From 39dc7f109baa49516e8061830e0cfc5cf563f2c2 Mon Sep 17 00:00:00 2001
From: mob-sakai <12690315+mob-sakai@users.noreply.github.com>
Date: Wed, 8 Jan 2025 04:13:31 +0900
Subject: [PATCH] feat: `Angle Gradient` gradation supports RectTransform pivot

---
 Packages/src/Runtime/UIEffectContext.cs       |  2 ++
 .../src/Runtime/Utilities/GradientUtil.cs     | 36 +++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/Packages/src/Runtime/UIEffectContext.cs b/Packages/src/Runtime/UIEffectContext.cs
index 82ac251..276078a 100644
--- a/Packages/src/Runtime/UIEffectContext.cs
+++ b/Packages/src/Runtime/UIEffectContext.cs
@@ -462,6 +462,7 @@ private void ApplyGradation(List<UIVertex> verts, Rect rect, Matrix4x4 m, bool c
                     GradientUtil.DoRadialGradient(verts, a, b, offset, scale, rect, m, 12);
                     break;
                 case GradationMode.Angle:
+                    rect = GradientUtil.RotateRectAsNormalized(rect, rot);
                     m = Matrix4x4.Rotate(Quaternion.Euler(0, 0, rot)) * m;
                     GradientUtil.DoHorizontalGradient(verts, a, b, offset, scale, rect, m);
                     break;
@@ -517,6 +518,7 @@ private void ApplyGradation(List<UIVertex> verts, Rect rect, Matrix4x4 m, bool c
                         GradientUtil.GetKeyTimes(grad, _keyTimes);
                     }
 
+                    rect = GradientUtil.RotateRectAsNormalized(rect, rot);
                     m = Matrix4x4.Rotate(Quaternion.Euler(0, 0, rot)) * m;
                     if (canModifyShape)
                     {
diff --git a/Packages/src/Runtime/Utilities/GradientUtil.cs b/Packages/src/Runtime/Utilities/GradientUtil.cs
index 26aaaff..2ef54ea 100644
--- a/Packages/src/Runtime/Utilities/GradientUtil.cs
+++ b/Packages/src/Runtime/Utilities/GradientUtil.cs
@@ -339,5 +339,41 @@ static bool Contains(List<float> list, float v)
                 return false;
             }
         }
+
+        public static Rect RotateRectAsNormalized(Rect rect, float rot)
+        {
+            var rad = -rot * Mathf.Deg2Rad;
+            var cos = Mathf.Cos(rad);
+            var sin = Mathf.Sin(rad);
+            var dir = new Vector2(cos, sin);
+            var center = rect.center;
+
+            if (Mathf.Abs(dir.x) < 0.0001f)
+            {
+                rect.width = rect.height;
+            }
+            else if (Mathf.Abs(dir.y) < 0.0001f)
+            {
+                rect.height = rect.width;
+            }
+            else
+            {
+                var d0 = GetPointToLineDistance(new Vector2(rect.xMin, rect.yMax), center, dir, out var p0);
+                var d1 = GetPointToLineDistance(new Vector2(rect.xMin, rect.yMin), center, dir, out var p1);
+                var closest = d0 < d1 ? p0 : p1;
+                rect.width = rect.height = Vector2.Distance(center, closest) * 2;
+            }
+
+            rect.center = new Vector2(Vector2.Dot(center, dir), 0);
+            return rect;
+        }
+
+        private static float GetPointToLineDistance(Vector2 point, Vector2 origin, Vector2 dir, out Vector2 closest)
+        {
+            var dirNormalized = dir.normalized;
+            var time = Vector2.Dot(point - origin, dirNormalized);
+            closest = origin + time * dirNormalized;
+            return Vector2.Distance(point, closest);
+        }
     }
 }