
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}
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}
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}
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