From 84c03d0f640243d9aaa92a99aec939fbfd1e8dfb Mon Sep 17 00:00:00 2001
From: Luke Zhao <me@lkzhao.com>
Date: Tue, 23 Apr 2024 14:16:38 -0700
Subject: [PATCH] add OffsetRenderNode

---
 .../Components/Layout/Inset/Insets.swift      |  1 -
 .../Components/Layout/Other/Offset.swift      | 82 +++++++++++++++++++
 .../Model/Component/Component+Modifier.swift  |  9 +-
 3 files changed, 85 insertions(+), 7 deletions(-)
 create mode 100644 Sources/UIComponent/Components/Layout/Other/Offset.swift

diff --git a/Sources/UIComponent/Components/Layout/Inset/Insets.swift b/Sources/UIComponent/Components/Layout/Inset/Insets.swift
index ded69bc2..bc42ee0b 100644
--- a/Sources/UIComponent/Components/Layout/Inset/Insets.swift
+++ b/Sources/UIComponent/Components/Layout/Inset/Insets.swift
@@ -66,4 +66,3 @@ struct InsetsRenderNode: RenderNode {
         [CGPoint(x: insets.left, y: insets.top)]
     }
 }
-
diff --git a/Sources/UIComponent/Components/Layout/Other/Offset.swift b/Sources/UIComponent/Components/Layout/Other/Offset.swift
new file mode 100644
index 00000000..19e9e649
--- /dev/null
+++ b/Sources/UIComponent/Components/Layout/Other/Offset.swift
@@ -0,0 +1,82 @@
+//
+//  File.swift
+//  
+//
+//  Created by Luke Zhao on 4/23/24.
+//
+
+import UIKit
+
+/// Wraps a content component and applies the specified offset to it.
+/// Instead of creating an instance directly, use the ``Component/offset(_:)`` modifier.
+public struct Offset: Component {
+    let content: any Component
+    let offset: CGPoint
+
+    public init(content: any Component, offset: CGPoint) {
+        self.content = content
+        self.offset = offset
+    }
+
+    public func layout(_ constraint: Constraint) -> some RenderNode {
+        OffsetRenderNode(content: content.layout(constraint), offset: offset)
+    }
+}
+
+public struct DynamicOffset: Component {
+    let content: any Component
+    let offsetProvider: (Constraint) -> CGPoint
+
+    public init(content: any Component, offsetProvider: @escaping (Constraint) -> CGPoint) {
+        self.content = content
+        self.offsetProvider = offsetProvider
+    }
+
+    public func layout(_ constraint: Constraint) -> some RenderNode {
+        let offset = offsetProvider(constraint)
+        return OffsetRenderNode(content: content.layout(constraint), offset: offset)
+    }
+}
+
+struct OffsetRenderNode: RenderNode {
+    typealias View = UIView
+
+    let content: any RenderNode
+    let offset: CGPoint
+
+    /// The size of the render node, adjusted for the insets.
+    var size: CGSize {
+        content.size
+    }
+
+    /// The content render nodes of this render node.
+    var children: [any RenderNode] {
+        [content]
+    }
+
+    /// The positions of the content render nodes within this render node.
+    var positions: [CGPoint] {
+        [offset]
+    }
+
+    func visibleIndexes(in frame: CGRect) -> any Collection<Int> {
+        [0]
+    }
+
+    func visibleRenderables(in frame: CGRect) -> [Renderable] {
+        var result = [Renderable]()
+        if shouldRenderView, frame.intersects(CGRect(origin: .zero, size: size)) {
+            result.append(Renderable(frame: CGRect(origin: .zero, size: size), renderNode: self, fallbackId: defaultReuseKey))
+        }
+        let indexes = visibleIndexes(in: frame)
+        for i in indexes {
+            let child = children[i]
+            let position = positions[i]
+            let childRenderables = child.visibleRenderables(in: frame).map {
+                Renderable(frame: $0.frame + position, renderNode: $0.renderNode, fallbackId: "item-\(i)-\($0.fallbackId)")
+            }
+            result.append(contentsOf: childRenderables)
+        }
+        return result
+    }
+}
diff --git a/Sources/UIComponent/Core/Model/Component/Component+Modifier.swift b/Sources/UIComponent/Core/Model/Component/Component+Modifier.swift
index 60c5e916..d90dd5cc 100644
--- a/Sources/UIComponent/Core/Model/Component/Component+Modifier.swift
+++ b/Sources/UIComponent/Core/Model/Component/Component+Modifier.swift
@@ -438,7 +438,7 @@ extension Component {
     /// - Parameter offset: The `CGPoint` value to apply as an offset.
     /// - Returns: A component offset by the specified point.
     public func offset(_ offset: CGPoint) -> some Component {
-        Insets(content: self, insets: UIEdgeInsets(top: offset.y, left: offset.x, bottom: -offset.y, right: -offset.x))
+        Offset(content: self, offset: offset)
     }
 
     /// Applies an offset to the component using separate x and y values.
@@ -447,17 +447,14 @@ extension Component {
     ///   - y: The vertical offset.
     /// - Returns: A component offset by the specified x and y values.
     public func offset(x: CGFloat = 0, y: CGFloat = 0) -> some Component {
-        Insets(content: self, insets: UIEdgeInsets(top: y, left: x, bottom: -y, right: -x))
+        Offset(content: self, offset: CGPoint(x: x, y: y))
     }
 
     /// Applies a dynamic offset to the component based on constraints at layout time.
     /// - Parameter offsetProvider: A closure that provides a `CGPoint` based on the given `Constraint`.
     /// - Returns: A component that dynamically adjusts its offset based on the provided point.
     public func offset(_ offsetProvider: @escaping (Constraint) -> CGPoint) -> some Component {
-        DynamicInsets(content: self) {
-            let offset = offsetProvider($0)
-            return UIEdgeInsets(top: offset.y, left: offset.x, bottom: -offset.y, right: -offset.x)
-        }
+        DynamicOffset(content: self, offsetProvider: offsetProvider)
     }
 
     // MARK: - Visible insets modifiers